Archive for the ‘Bone marrow derived cells’ Category

Blood forming precursors in bone marrow

Larry H. Bernstein, MD, FCAP, Curator



Blood stem cells study could pave the way for new cancer therapy



This image shows the formation of blood stem cells inside the embryonic vessel called dorsal aorta. In green is shown secreted molecule called NOGGIN, which plays an important role in this process. The University of Edinburgh

People with leukaemia could be helped by new research that sheds light on how the body produces its blood supply.

Scientists are a step closer to creating blood stem cells that could reduce the need for bone marrow transplants in patients with cancer or blood disorders.

Enabling scientists to grow the stem cells artificially from pluripotent stem cells could also lead to the development of personalised blood therapies, researchers say.

Blood stem cells are found in bone marrow and produce all blood cells in the body. These cells – known as haematopoietic stem cells (HSCs) – help to restore blood supply in patients who have been treated for leukaemia.

Researchers used a mouse model to pinpoint exactly how HSCs develop in the womb. They showed for the first time how three key molecules interact together to generate the cells, which are later found in adult bone marrow.

The discovery could help scientists to recreate this process in the lab, in the hope that HSCs could one day be developed for clinical use.

Scientists say this fundamental understanding of early development may also have an impact on other diseases that affect blood formation and supply.


The research has been published in Nature Communications.

Professor Alexander Medvinsky, of the University of Edinburgh’s MRC Centre for Regenerative Medicine said: “There is a pressing need to improve treatments for diseases like leukaemia and this type of research brings us a step closer to that milestone. The more we understand about how embryos develop these blood stem cells, the closer we come to being able to make them in the lab.”

Céline Souilhol, Christèle Gonneau, Javier G. Lendinez, Antoniana Batsivari, Stanislav Rybtsov, Heather Wilson, Lucia Morgado-Palacin, David Hills, Samir Taoudi, Jennifer Antonchuk, Suling Zhao, Alexander Medvinsky. Inductive interactions mediated by interplay of asymmetric signalling underlie development of adult haematopoietic stem cells. Nature Communications, 2016; 7: 10784 DOI: 10.1038/ncomms10784

During embryonic development, adult haematopoietic stem cells (HSCs) emerge preferentially in the ventral domain of the aorta in the aorta–gonad–mesonephros (AGM) region. Several signalling pathways such as Notch, Wnt, Shh and RA are implicated in this process, yet how these interact to regulate the emergence of HSCs has not previously been described in mammals. Using a combination of ex vivo and in vivo approaches, we report here that stage-specific reciprocal dorso–ventral inductive interactions and lateral input from the urogenital ridges are required to drive HSC development in the aorta. Our study strongly suggests that these inductive interactions in the AGM region are mediated by the interplay between spatially polarized signalling pathways. Specifically, Shh produced in the dorsal region of the AGM, stem cell factor in the ventral and lateral regions, and BMP inhibitory signals in the ventral tissue are integral parts of the regulatory system involved in the development of HSCs.

Haematopoietic stem cells (HSCs) lie at the foundation of the adult haematopoietic system, and give rise to cells of all blood lineages throughout the lifespan of an organism. An important property of adult (definitive) haematopoietic stem cells (dHSCs) is that they are capable of long-term reconstitution of the haematopoietic system upon transplantation into irradiated recipients. In the mouse, such cells develop by embryonic stages E10–E11 in the aorta–gonad–mesonephros (AGM) region1, 2, 3, 4. An ex vivo approach showed that the AGM region has a robust autonomous capacity to generate dHSCs1. The AGM region comprises the dorsal aorta flanked on both sides by the urogenital ridges (UGRs), which contain embryonic rudiments of kidney and mesonephros. HSCs develop in a polarized manner, predominantly in the ventral floor of the dorsal aorta (AoV), more rarely in the dorsal domain of the dorsal aorta (AoD), and are absent in the UGRs2, 5, 6, 7. Localization of dHSCs to the AoV in mouse and human embryos was shown by long-term reconstitution experiments5, 6.

Abundant evidence indicates that during development, a specialized embryonic endothelial compartment known as haematogenic (or haemogenic) endothelium gives rise to haematopoietic stem and progenitors cells7, 8, 9, 10. The haematopoietic programme in various vertebrate models is executed predominantly in the AoV, and is recognized by the expression of essential haematopoietic transcription factors, for example, Runx1 and cKit, and the appearance of clusters of haematopoietic cells budding from the endothelium of the dorsal aorta6, 8, 9, 11, 12, 13, 14.

It is broadly accepted that HSCs develop from the haematogenic endothelium within intra-aortic clusters. This transition involves several consecutive maturation steps of HSC precursors: pro-HSCsright arrowpre-HSC type Iright arrowpre-HSC type IIright arrowdHSC15, 16, 17. All these precursors express endothelial markers, such as vascular-endothelial cadherin (VC) and CD31, and sequentially upregulate haematopoietic surface markers: CD41 (pro-HSCs), CD43 (pre-HSC type I) and finally CD45 (pre-HSC type II). This maturation process occurs in the dorsal aorta between E9 and E11. Specifically, pro-HSCs emerge at E9, pre-HSCs Type I appear at E10 and pre-HSCs type II predominantly at E11. Unlike dHSCs, pre-HSCs cannot reconstitute the adult haematopoietic system by direct transplantation and require prior maturation in an embryonic or neonatal environment15, 16, 17, 18,19.

A number of signalling pathways (Notch, Wnt, retinoic acid, interleukin-3 and inflammatory) have been implicated in HSC development; however, a coherent picture is yet to be elucidated15, 17, 20,21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31. HSC precursors (pro-HSCs, pre-HSCs type I and pre-HSCs type II) express cKit17 from early developmental stages. A recent study has shown that the cKit ligand, known as stem cell factor (SCF), is a key regulator driving maturation of these HSC precursors into dHSCs in the AGM region17, which is in agreement with the marked decline of HSC activity in SCF mutant mice32, 33. In the adult, SCF is critically important for HSC maintenance in the bone marrow niche, mainly in the endothelial compartment32. Sonic Hedgehog (Shh) and bone morphogenetic protein 4 (BMP4) pathways are also important mediators; in zebrafish, these two morphogenes are involved in arterial specification and haematopoietic patterning, respectively34,35. In the mouse, subaortic BMP4 and Shh/Indian Hedgehog derived from gut were also proposed to be responsible for HSC development36, 37.

During development, interactions between spatially segregated compartments are essential for tissue patterning and specification, and are often mediated by gradients of secreted molecules38,39, 40. Molecules secreted by distant tissues, such as somites, can influence HSC development in the AGM region41, 42, 43, 44, 45. Developing HSCs are embedded in the complex AGM microenvironment, suggesting that HSC development may require signals derived from different compartments of the AGM region. We sought to test this hypothesis. However, the analysis of HSC development in vivo is significantly hampered by low accessibility of embryos developing in utero, fast maturation of dHSCs, lack of uniquely specific markers for HSC precursors and their low numbers in the AGM region. Therefore, we employed here a robust ex vivo culture system that models HSC development in the embryo in combination with functional HSC analysis using in vivolong-term reconstitution assay15, 16, 17. Specifically, to study interactions between AGM subregions, we took advantage of the in vitro reaggregation system that enables close juxtaposition of cell types15.

We show that interactions between three compartments of the AGM, the AoV, the AoD and the UGRs, are necessary for efficient generation of dHSCs. First, we show that dHSC activity in the isolated E10.5 AoV is limited but can be significantly enhanced by co-culture with the AoD, and that this is mediated at least partly by Shh, secreted dorsally in vivo. Second, while HSC activity in isolated E11.5 AoD is limited, co-culture with a competent AoV microenvironment activates dHSC generation in the AoD. We found that this effect is mediated by SCF, which is secreted abundantly by the AoV stroma in vivo as shown here. Third, we show that downregulation of BMP4 signalling by BMP antagonist Noggin, which is present at high levels in the AoV and especially in intra-aortic clusters as revealed here by in vivo observations, is required for HSC development. Fourth, UGRs, which express high levels of SCF, also enhance HSC development in the dorsal aorta.

Our results based on in vivo observations and ex vivo modelling strongly suggest that juxtaposed, anatomically distinct domains within the AGM region create a complex landscape of interactive signals that underpins HSC development.

Pre-HSCs localize preferentially to the AoV

As dHSCs mature from pre-HSCs, we investigated whether the emergence of dHSC predominantly in the AoV6 is a result of asymmetric (ventralized) distribution of pre-HSCs. Dorsal aortae were separated from UGRs and bisected into AoV and AoD (including notochord) as described previously6 (Supplementary Fig. 1a). The different domains were then directly transplanted into irradiated mice to detect dHSCs. We first confirmed our previous observation that at E11.5 dHSCs appear almost exclusively in the AoV, although some dHSCs were in the AoD and engrafted few recipients at high level (Supplementary Fig. 1b). Limiting dilution analysis showed that dHSCs are approximately four times more frequent in the AoV compared with AoD. UGRs did not contain HSCs in line with previous reports2, 6.

We then investigated the spatial distribution of pre-HSCs type I and pre-HSCs type II in E10.5–E11.5 embryos using the OP9 co-culture system supplemented with Il3+SCF+Flt3 (termed 3GF), which allows pre-HSCs (which do not engraft by direct transplantation) to mature into dHSC that become detectable by long-term repopulation assay as described previously16. Doses of transplanted cells (expressed in embryo equivalents, e.e.) were chosen based on the requirements of individual experiments (explained in Methods section). In these experiments (Fig. 1), the dose injected was high (1–2e.e.) to detect potentially low dHSC numbers in AoD and UGRs.

Figure 1: Localization of pre-HSCs in the AGM region.

Localization of pre-HSCs in the AGM region.

(a) E10.5 AoV, AoD and UGRs were co-aggregated with OP9 and cultured for 5 days, and the formation of dHSCs was then tested by transplantation into irradiated mice (2e.e. per recipient; AoV: six independent experiments; AoD: four independent experiments; UGRs: two independent experiments). Dashed line indicates the cutoff for high-level engraftment (>70% donor chimaerism). (b) E11.5 aortas and UGRs were transplanted after reaggregate culture (Ao: 0.2e.e. per recipient and UGRs: 1e.e. per recipient; two independent experiments). (c,d) Pre-HSCs type I (VC+CD45) (c) or type II (VC+CD45+) (d) sorted from E11.5 AoV and AoD were co-aggregated with OP9 cells and transplanted after culture (1e.e. per recipient; two independent experiments). (ad) Levels of engraftment are plotted, and number of repopulated versus total number of transplanted mice are shown in brackets. Number of embryo equivalents (ee) injected in each experiment are indicated on the graphs. (*P<0.05; ***P<0.005; Mann–Whitney U-test). In all these experiments, tissues were cultured with three growth factors (Flt3I, Il3 and SCF). AGM, aorta–gonad–mesonephros region; Ao, dorsal Aorta; AoV, ventral domain of the dorsal aorta; AoD, dorsal domain of the dorsal aorta; UGRs, urogenital ridges.

We have shown previously that E10.5 AGM region mainly contains type I pre-HSCs, whereas at E11.5, type I and type II pre-HSCs co-exist16. Dissected E10.5 AGM regions co-cultured with OP9 in 3GF for 5 days were transplanted into adult irradiated recipients. Out of 21 recipients that received cultured AoV, 20 showed high levels (>70%) of donor-derived long-term haematopoietic chimerism (Fig. 1a). In contrast, only 7 out of 16 recipients of cultured AoD were repopulated at high levels (>70%), while the remaining recipients showed lower or no repopulation (7 and 2, respectively). Cultured UGRs did not produce dHSCs (Fig. 1a). Thus, we conclude that the E10.5 AoD does contain pre-HSCs but at significantly lower numbers than the AoV.

We then investigated whether pre-HSCs localization changes in E11.5 embryos and found that pre-HSCs were still exclusively localized to the dorsal aorta; UGRs carefully separated from the lateral mesenchyme adjacent to the dorsal aorta did not give any repopulation after culture (Fig. 1b). To establish the location of pre-HSCs within the E11.5 dorsal aorta, cell populations enriched for pre-HSCs type I (VC+CD45) and pre-HSCs type II (VC+CD45+) were sorted from AoV and AoD, and co-cultured with OP9 stromal cells in the presence of 3GF as described previously16. We again were able to detect pre-HSC activity in AoD although at lower levels than in AoV. After maturation ex vivo, pre-HSCs type I from AoV and AoD repopulated 7 of 11 and 2 of 8 recipients, respectively (Fig. 1c). Similarly, cultured pre-HSCs type II from AoV and AoD repopulated 11 out of 12 and 4 out of 10 recipients, respectively (Fig. 1d). In all cases, multilineage engraftment was confirmed (Supplementary Fig. 2). These data show that pre-HSCs are significantly enriched in AoV.

Reciprocal inductive interactions between AoD and AoV

To explore hypothetical interactions between AoD and AoV, we made use of a dissociation–reaggregation system that recapitulates HSC development ex vivo15. This system allowed us to integrate AGM domains in a three-dimensional tissue-like organoid15 and study their interactions in HSC development. To track the origin of dHSCs, AoV and AoD from wild-type (WT) and green fluorescent protein (GFP) embryos with constitutive expression of GFP46 were co-aggregated (termed AoV//AoD co-aggregates) and cultured for 5 days in the presence of 3GF before transplantation (Fig. 2a). Mice transplanted with AoV//AoD co-aggregates can be reconstituted by dHSCs coming from AoD and AoV. The presence of GFP allowed the individual contributions of AoV and AoD to the total repopulation level within the same mouse to be assessed (Fig. 2b,c). This is presented in two separate columns in the graph. Namely, while columns 1 and 3 represent the same recipient mice, the former shows exclusively the contribution of the AoD and the latter shows exclusively the contribution of the AoV into each recipient. To assess the influence of AoD and AoV interaction on HSC development, the repopulation by co-aggregated AoD (column 1) or AoV (column 3) can then be compared with repopulation by independently cultured AoD (column 2) or AoV (column 4). All experiments included reciprocal use of WT and GFP tissues in AoV//AoD co-aggregates, and we observed no difference in repopulation properties between WT and GFP embryos. Homotypic AoV//AoV and AoD//AoD co-aggregates were always used as controls. Note that in these experiments, only 0.2e.e. were injected per recipient, to ensure that the repopulation levels were not saturated and to allow any inductive effects to be revealed.

Figure 2: Inductive interactions between AoV, AoD and UGRs as revealed by an ex vivomodel system.

Inductive interactions between AoV, AoD and UGRs as revealed by an ex vivo model system.

(a) Experimental design: the ventral domain (AoV) and the dorsal domain (AoD) of the aorta, and the urogenital ridges (UGRs) from wild-type (WT) and GFP+ embryos were subdissected, and chimeric reaggregates from tissues of these two genotypes were generated. Left column: to test interactions between AoV and AoD, chimeric AoV//AoD reaggregates were generated and transplanted into irradiated recipients after 4–5 days of culture (b,c). Right column: to test interactions between Ao and UGRs, chimeric Ao//UGR reaggregates were generated and transplanted into irradiated recipients after 4–5 days culture (d). GFP+ and/or GFP− donor-derived long-term repopulation allowed us to conclude whether dHSCs originated from AoV, AoD or UGRs. Accordingly, the tissue of origin of donor dHSCs is indicated below each graph. (b) E10.5 aortas from WT and GFP embryos were used to generate chimeric reaggregates as depicted schematically above plots. The reciprocal combination of WT and GFP tissues was used to generate AoV//AoD reaggregates. The tissue source of dHSCs is shown separately in the leftmost (AoD) and rightmost (AoV) columns as indicated below the plot (0.2e.e. per recipient; two independent experiments). (c) E11.5 aortas from WT and GFP embryos were used to generate chimeric reaggregates. The tissue source of dHSCs is shown separately in the leftmost (AoD) and rightmost (AoV) columns as indicated below the plot (0.2e.e. per recipient; two independent experiments). (d) E11.5 aortas (Ao) and UGRs from WT and GFP embryos were used to generate Ao//UGR chimeric reaggregates. As depicted schematically above the plot, the reciprocal combination of WT and GFP tissues was used to generate Ao//UGR reaggregates. The tissue source of dHSCs is shown separately in left (Ao) and right (UGRs) columns as indicated below the plot (0.01e.e. per recipient; six independent experiments). (e) Reaggregation of WT Ao with UGRs generate more dHSCs than Ao alone (0.05e.e. per recipient; two independent experiments). (be) In all these experiments, tissues were cultured with three growth factors.

Using this approach, we found that the E10.5 AoV generates more dHSCs when combined with AoD than on its own (Fig. 2b, compare two rightmost columns). One day later, E11.5 AoD had no positive influence on dHSC generation by AoV (Fig. 2c, compare two rightmost columns). Conversely, the E11.5 AoD produced more HSCs when reaggregated with the AoV than on its own (Fig. 2c, compare two leftmost columns). This inductive effect of AoV on AoD was not observed at E10.5 (Fig. 2b, compare two leftmost columns). These ex vivo modelling experiments revealed reciprocal stage-specific effects of AoV and AoD on HSC development, which could be explained by the differential release of factors by the two regions and/or by differences in the competency of the target cells to respond to signals.

UGRs enhance HSC development in the dorsal aorta  

SCF expression is involved in polarized HSC development

Figure 3: Involvement of polarized stem cell factor in HSC development.

Involvement of polarized stem cell factor in HSC development.

(a) qRT–PCR on fresh AoV, AoD and UGRs at E10.5 and E11.5 showed high expression levels of stem cell factor (SCF) in AoV and UGRs, compared with AoD (data are mean±s.e.m; *P<0.05, **P<0.01, t-test; three independent experiments). No significant difference was observed between E10.5 and E11.5 expression level in any of the tissues. (b) Expression of SCF-GFP and CD31 determined by immunostaining on thick section (300μm) of SCF-GFP-positive E10.5 AGM region and on SCF-GFP-negative control. Bars, 50μm. (c) Expression of SCF in sorted populations from fresh E10.5–E11.5 AoV (V) and AoD (D) determined by qRT–PCR. Endo, endothelial population (VC+CD45CD43); type I, pre-HSCs type I (VC+CD45CD43+); type II, pre-HSCs type II (VC+CD45+); stroma, stromal population (VCCD45CD43). (*P<0.05, t-test; five independent experiments). (d) E10.5 AoD were cultured as reaggregates in the presence of Il3 and Flt3L with or without SCF and human SCF antagonist (SCF-Rh). (0.5e.e. per recipient; three independent experiments). (e,f) E11.5 AoD (two independent experiments) (e) and E10.5 AoV (two independent experiments) (f) were cultured as explants with or without SCF (no other cytokines); (0.2e.e. per recipient).


Shh signalling enhances dHSC generation


Figure 4: Sonic Hedgehog is a positive modulator of pre-HSC type I.

Sonic Hedgehog is a positive modulator of pre-HSC type I.

(a) Expression level of Sonic Hedgehog (Shh) in E10.5 and E11.5 AGM region determined by qRT–PCR. (data are mean±s.e.m; *P<0.05, t-test; E10.5: three independent experiments and E11.5: two independent experiments). (b) Patched1 and Gli1 expression in endothelial cells (endo: VC+CD45CD43), pre-HSCs type I (I: VC+CD45CD43+) and type II (II: VC+CD45+) sorted from E11.5 AoV and AoD (two independent experiments). (c) E10.5 AoV and AoD explants were cultured in presence of Shh recombinant protein before transplantation (AoV: 0.1e.e. per recipient; two independent experiments and AoD: 0.2e.e. per recipient; three independent experiments). (d) E10.5 AoV and doxycyline-inducible OP9-Shh were co-aggregated and cultured in presence or absence of doxycycline and/or Hedgehog (Hh) antagonist (200nM) before transplantation (0.2e.e. per recipient; two independent experiments). (e) 10.5 AoV and AoD co-aggregated with OP9 were cultured in presence of three growth factors with Hh antagonist before transplantation; (0.2e.e. per recipient; two independent experiments). (f) E11.5 AoV explants were cultured in presence of Shh recombinant protein before transplantation; (0.2e.e. per recipient; two independent experiments). (g): E11.5 AGM reaggregates were cultured in presence of Hh antagonist before transplantation; (0.1e.e. per recipient; two independent experiments). (c,d,f,g) In all these experiments, tissues were cultured without cytokines. Hh anta, Hh antagonist; Dox, doxycycline.


BMP signalling is downregulated in the dHSC lineage

Figure 5: Bone morphogenetic protein signalling is downregulated in dHSC lineage.

Bone morphogenetic protein signalling is downregulated in dHSC lineage.

(a) Expression of bone morphogenetic protein 4 (BMP4) at E10.5 determined by qRT–PCR; (data are mean±s.e.m.; *P<0.05, t-test; three independent experiments). (b) Expression of BMP4 in the E10.5 AGM region determined by immunostaining on frozen sections. Bars, 50μm. Zoomed image shows the subendothelial localization of BMP4 (arrowheads). Bars, 10μm. (c) Expression of phosphorylated-Smad (P-Smad) in the E10.5 AGM region determined by immunostaining on frozen sections. Bars, 50μm. (d) Id genes expression in endothelial cells, pre-HSCs type I and type II directly isolated from E10.5 and E11.5 AoV determined by qRT–PCR. Endo, endothelial population (VC+CD45CD43); type I, pre-HSCs type I (VC+CD45CD43+); type II, pre-HSCs type II (VC+CD45+); stroma, stromal population (VCCD45CD43). (Data are mean±s.e.m.; *P<0.05, **P<0.01; t-test; five independent experiments). (eg) Expression of P-Smad, CD31 and CD45 in the endothelium and haematopoietic clusters of E10.5 dorsal aorta. White arrowheads indicate cells with pre-HSC type II phenotype (CD31+CD45+); green arrows show (CD31+CD45−/low) cells budding out of the dorsal aorta and expressing P-Smad; asterisks indicate CD31+CD45 cells expressing P-Smad within the endothelium. Bars, 10μm. A positive control showing P-Smad staining in the dorsal part of the neural tube can be found in h.


Figure 6: Haematopoietic clusters are exposed to low concentration of BMP4 and high levels of Noggin.

Haematopoietic clusters are exposed to low concentration of BMP4 and high levels of Noggin.

(a) Expression of BMP antagonists at E10.5 determined by qRT–PCR (data are mean±s.e.m.; *P<0.05,***P<0.005; t-test; three independent experiments). (b) Expression of Noggin in the E10.5 AGM region determined by immunostaining on frozen sections. Note the expression of Noggin in the notochord (Nt) as expected. Bar, 50μm. (c) Expression of Noggin and BMP4 in intra-aortic clusters characterized by cKit and CD31 expression. Note that BMP4 is mainly expressed underneath the dorsal aorta (arrowheads), while Noggin is expressed in the cluster (arrows). Bars, 10μm. (d) Expression of Noggin in isolated populations from E10.5 and E11.5 AoV (V) and AoD (D) determined by qRT–PCR. (*P<0.05, t-test; five independent experiments). (e) Model showing downregulation of BMP activity in dHSC lineage. BMP4 is mainly expressed in the ventral mesenchyme, while Noggin is found in haematopoeitic clusters. Accordingly, BMP activity, assessed by the phosphorylation of Smad1,5 and 8 (P-Smad), is high in mesenchymal cells underneath the aortic endothelium and in some endothelial cells (CD31+CD45) of the aortic endothelium and decreases in the haematopoeitic clusters. While some pre-HSC type I cells (CD31+CD45−/low) exhibit BMP signalling at a low level, acquisition of CD45 (shown in red) is accompanied by a complete loss of BMP activity. EC, endothelial cells; MC, mesenchymal cells; I, pre-HSC type I; II, pre-HSC type II.


BMP signalling inhibits HSC development


Interactions between SCF, Shh and BMP signalling pathways

Interplay between SCF, Shh and BMP pathways underpins inductive interactions in the AGM.


We have shown previously that during murine embryo development definitive HSCs emerge predominantly in the ventral domain of the dorsal aorta (AoV)6. This spatially polarized production of HSCs might be explained by different origins of dorsal and ventral endothelium and/or by asymmetric production of key factors involved in HSC development37, 52, 53 and we reasoned that directional inductive interactions between AGM compartments could be involved. Great insight into inductive interactions in various organs has previously been obtained through in vitro modelling39. Here we modelled interactions between AGM domains in a co-culture system, which supports HSC development15. Using this ex vivo system, we demonstrate that at early stages (E10.5) HSC maturation in the AoV region is enhanced by the presence of the AoD. One day later (E11.5), the AoV microenvironment is able to induce HSC development in the AoD, previously thought to be mostly devoid of HSC activity6. We also found that UGRs can enhance HSC production from the dorsal aorta, but cannot generate dHSCs themselves, even under influence of the dorsal aorta. Thus, our data strongly suggest that reciprocal stage-specific inductive AoD//AoV interactions and involvement of UGRs are required for execution of the robust development of HSCs in vivo.

Our data indicate that previously established dorso–ventrally polarized HSC development6 is defined by two main factors. First, our current data show that although the AoD contains pre-HSCs (both type I and type II), their numbers are lower than in AoV, in line with lower intra-aortic cluster formation previously described in mouse AoD6, 13. Second, as shown here, dHSCs can be induced in the AoD by the AoV, and therefore the dHSCs deficiency in AoD cannot be explained solely by asymmetric pre-HSC distribution, but may also be influenced by differences in the microenvironment.

To study this, we focused on SCF, Shh and BMP4, whose expressions are dorso–ventrally polarized in the AGM region36, 47, 49 (and current data). We found that SCF is an inductive signal that is expressed at high levels in the AoV and UGRs, and can stimulate HSC development in isolated AoD, a region which had previously been considered to be mostly devoid of HSC activity. This is in agreement with a key role of SCF in HSC maturation17. We found that the aortic endothelial compartment expresses high levels of SCF, suggesting its important role in HSC development comparable to the bone marrow microenvironment of adult HSCs32. Importantly, we found that the pre-HSC type I population expresses SCF suggesting a positive-autocrine loop, which could promote HSC development.

Shh signalling in zebrafish is required for aortic angioblast migration and subsequent arterial specification of the dorsal aorta34, 54. We found that in mouse Shh stimulates and a Hh antagonist inhibits the development of HSCs at E10.5 but not at E11.5, in keeping with a previous study37. The induction of dHSCs in AoV by AoD is also limited to the E10.5 stage. Since Shh is secreted by the notochord (which is included in AoD-dissected tissue), this stage specificity is likely defined by the predominant presence of pre-HSCs type I at E10.5, which express higher levels of Shh signalling components (Ptch1 and Gli1) compared with pre-HSCs type II. By E11.5, the pre-HSC population is mainly represented by type II cells15. Stage-specific loss of sensitivity to Hh signalling was also described in the developing neural tube55. Notably, the poor ability of AoD to develop HSCs despite abundant presence of Shh can also be explained by lower levels of Ptch1 and Gli1 detected in AoD- compared with AoV-derived pre-HSC type I. Our ex vivo modelling data indicate that AoD-derived Shh is an active inducer of HSC development in the AGM region. This conclusion does not exclude the possibility that Shh secreted by the gut could also reach the dorsal aorta37, although by E10.5 these sites are separated by an extended mesentery.

BMP4 signalling is a key factor involved during differentiation of ventral mesoderm and its further specification into haematopoietic cells. In zebrafish, BMP signalling is clearly required during the patterning of the dorsal aorta and for the emergence of dHSCs in the ventral wall34. Its role in mouse is less clear due to the early lethality of BMP mutants56. Several lines of evidence point to BMP4 as a good candidate regulating HSC development. Indeed, BMP4 is highly expressed in the ventral mesenchyme underneath the dorsal aorta34, 36, 49; some reports suggested its role in controlling dHSC emergence36, 57, 58. However, the in vitro systems used likely assayed the maintenance of dHSCs, rather than their maturation. It was also reported that BMP4 signalling can define their differentiation potential59. BMP4 is also involved in the regulation of essential haematopoietic transcription factors such as Scl/Gata2/Fli1 and Runx1 (refs 60, 61). Here we analysed BMP signalling activity in the dHSC lineage in the AGM region. We show that in vivo the pre-HSC type I to type II transition is accompanied by a downregulation of BMP targets (Id genes). This correlates with our data demonstrating that BMP activity is downregulated in intra-aortic clusters and the observations of others that Runx1 expression is attenuating in the developing HSC lineage60, 62, 63. How is this decrease of BMP activity achieved in vivo, despite the presence of BMP4 in AoV? It has previously been noted that in amphibian embryos several BMP inhibitors are also expressed in AoV34. Similarly, our analysis of the embryo showed high expression of a number of BMP antagonists as well as inhibitory Smad6 and Smad7 in mouse AoV that may counteract BMP4 action in HSC lineage. Furthermore, we found that in the AGM region BMP4 and Noggin are spatially segregated: Noggin being present in haematopoietic clusters and BMP4 being mainly expressed underneath the aortic endothelium. Therefore, maturing HSCs in clusters are exposed to low BMP4 concentration and high concentration of the BMP antagonist Noggin. Furthermore, our qRT–PCR analysis shows that the pre-HSC type I population expresses Noggin, which possibly creates a very effective shield that protects them from BMP4. Accordingly, our ex vivo analysis strongly suggests that downregulation of BMP signalling is functionally important for HSC development in the embryo. Indeed, forced BMP signalling activation by the addition of BMP4, strongly inhibits HSC development, and conversely the addition of Noggin stimulates HSC development in E10.5–E11.5 AGM cultures. These results are in line with recent observation that deletion of Smad4, a common transducer for BMP4/TGFβ signalling, markedly augments the formation of intra-aortic clusters64. Our data do not exclude the possibility that BMP4 is essential for specification of mouse dHSCs at earlier stages, as described in the zebrafish model, where BMP signalling is required for HSC development at stages closer to mouse E8.5 (ref. 34).

Our analysis indicates that all three signalling pathways studied can cooperate for HSC development (Fig. 8c). Notably, the interplay of Shh and BMP pathways is broadly involved in development. For example, counter gradients of polarized Shh and BMP signalling in the developing spinal cord specify neuronal subsets along the dorso–ventral axis65, and the dorsal aorta resembles the neural tube with inverse orientation of Shh- and BMP-secreting centres34. However, we detected an antagonistic relationship between Shh and BMP pathways. At the molecular level, Shh can induce Noggin and Smad6 expression, thus inhibiting BMP4 signalling. In turn, BMP4 suppresses and, accordingly, Noggin enhances Shh signalling. Cooperation between Shh and Noggin has been previously described as critically important for developmental specification of somitic, neural and hair follicle cells66, 67, 68. Our in vitro data suggest that the feed-forward loop Shhright arrowNoggin/Nogginright arrowShh is also involved in HSC development in vivo.

We propose a model where the polarized secreted factors form complex fields of gradients in vivo, which define an effector zone for optimal HSC development in the dorsal aorta and lead to the ventrally shifted appearance of dHSCs (Fig. 8c). Of interest, intra-aortic clusters are abundant in ventro–lateral positions69, which may reflect the position of this zone. The dissection close to such a zone could lead to accidental inclusion of powerful dHSCs in AoD samples observed here. Furthermore, it is possible that spatial segregation of co-operating and spatial overlap of antagonizing factors may also be important for adjustment of HSC development in vivo. Indeed, although the pool of pre-HSCs in the AGM region markedly expands during E9.5–11.5 (Rybtsov et al., submitted), complete maturation of the HSC pool is limited: while the majority of cells reach the pre-HSC type II stage, only one or two dHSCs are generated by the end of E11. Such controlled dynamics of HSC development may be needed to prevent a burst of active haematopoiesis in the AGM region. How exactly HSC maturation dynamics depend on overlapping concentrations of factors requires further analysis. Although ex vivo modelling is a powerful tool to dissect mechanisms of HSC development in vivo, there will likely be some variation in details. For example, spatial polarization in the developing HSC niche may define kinetics of HSC development in vivo.While we have demonstrated spatial polarization in vivo of the factors driving HSC development in our model system, it is currently unclear whether any factors become expressed in a polarized manner within the reaggregates and as such, whether polarization is also a pre-requisite for HSC maturation. Alternatively, if polarization is not required, the entire reaggregate may replicate the optimal zone for HSC development, resulting in massive generation of dHSCs. The distinction between these two scenarios will require further investigation.

In summary, our ex vivo modelling experiments suggest that HSC development in the embryo involves stage-dependent interactions between dorsal, ventral and lateral domains of the AGM region, mediated at least partly by the interplay of SCF, Shh, BMP4 and Noggin. Further detailed analysis will be required to better understand the complexity of the AGM signalling landscape in which HSC development takes place. Such knowledge may lead to development of novel protocols for the generation of definitive HSCs in vitro for clinical applications.

Integrated genomic DNA/RNA profiling of hematologic malignancies in the clinical setting

Jie He1Omar Abdel-Wahab2Michelle K. Nahas1Kai Wang1Raajit K. Rampal3Andrew M. Intlekofer4, et al. 10, 2016

Key Points

  • Novel clinically-available comprehensive genomic profiling of both DNA and RNA in hematologic malignancies.

  • Profiling of 3696 clinical hematologic tumors identified somatic alterations that impact diagnosis, prognosis, and therapeutic selection

The spectrum of somatic alterations in hematologic malignancies includes substitutions, insertions/deletions (indels), copy number alterations (CNAs) and a wide range of gene fusions; no current clinically available single assay captures the different types of alterations. We developed a novel next-generation sequencing-based assay to identify all classes of genomic alterations using archived formalin-fixed paraffin-embedded (FFPE), blood and bone marrow samples with high accuracy in a clinically relevant timeframe, which is performed in our CLIA-certified CAP-accredited laboratory. Targeted capture of DNA/RNA and next-generation sequencing reliably identifies substitutions, indels, CNAs and gene fusions, with similar accuracy to lower-throughput assays which focus on specific genes and types of genomic alterations. Profiling of 3696 samples identified recurrent somatic alterations that impact diagnosis, prognosis and therapy selection. This comprehensive genomic profiling approach has proved effective in detecting all types of genomic alterations, including fusion transcripts, which increases the ability to identify clinically-relevant genomic alterations with therapeutic relevance.

Cohesin Ring Rules Blood Stem Cells, Binds Them to Renewal or Expansion

GEN News

A genome-wide RNAi screen was used to assess the effects of 15,000 genes on the balance between self-renewal and differentiation of human hematopoietic stem cells (HSCs). The screen identified candidate genes whose knockdown maintained the HSC phenotype during culture. Such findings could lead to better protocols to grow these cells outside the body, potentially making bone marrow transplants more available to patients suffering blood cancers, or even identifying novel genes to target during the treatment of leukemia (left and right panels). Four genes in particular implicated cohesin, a ring-like protein complex that binds to the DNA in all of our cells, in the control of self-renewal versus differentiation in HSCs. Deficiency of cohesin causes an increase in self-renewal and a decrease in differentiation of HSCs. [Cell Reports]

Best known for its ability to regulate the separation of sister chromatids during cell division, the cohesin protein complex, a ring-shaped structure, has shown that it has other powers, such as the facilitation of DNA repair and the modification of transcription. And now, according to scientists based at Lund University, there is evidence that the cohesin complex controls the growth of blood stem cells. More to the point, the cohesin complex determines whether blood stem cells self-renew or differentiate.

The new finding is significant because it can help scientists improve the expansion of blood stem cells outside the body, thus increasing the supply of blood stem cells to patients suffering leukemia or hereditary blood disorders. Besides making bone marrow transplant material more available, the new finding could point scientists to new points of attack for the treatment of blood cancer, which is a disruption between blood stem cell multiplication and maturation.

The Lund University scientists, led by Jonas Larsson, presented their results March 17 in the journal Cell Reports, in an article entitled “Genome-wide RNAi Screen Identifies Cohesin Genes as Modifiers of Renewal and Differentiation in Human HSCs.” The article describes how a genome-wide RNA interference (RNAi) screen was performed in primary human CD34+ cells. This screen enabled the scientists to identify candidate genes whose knockdown maintained the HSC phenotype during culture.

“A striking finding was the identification of members of the cohesin complex (STAG2, RAD21, STAG1, and SMC3) among the top 20 genes from the screen,” wrote the authors. “Upon individual validation of these cohesin genes, we found that their knockdown led to an immediate expansion of cells with an HSC phenotype in vitro.”

A similar expansion, the authors added, was observed in vivo following transplantation to immunodeficient mice.

“Transcriptome analysis of cohesin-deficient CD34+ cells showed an upregulation of HSC-specific genes,” the authors continued. This finding, the authors asserted, demonstrates that when cohesin is deficient, transcription shifts to a more stem cell–like pattern.

“The research is unique as the study of so many genes alongside one another is unprecedented,” said Dr. Larsson. “In addition, we have used human blood stem cells, which is difficult in itself as it is requires the gathering of a large amount of material.”

Of the 15,000 genes that were tested, the Lund team found around 20 candidates with a strong capacity to affect the balance of growth in the blood stem cells. What was striking was that four of these 20 genes were physically connected through cooperation in a protein complex.

“The discovery showed that this protein complex is crucial and has an overarching function in the growth of the blood stem cells,” emphasized Dr. Larsson.

The cohesin complex acts as a sort of brace that holds different parts of the DNA strand together in the cell. The researchers believe that this allows the cohesin complex to control access to the “on/off switches” in DNA and to change the impulses the blood stem cells receive from various genes, thereby affecting cell division. The blood stem cell either multiplies or matures to become a specialized cell with other tasks.

Independently of the Lund researchers’ discovery, other research in the field of blood cancer has recently identified mutations in exactly the same four genes in patients with various forms of blood cancer.

“This is incredibly exciting! Together with the results from our study, this indicates that the cohesin genes are directly and crucially significant in the development of blood cancer,” exclaimed the study’s lead author, Ph.D. candidate Roman Galeev. “Our findings entail a new understanding of how the expansion of blood stem cells is controlled. Eventually, this can lead to new ways of affecting the process, either to prevent the development of cancer or to expand the stem cells for transplant.”


  • A genome-wide RNAi screen was performed in primary human CD34+ cells
  • Several cohesin genes were identified as modifiers of renewal and differentiation
  • Cohesin-deficient HSCs show enhanced reconstitution capacity in vivo
  • Cohesin deficiency induces immediate HSC-specific transcriptional programs


To gain insights into the regulatory mechanisms of hematopoietic stem cells (HSCs), we employed a genome-wide RNAi screen in human cord-blood derived cells and identified candidate genes whose knockdown maintained the HSC phenotype during culture. A striking finding was the identification of members of the cohesin complex (STAG2, RAD21, STAG1, andSMC3) among the top 20 genes from the screen. Upon individual validation of these cohesin genes, we found that their knockdown led to an immediate expansion of cells with an HSC phenotype in vitro. A similar expansion was observed in vivo following transplantation to immunodeficient mice. Transcriptome analysis of cohesin-deficient CD34+ cells showed an upregulation of HSC-specific genes, demonstrating an immediate shift toward a more stem-cell-like gene expression signature upon cohesin deficiency. Our findings implicate cohesin as a major regulator of HSCs and illustrate the power of global RNAi screens to identify modifiers of cell fate.

Figure thumbnail fx1

Human hematopoiesis is maintained by a small number of hematopoietic stem cells (HSCs) that are capable of generating all blood cell lineages at an extremely rapid pace for the entire lifespan of a human being (Orkin and Zon, 2008). HSCs have been studied extensively during the last four decades and are probably the best functionally characterized adult stem cells. However, despite this, the regulatory mechanisms that govern different cellular fate options in HSCs have remained incompletely defined. In particular, it has been challenging to understand the molecular basis of the inherent ability of HSCs to self-renew and preserve their undifferentiated state, which has hampered efforts to expand HSCs ex vivo for therapeutic benefit (Dahlberg et al., 2011). Ex vivo expansion of HSCs would allow for critical improvements of bone marrow transplantation procedures in treatment of malignant and inherited hematological diseases (Chou et al., 2010). Defining the genetic and molecular basis of self-renewal of HSCs is thus important to enhance current cell-therapy strategies, but it is also essential in order to better understand mechanisms behind dysregulated hematopoiesis that may cause leukemia. Genes and pathways balancing cell-fate options between renewal and differentiation in stem cells are often key players in cancer development (Orkin and Zon, 2008).

Thumbnail image of Figure 1. Opens large image

Figure 1

Genome-wide RNAi Screen in Primitive Human Hematopoietic Cells Defines Genes and Pathways Associated with Cancer Progression and Cell Proliferation

(A) Overview of the experimental outline for the primary screen. 60 million cord blood-derived CD34+ cells were transduced with a pooled lentiviral library containing 75,000 shRNAs across six transduction replicates in total. A fraction of the cells were isolated after 72 hr, and proviral inserts were deep sequenced to determine the initial library distribution. Following 20 days of culture, CD34+ cells were magnetically isolated and proviral inserts were sequenced again to determine the changes in distribution for all shRNAs.

(B) Relative distribution of shRNAs following 20 days of in vitro culture, ranked from the most enriched to the most depleted. The y axis shows the average enrichment value across six replicate screens.

(C) Gene ontology analysis for all genes represented by multiple shRNAs in the most enriched (10%) fraction.

(D) KEGG pathway analysis showing strong enrichment for cancer-associated pathways among the top-scoring genes.

See also Figure S1 and Table S1.

We report here on the successful development of a genome-wide RNAi screening approach targeted to primary human hematopoietic stem and progenitor cells to define genes and pathways associated with self-renewal and differentiation. Based on findings from the screen, we implicate the cohesin complex as a crucial regulator of cell-fate decisions influencing self- renewal and differentiation in HSCs both in vitro and in vivo.

These efforts represent a genome-wide RNAi screen targeted to primary human HSPCs. The main limiting factor when performing functional screens in primary human cells is cell number. This obviously becomes even more challenging when rare cell subsets, such as stem and progenitor cells, are studied. Through unique access to cord blood with daily deliveries from several local hospitals, we were able to gather the necessary quantities to perform a screen in enriched primary HSPCs with reasonable coverage (300X).



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Targeting hematopoietic stem cells

Larry H. Bernstein, MD, FCAP, Curator



New technology uncovered the stem cell niche in the bone marrow

HSCs, Stem cells, hematopoiesis

Hematopoietic stem cells (HSCs) are so rare that it’s difficult to comprehensively localize dividing and non-dividing HSCs. Thus, there has controversy about their specific location in the bone marrow. A recent Nature publication reported that the HSCs resides mainly in perisinusoidal niches through out the bone marrow and there are no spatially distinct niches for dividing and non-dividing blood-forming stem cells. This group of researchers at UT Southwestern Medical Center started the generation of a GFP knock-in for the gene Ctnnal1, a generic marker for HSCs in mice (α-catulinGFP mice) and confirmed that α-catulin-GFP+c-kit+ cells represent blood-forming HSCs by showing that α-catulin-GFP+c-kit+ cells gave long term multi-lineage reconstitution of irradiated mice. Using a tissue-clearing technique and deep confocal imaging, they were able to image thousands of α-catulin-GFP+c-kit+ cells and see their relation to other cells. This publication improved the understanding of the microenvironment of HSCs in the bone marrow, which would significantly improve the safety and effectiveness of bone marrow transplantation.

Melih Acar, etc. (October 2015) Deep imaging of bone marrow shows non-dividing stem cells are mainly perisinusoidal. Nature


Deep imaging of bone marrow shows non-dividing stem cells are mainly perisinusoidal

AcarKS. KocherlakotaMM. MurphyJG. PeyerH OguroCN. InraC JaiyeolaZ ZhaoK Luby-Phelps & Sean J. Morrison
Nature526,126–130(01 October 2015)


Haematopoietic stem cells (HSCs) reside in a perivascular niche but the specific location of this niche remains controversial1. HSCs are rare and few can be found in thin tissue sections2, 3 or upon live imaging4, making it difficult to comprehensively localize dividing and non-dividing HSCs. Here, using a green fluorescent protein (GFP) knock-in for the gene Ctnnal1 in mice (hereafter denoted as αcatulinGFP), we discover that αcatulinGFP is expressed by only 0.02% of bone marrow haematopoietic cells, including almost all HSCs. We find that approximately 30% of αcatulin−GFP+c-kit+ cells give long-term multilineage reconstitution of irradiated mice, indicating thatαcatulin−GFP+c-kit+ cells are comparable in HSC purity to cells obtained using the best markers currently available. We optically cleared the bone marrow to perform deep confocal imaging, allowing us to image thousands of αcatulin–GFP+c-kit+ cells and to digitally reconstruct large segments of bone marrow. The distribution of αcatulin–GFP+c-kit+ cells indicated that HSCs were more common in central marrow than near bone surfaces, and in the diaphysis relative to the metaphysis. Nearly all HSCs contacted leptin receptor positive (Lepr+) and Cxcl12high niche cells, and approximately 85% of HSCs were within 10 μm of a sinusoidal blood vessel. Most HSCs, both dividing (Ki-67+) and non-dividing (Ki-67), were distant from arterioles, transition zone vessels, and bone surfaces. Dividing and non-dividing HSCs thus reside mainly in perisinusoidal niches with Lepr+Cxcl12high cells throughout the bone marrow.


Figure 1: Deep imaging of αcatulin−GFP+ HSCs in digitally reconstructed bone marrow.close


Deep imaging of [agr]-catulin-GFP+ HSCs in digitally reconstructed bone marrow.

a, Only 0.021 ± 0.006% of αcatulinGFP/+ bone marrow cells were GFP+ (n = 14 mice in 11 independent experiments). b, Nearly allαcatulin−GFP+c-kit+ bone marrow cells were CD150+CD48 (n = 9 mice in 3 independent experiments;


Extended Data Figure 3: αcatulin−GFP expression among haematopoietic cells is highly restricted to HSCs.


[agr]-catulin-GFP expression among haematopoietic cells is highly restricted to HSCs.


a, The frequency of αcatulin−GFP+ bone marrow cells in negative control αcatulin+/+ (WT) mice and α-catulinGFP/+ mice (n = 14 mice per genotype in 11 independent experiments). In all cases in this figure, percentages refer to the frequency of each population as a percentage of WBM cells. b, αcatulin−GFP+c-kit+ cells from Fig. 1b are shown (blue dots) along with all other bone marrow cells in the same sample (red dots). c, CD150+CD48LSK HSCs express αcatulin−GFP but CD150CD48LSK MPPs do not (n = 17 mice in 12 independent experiments). A minority of the αcatulin−GFP+c-kit+ cells had high forward scatter, lacked reconstituting potential, and were gated out when isolating HSCs by flow cytometry and when identifying HSCs during imaging (see Extended Data Fig. 5for further explanation). d, Linc-kitlowSca-1lowCD127+CD135+ common lymphoid progenitors (CLPs), Linc-kit+Sca-1CD34+CD16/32 common myeloid progenitors (CMPs), Linc-kit+Sca-1CD34+CD16/32+ granulocyte-macrophage progenitors (GMPs), and Linc-kit+Sca-1CD34CD16/32 megakaryocyte-erythroid progenitors (MEPs) did not express αcatulin−GFP. αcatulinGFP/+ and control cell populations had similar levels of background GFP signals that accounted for fewer than 1% of the cells in each population (n = 9 mice per genotype in 2 independent experiments).


Extended Data Figure 7: HSC density is higher in the diaphysis as compared to the metaphysis.

HSC density is higher in the diaphysis as compared to the metaphysis.

a, Schematic of a femur showing the separation of epiphysis/metaphysis from diaphysis. We divided metaphysis from diaphysis at the point where the central sinus branched (see red line in panels a, f,and i). This is also the point at wh…



Extended Data Figure 9: Bone marrow blood vessel types can be distinguished based on vessel diameter, continuity of basal lamina, morphology, and position; and no difference in the distribution of HSCs in the bone marrow of male and female mice was detected.close

Bone marrow blood vessel types can be distinguished based on vessel diameter, continuity of basal lamina, morphology, and position; and no difference in the distribution of HSCs in the bone marrow of male and female mice was detected.

a, b, Schematic (a) and properties (b) of blood vessels in the bone marrow. Blood enters the marrow through arterioles that branch as they become smaller in diameter and approach the endosteum, where they connect to smaller diameter tra…

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Blocking Differentiation to Produce Stem Cells

Larry H. Bernstein, MD, FCAP, Curator



Blocking Differentiation is Enough to Turn Mature Cells into Stem Cells



ID3 inhibitor of DNA binding 3, dominant negative helix-loop-helix protein [ Homo sapiens (human) ]

Gene ID: 3399, updated on 15-Nov-2015


Official Symbol ID3 provided by HGNC 

Official Full Name inhibitor of DNA binding 3, dominant negative helix-loop-helix protein provided by HGNC

Primary source HGNC:HGNC:5362 See related Ensembl:ENSG00000117318; HPRD:02608; MIM:600277; Vega:OTTHUMG00000003229

Gene type protein coding

RefSeq status REVIEWED

OrganismHomo sapiens

LineageEukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Mammalia; Eutheria; Euarchontoglires; Primates; Haplorrhini; Catarrhini; Hominidae; Homo

Also known as HEIR-1; bHLHb25

Summary The protein encoded by this gene is a helix-loop-helix (HLH) protein that can form heterodimers with other HLH proteins. However, the encoded protein lacks a basic DNA-binding domain and therefore inhibits the DNA binding of any HLH protein with which it interacts. [provided by RefSeq, Aug 2011]

Orthologs mouse all


Exon count:
Annotation release Status Assembly Chr Location
107 current GRCh38.p2 (GCF_000001405.28) 1 NC_000001.11 (23557930..23559794, complement)
105 previous assembly GRCh37.p13 (GCF_000001405.25) 1 NC_000001.10 (23884421..23886285, complement)

Chromosome 1 – NC_000001.11Genomic Context describing neighboring genes

Related articles in PubMed


Induced Developmental Arrest of Early Hematopoietic Progenitors Leads to the Generation of Leukocyte Stem Cells

Tomokatsu Ikawa, Kyoko Masuda, Mirelle J.A.J. Huijskens, Rumi Satoh, Kiyokazu Kakugawa, Yasutoshi Agata, Tomohiro Miyai, Wilfred T.V. Germeraad, Yoshimoto Katsura, Hiroshi Kawamoto
Stem Cell Reports Nov 10, 2015; Volume 5, Issue 5, 716–727.   DOI:
  • Overexpression of ID3 endows hematopoietic progenitors with self-renewal activity
  • A simple block of cell differentiation is sufficient to induce stem cells
  • Induced leukocyte stem (iLS) cells exhibit robust multi-lineage reconstitution
  • Equivalent progenitors were produced from human cord blood hematopoietic stem cells

Self-renewal potential and multipotency are hallmarks of a stem cell. It is generally accepted that acquisition of such stemness requires rejuvenation of somatic cells through reprogramming of their genetic and epigenetic status. We show here that a simple block of cell differentiation is sufficient to induce and maintain stem cells. By overexpression of the transcriptional inhibitor ID3 in murine hematopoietic progenitor cells and cultivation under B cell induction conditions, the cells undergo developmental arrest and enter a self-renewal cycle. These cells can be maintained in vitro almost indefinitely, and the long-term cultured cells exhibit robust multi-lineage reconstitution when transferred into irradiated mice. These cells can be cloned and re-expanded with 50% plating efficiency, indicating that virtually all cells are self-renewing. Equivalent progenitors were produced from human cord blood stem cells, and these will ultimately be useful as a source of cells for immune cell therapy.

Figure thumbnail fx1


Somatic tissues with high turnover rates, such as skin, intestinal epithelium, and hematopoietic cells, are maintained by the activity of self-renewing stem cells, which are present in only limited numbers in each organ (Barker et al., 2012,Copley et al., 2012, Fuchs and Chen, 2013). For example, the frequency of hematopoietic stem cells (HSCs) in the mouse is about 1 in 105 of total bone marrow (BM) cells (Spangrude et al., 1988). Once HSCs begin the differentiation process, their progeny cells have hardly any self-renewal capacity, indicating that self-renewal is a special feature endowed only to stem cells.

Cells such as embryonic stem (ES) cells that retain self-renewal potential and multipotency only in vitro can also be included in the category of stem cells. Such stemness of ES cells is thought to be maintained by formation of a core transcriptional network and an epigenetic status unique to ES cells (Lund et al., 2012, Meissner, 2010, Ng and Surani, 2011). A stem cell equivalent to ES cells, called induced pluripotent stem (iPS) cells, can be produced from somatic cells by overexpression of only a few specific transcription factors (OCT3/4, SOX2, KLF4, and C-MYC), which are thought to be the essential components in forming the core network of transcriptional factors that define the status of ES cells (Takahashi et al., 2007, Takahashi and Yamanaka, 2006, Yamanaka, 2012). It is thus generally conceived that acquisition of such a network for a somatic cell depends on the reprogramming of the epigenetic status of that cell.

On the other hand, it could be envisioned that the self-renewing status of cells represents a state in which their further differentiation is inhibited. It is known, for example, that to maintain ES/iPS cells, factors such as leukemia inhibitory factor and basic fibroblast growth factor, for mouse and human cultures, respectively (Williams et al., 1988, Xu et al., 2005), are required, and these factors are thought to block further differentiation of the cells. In this context, it has previously been shown that systemic disruption of transcription factors essential for the B cell lineage, such as PAX5, E2A, and EBF1, leads to the emergence of self-renewing multipotent hematopoietic progenitors, which can be maintained under specific culture conditions (Ikawa et al., 2004a, Nutt et al., 1999, Pongubala et al., 2008). It has recently been shown that the suppression of lymphoid lineage priming promotes the expansion of both mouse and human hematopoietic progenitors (Mercer et al., 2011, van Galen et al., 2014). Therefore, it would seem theoretically possible to make a stem cell by inducing inactivation of these factors at particular developmental stages. Conditional depletion of PAX5 in B cell lineage committed progenitors, as well as mature B cells, resulted in the generation of T cells from the B lineage cells (Cobaleda et al., 2007, Nutt et al., 1999, Rolink et al., 1999). These studies, however, were mainly focused on the occurrence of cell-fate conversion by de-differentiation of target cells. Therefore, the minimal requirement for the acquisition of self-renewal potential remains undetermined.

Our ultimate goal is to obtain sufficient number of stem cells by expansion to overcome the limitation of cell numbers for immune therapies. We hypothesize that stem cells can be produced by simply blocking differentiation. As mentioned earlier, self-renewing multipotent progenitors (MPPs) can be produced by culturing E2A-deficient hematopoietic progenitors in B cell-inducing conditions (Ikawa et al., 2004a). Because it remains unclear at which developmental stage the acquisition of self-renewing potential has occurred in the case of such a systemic deletion, we thought to develop a method in which E2A function could be inactivated and reactivated in an inducible manner. We decided to use the ID3 protein for this purpose, because it is known that ID proteins serve as dominant-negative inhibitors of E proteins (Norton et al., 1998, Sayegh et al., 2003). Here we show that the overexpression of ID3 into HSCs or hematopoietic progenitor cells (HPCs) in both mouse and human induces the stemness of the progenitors and that the cells acquire the self-renewal activity. The ID3-expressing cells can be maintained in vitro as MPPs with T, B, and myeloid lineage potentials.



Jump to Section
  Generation of ID3-Transduced Hematopoietic Progenitors
  IdHP Cells Are Multipotent, Maintaining T, B, and Myeloid Lineage Potentials
  IdHP Cells Are Multipotent at a Clonal Level
  Generation of IdHP Cells from Mouse BM
  Generation of Inducible IdHP Cells Using ID3-ER Retrovirus
  Generation of IdHP Cells from Human Cord Blood Hematopoietic Progenitors
Experimental Procedures
  Growth Factors
  Isolation of Hematopoietic Progenitors
  Retroviral Constructs, Viral Supernatants, and Transduction
  In Vitro Differentiation Culture System
  Cloning of mIdHP Cells
  Colony-Forming Unit in Culture Assay
  Cell Cycle Assay
  Adoptive Transfer of mIdHP and hIdHP Cells
  PCR Analysis of Igh Gene Rearrangement
  RNA Extraction and qRT-PCR
  Microarray Analysis
Author Contributions
Supplemental Information

Generation of ID3-Transduced Hematopoietic Progenitors

IdHP Cells Are Multipotent, Maintaining T, B, and Myeloid Lineage Potentials

IdHP Cells Are Multipotent at a Clonal Level

Generation of IdHP Cells from Mouse BM

Generation of Inducible IdHP Cells Using ID3-ER Retrovirus

Generation of IdHP Cells from Human Cord Blood Hematopoietic Progenitors

Thumbnail image of Figure 1. Opens large image


Identification of cellular and molecular events regulating self-renewal or differentiation of the cells is a fundamental issue in the stem cell biology or developmental biology field. In the present study, we revealed that the simple inhibition of differentiation in HSCs or HPCs by overexpressing ID proteins and culturing them in suitable conditions induced the self-renewal of hematopoietic progenitors and allowed the extensive expansion of the multipotent cells. The reduction of ID proteins in MPPs resulted in the differentiation of the cells into lymphoid and myeloid lineage cells. Thus, it is possible to manipulate the cell fate by regulating E-protein or ID-protein activities. This inducible system will be a useful tool to figure out the genetic and epigenetic program controlling the self-renewal activity of multipotent stem cells.

Previous studies have shown that hematopoietic progenitors deficient for E2A, EBF1, and PAX5 maintain multilineage differentiation potential without losing their self-renewing capacity (Ikawa et al., 2004a, Nutt et al., 1999, Pongubala et al., 2008), indicating that the inhibition of the differentiation pathway at certain developmental stages leads to the expansion of multipotent stem cells. However, the MPPs were not able to differentiate into B cells because they lacked the activities of transcription factors essential for the initiation of the B lineage program. In addition, a restriction point regulating the lineage-specific patterns of gene expression during B cell specification remained to be determined because of the lack of an inducible system that regulates B cell differentiation. Here we have established the multipotent iLS cells using ID3-ER retrovirus, which can be maintained and differentiated into B cells in an inducible manner by simply adding or withdrawing 4-OHT. The data indicated the essential role of E2A for initiation of the B cell program that restricts other lineage potentials, because the depletion of 4-OHT from the culture immediately leads to the activation of E proteins, such as E2A, HEB, and E2-2, that promote B cell differentiation. This strategy is useful in understanding the cues regulating the self-renewal or differentiation of uncommitted progenitors to the B cell pathway. Analysis of genome-wide gene expression patterns and histone modifications will determine the exact mechanisms that underlie the B cell commitment process.

The iLS cells can also be generated from human CB hematopoietic progenitors. Human iLS cells exhibited differentiation potential and self-renewal activity similar to those of murine iLS cells, suggesting a similar developmental program during human B cell fate specification. Our data are consistent with a study demonstrating the critical role of the activity of ID and E proteins for controlling the status of human HSCs and progenitors (van Galen et al., 2014). This study reported that the overexpression of ID2 in human CB HSCs enhanced the myeloid and stem cell program at the expense of lymphoid commitment. Specifically, ID2 overexpression resulted in a 10-fold expansion of HSCs, suggesting that the inhibition of E-protein activities promotes the self-renewal of HSCs by antagonizing the differentiation. This raises a question about the functional differences between ID2 and ID3. Id3 seems to suppress the B cell program and promote the myeloid program more efficiently than does ID2, because the ID2-expressing HPCs appear to retain more B cell potential than ID3-expressing iLS cells (Mercer et al., 2011, van Galen et al., 2014). The self-renewal activity and differentiation potential of ID2-HPCs derived from murine HSCs in the BM seemed to be limited both in vivo and in vitro analysis (Mercer et al., 2011). In our study, the iLS cells retained more myeloid potential and self-renewal capacity during the culture. Strikingly, the multipotent iLS cells enormously proliferated (>103-fold in 1 month) as long as the cells were cultured in undifferentiated conditions. This could be due to the functional differences among Id family genes. Alternatively, combination with additional environmental signals, such as cytokines or chemokines, may affect the functional differences of ID proteins, although any ID proteins can repress the activation of the E2A targets, such as Ebf1 and Foxo1, that are essential for B cell differentiation. ID1 and ID3, but not ID2, are demonstrated to be negative regulators of the generation of hematopoietic progenitors from human pluripotent stem cells (Hong et al., 2011). Further analysis is required to determine the physiological role of ID proteins in regulating hematopoietic cell fate. It also remains to be determined whether the ID3-ER system can be applied to human progenitors. It would be informative to compare the regulatory networks that control B cell differentiation in mouse and human.

Immune cell therapy has become a major field of interest in the last two decades. However, the required high cell numbers restrain the application and success of immune reconstitution or anti-cancer treatment. For example, DCs are already being used in cell therapy against tumors. One of the major limitations of DC vaccine therapy is the difficulty in obtaining sufficient cell numbers, because DCs do not proliferate in the currently used systems. The method of making iLS cells could be applied to such cell therapies. Taken together, the simplicity of this method and the high expansion rate and retention of multilineage potential of the cells make this cell source appealing for regenerative medicine or immune cell therapy.

In summary, we showed that an artificially induced block of differentiation in uncommitted progenitors is sufficient to produce multipotent stem cells that retain self-renewal activity. Once the differentiation block is released, the cells start differentiating into mature cells both in vivo and in vitro. Thus, this method could be applicable for establishing somatic stem cells from other organs in a similar manner, which would be quite useful for regenerative medicine. The relative ease of making stem cells leads us to conceive that a block in differentiation is essential not only in other types of artificially engineered stem cells, such as ES cells and iPS cells, but also in any type of physiological somatic stem cell. In this context, it is tempting to speculate that it could have been easy for a multicellular organism to establish somatic stem cells by this mechanism during evolution.

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Treatment of Acute Leukemias

Author and Curator: Larry H. Bernstein, MD, FCAP

2.4.4 Treatment of Acute Leukemias

Treatment of Acute Lymphoblastic Leukemia

Ching-Hon Pu, and William E. Evans
N Engl J Med Jan 12, 2006; 354:166-178

Although the overall cure rate of acute lymphoblastic leukemia (ALL) in children is about 80 percent, affected adults fare less well. This review considers recent advances in the treatment of ALL, emphasizing issues that need to be addressed if treatment outcome is to improve further.

Acute Lymphoblastic Leukemia

Ching-Hon Pui, Mary V. Relling, and James R. Downing
N Engl J Med Apr 8, 2004; 350:1535-1548

This comprehensive survey emphasizes how recent advances in the knowledge of molecular mechanisms involved in acute lymphoblastic leukemia have influenced diagnosis, prognosis, and treatment.

Gene-Expression Patterns in Drug-Resistant Acute Lymphoblastic Leukemia Cells and Response to Treatment

Amy Holleman, Meyling H. Cheok, Monique L. den Boer, et al.
N Engl J Med 2004; 351:533-42

Childhood acute lymphoblastic leukemia (ALL) is curable with chemotherapy in approximately 80 percent of patients. However, the cause of treatment failure in the remaining 20 percent of patients is largely unknown.

Methods We tested leukemia cells from 173 children for sensitivity in vitro to prednisolone, vincristine, asparaginase, and daunorubicin. The cells were then subjected to an assessment of gene expression with the use of 14,500 probe sets to identify differentially expressed genes in drug-sensitive and drug-resistant ALL. Gene-expression patterns that differed according to sensitivity or resistance to the four drugs were compared with treatment outcome in the original 173 patients and an independent cohort of 98 children treated with the same drugs at another institution.

Results We identified sets of differentially expressed genes in B-lineage ALL that were sensitive or resistant to prednisolone (33 genes), vincristine (40 genes), asparaginase (35 genes), or daunorubicin (20 genes). A combined gene-expression score of resistance to the four drugs, as compared with sensitivity to the four, was significantly and independently related to treatment outcome in a multivariate analysis (hazard ratio for relapse, 3.0; P=0.027). Results were confirmed in an independent population of patients treated with the same medications (hazard ratio for relapse, 11.85; P=0.019). Of the 124 genes identified, 121 have not previously been associated with resistance to the four drugs we tested.

Conclusions  Differential expression of a relatively small number of genes is associated with drug resistance and treatment outcome in childhood ALL.

Leukemias Treatment & Management

Author: Lihteh Wu, MD; Chief Editor: Hampton Roy Sr

The treatment of leukemia is in constant flux, evolving and changing rapidly over the past few years. Most treatment protocols use systemic chemotherapy with or without radiotherapy. The basic strategy is to eliminate all detectable disease by using cytotoxic agents. To attain this goal, 3 phases are typically used, as follows: remission induction phase, consolidation phase, and maintenance therapy phase.

Chemotherapeutic agents are chosen that interfere with cell division. Tumor cells usually divide more rapidly than host cells, making them more vulnerable to the effects of chemotherapy. Primary treatment will be under the direction of a medical oncologist, radiation oncologist, and primary care physician. Although a general treatment plan will be outlined, the ophthalmologist does not prescribe or manage such treatment.

  • The initial treatment of ALL uses various combinations of vincristine, prednisone, and L-asparaginase until a complete remission is obtained.
  • Maintenance therapy with mercaptopurine is continued for 2-3 years following remission.
  • Use of intrathecal methotrexate with or without cranial irradiation to cover the CNS varies from facility to facility.
  • Daunorubicin, cytarabine, and thioguanine currently are used to obtain induction and remission of AML.
  • Maintenance therapy for 8 months may lengthen remission. Once relapse has occurred, AML generally is curable only by bone marrow transplantation.
  • Presently, treatment of CLL is palliative.
  • CML is characterized by a leukocytosis greater than 100,000 cells. Emergent treatment with leukopheresis sometimes is necessary when leukostastic complications are present. Otherwise, busulfan or hydroxyurea may control WBC counts. During the chronic phase, treatment is palliative.
  • When CML converts to the blastic phase, approximately one third of cases behave as ALL and respond to treatment with vincristine and prednisone. The remaining two thirds resemble AML but respond poorly to AML therapy.
  • Allogeneic bone marrow transplant is the only curative therapy for CML. However, it carries a high early mortality rate.
  • Leukemic retinopathy usually is not treated directly. As the hematological parameters normalize with systemic treatment, many of the ophthalmic signs resolve. There are reports that leukopheresis for hyperviscosity also may alleviate intraocular manifestations.
  • When definite intraocular leukemic infiltrates fail to respond to systemic chemotherapy, direct radiation therapy is recommended.
  • Relapse, manifested by anterior segment involvement, should be treated by radiation. In certain cases, subconjunctival chemotherapeutic agents have been injected.
  • Optic nerve head infiltration in patients with ALL is an emergency and requires prompt radiation therapy to try to salvage some vision.

Treatments and drugs

Common treatments used to fight leukemia include:

  • Chemotherapy. Chemotherapy is the major form of treatment for leukemia. This drug treatment uses chemicals to kill leukemia cells.

Depending on the type of leukemia you have, you may receive a single drug or a combination of drugs. These drugs may come in a pill form, or they may be injected directly into a vein.

  • Biological therapy. Biological therapy works by using treatments that help your immune system recognize and attack leukemia cells.
  • Targeted therapy. Targeted therapy uses drugs that attack specific vulnerabilities within your cancer cells.

For example, the drug imatinib (Gleevec) stops the action of a protein within the leukemia cells of people with chronic myelogenous leukemia. This can help control the disease.

  • Radiation therapy. Radiation therapy uses X-rays or other high-energy beams to damage leukemia cells and stop their growth. During radiation therapy, you lie on a table while a large machine moves around you, directing the radiation to precise points on your body.

You may receive radiation in one specific area of your body where there is a collection of leukemia cells, or you may receive radiation over your whole body. Radiation therapy may be used to prepare for a stem cell transplant.

  • Stem cell transplant. A stem cell transplant is a procedure to replace your diseased bone marrow with healthy bone marrow.

Before a stem cell transplant, you receive high doses of chemotherapy or radiation therapy to destroy your diseased bone marrow. Then you receive an infusion of blood-forming stem cells that help to rebuild your bone marrow.

You may receive stem cells from a donor, or in some cases you may be able to use your own stem cells. A stem cell transplant is very similar to a bone marrow transplant. Acute Myeloid Leukemia

New treatment approaches in acute myeloid leukemia: review of recent clinical studies.

Norsworthy K1Luznik LGojo I.
Rev Recent Clin Trials. 2012 Aug; 7(3):224-37.

Standard chemotherapy can cure only a fraction (30-40%) of younger and very few older patients with acute myeloid leukemia (AML). While conventional allografting can extend the cure rates, its application remains limited mostly to younger patients and those in remission. Limited efficacy of current therapies and improved understanding of the disease biology provided a spur for clinical trials examining novel agents and therapeutic strategies in AML. Clinical studies with novel chemotherapeutics, antibodies, different signal transduction inhibitors, and epigenetic modulators demonstrated their clinical activity; however, it remains unclear how to successfully integrate novel agents either alone or in combination with chemotherapy into the overall therapeutic schema for AML. Further studies are needed to examine their role in relation to standard chemotherapy and their applicability to select patient populations based on recognition of unique disease and patient characteristics, including the development of predictive biomarkers of response. With increasing use of nonmyeloablative or reduced intensity conditioning and alternative graft sources such as haploidentical donors and cord blood transplants, the benefits of allografting may extend to a broader patient population, including older AML patients and those lacking a HLA-matched donor. We will review here recent clinical studies that examined novel pharmacologic and immunologic approaches to AML therapy.

Novel approaches to the treatment of acute myeloid leukemia.

Roboz GJ1
Hematology Am Soc Hematol Educ Program. 2011:43-50.

Approximately 12 000 adults are diagnosed with acute myeloid leukemia (AML) in the United States annually, the majority of whom die from their disease. The mainstay of initial treatment, cytosine arabinoside (ara-C) combined with an anthracycline, was developed nearly 40 years ago and remains the worldwide standard of care. Advances in genomics technologies have identified AML as a genetically heterogeneous disease, and many patients can now be categorized into clinicopathologic subgroups on the basis of their underlying molecular genetic defects. It is hoped that enhanced specificity of diagnostic classification will result in more effective application of targeted agents and the ability to create individualized treatment strategies. This review describes the current treatment standards for induction, consolidation, and stem cell transplantation; special considerations in the management of older AML patients; novel agents; emerging data on the detection and management of minimal residual disease (MRD); and strategies to improve the design and implementation of AML clinical trials.

Age ≥ 60 years has consistently been identified as an independent adverse prognostic factor in AML, and there are very few long-term survivors in this age group.5 Poor outcomes in elderly AML patients have been attributed to both host- and disease-related factors, including medical comorbidities, physical frailty, increased incidence of antecedent myelodysplastic syndrome and myeloproliferative disorders, and higher frequency of adverse cytogenetics.28 Older patients with multiple poor-risk factors have a high probability of early death and little chance of long-term disease-free survival with standard chemotherapy. In a retrospective analysis of 998 older patients treated with intensive induction at the M.D. Anderson Cancer Center, multivariate analysis identified age ≥ 75 years, unfavorable karyotype, poor performance status, creatinine > 1.3 mg/dL, duration of antecedent hematologic disorder > 6 months, and treatment outside a laminar airflow room as adverse prognostic indicators.29 Patients with 3 or more of these factors had expected complete remission rates of < 20%, 8-week mortality > 50%, and 1-year survival < 10%. The Medical Research Council (MRC) identified cytogenetics, WBC count at diagnosis, age, and de novo versus secondary disease as critical factors influencing survival in > 2000 older patients with AML, but cautioned in their conclusions that less objective factors, such as clinical assessment of “fitness” for chemotherapy, may be equally important in making treatment decisions in this patient population.30 It is hoped that data from comprehensive geriatric assessments of functional status, cognition, mood, quality of life, and other measures obtained during ongoing cooperative group trials will improve our ability to predict how older patients will tolerate treatment.

Current treatment of acute myeloid leukemia.

Roboz GJ1.
Curr Opin Oncol. 2012 Nov; 24(6):711-9.

The objectives of this review are to discuss standard and investigational nontransplant treatment strategies for acute myeloid leukemia (AML), excluding acute promyelocytic leukemia.

RECENT FINDINGS: Most adults with AML die from their disease. The standard treatment paradigm for AML is remission induction chemotherapy with an anthracycline/cytarabine combination, followed by either consolidation chemotherapy or allogeneic stem cell transplantation, depending on the patient’s ability to tolerate intensive treatment and the likelihood of cure with chemotherapy alone. Although this approach has changed little in the last three decades, increased understanding of the pathogenesis of AML and improvements in molecular genomic technologies are leading to novel drug targets and the development of personalized, risk-adapted treatment strategies. Recent findings related to prognostically relevant and potentially ‘druggable’ molecular targets are reviewed.

SUMMARY: At the present time, AML remains a devastating and mostly incurable disease, but the combination of optimized chemotherapeutics and molecularly targeted agents holds significant promise for the future.

Adult Acute Myeloid Leukemia Treatment (PDQ®)

About This PDQ Summary

This summary is reviewed regularly and updated as necessary by the PDQ Adult Treatment Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent review of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).

Board members review recently published articles each month to determine whether an article should:

  • be discussed at a meeting,
  • be cited with text, or
  • replace or update an existing article that is already cited.

Treatment Option Overview for AML

Successful treatment of acute myeloid leukemia (AML) requires the control of bone marrow and systemic disease and specific treatment of central nervous system (CNS) disease, if present. The cornerstone of this strategy includes systemically administered combination chemotherapy. Because only 5% of patients with AML develop CNS disease, prophylactic treatment is not indicated.[13]

Treatment is divided into two phases: remission induction (to attain remission) and postremission (to maintain remission). Maintenance therapy for AML was previously administered for several years but is not included in most current treatment clinical trials in the United States, other than for acute promyelocytic leukemia. (Refer to the Adult Acute Myeloid Leukemia in Remission section of this summary for more information.) Other studies have used more intensive postremission therapy administered for a shorter duration of time after which treatment is discontinued.[4] Postremission therapy appears to be effective when given immediately after remission is achieved.[4]

Since myelosuppression is an anticipated consequence of both the leukemia and its treatment with chemotherapy, patients must be closely monitored during therapy. Facilities must be available for hematologic support with multiple blood fractions including platelet transfusions and for the treatment of related infectious complications.[5] Randomized trials have shown similar outcomes for patients who received prophylactic platelet transfusions at a level of 10,000/mm3 rather than 20,000/mm3.[6] The incidence of platelet alloimmunization was similar among groups randomly assigned to receive pooled platelet concentrates from random donors; filtered, pooled platelet concentrates from random donors; ultraviolet B-irradiated, pooled platelet concentrates from random donors; or filtered platelets obtained by apheresis from single random donors.[7] Colony-stimulating factors, for example, granulocyte colony–stimulating factor (G-CSF) and granulocyte-macrophage colony–stimulating factor (GM-CSF), have been studied in an effort to shorten the period of granulocytopenia associated with leukemia treatment.[8] If used, these agents are administered after completion of induction therapy. GM-CSF was shown to improve survival in a randomized trial of AML in patients aged 55 to 70 years (median survival was 10.6 months vs. 4.8 months). In this Eastern Cooperative Oncology Group (ECOG) (EST-1490) trial, patients were randomly assigned to receive GM-CSF or placebo following demonstration of leukemic clearance of the bone marrow;[9] however, GM-CSF did not show benefit in a separate similar randomized trial in patients older than 60 years.[10] In the latter study, clearance of the marrow was not required before initiating cytokine therapy. In a Southwest Oncology Group (NCT00023777) randomized trial of G-CSF given following induction therapy to patients older than 65 years, complete response was higher in patients who received G-CSF because of a decreased incidence of primary leukemic resistance. Growth factor administration did not impact on mortality or on survival.[11,12] Because the majority of randomized clinical trials have not shown an impact of growth factors on survival, their use is not routinely recommended in the remission induction setting.

The administration of GM-CSF or other myeloid growth factors before and during induction therapy, to augment the effects of cytotoxic therapy through the recruitment of leukemic blasts into cell cycle (growth factor priming), has been an area of active clinical research. Evidence from randomized studies of GM-CSF priming have come to opposite conclusions. A randomized study of GM-CSF priming during conventional induction and postremission therapy showed no difference in outcomes between patients who received GM-CSF and those who did not receive growth factor priming.[13,14][Level of evidence: 1iiA] In contrast, a similar randomized placebo-controlled study of GM-CSF priming in patients with AML aged 55 to 75 years showed improved disease-free survival (DFS) in the group receiving GM-CSF (median DFS for patients who achieved complete remission was 23 months vs. 11 months; 2-year DFS was 48% vs. 21%), with a trend towards improvement in overall survival (2-year survival was 39% vs. 27%, = .082) for patients aged 55 to 64 years.[15][Level of evidence: 1iiDii]


  1. Kebriaei P, Champlin R, deLima M, et al.: Management of acute leukemias. In: DeVita VT Jr, Lawrence TS, Rosenberg SA: Cancer: Principles and Practice of Oncology. 9th ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 2011, pp 1928-54.
  2. Wiernik PH: Diagnosis and treatment of acute nonlymphocytic leukemia. In: Wiernik PH, Canellos GP, Dutcher JP, et al., eds.: Neoplastic Diseases of the Blood. 3rd ed. New York, NY: Churchill Livingstone, 1996, pp 283-302.
  3. Morrison FS, Kopecky KJ, Head DR, et al.: Late intensification with POMP chemotherapy prolongs survival in acute myelogenous leukemia–results of a Southwest Oncology Group study of rubidazone versus adriamycin for remission induction, prophylactic intrathecal therapy, late intensification, and levamisole maintenance. Leukemia 6 (7): 708-14, 1992. [PUBMED Abstract]
  4. Cassileth PA, Lynch E, Hines JD, et al.: Varying intensity of postremission therapy in acute myeloid leukemia. Blood 79 (8): 1924-30, 1992. [PUBMED Abstract]
  5. Supportive Care. In: Wiernik PH, Canellos GP, Dutcher JP, et al., eds.: Neoplastic Diseases of the Blood. 3rd ed. New York, NY: Churchill Livingstone, 1996, pp 779-967.
  6. Rebulla P, Finazzi G, Marangoni F, et al.: The threshold for prophylactic platelet transfusions in adults with acute myeloid leukemia. Gruppo Italiano Malattie Ematologiche Maligne dell’Adulto. N Engl J Med 337 (26): 1870-5, 1997. [PUBMED Abstract]
  7. Leukocyte reduction and ultraviolet B irradiation of platelets to prevent alloimmunization and refractoriness to platelet transfusions. The Trial to Reduce Alloimmunization to Platelets Study Group. N Engl J Med 337 (26): 1861-9, 1997. [PUBMED Abstract]
  8. Geller RB: Use of cytokines in the treatment of acute myelocytic leukemia: a critical review. J Clin Oncol 14 (4): 1371-82, 1996. [PUBMED Abstract]
  9. Rowe JM, Andersen JW, Mazza JJ, et al.: A randomized placebo-controlled phase III study of granulocyte-macrophage colony-stimulating factor in adult patients (> 55 to 70 years of age) with acute myelogenous leukemia: a study of the Eastern Cooperative Oncology Group (E1490). Blood 86 (2): 457-62, 1995. [PUBMED Abstract]
  10. Stone RM, Berg DT, George SL, et al.: Granulocyte-macrophage colony-stimulating factor after initial chemotherapy for elderly patients with primary acute myelogenous leukemia. Cancer and Leukemia Group B. N Engl J Med 332 (25): 1671-7, 1995. [PUBMED Abstract]
  11. Dombret H, Chastang C, Fenaux P, et al.: A controlled study of recombinant human granulocyte colony-stimulating factor in elderly patients after treatment for acute myelogenous leukemia. AML Cooperative Study Group. N Engl J Med 332 (25): 1678-83, 1995. [PUBMED Abstract]
  12. Godwin JE, Kopecky KJ, Head DR, et al.: A double-blind placebo-controlled trial of granulocyte colony-stimulating factor in elderly patients with previously untreated acute myeloid leukemia: a Southwest oncology group study (9031). Blood 91 (10): 3607-15, 1998. [PUBMED Abstract]
  13. Buchner T, Hiddemann W, Wormann B, et al.: GM-CSF multiple course priming and long-term administration in newly diagnosed AML: hematologic and therapeutic effects. [Abstract] Blood 84 (10 Suppl 1): A-95, 27a, 1994.
  14. Löwenberg B, Boogaerts MA, Daenen SM, et al.: Value of different modalities of granulocyte-macrophage colony-stimulating factor applied during or after induction therapy of acute myeloid leukemia. J Clin Oncol 15 (12): 3496-506, 1997. [PUBMED Abstract]
  15. Witz F, Sadoun A, Perrin MC, et al.: A placebo-controlled study of recombinant human granulocyte-macrophage colony-stimulating factor administered during and after induction treatment for de novo acute myelogenous leukemia in elderly patients. Groupe Ouest Est Leucémies Aiguës Myéloblastiques (GOELAM). Blood 91 (8): 2722-30, 1998. [PUBMED Abstract]

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Treatments other than Chemotherapy for Leukemias and Lymphomas

Author, Curator, Editor: Larry H. Bernstein, MD, FCAP

2.5.1 Radiation Therapy

Radiation therapy, also called radiotherapy or irradiation, can be used to treat leukemia, lymphoma, myeloma and myelodysplastic syndromes. The type of radiation used for radiotherapy (ionizing radiation) is the same that’s used for diagnostic x-rays. Radiotherapy, however, is given in higher doses.

Radiotherapy works by damaging the genetic material (DNA) within cells, which prevents them from growing and reproducing. Although the radiotherapy is directed at cancer cells, it can also damage nearby healthy cells. However, current methods of radiotherapy have been improved upon, minimizing “scatter” to nearby tissues. Therefore its benefit (destroying the cancer cells) outweighs its risk (harming healthy cells).

When radiotherapy is used for blood cancer treatment, it’s usually part of a treatment plan that includes drug therapy. Radiotherapy can also be used to relieve pain or discomfort caused by an enlarged liver, lymph node(s) or spleen.

Radiotherapy, either alone or with chemotherapy, is sometimes given as conditioning treatment to prepare a patient for a blood or marrow stem cell transplant. The most common types used to treat blood cancer are external beam radiation (see below) and radioimmunotherapy.
External Beam Radiation

External beam radiation is the type of radiotherapy used most often for people with blood cancers. A focused radiation beam is delivered outside the body by a machine called a linear accelerator, or linac for short. The linear accelerator moves around the body to deliver radiation from various angles. Linear accelerators make it possible to decrease or avoid skin reactions and deliver targeted radiation to lessen “scatter” of radiation to nearby tissues.

The dose (total amount) of radiation used during treatment depends on various factors regarding the patient, disease and reason for treatment, and is established by a radiation oncologist. You may receive radiotherapy during a series of visits, spread over several weeks (from two to 10 weeks, on average). This approach, called dose fractionation, lessens side effects. External beam radiation does not make you radioactive.

2.5.2  Bone marrow (BM) transplantation

There are three kinds of bone marrow transplants:

Autologous bone marrow transplant: The term auto means self. Stem cells are removed from you before you receive high-dose chemotherapy or radiation treatment. The stem cells are stored in a freezer (cryopreservation). After high-dose chemotherapy or radiation treatments, your stems cells are put back in your body to make (regenerate) normal blood cells. This is called a rescue transplant.

Allogeneic bone marrow transplant: The term allo means other. Stem cells are removed from another person, called a donor. Most times, the donor’s genes must at least partly match your genes. Special blood tests are done to see if a donor is a good match for you. A brother or sister is most likely to be a good match. Sometimes parents, children, and other relatives are good matches. Donors who are not related to you may be found through national bone marrow registries.

Umbilical cord blood transplant: This is a type of allogeneic transplant. Stem cells are removed from a newborn baby’s umbilical cord right after birth. The stem cells are frozen and stored until they are needed for a transplant. Umbilical cord blood cells are very immature so there is less of a need for matching. But blood counts take much longer to recover.

Before the transplant, chemotherapy, radiation, or both may be given. This may be done in two ways:

Ablative (myeloablative) treatment: High-dose chemotherapy, radiation, or both are given to kill any cancer cells. This also kills all healthy bone marrow that remains, and allows new stem cells to grow in the bone marrow.

Reduced intensity treatment, also called a mini transplant: Patients receive lower doses of chemotherapy and radiation before a transplant. This allows older patients, and those with other health problems to have a transplant.

A stem cell transplant is usually done after chemotherapy and radiation is complete. The stem cells are delivered into your bloodstream usually through a tube called a central venous catheter. The process is similar to getting a blood transfusion. The stem cells travel through the blood into the bone marrow. Most times, no surgery is needed.

Donor stem cells can be collected in two ways:

  • Bone marrow harvest. This minor surgery is done under general anesthesia. This means the donor will be asleep and pain-free during the procedure. The bone marrow is removed from the back of both hip bones. The amount of marrow removed depends on the weight of the person who is receiving it.
  • Leukapheresis. First, the donor is given 5 days of shots to help stem cells move from the bone marrow into the blood. During leukapheresis, blood is removed from the donor through an IV line in a vein. The part of white blood cells that contains stem cells is then separated in a machine and removed to be later given to the recipient. The red blood cells are returned to the donor.

Why the Procedure is Performed

A bone marrow transplant replaces bone marrow that either is not working properly or has been destroyed (ablated) by chemotherapy or radiation. Doctors believe that for many cancers, the donor’s white blood cells can attach to any remaining cancer cells, similar to when white cells attach to bacteria or viruses when fighting an infection.

Your doctor may recommend a bone marrow transplant if you have:

Certain cancers, such as leukemia, lymphoma, and multiple myeloma

A disease that affects the production of bone marrow cells, such as aplastic anemia, congenital neutropenia, severe immunodeficiency syndromes, sickle cell anemia, thalassemia

Had chemotherapy that destroyed your bone

2.5.3 Autologous stem cell transplantation

Phase II trial of 131I-B1 (anti-CD20) antibody therapy with autologous stem cell transplantation for relapsed B cell lymphomas

O.W Press,  F Appelbaum,  P.J Martin, et al.

25 patients with relapsed B-cell lymphomas were evaluated with trace-labelled doses (2·5 mg/kg, 185-370 MBq [5-10 mCi]) of 131I-labelled anti-CD20 (B1) antibody in a phase II trial. 22 patients achieved 131I-B1 biodistributions delivering higher doses of radiation to tumor sites than to normal organs and 21 of these were treated with therapeutic infusions of 131I-B1 (12·765-29·045 GBq) followed by autologous hemopoietic stem cell reinfusion. 18 of the 21 treated patients had objective responses, including 16 complete remissions. One patient died of progressive lymphoma and one died of sepsis. Analysis of our phase I and II trials with 131I-labelled B1 reveal a progression-free survival of 62% and an overall survival of 93% with a median follow-up of 2 years. 131I-anti-CD20 (B1) antibody therapy produces complete responses of long duration in most patients with relapsed B-cell lymphomas when given at maximally tolerated doses with autologous stem cell rescue.

Autologous (Self) Transplants

An autologous transplant (or rescue) is a type of transplant that uses the person’s own stem cells. These cells are collected in advance and returned at a later stage. They are used to replace stem cells that have been damaged by high doses of chemotherapy, used to treat the person’s underlying disease.

In most cases, stem cells are collected directly from the bloodstream. While stem cells normally live in your marrow, a combination of chemotherapy and a growth factor (a drug that stimulates stem cells) called Granulocyte Colony Stimulating Factor (G-CSF) is used to expand the number of stem cells in the marrow and cause them to spill out into the circulating blood. From here they can be collected from a vein by passing the blood through a special machine called a cell separator, in a process similar to dialysis.

Most of the side effects of an autologous transplant are caused by the conditioning therapy used. Although they can be very unpleasant at times it is important to remember that most of them are temporary and reversible.

Procedure of Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is the transplantation of multipotent hematopoietic stem cells, usually derived from bone marrow, peripheral blood, or umbilical cord blood. It may be autologous (the patient’s own stem cells are used) or allogeneic (the stem cells come from a donor).

Hematopoietic Stem Cell Transplantation

Author: Ajay Perumbeti, MD, FAAP; Chief Editor: Emmanuel C Besa, MD

Hematopoietic stem cell transplantation (HSCT) involves the intravenous (IV) infusion of autologous or allogeneic stem cells to reestablish hematopoietic function in patients whose bone marrow or immune system is damaged or defective.

The image below illustrates an algorithm for typically preferred hematopoietic stem cell transplantation cell source for treatment of malignancy.

An algorithm for typically preferred hematopoietic stem cell transplantation cell source for treatment of malignancy: If a matched sibling donor is not available, then a MUD is selected; if a MUD is not available, then choices include a mismatched unrelated donor, umbilical cord donor(s), and a haploidentical donor.

Supportive Therapies

2.5.4  Blood transfusions – risks and complications of a blood transfusion

  • Allogeneic transfusion reaction (acute or delayed hemolytic reaction)
  • Allergic reaction
  • Viruses Infectious Diseases

The risk of catching a virus from a blood transfusion is very low.

HIV. Your risk of getting HIV from a blood transfusion is lower than your risk of getting killed by lightning. Only about 1 in 2 million donations might carry HIV and transmit HIV if given to a patient.

Hepatitis B and C. The risk of having a donation that carries hepatitis B is about 1 in 205,000. The risk for hepatitis C is 1 in 2 million. If you receive blood during a transfusion that contains hepatitis, you’ll likely develop the virus.

Variant Creutzfeldt-Jakob disease (vCJD). This disease is the human version of Mad Cow Disease. It’s a very rare, yet fatal brain disorder. There is a possible risk of getting vCJD from a blood transfusion, although the risk is very low. Because of this, people who may have been exposed to vCJD aren’t eligible blood donors.

  • Fever
  • Iron Overload
  • Lung Injury
  • Graft-Versus-Host Disease

Graft-versus-host disease (GVHD) is a condition in which white blood cells in the new blood attack your tissues.

2.5.5 Erythropoietin

Erythropoietin, (/ɨˌrɪθrɵˈpɔɪ.ɨtɨn/UK /ɛˌrɪθr.pˈtɪn/) also known as EPO, is a glycoprotein hormone that controls erythropoiesis, or red blood cell production. It is a cytokine (protein signaling molecule) for erythrocyte (red blood cell) precursors in the bone marrow. Human EPO has a molecular weight of 34 kDa.

Also called hematopoietin or hemopoietin, it is produced by interstitial fibroblasts in the kidney in close association with peritubular capillary and proximal convoluted tubule. It is also produced in perisinusoidal cells in the liver. While liver production predominates in the fetal and perinatal period, renal production is predominant during adulthood. In addition to erythropoiesis, erythropoietin also has other known biological functions. For example, it plays an important role in the brain’s response to neuronal injury.[1] EPO is also involved in the wound healing process.[2]

Exogenous erythropoietin is produced by recombinant DNA technology in cell culture. Several different pharmaceutical agents are available with a variety ofglycosylation patterns, and are collectively called erythropoiesis-stimulating agents (ESA). The specific details for labelled use vary between the package inserts, but ESAs have been used in the treatment of anemia in chronic kidney disease, anemia in myelodysplasia, and in anemia from cancer chemotherapy. Boxed warnings include a risk of death, myocardial infarction, stroke, venous thromboembolism, and tumor recurrence.[3]

2.5.6  G-CSF (granulocyte-colony stimulating factor)

Granulocyte-colony stimulating factor (G-CSF or GCSF), also known as colony-stimulating factor 3 (CSF 3), is a glycoprotein that stimulates the bone marrow to produce granulocytes and stem cells and release them into the bloodstream.

There are different types, including

  • Lenograstim (Granocyte)
  • Filgrastim (Neupogen, Zarzio, Nivestim, Ratiograstim)
  • Long acting (pegylated) filgrastim (pegfilgrastim, Neulasta) and lipegfilgrastim (Longquex)

Pegylated G-CSF stays in the body for longer so you have treatment less often than with the other types of G-CSF.

2.5.7  Plasma Exchange (plasmapheresis)

Plasmapheresis is a term used to refer to a broad range of procedures in which extracorporeal separation of blood components results in a filtered plasma product.[1, 2] The filtering of plasma from whole blood can be accomplished via centrifugation or semipermeable membranes.[3] Centrifugation takes advantage of the different specific gravities inherent to various blood products such as red cells, white cells, platelets, and plasma.[4] Membrane plasma separation uses differences in particle size to filter plasma from the cellular components of blood.[3]

Traditionally, in the United States, most plasmapheresis takes place using automated centrifuge-based technology.[5] In certain instances, in particular in patients already undergoing hemodialysis, plasmapheresis can be carried out using semipermeable membranes to filter plasma.[4]

In therapeutic plasma exchange, using an automated centrifuge, filtered plasma is discarded and red blood cells along with replacement colloid such as donor plasma or albumin is returned to the patient. In membrane plasma filtration, secondary membrane plasma fractionation can selectively remove undesired macromolecules, which then allows for return of the processed plasma to the patient instead of donor plasma or albumin. Examples of secondary membrane plasma fractionation include cascade filtration,[6] thermofiltration, cryofiltration,[7] and low-density lipoprotein pheresis.

The Apheresis Applications Committee of the American Society for Apheresis periodically evaluates potential indications for apheresis and categorizes them from I to IV based on the available medical literature. The following are some of the indications, and their categorization, from the society’s 2010 guidelines.[2]

  • The only Category I indication for hemopoietic malignancy is Hyperviscosity in monoclonal gammopathies

2.5.8  Platelet Transfusions

Indications for platelet transfusion in children with acute leukemia

Scott Murphy, Samuel Litwin, Leonard M. Herring, Penelope Koch, et al.
Am J Hematol Jun 1982; 12(4): 347–356;jsessionid=A6001D9D865EA1EBC667EF98382EF20C.f03t01

In an attempt to determine the indications for platelet transfusion in thrombocytopenic patients, we randomized 56 children with acute leukemia to one of two regimens of platelet transfusion. The prophylactic group received platelets when the platelet count fell below 20,000 per mm3 irrespective of clinical events. The therapeutic group was transfused only when significant bleeding occurred and not for thrombocytopenia alone. The time to first bleeding episode was significantly longer and the number of bleeding episodes were significantly reduced in the prophylactic group. The survival curves of the two groups could not be distinguished from each other. Prior to the last month of life, the total number of days on which bleeding was present was significantly reduced by prophylactic therapy. However, in the terminal phase (last month of life), the duration of bleeding episodes was significantly longer in the prophylactic group. This may have been due to a higher incidence of immunologic refractoriness to platelet transfusion. Because of this terminal bleeding, comparison of the two groups for total number of days on which bleeding was present did not show a significant difference over the entire study period.

Clinical and Laboratory Aspects of Platelet Transfusion Therapy
Yuan S, Goldfinger D

INTRODUCTION — Hemostasis depends on an adequate number of functional platelets, together with an intact coagulation (clotting factor) system. This topic covers the logistics of platelet use and the indications for platelet transfusion in adults. The approach to the bleeding patient, refractoriness to platelet transfusion, and platelet transfusion in neonates are discussed elsewhere.

Pooled Platelets – A single unit of platelets can be isolated from every unit of donated blood, by centrifuging the blood within the closed collection system to separate the platelets from the red blood cells (RBC). The number of platelets per unit varies according to the platelet count of the donor; a yield of 7 x 1010 platelets is typical [1]. Since this number is inadequate to raise the platelet count in an adult recipient, four to six units are pooled to allow transfusion of 3 to 4 x 1011 platelets per transfusion [2]. These are called whole blood-derived or random donor pooled platelets.

Advantages of pooled platelets include lower cost and ease of collection and processing (a separate donation procedure and pheresis equipment are not required). The major disadvantage is recipient exposure to multiple donors in a single transfusion and logistic issues related to bacterial testing.

Apheresis (single donor) Platelets – Platelets can also be collected from volunteer donors in the blood bank, in a one- to two-hour pheresis procedure. Platelets and some white blood cells are removed, and red blood cells and plasma are returned to the donor. A typical apheresis platelet unit provides the equivalent of six or more units of platelets from whole blood (ie, 3 to 6 x 1011 platelets) [2]. In larger donors with high platelet counts, up to three units can be collected in one session. These are called apheresis or single donor platelets.

Advantages of single donor platelets are exposure of the recipient to a single donor rather than multiple donors, and the ability to match donor and recipient characteristics such as HLA type, cytomegalovirus (CMV) status, and blood type for certain recipients.

Both pooled and apheresis platelets contain some white blood cells (WBC) that were collected along with the platelets. These WBC can cause febrile non-hemolytic transfusion reactions (FNHTR), alloimmunization, and transfusion-associated graft-versus-host disease (ta-GVHD) in some patients.

Platelet products also contain plasma, which can be implicated in adverse reactions including transfusion-related acute lung injury (TRALI) and anaphylaxis. (See ‘Complications of platelet transfusion’ .)

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Hematological Cancer Classification

Author and Curator: Larry H. Bernstein, MD, FCAP



Introduction to leukemias and lymphomas


2.4.1 Ontogenesis of the blood elements: hematopoiesis

Blood cells are divided into three groups: the red blood cells (erythrocytes), the white blood cells (leukocytes), and the blood platelets (thrombocytes). The white blood cells are subdivided into three broad groups: granulocytes, lymphocytes, and monocytes.

Blood cells do not originate in the bloodstream itself but in specific blood-forming organs, notably the marrow of certain bones. In the human adult, the bone marrow produces all of the red blood cells, 60–70 percent of the white cells (i.e., the granulocytes), and all of the platelets. The lymphatic tissues, particularly the thymus, the spleen, and the lymph nodes, produce the lymphocytes (comprising 20–30 percent of the white cells). The reticuloendothelial tissues of the spleen, liver, lymph nodes, and other organs produce the monocytes (4–8 percent of the white cells). The platelets, which are small cellular fragments rather than complete cells, are formed from bits of the cytoplasm of the giant cells (megakaryocytes) of the bone marrow.

In the human embryo, the first site of blood formation is the yolk sac. Later in embryonic life, the liver becomes the most important red blood cell-forming organ, but it is soon succeeded by the bone marrow, which in adult life is the only source of both red blood cells and the granulocytes. Both the red and white blood cells arise through a series of complex, gradual, and successive transformations from primitive stem cells, which have the ability to form any of the precursors of a blood cell. Precursor cells are stem cells that have developed to the stage where they are committed to forming a particular kind of new blood cell.

In a normal adult the red cells of about half a liter (almost one pint) of blood are produced by the bone marrow every week. Almost 1 percent of the body’s red cells are generated each day, and the balance between red cell production and the removal of aging red cells from the circulation is precisely maintained.



Erythropoiesis – Formation of Red Blood Cells

Because of the inability of erythrocytes (red blood cells) to divide to replenish their own numbers, the old ruptured cells must be replaced by totally new cells. They meet their demise because they don’t have the usual specialized intracellular machinery, which controls cell growth and repair, leading to a short life span of 120 days.

This short life span necessitates the process erythropoiesis, which is the formation of red blood cells. All blood cells are formed in the bone marrow. This is the erythrocyte factory, which is soft, highly cellar tissue that fills the internal cavities of bones.

Erythrocyte differentiation takes place in 8 stages. It is the pathway through which an erythrocyte matures from a hemocytoblast into a full-blown erythrocyte. The first seven all take place within the bone marrow. After stage 7 the cell is then released into the bloodstream as a reticulocyte, where it then matures 1-2 days later into an erythrocyte. The stages are as follows:

  1. Hemocytoblast, which is a pluripotent hematopoietic stem cell
  2. Common myeloid progenitor, a multipotent stem cell
  3. Unipotent stem cell
  4. Pronormoblast
  5. Basophilic normoblast also called an erythroblast.
  6. Polychromatophilic normoblast
  7. Orthochromatic normoblast
  8. Reticulocyte

These characteristics can be seen during the course of erythrocyte maturation:

  • The size of the cell decreases
  • The cytoplasm volume increases
  • Initially there is a nucleus and as the cell matures the size of the nucleus decreases until it vanishes with the condensation of the chromatin material.

Low oxygen tension stimulates the kidneys to secrete the hormone erythropoietin into the blood, and this hormone stimulates the bone marrow to produce erythrocytes.

Rarely, a malignancy or cancer of erythropoiesis occurs. It is referred to as erythroleukemia. This most likely arises from a common myeloid precursor, and it may occur associated with a myelodysplastic syndrome.

Summary of erythrocyte maturation

White blood cell series: myelopoiesis

There are various types of white blood cells (WBCs) that normally appear in the blood: neutrophils (polymorphonuclear leukocytes; PMNs), band cells (slightly immature neutrophils), T-type lymphocytes (T cells), B-type lymphocytes (B cells), monocytes, eosinophils, and basophils. T and B-type lymphocytes are indistinguishable from each other in a normal slide preparation. Any infection or acute stress will result in an increased production of WBCs. This usually entails increased numbers of cells and an increase in the percentage of immature cells (mainly band cells) in the blood. This change is referred to as a “shift to the left” People who have had a splenectomy have a persistent mild elevation of WBCs. Drugs that may increase WBC counts include epinephrine, allopurinol, aspirin, chloroform, heparin, quinine, corticosteroids, and triamterene. Drugs that may decrease WBC counts include antibiotics, anticonvulsants, antihistamine, antithyroid drugs, arsenicals, barbiturates, chemotherapeutic agents, diuretics and sulfonamides.   (Updated by: David C. Dugdale, III, MD)

Note that the mature forms of the myeloid series (neutrophils, eosinophils, basophils), all have lobed (segmented) nuclei. The degree of lobation increases as the cells mature.

The earliest recognizable myeloid cell is the myeloblast (10-20m dia) with a large round to oval nucleus. There is fine diffuse immature chromatin (without clumping) and a prominant nucleolus.

The cytoplasm is basophilic without granules. Although one may see a small golgi area adjacent to the nucleus, granules are not usually visible by light microscopy. One should not see blast cells in the peripheral blood.

myeloblast x100b

The promyelocyte (10-20m) is slightly larger than a blast. Its nucleus, although similar to a myeloblast shows slight chromatin condensation and less prominent nucleoli. The cytoplasm contains striking azurophilic granules or primary granules. These granules contain myeloperoxidase, acid phosphatase, and esterase enzymes. Normally no promyelocytes are seen in the peripheral blood.

At the point in development when secondary granules can be recognized, the cell becomes a myelocyte.

promyelocyte x100×100%20a.jpeg

Myelocytes (10-18m) are not normally found in the peripheral blood. Nucleoli may not be seen in the late myelocyte. Primary azurophilic granules are still present, but secondary granules predominate. Secondary granules (neut, eos, or baso) first appear adjacent to the nucleus. In neutrophils this is the “dawn” of neutrophilia.

Metamyelocytes (10-18m) have kidney shaped indented nuclei and dense chromatin along the nuclear membrane. The cytoplasm is faintly pink, and they have secondary granules (neutro, eos, or baso). Zero to one percent of the peripheral blood white cells may be metamyelocytes (juveniles).

metamyelocyte x100×100.jpeg

Bands, slightly smaller than juveniles, are marked by a U-shaped or deeply indented nucleus.

band neutrophilx100a

Segmented (segs) or polymorphonuclear (PMN) leukocytes (average 14 m dia) are distinguished by definite lobation with thin thread-like filaments of chromatin joining the 2-5 lobes. 45-75% of the peripheral blood white cells are segmented neutrophils.×100%20d.jpeg


The incredible journey: From megakaryocyte development to platelet formation

Kellie R. Machlus1,2 and Joseph E. Italiano Jr
JCB 2013; 201(6): 785-796

Large progenitor cells in the bone marrow called megakaryocytes (MKs) are the source of platelets. MKs release platelets through a series of fascinating cell biological events. During maturation, they become polyploid and accumulate massive amounts of protein and membrane. Then, in a cytoskeletal-driven process, they extend long branching processes, designated proplatelets, into sinusoidal blood vessels where they undergo fission to release platelets.

megakaryocyte production of platelets

platelets and the immune continuum nri2956-f3

2.4.2 Classification of hematological malignancies
Practical Diagnosis of Hematologic Disoreders. 4th edition. Vol 2.
Kjeldsberg CR, Ed.  ASCP Press.  2006. Chicago, IL. Primary Classification

Acute leukemias

Myelodysplastic syndromes

Acute myeloid leukemia

Acute lymphoblastic leukemia

Myeloproliferative Disorders

Chronic myeloproliferative disorders

Chronic myelogenous leukemia and related disorders

Myelofibrosis, including chronic idiopathic

Polycythemia, including polycythemia rubra vera

Thrombocytosis, including essential thrombocythemia

Chronic lymphoid leukemia and other lymphoid leukemias


Non-Hodgkin Lymphoma

Hodgkin lymphoma

Lymphoproliferative disorders associated with immunodeficiency

Plasma Cell dyscrasias

Mast cell disease and Histiocytic neoplasms Secondary Classification Nuance – PathologyOutlines
Nat Pernick, Ed.

Leukemia – Acute

Primary referencesacute leukemia-generalAML generalAML classificationtransient abnormal myelopoiesis

Recurrent genetic abnormalities: AML with t(6;9)AML with t(8;21)AML with 11q23 abnormalitiesAML with inv(16) or t(16;16)AML with Down syndromeAML with FLT3 mutationsAML with myelodysplastic related changesAML therapy relatedAPL microgranular variantAPL with t(15;17)APL with t(V;17)APL therapy related

AML not otherwise categorized: minimally differentiated (M0)without maturation (M1)with maturation (M2)M3myelomonocyticmonoblastic and monocyticerythroidmegakaryoblasticCD13/CD33 negativebasophilicmyeloid sarcomaacute panmyelosis with myelofibrosiswith Philadelphia chromosomewith pseudo Chediak-Higashi anomalyhypocellular

ALL: generalWHO classificationwith eosinophilia

PreB ALL: generalt(9;22)t(v;11q23)t(1;19)t(5;14)t(12;21)hyperdiploidyhypodiploidymature B ALL/Burkitt

Other ALL: T ALLambiguous lineagemixed phenotype

AML and related malignancies

Acute myeloid leukemias with recurrent genetic abnormalities:

  • AML with t(8;21)(q22;q22); RUNX1-RUNX1T1
  • AML with inv(16)(p13.1;q22) or t(16;16)(p13.1;q22); CBF&beta-MYH11
  • Acute promyelocytic leukemia with t(15;17)(q22;q12); PML/RAR&alpha and variants
  • AML with t(9;11)(p22;q23); MLLT3-MLL
  • AML with t(6;9)(p23;q34); DEK-NUP214
  • AML with inv(3)(q21q26.2) or t(3;3)(q21;q26.2); RPN1-EVI1
  • AML (megakaryoblastic) with t(1;22)(p13;q13); RBM15-MKL1
  • AML with mutated NPM1*
  • AML with mutated CEBPA*

* provisional

Acute myeloid leukemia with myelodysplasia related changes

Therapy related acute myeloid leukemia

  • Alkylating agent related
  • Topoisomerase II inhibitor related (some maybe lymphoid)

Acute myeloid leukemia not otherwise categorized:

  • AML minimally differentiated (M0)
  • AML without maturation (M1)
  • AML with maturation (M2)
  • Acute myelomonocytic leukemia (M4)
  • Acute monoblastic and monocytic leukemia (M5a, M5b)
  • Acute erythroid leukemia (M6)
  • Acute megakaryoblastic leukemia (M7)
  • Acute basophilic leukemia
  • Acute panmyelosis with myelofibrosis

Myeloid Sarcoma

Myeloid proliferations related to Down syndrome:

  • Transient abnormal myelopoeisis
  • Myeloid leukemia associated with Down syndrome

Blastic plasmacytoid dentritic cell neoplasm:

Acute leukemia of ambiguous lineage:

  • Acute undifferentiated leukemia
  • Mixed phenotype acute leukemia with t(9;22)(q34;q11.2); BCR-ABL1
  • Mixed phenotype acute leukemia with t(v;11q23); MLL rearranged
  • Mixed phenotype acute leukemia, B/myeloid, NOS
  • Mixed phenotype acute leukemia, T/myeloid, NOS
  • Mixed phenotype acute leukemia, NOS, rare types
  • Other acute leukemia of ambiguous lineage
  • References: WHO Classification of Tumours of Haematopoietic and Lymphoid Tissue (IARC, 2008), Discovery Medicine 2010, eMedicine

Acute lymphocytic leukemia


  • WHO classification system includes former FAB classifications ALL-L1 and L2
    ● FAB L3 is now considered Burkitt lymphoma

WHO classification of acute lymphoblastic leukemia

Precursor B lymphoblastic leukemia / lymphoblastic lymphoma:
● ALL with t(9;22)(q34;q11.2); BCR-ABL (Philadelphia chromosome)
● ALL with t(v;11q23) (MLL rearranged)
● ALL with t(1;19)(q23;p13.3); TCF3-PBX1 (E2A-PBX1)
● ALL with t(12;21)(p13;q22); ETV6-RUNX1 (TEL-AML1)
● Hyperdiploid > 50
● Hypodiploid
● t(5;14)(q31;q32); IL3-IGH

Precursor T lymphoblastic leukemia / lymphoma

Additional references

Mixed phenotype acute leukemia (MPAL)


  • De novo acute leukemia containing separate populations of blasts of more than one lineage (bilineal or bilineage), or a single population of blasts co-expressing antigens of more than one lineage (biphenotypic)Excludes:
    ● Acute myeloid leukemia (AML) with recurrent translocations t(8;21), t(15;17) or inv(16)
    ● Leukemias with FGFR1 mutations
    ● Chronic myelogenous leukemia (CML) in blast crisis
    ● Myelodysplastic syndrome (MDS)-related AML and therapy-related AML, even if they have MPAL immunophenotypeCriteria for biphenotypic leukemia:
    ● Score of 2 or more for each of two separate lineages:The European Group for the Immunological Classification of Leukemias (EGIL) scoring system2008 WHO classification of acute leukemias of ambiguous lineage 


  • Poor, overall survival of 18 months
    ● Young age, normal karyotype and ALL induction therapy are associated with favorable survival
    ● Ph+ is a predictor for poor prognosis
    ● Bone marrow transplantation should be considered in first remission

Major Categories

MPAL with t(9;22)(q34;q11.2); BCR-ABL1

  • 20% of all MPAL
    ● Blasts with t(9;22)(q34;q11.2) translocation or BCR-ABL1 rearrangement (Ph+) without history of CML
    ● Majority in adults
    ● High WBC counts● Most of the cases B/myeloid phenotype
    ● Rare T/myeloid, B and T lineage, or trilineage leukemiasMorphology:
    ● Many cases show a dimorphic blast population, one resembling myeloblasts and the other lymphoblastsCytogenetic abnormalities:
    ● Conventional karyotyping for t(9;22), FISH or PCR for BCR-ABL1 translocation
    ● Additional complex karyotypes
    ● Ph+ is a poor prognostic factor for MPAL, with a reported median survival of 8 months
    ● Worse than patients of all other types of MPAL

MPAL with t(v;11q23); MLL rearranged

  • Meeting the diagnostic criteria for MPAL with blasts bearing a translocation involving the 11q23 breakpoint (MLL gene)
    ● MPAL with MLL rearranged rare
    ● More often seen in children and relatively common in infancy
    ● High WBC counts
    ● Poor prognosis
    ● Dimorphic blast population, with one resembling monoblasts and the other resembling lymphoblasts
    ● Lymphoblast population often shows a CD19+, CD10- B precursor immunophenotype, frequently CD15+
    ● Expression of other B markers usually weak
    ● Translocations involving MLL gene include t(4;11)(q21;q23), t(11;19)(q23;p13), and t(9;11)(p22;q23)
    ● Cases with chromosome 11q23 deletion should not be classified in this category

B cell acute lymphoblastic leukemia (ALL) / lymphoblastic lymphoma (LBL)



  • Current 2008 WHO classification: B lymphoblastic leukemia / lymphoma, NOS or B lymphoblastic leukemia / lymphoma with recurrent genetic abnormalities
  • See also lymphomas: B cell chapter
  • Also called B cell acute lymphoblastic leukemia / lymphoblastic lymphoma, pre B ALL / LBL
  • Usually children
  • B acute lymphoblastic leukemia presents with pancytopenia due to extensive marrow involvement, stormy onset of symptoms, bone pain due to marrow expansion, hepatosplenomegaly due to neoplastic infiltration, CNS symptoms due to meningeal spread and testicular involvement
  • B acute lymphoblastic lymphoma often presents with cutaneous nodules, bone or nodal involvement, < 25% lymphoblasts in bone marrow and peripheral blood; aleukemic cases are usually asymptomatic
  • Depending on specific leukemia, arises in either hematopoietic stem cell or B-cell progenitor
  • Tumors are derived from pre-germinal center naive B cells with unmutated VH region genes
  • Have multiple immunophenotyping aberrancies relative to normal B cell precursors (hematogones); at relapse, 73% show loss of 1+ aberrance and 60% show new aberrancies (Am J Clin Pathol 2007;127:39)

Prognostic features


  • Favorable prognosis: age 1-10 years, female, white; preB phenotype, hyperdiploidy>50, t(12,21), WBC count at presentation <50×108/L, non-traumatic tap with no blasts in CNS, rapid response to chemotherapy < 5% blasts on morphology on day 15, remission status after induction <5% blasts on morphology and <0.01% blast on flow or PCR, CD10+
  • Intermediate prognosis: hyperdiploidy 47-50, diploid, 6q- and rearrangements of 8q24
  • Unfavorable prognosis: under age 1 (usually have 11q23 translocations) or over age 10; t(9;22) (but not if age 59+ years, Am J Clin Pathol 2002;117:716); male, > 50×108/L WBC at presentation, hypodiploidy, near tetraploidy, 17p- and MLL rearrangements t(v;11q23); CD10-; non-traumatic tap with > 5% blasts or traumatic tap (7%); also increased microvessel staining using CD105 in children (Leuk Res 2007;31:1741), MDR1 expression in children (Oncol Rep 2004;12:1201) and adults (Blood 2002;100:974), 25%+ blasts on morphology on day 15, remission status after induction ≥ 5% blasts on morphology and ≥ 0.1% blasts on flow or PCR

Case reports


  • 12 month old girl and 13 month old boy with mature phenotype but no translocations (Arch Pathol Lab Med 2003;127:1340)
  • 56 year old man with ALL arising from follicular lymphoma (Arch Pathol Lab Med 2002;126:997)
  • 76 year old man with basal cell carcinoma (Diagn Pathol 2007;2:32)
  • With hemophagocytic lymphohistiocytosis (Pediatr Blood Cancer 2008;50:381)



  • Chemotherapy cures more children than adults; adolescents benefit from intensive regimens (Hematology Am Soc Hematol Educ Program 2005:123)

Micro description


  • Bone marrow smears: small to intermediate blast-like cells with scant, variably basophilic cytoplasm, round / oval or convoluted nuclei, fine chromatin and indistinct nucleoli; frequent mitotic figures; may have “starry sky” appearance similar to Burkitt lymphoma; may have large lymphoblasts with 1-4 prominent nucleoli resembling myeloblasts; usually no sclerosis
  • Bone marrow biopsy: usually markedly hypercellular with reduction of trilinear maturation; cells have minimal cytoplasm, medium sized nuclei that are often convoluted, moderately dense chromatin and indistinct nucleoli, brisk mitotic activity
  • Other tissues: may have “starry sky” appearance similar to Burkitt lymphoma; collagen dissection, periadipocyte growth pattern and single cell linear filing

Chronic Leukemia

Chronic Myeloid Neoplasms

Myelodysplastic syndromes (MDS): general, WHO classification, childhood, refractory anemia, refractory anemia with ringed sideroblasts, refractory cytopenia with multilineage dysplasia, refractory anemia with excess blasts, 5q-syndrome, therapy related, unclassified, arsenic toxicity

Myeloproliferative neoplasms (MPN): general, WHO classification, chronic eosinophilic leukemia, chronic myelogenous leukemia, chronic neutrophilic leukemia, essential thrombocythemia, hypereosinophilic syndrome, mast cell disease, polycythemia vera, primary myelofibrosis, unclassifiable

MDS/MPN: general, WHO classification, atypical CML, chronic myelomonocytic leukemia (CMML), chronic myelomonocytic leukemia with eosinophilia, juvenile myelomonocytic leukemia, unclassifiable

Myeloid neoplasms associated with eosinophilia and abnormalities of PDGFRA, PDGFRB, or FGFR1: PDGFRA, PDGFRB, FGFR1

Miscellaneous: transient myeloproliferative disorder of Downís syndrome

Lymphoma and plasma cell neoplasms

Lymph nodes: normal development-generalB cellsT cellsNK cellsnormal histologygrossing lymph nodesfeatures to report

Molecular testing: theoryFISHnorthern blotPCRsouthern blot

Non-Hodgkin lymphoma: generalcytogeneticsstagingstaging-pediatricmorphologic clueshemophagocytic syndromechemotherapeutic atypia

B cell disorders: generalpost-rituximabbone marrow biopsyclassification-historicalWHO classification

B cell lymphoma subtypes: age-related EBV-associatedALK positive large cellBurkittunclassifiable-intermediate between Burkitt and diffuse large B cell lymphomaCLL
diffuse large B cell: 
diffuse-NOSCD5+T cell / histiocyte richprimary cutaneous-generalprimary cutaneous-legprimary sites-other
hairy cell leukemiaHCL variantintravascular large B celllymphomatoid granulomatosislymphoplasmacyticmantle cell-classicmantle cell-blastoidmarginal zone-generalmarginal zone-MALTMALT-primary sitesmarginal zone-nodalmediastinal (thymic)plasmablasticpre B lymphoblastic leukemia/lymphomaprimary effusionprolymphocytic leukemiapyothorax associatedSLLsplenic marginal zonesplenic lymphoma with villous lymphocytes

Plasma cell neoplasms: generalmyelomaplasmacytomaheavy chain diseaseprimary amyloidosisMGUSOsteosclerotic myeloma (POEMS)cryoglobulinemia

T/NK cell disorders: generalWHO classificationadult T cellaggressive NK cell leukemiaanaplastic large cell ALK+ALK-angioimmunoblastic T cellblastic plasmacytoidchronic lymphoproliferative disorders of NK cellscutaneous CD4+ small/medium sized T cell lymphomacutaneous CD30 positive T cell lymphoproliferative disorderscutaneous gamma delta T cell lymphomaenteropathyepidermotropic CD8+ T cell lymphomahepatosplenicindolent T cell proliferationsmycosis fungoidesNK/T cell lymphoma-nasal typenodal CD8+ cytotoxic T cellnonB nonT lymphoblasticperipheral T cell lymphoma, NOSprimary effusion lymphomaSezary syndromestagingsubcutaneous panniculitis-likeT cell large granular lymphocytic leukemiaT cell lymphoblastic leukemia/lymphomaT cell prolymphocytic leukemia

Hodgkin lymphoma: general/stagingclassiclymphocyte depletedlymphocyte rich classicalmixed cellularitynodular lymphocyte predominantnodular sclerosis

Post-transplantation: generalWHO classificationplasmacytic hyperplasia/IM-like lesionspolymorphic B cell lymphoproliferative disordersmonomorphic B cell lymphoproliferative disordersothergraft versus host disease

Other: AIDS associated-generalAIDS associated-examplesEBV+ T cell lymphoproliferative disorders of childhoodprimary immune disorders related

Myeloproliferative neoplasms (MPN)

WHO 2008 – Myeloproliferative neoplasms (MPN) 


  • Chronic myelogenous leukemia
    ● Polycythemia vera
    ● Essential thrombocythemia
    ● Primary myelofibrosis
    ● Chronic neutrophilic leukemia
    ● Chronic eosinophilic leukemia, not otherwise categorized
    ● Mast cell disease
    ● MPNs, unclassifiable

WHO 2001 – Chronic myeloproliferative diseases 


  • Chronic myelogenous leukemia (Philadelphia chromosome, t(9;22)(q34;q11), BCR-ABL positive)
    ● Chronic neutrophilic leukemia
    ● Chronic eosinophilic leukemia (and the hypereosinophilic syndrome)
    ● Polycythemia vera
    ● Chronic idiopathic myelofibrosis (with extramedullary hematopoiesis)
    ● Essential thrombocythemia
    ● Chronic myeloproliferative disease, unclassifiable

Additional references

The World Health Organization (WHO) classification of the myeloid neoplasms  James W. Vardiman, Nancy Lee Harris, and Richard D. Brunning
Blood 2002; 100(7)

Lymphoma – Non B cell neoplasms

T/NK cell disorders/WHO classification (2008)

Principles of classification

  • Based on all available information (morphology, immunophenotype, genetics, clinical)
    ● No one antigenic marker is specific for any neoplasm (except ALK1)
    ● Immune profiling less helpful in subclassification of T cell lymphomas then B cell lymphomas
    ● Certain antigens commonly associated with specific disease entities but not entirely disease specific
    ● CD30: common in anaplastic large cell lymphoma but also classic Hodgkin lymphoma and other B and T cell lymphomas
    ● CD56: characteristic for nasal NK/T cell lymphoma, but also other T cell neoplasms and plasma cell disorders
    ● Variation of immunophenotype within a given disease (hepatosplenic T cell lymphoma: usually γδ but some are αβ)
    ● Recurrent genetic alterations have been identified for many B cell lymphomas but not for most T cell lymphomas
    ● No attempt to stratify lymphoid malignancies by grade
    ● Recognize the existence of grey zone lymphomas
    ● This multiparameter approach has been validated in international studies as highly reproducible

WHO 2008 classification of tumors of hematopoietic and lymphoid tissues (T/NK)

Precursor T-lymphoid neoplasms
● T lymphoblastic leukemia/lymphoma, 9837/3

Mature T cell and NK cell neoplasms
● T cell prolymphocytic leukemia, 9834/3
● T cell large granular lymphocytic leukemia, 9831/3
● Chronic lymphoproliferative disorder of NK cells, 9831/3
● Aggressive NK cell leukemia, 9948/3
● Systemic EBV-positive T cell lymphoproliferative disease of childhood, 9724/3
● Hydroa vacciniforme-like lymphoma, 9725/3
● Adult T cell leukemia/lymphoma, 9827/3
● Extranodal NK/T cell lymphoma, nasal type, 9719/3
● Enteropathy-associated T cell lymphoma, 9717/3
● Hepatosplenic T cell lymphoma, 9716/3
● Subcutaneous panniculitis-like T cell lymphoma, 9708/3
● Mycosis fungoides, 9700/3
● Sézary syndrome, 9701/3
● Primary cutaneous CD30-positive T cell lymphoproliferative disorders
● Lymphomatoid papulosis, 9718/1
● Primary cutaneous anaplastic large cell lymphoma, 9718/3
● Primary cutaneous gamma-delta T cell lymphoma, 9726/3
● Primary cutaneous CD8-positive aggressive epidermotropic cytotoxic T cell lymphoma, 9709/3
● Primary cutaneous CD4-positive small/medium T cell lymphoma, 9709/3
● Peripheral T cell lymphoma, NOS, 9702/3
● Angioimmunoblastic T cell lymphoma, 9705/3
● Anaplastic large cell lymphoma, ALK-positive, 9714/3
● Anaplastic large cell lymphoma, ALK-negative, 9702/3

Chronic Lymphocytic Leukemia

Chronic Lymphocytic Leukemia Staging
Author: Sandy D Kotiah, MD; Chief Editor: Jules E Harris, MD
Medscape Sep 6, 2013

General considerations in the staging of chronic lymphocytic leukemia (CLL) and the revised Rai (United States) and Binet (Europe) staging systems for CLL are provided below.[1, 2, 3]

See Chronic Leukemias: 4 Cancers to Differentiate, a Critical Images slideshow, to help detect chronic leukemias and determine the specific type present.

General considerations

  • CLL and small lymphocytic lymphoma (SLL) are different manifestations of the same disease; SLL is diagnosed when the disease is mainly nodal, and CLL is diagnosed when the disease is seen in the blood and bone marrow
  • CLL is diagnosed by > 5000 monoclonal lymphocytes/mm3 for longer than 3mo; the bone marrow usually has more than 30% monoclonal lymphocytes and is either normocellular or hypercellular
  • Monoclonal B lymphocytosis is a precursor form of CLL that is defined by a monoclonal B cell lymphocytosis < 5000 monoclonal lymphocytes/mm3; all lymph nodes smaller than 1.5 cm; no anemia; and no thrombocytopenia

Revised Rai staging system (United States)

Low risk (formerly stage 0)[1] :

  • Lymphocytosis, lymphocytes in blood > 15000/mcL, and > 40% lymphocytes in the bone marrow

Intermediate risk (formerly stages I and II):

  • Lymphocytosis as in low risk with enlarged node(s) in any site, or splenomegaly or hepatomegaly or both

High risk (formerly stages III and IV):

  • Lymphocytosis as in low risk and intermediate risk with disease-related anemia (hemoglobin level < 11.0 g/dL or hematocrit < 33%) or platelets < 100,000/mcL

Binet staging system (Europe)

Stage A:

  • Hemoglobin ≥ 10 g/dL, platelets ≥ 100,000/mm3, and < 3 enlarged areas

Stage B:

  • Hemoglobin ≥ 10 g/dL, platelets ≥ 100,000/mm3, and ≥ 3 enlarged areas

Stage C:

  • Hemoglobin < 10 g/dL, platelets < 100,000/mm3, and any number of enlarged areas

Read Full Post »

Allogeneic Stem Cell Transplantation

Writer and Curator: Larry H. Bernstein, MD, FCAP

This article has the following structure:

9.3.1  Cell based immunotherapy

9.3.2  Photodynamic therapy (PDT)

9.3.3  Small molecules targeted therapy drugs; Tyrosine kinase inhibitors; imatinib (Gleevec/Glivec) and gefitinib (Iressa).

9.3.4 Graft versus Host Disease

9.3.5 Aspergillus Complicating Allogeneic Transplantation


9.3.1 Allogeneic Stem Cell Treatment

Allogeneic stem cell transplantation involves transferring the stem cells from a healthy person (the donor) to your body after high-intensity chemotherapy or radiation.

Allogeneic stem cell transplantation is used to cure some patients who:

  • Are at high risk of relapse
  • Don’t respond fully to treatment
  • Relapse after prior successful treatment

Allogeneic stem cell transplantation can be a high-risk procedure. The high-conditioning regimens are meant to severely or completely impair your ability to make stem cells and you will likely experience side effects during the days you receive high-dose conditioning radiation or chemotherapy. The goals of high-conditioning therapy are to:

treat the remaining cancer cells intensively, thereby making a cancer recurrence less likely
inactivate the immune system to reduce the chance of stem cell graft rejection
enable donor cells to travel to the marrow (engraftment), produce blood cells and bring about graft versus tumor effect

Possible Adverse Effects

The immune system and the blood system are closely linked and can’t be separated from each other. Because of this, allogeneic transplantation means that not only the donor’s blood system but also his or her immune system is transferred. As a result, these adverse effects are possible:

  • Immune rejection of the donated stem cells by the recipient (host-versus-graft effect)
  • Immune reaction by the donor cells against the recipient’s tissues (graft-versus-host disease [GVHD])

The immune reaction, or GVHD, is treated by administering drugs to the patient after the transplant that reduce the ability of the donated immune cells to attack and injure the patient’s tissues. See Graft Versus Host Disease.

Allogeneic stem cell transplants for patients who are older or have overall poor health are relatively uncommon. This is because the pre-transplant conditioning therapy is generally not well tolerated by such patients, especially those with poorly functioning internal organs. However, reduced intensity allogeneic stem cell transplants may be an appropriate treatment for some older or sicker patients.

T-Lymphocyte Depletion

One goal of allogeneic stem cell transplant is to cause the T lymphocytes in the donor’s blood or marrow to take hold (engraft) and grow in the patient’s marrow. Sometimes the T lymphocytes attack the cancer cells. When this happens, it’s called graft versus tumor (GVT) effect (also called graft versus cancer effect). The attack makes it less likely that the disease will return. This effect is more common in myeloid leukemias than it is in other blood cancers.

Unfortunately, T lymphocytes are the same cells that cause graft versus host disease (GVHD). Because of this serious and sometimes life-threatening side effect, doctors in certain cases want to decrease the number of T lymphocytes to be infused with the stem cells. This procedure, called T-lymphocyte depletion, is currently being studied by researchers. The technique involves treating the stem cells collected for transplant with agents that reduce the number of T lymphocytes.

The aim of T-lymphocyte depletion is to lessen GVHD’s incidence and severity. However, it can also cause increased rates of graft rejection, a decreased GVT effect and a slower immune recovery. Doctors must be careful about the number of T lymphocytes removed when using this technique.

Stem Cell Selection

Stem cell selection is another technique being studied in clinical trials that can reduce the number of T lymphocytes that a patient receives. Because of specific features on the outer coat of stem cells, doctors can selectively remove stem cells from a cell mixture. This technique produces a large number of stem cells and fewer other cells, including T lymphocytes.

9.3.2 Defining Characteristics of  Stem Cells

Stem cells have the remarkable potential to develop into many different cell types in the body during early life and growth. In addition, in many tissues they serve as a sort of internal repair system, dividing essentially without limit to replenish other cells as long as the person or animal is still alive. When a stem cell divides, each new cell has the potential either to remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell.

Stem cells are distinguished from other cell types by two important characteristics. First, they are unspecialized cells capable of renewing themselves through cell division, sometimes after long periods of inactivity. Second, under certain physiologic or experimental conditions, they can be induced to become tissue- or organ-specific cells with special functions. In some organs, such as the gut and bone marrow, stem cells regularly divide to repair and replace worn out or damaged tissues. In other organs, however, such as the pancreas and the heart, stem cells only divide under special conditions.

Until recently, scientists primarily worked with two kinds of stem cells from animals and humans: embryonic stem cells and non-embryonic “somatic” or “adult” stem cells. The functions and characteristics of these cells will be explained in this document. Scientists discovered ways to derive embryonic stem cells from early mouse embryos more than 30 years ago, in 1981. The detailed study of the biology of mouse stem cells led to the discovery, in 1998, of a method to derive stem cells from human embryos and grow the cells in the laboratory. These cells are called human embryonic stem cells. The embryos used in these studies were created for reproductive purposes through in vitro fertilization procedures.

When they were no longer needed for that purpose, they were donated for research with the informed consent of the donor. In 2006, researchers made another breakthrough by identifying conditions that would allow some specialized adult cells to be “reprogrammed” genetically to assume a stem cell-like state. This new type of stem cell is called induced pluripotent stem cells (iPSCs).

Stem cells differ from other kinds of cells in the body. All stem cells—regardless of their source—have three general properties: they are capable of dividing and renewing themselves for long periods; they are unspecialized; and they can give rise to specialized cell types.

Stem cells are capable of dividing and renewing themselves for long periods. Unlike muscle cells, blood cells, or nerve cells—which do not normally replicate themselves—stem cells may replicate many times, or proliferate. A starting population of stem cells that proliferates for many months in the laboratory can yield millions of cells. If the resulting cells continue to be unspecialized, like the parent stem cells, the cells are said to be capable of long-term self-renewal.

Scientists are trying to understand two fundamental properties of stem cells that relate to their long-term self-renewal:

  1. Why can embryonic stem cells proliferate for a year or more in the laboratory without differentiating, but most adult stem cells cannot; and
  2. What are the factors in living organisms that normally regulate stem cell proliferation and self-renewal?

Discovering the answers to these questions may make it possible to understand how cell proliferation is regulated during normal embryonic development or during the abnormal cell division that leads to cancer.

Stem cells are unspecialized. One of the fundamental properties of a stem cell is that it does not have any tissue-specific structures that allow it to perform specialized functions. For example, a stem cell cannot work with its neighbors to pump blood through the body (like a heart muscle cell), and it cannot carry oxygen molecules through the bloodstream (like a red blood cell). However, unspecialized stem cells can give rise to specialized cells, including heart muscle cells, blood cells, or nerve cells.

Stem cells can give rise to specialized cells. When unspecialized stem cells give rise to specialized cells, the process is called differentiation. While differentiating, the cell usually goes through several stages, becoming more specialized at each step. Scientists are just beginning to understand the signals inside and outside cells that trigger each step of the differentiation process. The internal signals are controlled by a cell’s genes, which are interspersed across long strands of DNA and carry coded instructions for all cellular structures and functions. The external signals for cell differentiation include chemicals secreted by other cells, physical contact with neighboring cells, and certain molecules in the microenvironment. The interaction of signals during differentiation causes the cell’s DNA to acquire epigenetic marks that restrict DNA expression in the cell and can be passed on through cell division.

Adult stem cells typically generate the cell types of the tissue in which they reside. For example, a blood-forming adult stem cell in the bone marrow normally gives rise to the many types of blood cells. It is generally accepted that a blood-forming cell in the bone marrow—which is called a hematopoietic stem cell—cannot give rise to the cells of a very different tissue, such as nerve cells in the brain.

Through years of experimentation, scientists have established some basic protocols or “recipes” for the directed differentiation of embryonic stem cells into some specific cell types (Figure 1). (For additional examples of directed differentiation of embryonic stem cells, refer to the NIH stem cell report available at

stem cell differentiation figure1_sm

stem cell differentiation figure1_sm

9.3.3 Types of Stem Cell Transplants for Treating Cancer

In a typical stem cell transplant for cancer very high doses of chemo are used, often along with radiation therapy, to try to destroy all the cancer cells. This treatment also kills the stem cells in the bone marrow. Soon after treatment, stem cells are given to replace those that were destroyed. These stem cells are given into a vein, much like a blood transfusion. Over time they settle in the bone marrow and begin to grow and make healthy blood cells. This process is called engraftment.

There are 3 basic types of transplants. They are named based on who gives the stem cells.

  • Autologous (aw-tahl-uh-gus)—the cells come from you
  • Allogeneic (al-o-jen-NEE-ick or al-o-jen-NAY-ick)—the cells come from a matched related or unrelated donor
  • Syngeneic (sin-jen-NEE-ick or sin-jen-NAY-ick)—the cells come from your identical twin or triplet
hematopoietic stem cell transplant

hematopoietic stem cell transplant

Autologous stem cell transplants

These stem cells come from you alone. In this type of transplant, your stem cells are taken before you get cancer treatment that destroys them. Your stem cells are removed, or harvested, from either your bone marrow or your blood and then frozen. To find out more about that process, please see the section “What’s it like to donate stem cells?” After you get high doses of chemo and/or radiation the stem cells are thawed and given back to you.

One advantage of autologous stem cell transplant is that you are getting your own cells back. When you donate your own stem cells you don’t have to worry about the graft attacking your body (graft-versus-host disease) or about getting a new infection from another person. But there can still be graft failure, and autologous transplants can’t produce the “graft-versus-cancer” effect.

This kind of transplant is mainly used to treat certain leukemias, lymphomas, and multiple myeloma. It’s sometimes used for other cancers, like testicular cancer and neuroblastoma, and certain cancers in children.

Getting rid of cancer cells in autologous transplants

A possible disadvantage of an autologous transplant is that cancer cells may be picked up along with the stem cells and then put back into your body later. Another disadvantage is that your immune system is still the same as before when your stem cells engraft. The cancer cells were able to grow despite your immune cells before, and may be able to do so again. The need to remove cancer cells from transplants or transplant patients and the best way to do it is being researched.

Doing 2 autologous transplants in a row is known as a tandem transplant or a double autologous transplant. In this type of transplant, the patient gets 2 courses of high-dose chemo, each followed by a transplant of their own stem cells. All of the stem cells needed are collected before the first high-dose chemo treatment, and half of them are used for each transplant. Most often both courses of chemo are given within 6 months, with the second one given after the patient recovers from the first one.

Allogeneic stem cell transplants

In the most common type of allogeneic transplant, the stem cells come from a donor whose tissue type closely matches the patient’s. (This is discussed later under “HLA matching” in the section called “ Donor matching for allogeneic transplant.”) The best donor is a close family member, usually a brother or sister. If you do not have a good match in your family, a donor might be found in the general public through a national registry. This is sometimes called a MUD (matched unrelated donortransplant. Transplants with a MUD are usually riskier than those with a relative who is a good match.

Blood taken from the placenta and umbilical cord of newborns is a newer source of stem cells for allogeneic transplant. Called cord blood, this small volume of blood has a high number of stem cells that tend to multiply quickly. But the number of stem cells in a unit of cord blood is often too low for large adults, so this source of stem cells is limited to small adults and children. Doctors are now looking at different ways to use cord blood for transplant in larger adults, such as using cord blood from 2 donors.

Pros of allogeneic stem cell transplant: The donor stem cells make their own immune cells, which could help destroy any cancer cells that remain after high-dose treatment. This is called the graft-versus-cancer effect. Other advantages are that the donor can often be asked to donate more stem cells or even white blood cells if needed, and stem cells from healthy donors are free of cancer cells.

Cons to allogeneic stem cell transplants: The transplant, also known as the graft, might not take — that is, the donor cells could die or be destroyed by the patient’s body before settling in the bone marrow. Another risk is that the immune cells from the donor may not just attack the cancer cells – they could attack healthy cells in the patient’s body. This is called graft-versus-host disease (described in the section called “Problems that may come up shortly after transplant”). There is also a very small risk of certain infections from the donor cells, even though donors are tested before they donate. A higher risk comes from infections you have had, and which your immune system has under control. These infections often surface after allogeneic transplant because your immune system is held in check (suppressed) by medicines called immunosuppressive drugs. These infections can cause serious problems and even death.

Allogeneic transplant is most often used to treat certain types of leukemia, lymphomas, multiple myeloma,myelodysplastic syndrome, and other bone marrow disorders such as aplastic anemia.

Mini transplants (non-myeloablative transplants)

For some people, age or certain health conditions make it more risky to wipe out all of their bone marrow before a transplant. For those people, doctors can use a type of allogeneic transplant that’s sometimes called a mini-transplant. Compared with a standard allogeneic transplant, this one uses less chemo and/or radiation to get the patient ready for the transplant. Your doctor might refer to it as a non-myeloablative transplant or mention reduced-intensity conditioning (RIC). The idea here is to kill some of the cancer cells along with some of the bone marrow, and suppress the immune system just enough to allow donor stem cells to settle in the bone marrow.

Unlike the standard allogeneic transplant, cells from both the donor and the patient exist together in the patient’s body for some time after a mini-transplant. But slowly, over the course of months, the donor cells take over the bone marrow and replace the patient’s own bone marrow cells. These new cells can then develop an immune response to the cancer and help kill off the patient’s cancer cells — the graft-versus-cancer effect.

Syngeneic stem cell transplants – for those with an identical sibling

This is a special kind of allogeneic transplant that can only be used when the recipient has an identical sibling (twin or triplet) who can donate — someone who will have the same tissue type. An advantage of syngeneic stem cell transplant is that graft-versus-host disease will not be a problem. There are no cancer cells in the transplant, either, as there would be in an autologous transplant.

A disadvantage is that because the new immune system is so much like the recipient’s immune system, there is no graft-versus-cancer effect, either. Every effort must be made to destroy all the cancer cells before the transplant is done to help keep the cancer from relapsing (coming back).

9.3.4 Graft versus Host Disease–GVHD-/

Graft-versus-host disease(GVHD) occurs because of differences between the cells of your body and the donated cells and is a common side effect of an allogeneic bone marrow transplant.

An allogeneic transplant uses blood cells from a family member, unrelated donor or cord blood unit. GVHD can affect many different parts of the body including the skin, eyes, mouth, stomach, and intestines.

There are two types of GVHD:

  • Acute GVHD: Develops in the first 100 days or so after transplant but can occur later. This primarily affects the skin, stomach, intestines, and liver.
  • Chronic GVHD: Usually develops 3-6 months after transplant, but signs can appear earlier or later. If you have had or currently have acute GVHD, you are more likely to have chronic GVHD.

The severity of acute and chronic GVHD can range from mild to life-threatening.

Doctors often see mild GVHD as a good thing after an allogeneic transplant when the transplant was done for a blood cancer. It is a sign that the donor’s immune system is working to destroy any remaining cancer cells. Patients who experience some GVHD have a lower risk of the cancer returning after transplant than patients who do not develop GVHD. If the transplant was to treat a disease other than cancer disease, like aplastic anemia, then the doctor may want to treat even mild GVHD.

Graft-versus-Host Disease

JLM FerraraJE LevineP Reddy, and E Holler
Lancet. 2009 May 2; 373(9674): 1550–1561.

The number of allogeneic hematopoietic cell transplantations (HCT) continues to increase with more than 25,000 allogeneic transplantations performed annually. The graft-versus-leukemia / tumor (GVL) effect during allogeneic HCT effectively eradicates many hematological malignancies.1 The development of novel strategies that use donor leukocyte infusions, non-myeloablative conditioning and umbilical cord blood (UCB) transplantation have helped expand the indications for allogeneic HCT over the last several years, especially among older patients.2 Improvements in infectious prophylaxis, immunosuppressive medications, supportive care and DNA-based tissue typing have also contributed to improved outcomes after allogeneic HCT.1 Yet the major complication of allogeneic HCT, graft-versus-host disease (GVHD), remains lethal and limits the use of this important therapy.2 Given current trends, the number of transplants from unrelated donors is expected to double within the next five years, significantly increasing the population of patients with GVHD. In this seminar we review advances made in identifying the genetic risk factors and pathophysiology of this major HCT complication, as well as its prevention, diagnosis and treatment.

Etiology and Clinical Features

Fifty years ago Billingham formulated three requirements for the development of GVHD: the graft must contain immunologically competent cells; the recipient must express tissue antigens that are not present in the transplant donor; and the recipient must be incapable of mounting an effective response to eliminate the transplanted cells.3 We know now that the immunologically competent cells are T cells, and that GVHD can develop in various clinical settings when tissues containing T cells (blood products, bone marrow, and solid organs) are transferred from one person to another who is not able to eliminate those cells.45 Patients, whose immune systems are suppressed, and who receive white blood cells from another individual, are at particularly high risk for GVHD.

GVHD occurs when donor T cells respond to genetically defined proteins on host cells. The most important proteins are Human Leukocyte Antigens (HLA)267, which are highly polymorphic and are encoded by the major histocompatibility complex (MHC). Class I HLA (A, B, and C) proteins are expressed on almost all nucleated cells of the body at varying densities. Class II proteins (DR, DQ, and DP) are primarily expressed on hematopoietic cells (B cells, dendritic cells, monocytes), but their expression can be induced on many other cell types following inflammation or injury. High-resolution DNA typing of HLA genes with polymerase chain reaction (PCR)-based techniques have now largely replaced earlier methods. The incidence of acute GVHD is directly related to the degree of mismatch between HLA proteins89 and thus ideally, donors and recipients are matched at HLA-A, -B, -C, and -DRB1, (“8/8 matches”), but mismatches may be tolerated for UCB grafts (see below).1012

Non-HLA Genetics

Despite HLA identity between a patient and donor, approximately 40% of patients receiving HLA-identical grafts develop acute GVHD due to genetic differences that lie outside the HLA loci, or “minor” histocompatibility antigens (HA). Some minor HAs, such as HY and HA-3, are expressed on all tissues and are targets for both GVHD and GVL.13 Other minor HAs, such as HA-1 and HA-2, are expressed most abundantly on hematopoietic cells (including leukemic cells) and may therefore induce a greater GVL effect with less GVHD.1314

Polymorphisms in both donors and recipients for cytokines that are involved in the classical `cytokine storm’ of GVHD (discussed below) have been implicated as risk factors for GVHD.15 Tumor Necrosis Factor (TNF)-α, Interleukin 10 (IL-10), Interferon-γ (IFNγ) variants have correlated with GVHD in some, but not all, studies.1618 Genetic polymorphisms of proteins involved in innate immunity, such as nucleotide oligomerization domain 2 and Keratin 18 receptors, have also been associated with GVHD.1922 Future strategies to identify the best possible transplant donor will probably incorporate both HLA and non-HLA genetic factors.

Clinical Features of Acute GVHD

Based on an early Seattle experience, acute GVHD was defined to occur prior to day 100, whereas chronic GVHD occurred after that time.2325 This definition is far from satisfactory, and a recent National Institutes of Health classification includes late-onset acute GVHD (after day 100) and an overlap syndrome with features of both acute and chronic GVHD.26 Late-onset acute GVHD and the overlap syndrome occur with greater frequency after reduced-intensity conditioning (RIC), an increasingly widespread technique (see below). As shown in Table 1, the clinical manifestations of acute GVHD occur in the skin, gastrointestinal tract and liver.27 In a comprehensive review, Martin et al found that at the onset of acute GVHD, 81% of patients had skin involvement, 54% had GI involvement, and 50% had liver involvement.23 Recent data suggest that lungs might also be targets of experimental GVHD.28

Acute GVHD Symptoms

Table 1

Pathophysiology of Acute GVHD

Two important principles are important to consider regarding the pathophysiology of acute GVHD. First, acute GVHD reflects exaggerated but normal inflammatory mechanisms mediated by donor lymphocytes infused into the recipient where they function appropriately, given the foreign environment they encounter. Second, the recipient tissues that stimulate donor lymphocytes have usually been damaged by underlying disease, prior infections, and the transplant conditioning regimen.29 As a result, these tissues produce molecules (sometimes referred to as “danger” signals) that promote the activation and proliferation of donor immune cells.4245 Mouse models havebeen central to our identification and understanding of the pathophysiologic mechanisms of GVHD, and canine models have been critical to the development of clinically useful strategies for GVHD prophylaxis and treatment and to the development of donor leukocyte infusions.364647 Based largely on these experimental models, the development of acute GVHD can be conceptualized in three sequential steps or phases: (1) activation of the APCs; (2) donor T cell activation, proliferation, differentiation and migration; and (3) target tissue destruction (Figure 3).

Figure 3

GVHD Pathophysiology

In Phase I, the recipient conditioning regimen damages host tissues and causes release of inflammatory cytokines such as TNFα, IL-1 and IL-6. Increased levels of these cytokines leads to activation of host antigen presenting cells (APCs). In Phase II, host APCs activate mature donor cells. The subsequent proliferation and differentiation of these activated T cells produces additional effectors that mediate the tissue damage, including Cytotoxic T Lymphocytes, Natural Killer (NK) cells, TNFα and IL-1. Lipopolysaccharide (LPS) that has leaked through the damaged intestinal mucosa triggers additional TNFα production. TNFα can damage tissue directly by inducing necrosis and apoptosis in the skin and GI tract through either TNF receptors or the Fas pathway. TNFα plays a direct role in intestinal GVHD damage which further amplifies damage in the skin, liver and lung in a “cytokine storm.”

GVHD pathophysiology nihms-115970-f0003

GVHD pathophysiology nihms-115970-f0003

Phase I: Activation of Antigen Presenting Cells (APCs)

The first step involves the activation of APCs by the underlying disease and the HCT conditioning regimen. Damaged host tissues respond by producing “danger” signals, including proinflammatory cytokines (e.g., TNF-α), chemokines, and increased expression of adhesion molecules, MHC antigens and costimulatory molecules on host APCs.424850 A recent report demonstrated that at one week after HCT, increased levels of TNF-α receptor I, a surrogate marker for TNF-α, strongly correlated with the later development of GVHD.51 Damage to the GI tract from the conditioning is particularly important because it allows for systemic translocation of additional inflammatory stimuli such as microbial products including lipopolysaccaride (LPS) or other pathogen-associated molecular patterns that further enhance the activation of host APCs.49 The secondary lymphoid tissue in the GI tract is likely the initial site of interaction between activated APCs and donor T cells.52 These observations have led an important clinical strategy to reduce acute GVHD by reducing the intensity of the conditioning regimen. Experimental GVHD can also be reduced by manipulating distinct subsets of APCs.53,54 In addition, non-hematopoietic stem cells, such as mesenchymal stem cells or stromal cells, can reduce allogeneic T cell responses, although the mechanism for such inhibition remains unclear.2

The concept that enhanced activation of host APCs increases the risk for acute GVHD unifies a number of seemingly disparate clinical associations with that risk, such as advanced stages of malignancy, more intense transplant conditioning regimens and histories of viral infections. APCs detect infections by recognizing conserved molecular patterns that are unique to microbes, called pathogen-associated molecular patterns (PAMPs). Among the classes of receptors that recognize such patterns, the Toll-like receptors (TLR) are the best characterized.55 For example, TLR4 recognizes LPS55 and mice with mutant TLR4 receptors that do not respond to LPS cause less GVHD when used as donors.56 Other TLRs that recognize viral DNA or RNA also activate APCs and may enhance GVHD, providing a potential mechanistic basis for increased GVHD associated with viral infections such as cytomegalovirus (CMV).57

Phase II: Donor T Cell Activation

The core of the GVH reaction is Step 2, where donor T cells proliferate and differentiate in response to host APCs. The “danger” signals generated in Phase I augment this activation at least in part by increasing the expression of costimulatory molecules.58 Blockade of co-stimulatory pathways to prevent GVHD is successful in animal models, but this approach has not yet been tested in large clinical trials.2

In mouse models, where genetic differences between donor and recipient strains can be tightly controlled, CD4+ cells induce acute GVHD to MHC class II differences, and CD8+ cells induce acute GVHD to MHC class I differences.5961 In the majority of HLA-identical HCTs, both CD4+ and CD8+ subsets respond to minor histocompatibility antigens and can cause GVHD in HLA-identical HCT.

Regulatory T cells can suppress the proliferation of conventional T cells and prevent GVHD in animal models when added to donor grafts containing conventional T cells.62 In mice, the Foxp3 protein functions as a master switch in the development of regulatory T cells, which normally constitute 5% of the CD4+ T cell population.62 Regulatory T cells secrete anti-inflammatory cytokines IL-10 and Transforming Growth Factor(TGF)-β and can also act through contact-dependent inhibition of APCs.62 It is likely that the use of regulatory T cells in clinical acute GVHD will require improved techniques to identify and expand them.

Natural Killer T cell (NKT) 1.1+ subsets of both the host and donors that have been shown to modulate acute GVHD.63 Host NKT cells have been shown to suppress acute GVHD in an IL-4 dependent manner.64 A recent clinical trial of total lymphoid irradiation used as conditioning significantly reduced GVHD and enhanced host NKT cell function.65 By contrast, donor NKT cells can reduce GVHD and enhance perforin mediated GVL in an experimental model.66

Activation of immune cells results in rapid intracellular biochemical cascades that induce transcription of genes for many proteins including cytokines and their receptors. Th1 cytokines (IFN-γ, IL-2 and TNF-α) are produced in large amounts during acute GVHD. IL-2 production by donor T cells remains the principal target of many current clinical therapeutic and prophylactic approaches to GVHD, such as cyclosporine, tacrolimus and monoclonal antibodies (mAbs) directed against IL-2 and its receptor.9 But emerging data indicate an important role for IL-2 in the generation and maintenance of CD4+ CD25+ T regs, suggesting that prolonged interference with IL-2 may have an unintended consequence of preventing the development of long term tolerance after allogeneic HCT.67 IFN-γ has multiple functions and can either amplify or reduce GVHD.68,69 IFN-γ may amplify GVHD by increasing the expression of molecules such as chemokines receptors, MHC proteins, and adhesion molecules; it also increases the sensitivity of monocytes and macrophages to stimuli such as LPS and accelerates intracellular cascades in response to these stimuli.70Early polarization of donor T cells so that they secrete less IFN-γ and more IL-4 can also attenuate experimental acute GVHD.71 IFN-γ may amplify GVHD by directly damaging epithelium in the GI tract and skin and inducing immnosuppression through the induction of nitric oxide.72 By contrast, IFN-γ may suppress GVHD by hastening the apoptosis of activated donor T cells.6973. This complexity means the manipulation of IFN-γ may have diverse effects in vivo, making it a challenging target with respect to therapeutic intervention. IL-10 plays a key role in suppression of immune responses, and clinical data suggest it may regulate acute GVHD.17 TGF-β, another suppressive cytokine can suppress acute GVHD but exacerbate chronic GVHD.74 Thus the timing and duration of the secretion of any given cytokine may determine the specific effects of that cytokine on GVHD severity.

Phase III: Cellular and Inflammatory Effector Phase

The effector phase of this process is a complex cascade of both cellular mediators such as cytotoxic T lymphocytes(CTLs) and NK cells and soluble inflammatory mediators such as TNF-α, IFN-γ, IL-1 and nitric oxide.229 These soluble and cellular mediators synergize to amplify local tissue injury and further promote inflammation and target tissue destruction.

Cellular Effectors

The cellular effectors of acute GVHD are primarily CTLs and NK cells.49 CTLs that preferentially use the Fas/FasL pathway of target lysis and appear to predominate in GVHD liver damage (hepatocytes express large amounts of Fas) whereas GVHD CTLs that use the perforin /granzyme pathways are more important in the GI tract and skin.275 Chemokines direct the migration of donor T cells from lymphoid tissues to the target organs where they cause damage. Macrophage inflammatory protein-1alpha (MIP-1α) and other chemokines such as CCL2-5, CXCL2, CXCL9-11, CCL17 and CCL27 are over-expressed and enhance the homing of cellular effectors to target organs during experimental GVHD.76Expression of integrins, such as α4β7 and its ligand MadCAM-1, are also important for homing of donor T cells to Peyer’s patches during intestinal GVHD.527778

Prevention of GVHD

Based on the evidence from animal models regarding the central role of T cells in initiating GVHD, numerous clinical studies evaluating T cell depletion (TCD) as prophylaxis for GVHD were performed in the 1980’s and 1990’s. There were three principal TCD strategies: (1) negative selection of T cells ex vivo, (2) positive selection of CD34+ stem cells ex vivo; and (3) anti-T cell antibodies in vivo.83Most strategies showed a significant limitation in both acute and chronic GVHD.8488 Unfortunately, the lower incidence of severe GVHD was offset by high rates of graft failure, relapse of malignancy, infections, and Epstein-Barr virus-associated lymphoproliferative disorders. Negative selection purging strategies using various anti-T cell antibodies achieved similar long-term results regardless of the breadth of antibody specificity.8993 One large registry study demonstrated that purging strategies using antibodies with broad specificities produced inferior leukemia-free survival than standard immunosuppression in patients receiving unrelated donor transplants.94 Several studies have investigated partial T cell depletion, either by eliminating specific T cell subsets (e.g., CD8+) or by titrating the dose of T cells present in the inoculum.9597 None of these approaches, however, has convincingly demonstrated an optimal strategy that improves long-term survival.

Alemtuzumab is a monoclonal antibody that binds CD52, a protein expressed on a broad spectrum of leukocytes including lymphocytes, monocytes, and dendritic cells. Its use in GVHD prophylaxis in a Phase II trial decreased the incidence of acute and chronic GVHD following reduced intensity transplant.98 In two prospective studies, patients who received alemtuzumab rather than methotrexate showed significantly lower rates of acute and chronic GVHD,99 but experienced more infectious complications and higher rates of relapse, so that there was no overall survival benefit. Alemtuzumab may also contribute to graft failure when used with minimal intensity conditioning regimens.100

An alternative strategy to TCD attempted to induce anergy in donor T cells by ex vivo antibody blockade of co-stimulatory pathways prior to transplantation. A small study using this approach in haploidentical HCT recipients was quite encouraging, but has not yet been replicated.101 Thus the focus of most prevention strategies remains pharmacological manipulation of T cells after transplant.

Administration of anti-T cell antibodies in vivo as GVHD prophylaxis has also been extensively tested. The best studied drugs are anti-thymocyte globulin (ATG) or antilymphocyte globulin (ALG) preparations. These sera, which have high titers of polyclonal antibodies, are made by immunizing animals (horses or rabbits) to thymocytes or lymphocytes, respectively. A complicating factor in determining the role of these polyclonal sera in transplantation is the observation that even different brands of the same class of sera exert different biologic effects.102 However, the side effects of ATG/ALG infusions are common across different preparations and include fever, chills, headache, thrombocytopenia (from cross-reactivity to platelets), and, infrequently, anaphylaxis. In retrospective studies, rabbit ATG reduced the incidence of GVHD in related donor HSCT recipients without appearing to improve survival.103104 In recipients of unrelated donor HSCT, addition of ALG to standard GVHD prophylaxis effectively prevented severe GVHD, but did not result in improved survival because of increased infections.105 In a long term follow-up study, however, pretransplant ATG provided significant protection against extensive chronic GVHD and chronic lung dysfunction.106

The primary pharmacologic strategy to prevent GVHD is the inhibition of the cytoplasmic enzyme, calcineurin, that is critical for in the activation of T cells. The calcineurin inhibitors, cyclosporine and tacrolimus, have similar mechanisms of action, clinical effectiveness and toxicity profiles, including hypomagnesemia, hyperkalemia, hypertension, and nephrotoxicity.9107 Serious side effects include transplant-associated thrombotic microangiopathy (TAM) and neurotoxicity that can lead to premature discontinuation. Although clinically similar to thrombotic thrombocytopenic purpura, TAM does not reliably respond to therapeutic plasmapheresis, carries a high mortality rate, and removal of the offending agent does not always result in improvement.108 Posterior reversible encephalopathy syndrome includes mental status changes, seizures, neurological deficits and characteristic magnetic resonance imaging findings; this syndrome has been seen in 1-2% of HCT recipients receiving and calcineurin inhibitors.109 Side effects of these drugs decrease as the dose is tapered, usually two to four months after HCT.

Calcineurin inhibitors are often administered in combination with other immunosuppressants, such as methotrexate, which is given at low doses in the early post-transplant period.9107 The toxicities of methotrexate (neutropenia and mucositis) have led some investigators to replace it with mycophenolate mofetil (MMF). In one prospective randomized trial, patients who received MMF as part of GVHD prophylaxis experienced significantly less severe mucositis and more rapid neutrophil engraftment than those who received methotrexate.110 The incidence and severity of acute GVHD was similar between the two groups, but the study closed early due to superiority of the MMF arm with respect to reduced mucositis and the speed of hematopoietic engraftment. A desire for faster neutrophil engraftment has led to the use of MMF in UCB blood transplants where graft failure is a major concern.111 MMF is also often used after RIC regimens for similar reasons.112113

Sirolimus is an immunosuppressant that is structurally similar to tacrolimus but does not inhibit calcineurin. In a small Phase II trial, it showed excellent efficacy in combination with tacrolimus;114 the drug damages endothelial cells, however, and it may enhance TAM that is associated with calcineurin inhibitors.115 The combination of tacrolimus and sirolimus is currently being compared in a large randomized multi-center trial.

RIC regimens attempt to suppress the host immune system sufficiently so that donor T cells can engraft and then ablate the lympho-hematopoietic compartment of the recipient. The term “non-myeloablative” is therefore somewhat misleading. RIC regimens produce less tissue damage and lower levels of the inflammatory cytokines that are important in the initiation of GVHD pathophysiology; this effect may explain the reduced incidence of severe GVHD following RIC compared to the full intensity conditioning used in historical controls.98116 The onset of acute GVHD may be delayed after RIC until after day 100, however, and it may present simultaneously with elements of chronic GVHD (“overlap syndrome”).116120

Treatment of Acute GVHD

GVHD generally first develops in the second month after HCT, during continued treatment with calcineurin-based prophylaxis.23121 Steroids, with their potent antilymphocyte and anti-inflammatory activity, are the gold standard for treatment of GVHD. Many centers treat mild GVHD of the skin (Grade I) with topical steroids alone, but for more severe skin GVHD and any degree of visceral GVHD involvement, high-dose systemic steroids are usually initiated. Steroid therapy results in complete remission in less than half of the patients,122 and more severe GVHD is less likely to respond to treatment.123124 In a prospective randomized study, the addition of ATG to steroids as primary therapy did not increase the response rate.124 In a retrospective study, the use of ATG in patients who showed early signs of steroid-resistance was beneficial,122 but not all studies show such benefit and ATG is not standardly used because of increased infection risks.106125126.

An increasingly common treatment for GVHD is extracorporeal photopheresis (ECP). During ECP, the patient’s white blood cells are collected by apheresis, incubated with the DNA-intercalating agent, 8-methoxypsoralen, exposed to ultraviolet light (UVA), and returned to the patient. ECP is known to induce cellular apoptosis, which has strong anti-inflammatory effects in a number of systems, including prevention of rejection of solid organ grafts.127 Animal studies show that ECP reverses acute GVHD by increasing the number of regulatory T cells.128 A Phase II clinical study of steroid-dependent or steroid refractory GVHD showed resolution of GVHD in a large majority of patients, with 50% long-term survival in this very high risk group.129 Randomized multi-center studies of this approach are needed to determine its place in the management of acute GVHD.

Another interesting strategy to treat GVHD is the blockade of the inflammatory cytokine TNF-α. TNF-α can activate APCs, recruit effector cells and cause direct tissue damage.130 In animal models, TNF-α plays a central role in GVHD of the GI tract, which is central to the “cytokine storm” and plasma levels of TNFR I (a surrogate marker for TNF-α) rise in patients before the clinical manifestations of GVHD appear. 51 A recent Phase II trial of etanercept, a solubilized TNFR II, showed significant efficacy when added to systemic steroids as primary therapy for acute GVHD. Seventy percent of patients had complete resolution of all GVHD symptoms within one month, with 80% complete responses in the GI tract and the skin. The authors also showed that plasma levels of TNFR I were a significant biomarker for clinical GVHD.131

Treatment of Chronic GVHD

In contrast to acute GVHD, the pathophysiology of chronic GVHD remains poorly understood, and it is treated with a variety of immunosuppressive agents. The response of chronic GVHD to treatment is unpredictable, and mixed responses in different organs can occur in the same patient. Confounding variables such as infection and co-morbidities also make responses hard to measure. The use of corticosteroids (with or without a calcineurin inhibitor) is the standard of care, but a randomized trial of more than 300 patients with chronic GVHD found no difference between cyclosporine plus prednisone versus prednisone alone.132 Chronic immunosuppressants, especially those containing steroids, are highly toxic and result in infectious deaths. Many second line therapies have been studied, but none has achieved widespread acceptance. As mentioned above, ECP shows some promise, with significant response rates in high-risk patients. The best responses were observed in skin, liver, oral mucosa, eye, and lung.133 This observation is particularly relevant because lung GVHD has the potential to be a particularly devastating complication necessitating lung transplant as the only therapeutic option.134135

Essential Supportive Care in GVHD Patients

Meticulous supportive care is critical for patients with both acute and chronic GVHD because of the extended duration of immunosuppressive treatments and because the multiple medications required may have synergistic toxicities. Such care includes extensive infectious prophylaxis, early interventions in cases of suspected infections, and prophylaxis against non-infectious side effects of medications (See Table 3). These complications often require rapid responses to prevent serious or irreversible damage, and are best handled in close collaboration between the primary physician and the transplant specialist.

Table 3

Recommendations for Supportive Care

All patients should receive at least fluconazole as prophylaxis against fungal infections. Invasive molds, especially aspergillus, are common in patients with prolonged steroid use.136 Prophylaxis with voriconazole or posaconazole should be considered for these patients. Usual sites of infection are the lungs, sinuses, brain, skin,137 and serial galactomannan assays may aid in the early detection.138 Candida can cause lesions in the lung and spleen, which may need screening with ultrasonography. Pneumocystis is another opportunistic infection that should receive cotrimoxazol (bactrim) prophylaxis.139

Viral infections are frequent in these patients with GVHD. Cytomegalovirus causes interstitial pneumonia and gastritis. Patients who are at risk should have their blood monitored several times monthly. Techniques that directly detect virus should be performed, such as CMV PCR or pp65 antigen, and evidence of increased viral load should prompt preemptive treatment with ganciclovir or foscarnet prior to clinical manifestations of disease. Shingles is not uncommon and acyclovir prophylaxis may be beneficial.140 Patients and caregivers should receive vaccinations against influenza, and treatment with neuraminidase inhibitors is recommended in the event of influenza infection.141142

Patients with GVHD often have IgG2 and IgG4 subclass deficiencies despite normal lgG levels, making them susceptible to infections with encapsulated organisms. Treatment of severe hypogammaglobulinemia with intravenous immunoglobulin is standard in many centers,143 but the level that triggers replacement varies considerably among transplant specialists. There is little supporting evidence for the routine use of intravenous immunoglobulin as prophylaxis144 but patients should receive routine prophylaxis (penicillin or its equivalent) due to the increased risk of streptococcal sepsis.145 Pneumococcal conjugate and hemophilus influenza vaccine may provide additional protection and are also recommended for all patients, including those with chronic GVHD.139146147 The sites of any indwelling catheters should be assessed regularly and early treatment of a suspected infection initiated. Early signs or symptoms of septic shock such as shaking chills or low blood pressure requires prompt evaluation with chest X-ray and/or CT scan, blood culture and broad spectrum antibiotics because shock may progress rapidly in these patients.

9.3.5 Aspergillus Complicating Allogeneic Transplantation

Aspergillus infections in allogeneic stem cell transplant recipients: have we made any progress?

E Jantunen, V-J Anttila and T Ruutu
BMT 2002; 30(12):925-929

Invasive aspergillosis (IA) is common in allogeneic SCT recipients, with an incidence of 4-10%. The majority of these infections are diagnosed several months after SCT and they are frequently associated with GVHD. The diagnosis is difficult and often delayed. Established IA is notoriously difficult to treat with a death rate of 80-90%. This review summarises recent data on this problem to assess whether there has been any progress. Effective prophylactic measures are still lacking. Severe immunosuppression is the main obstacle to the success of therapy. Recent and ongoing developments in diagnostic measures and new antifungal agents may improve treatment results to some extent, but Aspergillus infections still remain a formidable problem in allogeneic transplantation. Further studies in this field will focus on the role of various cytokines and combinations of antifungal agents.


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