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Posts Tagged ‘cell movement and metastasis’


Metastatic Disease (4.3)

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

In the preceding discussions the hematological and nonhematological cancers were elaborated.  These were tumors of blood or solid tumors that are malignant.  Malignant solid tumors have a loss of normal architecture.  Malignant cancers of the blood forming organ also have a disruption of the architecture in the blood forming organs, and they are circulating elements that are either acutely increased in number or chronically increased to very high circulating counts as well as many cells in the marrow.  The diagnosis depends on the type of cell elements and the stage of maturation.  In the case of blood cell cancers, one might consider an intermediate stage that has a long course that is in the case of the myelogenous series, myeloid dysplasia, which includes myelofibrosis, which in either case is not a benign course. In the case of solid tumors, there is an anatomic structure of the cancer site.

The usual structure for a carcinoma is either adjoining cells surrounding a vascular supply, as in the liver, a parenchymal gland, as in pancreas, a tubular structure, as the gastrointestinal tract and lungs (which are embryologically and outpouching of the gut), or a skin surface.  In the case of carcinomas, the cells mature from a basement membrane of small flattened cells that overlie a fibrovascular matrix and an underlying myxoid stroma, perhaps beneath which is a muscular organ, then covered by a flat layer of cells. In the case of all epithelial structures there is an orderly maturation of epithelium from the basal layer to the mature epithelial cells that are elongate, have a brush border, and secrete into the glandular structure.  The cell maturation becomes disrupted and disorderly to different degrees in the development of malignancy from a dysplasia to low grade malignancy, to high grade anaplastic cancer.

The development of a cancer implies the loss of tissue architecture, the replication of cells, the development of a neoplasms circulation (which is the topic of vascular endothelial growth factor (VEGF)), the overgrowth of the circulation so that the tumor has insufficient blood supply, and vascular invasion.  We refer to the Warburg Hypothesis with respect to the malignancy relying on glycolysis in the presence of oxygen (aerobic glycolysis), but it may be questionable to imply that there is sufficient oxygen supply.  In some cases a cancer may occur from a longstanding inflammatory focus.  This has been seen to occur in osteomyelitis and in gastrointestinal fistulas.  The growth of a neoplasm, when it exceeds its blood supply, requires adaptive changes. The most obvious to consider would be a decreased reliance of mitochondrial respiration.  Warburg refer to the increase production of lactic acid as analogous to Pasteur observation of fermentation in yeast (Pasteur effect).  He measured the lactic acid production by various tissues, and the consumption with the oxygen consumption showed that in many tissues approximately two molecules of lactate are prevented from appearing when one molecule of oxygen is consumed – a relationship that Meyerhof had found in muscle. This he expressed as the “Meyerhof quotient”:

Anaerobic glycolysis – aerobic glycolysis/oxygen consumption

Ref: Otto Warburg: Cell Physiologist, Biochemist, and Eccentric
Hans Krebs in collaboration with Roswitha Schmid
Clarendon Press, Oxford, 1981. Pp 19-25.

The special feature of cancer cells was the high rate of glycolysis in the presence of oxygen, whereas muscle can form lactate from carbohydrate in the absence of oxygen. This led to the discovery that all animal tissues are capable of glycolysis both aerobically and anaerobically.  Pasteur had established 60 years earlier that the rates of fermentation are generally hiugh anaerobically, but low aerobically. This led Warburg to the conclusion that cancer cells are distinguished from noncancer cells by their failure to suppress glycolysis in the presence of oxygen. He discovered in 1926 that the link between respiration and fermentation can be severed by a specific inhibitor, ethylcarbylamine. He looked at carbylethylamine as an inhibitor of the ‘Pasteur effect’, and determined that the catalyst was a heavy metal ion. But the proposed mechanism was shown not to be correct by Engelhardt, Lynen, Bucher, Lowry, Racker, and Sols.The activity of the enzyme phospofructokinase is regulated by the concentrations of ATP, ADP and inorganic phosphate (Pi). The “allosteric properties” of PFK could account for the ‘Pasteur effect’.  ATP inactivates PFK, while ADP and Pi activate it. Further, etylcarbylamine was found to be an uncoupler of oxidative phosphorylation (OxPhos), but Warburg was right in postulating that a heavy metal was involved since heavy metals are involved in
OxPhos.  The explanation for this is now that when malignant transformation occurs, the cells’ energy supply is redirected from their normal function to growth. This change was found to be irreversible upon restoration of oxygen supply.

The topic of discussion is metastasis. What does it have to do with malignancy and respiration? Metastasis is the other key feature of cancer cells. What it has to do with respiration would probably tie in with the change in the cells’ energy supply that is directed toward proliferation. As the cell metabolism is reconfigured, there is also a change in the cell signaling with respect to apoptosis and the events regarding autophagy.  This has to extend beyond the mitochondria, mainly because autophagy involves mitophagy, the ER and the entire cytoskeleton.  This means that the cytoplasmic relationship to the intercellular matrix and the fibroblast stroma would have to be affected, as the cell breaks away from its close association with adjacent cells.  Cells can migrate to adjacent lymphatic structures, and either enter the circulation by way of the lymphatics or by invasion of the venous circulation directly. In any case, entry into the circulation allows for transport to distant sites.  With respect to migration to distant sites, we recall the hypothesis of Paget that the cells metastasize directly into the circulating blood, and they may ‘seed’ to favorable organs.

The discussion now turns to the assessment of apoptosis as a means to inhibition of cancer cell lines, which proliferate if unchecked and migrate away from the primary site.  I use a few examples from a symposium volume of the Annals of the New York Academy of Sciences:

Apoptosis: From Signaling Pathways to Therapeutic Tools.
Ed, Mark Diederich
ANYAA9 2003; 1010:1-799
The role of β-glucuronidase in induction of apoptosis by Genistein Combined Polysaccharide (GCP) in xenogenetic mice bearing human mammary cancer cells.
Yuan L, Wagatsuma C, Sun B, Kim Jung-Hwan, Surh Young-Joon
Ann NY Acad Sci 2003;1010: 347-349.
http://dx.doi.org:/10.1196/annals.1299.063

  • GCP inhibits tumor cell growth through multiple mechanisms, including induction of tumor apoptosis
  • The biological activities of genistein (aglycon) are more evident in tumor tissues than in normal tissues.
  • Hiugh doses of genistein administration rarely induces toxicity to normal tissues.
  • Higher levels of β-glucuronidase expression in tumor tissues results in more genistein aglycon, leading to tumor destruction.

Induction of apoptosis in human pancreatic cancer cells by docosahexanoic acid
Merendino N, Molinari R, Loppi B, Pessina G, D’Aquino M, Tomassi G, Velotti F.
Ibid 361-364. http://dx.doi.org:/10.1196/annals.1299.143

Polyunsaturated fatty acids have been indicated to induce anti-proliferative and/or apoptotic effects in various tumor cells. We showed that, at a 200-μM concentration, both alpha-linoleic (18:2 n-6; LA) or docosahexaenoic (22:6 n-3; DHA) acid inhibited cell growth, while only DHA induced apoptosis in the human Paca-44 pancreatic cancer cell line. Investigating the mechanism underlying DHA-induced apoptosis, we showed that DHA induced a rapid and dramatic (>60%) intracellular depletion of reduced glutathione (GSH), without affecting oxidized glutathione (GSSG). Moreover, using two specific inhibitors of carrier-mediated GSH extrusion, cystathionine or methionine, we observed that GSH depletion occurred via an active GSH extrusion, and that inhibition of GSH efflux completely reversed apoptosis. These results provide the first evidence for a possible causative role of GSH depletion in DHA-induced apoptosis.

Opposite phenotypes of cancer and aging arise from alternative regulation of common signaling pathways.
Ukraintseva SV1, Yashin AI.
Ann N Y Acad Sci. 2003 Dec; 1010:489-92.
http://dx.doi.org:/10.1196/annals.1299.089

Phenotypic features of malignant and senescent cells are in many instances opposite. Cancer cells do not “age”; their metabolic, proliferative, and growth characteristics are opposite to those observed with cellular aging (both replicative and functional). In many such characteristics cancer cells resemble embryonic cells. One can say that cancer manifests itself as a local, uncontrolled “rejuvenation” in an organism. Available evidence from human and animal studies suggests that the opposite phenotypic features of aging and cancer arise from the opposite regulation of genes participating in apoptosis/growth arrest or growth signal transduction pathways in cells. This fact may be applicable in the development of new anti-aging treatments. Genes that are contrarily regulated in cancer and aging cells (e.g., proto-oncogenes or tumor suppressors) could be candidate targets for anti-aging interventions. Their “cancer-like” regulation, if strictly controlled, might help to rejuvenate the human organism.

CUGBP2 Plays a Critical Role in Apoptosis of Breast Cancer Cells in Response to Genotoxic Injury
Mukhopadhyay D, Jung J, Murmu N, Houchen CW, Dieckgraefe BK, Anant A
Ibid 504–509. http://dx.doi.org:/10.1196/annals.1299.093

 Posttranscriptional control of gene expression plays a key role in regulating gene expression in cells undergoing apoptosis. Cyclooxygenase-2 (COX-2) is a crucial enzyme in the conversion of arachidonic acid to prostaglandin E2 (PGE2) and is significantly upregulated in many types of adenocarcinomas. COX-2 overexpression leads to increased PGE2 production, resulting in increased cellular proliferation. PGE2 enhances the resistance of cells to ionizing radiation. Accordingly, understanding mechanisms regulating COX-2 expression may lead to important therapeutic advances. Besides transcriptional control, COX-2 expression is significantly regulated by mRNA stability and translation. We have previously demonstrated that RNA binding protein CUGBP2 binds AU-rich sequences to regulate COX-2 mRNA translation. In the current study, we have determined that expression of both COX-2 mRNA and CUGBP2 mRNA are induced in MCF-7 cells, a breast cancer cell line, following exposure to 12 Gy γ-irradiation. However, only CUGBP2 protein is induced, but COX-2 protein levels were not altered. Silencer RNA (siRNA)-mediated inhibition of CUGBP2 reversed the block in COX-2 protein expression. Furthermore, MCF-7 cells underwent apoptosis in response to radiation injury, which was also reversed by CUGBP2 siRNAs. These data suggest that CUGBP2 is a critical regulator of the apoptotic response to genotoxic injury in breast cancer cells.

Multiple and synergistic deregulations of apoptosis-controlling genes in pancreatic carcinoma cells
A Trauzold,1 S Schmiedel,1 C Röder,1 C Tams,1 M Christgen,1 S Oestern,1 A Arlt,2 S Westphal,1 M Kapischke,1 H Ungefroren,1 and H Kalthoff1,
Ibid 510-513.  Br J Cancer. 2003 Nov 3; 89(9): 1714–1721.
http://dx.doi.org/10.1038%2Fsj.bjc.6601330

CD95, TRAIL-R1 (tumor necrosis factor-related apoptosis inducing ligand-receptor 1) and TRAIL-R2 are members of the TNF-receptor family of transmembrane proteins that are capable of inducing apoptosis (Wiley et al, 1995Pitti et al, 1996Pan et al, 1997Peter et al, 1998). Following ligand binding, the receptors oligomerize and the pro-apoptotic molecules TRADD, FADD and FLICE/caspase-8 are recruited to their intracellular death domain forming the ‘death-inducing signaling complex’ (DISC) (Krammer, 1999). The subsequent events leading to apoptosis depend on the specific cell type being challenged. In type I cells the bulk induction of caspase-8 at the DISC leads to the direct activation of the effector caspase 3. In type II cells only little amounts of caspase-8 are activated at the DISC requiring the pro-apoptotic mitochondrial amplification loop for efficient caspase-3 activation (Scaffidi et al, 1998).
In Vivo Imaging of Chemotherapy-Induced Apoptosis in Human Cancers
T Belhocine, N Steinmetz, A Green, P Rigo
Ibid 525-529. http://dx.doi.org:/10.1196/annals.1299.097

Rationale. Induction of apoptosis in sensitive tumor cells is the main mechanism of action of chemotherapy agents in human cancers. Also, the assessment of drug-induced apoptosis soon after chemotherapy may be an early predictor of treatment efficacy. Patients and Methods. A phase I/II study was prospectively conducted in 15 patients presenting with proven lung cancers (n= 10), breast cancers (n= 2), and lymphomas (n= 3) to assess the value of the 99mTc-radiolabeled recombinant human (rh) Annexin V for imaging apoptosis immediately after completion of the first course of chemotherapy. Early Annexin V findings post-chemotherapy (day+1, day+2) were also compared to the tumor status at 6 to 12 weeks post-treatment.
Results. All lung and lymphoma patients with an increased tracer uptake post-treatment (n= 8) had either partial or complete tumor response. Five patients with no tracer uptake had progressive disease. However, two breast cancers had a response to treatment, although no significant tracer uptake was observed. Tumor response and survival time were significantly correlated with the 99mTc-labeled Annexin V uptake. No serious events related to tracer administration were noted. Conclusion. Preliminary results of this pilot study demonstrate the feasibility of the 99mTc-labeled Annexin V uptake for the in vivo imaging of apoptosis after one course of chemotherapy. If confirmed on larger series, these promising results may open new perspectives in the management of oncology patients.

In vivo photoacoustic imaging of chemotherapy-induced apoptosis in squamous cell carcinoma using a near-infrared caspase-9 probe.
Yang Q1Cui HCai SYang XForrest ML.
J Biomed Opt. 2011 Nov; 16(11):116026.
http://dx.doi.org:/10.1117/1.3650240

Anti-cancer drugs typically exert their pharmacological effect on tumors by inducing apoptosis, or programmed cell death, within the cancer cells. However, no tools exist in the clinic for detecting apoptosis in real time. Microscopic examination of surgical biopsies and secondary responses, such as morphological changes, are used to verify efficacy of a treatment. Here, we developed a novel near-infrared dye-based imaging probe to directly detect apoptosis with high specificity in cancer cells by utilizing a noninvasive photoacoustic imaging (PAI) technique. Nude mice bearing head and neck tumors received cisplatin chemotherapy (10 mg/kg) and were imaged by PAI after tail vein injection of the contrast agent. In vivo PAI indicated a strong apoptotic response to chemotherapy on the peripheral margins of tumors, whereas untreated controls showed no contrast enhancement by PAI. The apoptotic status of the mouse tumor tissue was verified by immunohistochemical techniques staining for cleaved caspase-3 p11 subunit. The results demonstrated the potential of this imaging probe to guide the evaluation of chemotherapy treatment.

Noninvasive imaging techniques are necessary for early cancer detection and evaluation of the chemotherapeutic effect on tumors. Current diagnostic imaging techniques generally include γ-scintigraphy, magnetic resonance imaging, computed tomography, and ultrasonography; however, these techniques only give morphological information on the tumor. These techniques do not report the biochemical response of the tumor to treatment and physical changes in the tumor in response to treatment may take days to weeks to fully manifest. Positron emission topography and SPECT can indirectly detect tumor response to treatment due to changes in metabolic activity and blood perfusion, respectively. However, no clinical imaging technique can directly detect the biochemical response, e.g., apoptosis, of tumors to treatment. Since apoptosis often occurs within in the first 18 to 36 h after treatment, direct imaging of apoptosis would rapidly indicate if there is a response in the tumor to chemotherapy.

Photoacoustic imaging (PAI) overcomes the spatial and resolution limitations of conventional imaging techniques at a relatively low cost,12 and it has shown its potential to monitor the growth of melanoma brain tumors3 and melanoma metastasis in sentinel lymph nodes.4 However, ascribed to the fact that PAI utilizes the optical absorption of tissues for contrast, it cannot differentiate normal from cancerous cells unless the cells are overexpressing chromomeric marker (e.g., melanomas) or labeled by reporter moieties as contrast agent to enhance the contrast between normal and pathological tissues. In this case, application of a contrast agent such as fluorochromes is expected to facilitate both the visualization of head and neck squamous cell carcinoma (HNSCC) cancer cells and their response to treatment in vivo by PAI.

We have synthesized a near-infrared fluorescent imaging probe – IR780-linker-Val-Ala-Glu(OMe)-FMK by conjugating a fluorochrome (IR780) to Z-Val-Ala-Glu (OMe), a cell permeable caspase inhibitor. The activation of caspase family of cysteine proteases has been recognized as a critical event of apoptosis, which is a physiological process of type I programmed cell death. Typically anti-cancer agents act on cancer cells to induce apoptosis, so apoptosis is a rapid and definite indicator of tumor response. For this reason, apoptosis is used in screening drug candidates in cell culture. The fluoromethyl ketone of the tripeptides valine, alanine, and O-methyle-glutamic acid [Val-Ala-Glu(OMe)-FMK] can specifically and irreversibly bind to the cysteine residue at the active site of caspase-9.5 Our preliminary in vitro cell-imaging test with prostate cancer DU 145 cells demonstrated the sensitivity of this imaging probe for cell apoptosis.6 In this study, we evaluated the application of IR780-linker-Val-Ala-Glu(OMe)-FMK for PAI to detect procaspase-9 activation caused by anticancer drug treatment in living nude mice bearing HNSCC tumors.

Increase in PA amplitude within the HNSCC tumor after intravenous injection of imaging agent

Increase in PA amplitude within the HNSCC tumor after intravenous injection of imaging agent

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3221716/bin/JBOPFO-000016-116026_1-g002.jpg

Fourteen micron (thickness) sections of the tumor tissue were stained with a goat primary polyclonal antibody for cleaved caspase-3 p11 subunit (Asp-175-Ser-176) and a donkey anti-goat secondary antibody with a fluorescein isothiocyanate (FITC) fluorophore (Santa Cruz Biotechnology Inc., Santa Cruz, California). Cell nuclei were stained with 4,6-diamidino-2-phenylindole (DAPI).

Maximum amplitude projection images obtained from the PAI of the HNSCC tumor region shown in Fig. ​(Fig.2).2 were converted to grayscale images. The grayscale images at various time points were linearly aligned using the scale-invariant feature transform function of Fiji/ImageJA software (ver. 20110307, http://pacific.mpi-cbg.de/wiki/index.php/Fiji) (Fig. ​(Fig.3).3). Quantification of PA signal intensity within the tumor region was performed in triplet for each image by measuring the mean gray value (units: gray/pixel) of the circled tumor region. The extent of signal enhancement was calculated by normalizing the tumor signal against a background reading taken immediately before injection of the imaging agent (Fig. ​(Fig.2).2)

Apoptosis in the tumor tissues was independently verified by immunohistochemical staining for caspase 3, a downstream indicator of apoptosome-activated caspase-mediated apoptosis that would not cross-react with the caspase-9 PA probe. Figure ​(Figure4a) 4a represents a control section stained with the secondary antibody alone (autofluorescence of the tissue without apparent staining); while, Fig. ​(Fig.4b).4b shows the immunostaining of the caspase-3 p11 subunit (green) and the DAPI staining of cell nuclei. The intense green fluorescence in these sections suggests the wide spread apoptosis of cells in the tumor tissues after intravenous administration of high-dose cisplatin. In addition, cells on the peripheral of the tumor stained more strongly for caspase 3 (green fluorescence) compared to cells at the tumor interior. This was consistent with the PA imaging of apoptosis that showed strong apoptosis at the tumor peripheral, suggesting chemotherapeutics had penetrated the outer layers of the tumor and induced apoptosis.

Immunostaining for apoptosis in tumor

Immunostaining for apoptosis in tumor

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3221716/bin/JBOPFO-000016-116026_1-g004.jpg

Immunostaining for apoptosis in tumor. (a) Representative control section stained with secondary antibody alone and (b) tissue section of the HNSCC tumor stained for caspase-3 p11 subunit after cisplatin treatment.

I now consider mechanisms of metastasis as currently viewed.

Metastasis mechanisms.
Geiger TR1Peeper DS.
Biochim Biophys Acta. 2009 Dec; 1796(2):293-308.  http://dx.doi.org:/10.1016/j.bbcan.2009.07.006.

Metastasis, the spread of malignant cells from a primary tumor to distant sites, poses the biggest problem to cancer treatment and is the main cause of death of cancer patients. It occurs in a series of discrete steps, which have been modeled into a “metastatic cascade”. In this review, we comprehensively describe the molecular and cellular mechanisms underlying the different steps, including Epithelial-Mesenchymal Transition (EMT), invasion, anoikis, angiogenesis, transport through vessels and outgrowth of secondary tumors. Furthermore, we implement recent findings that have broadened and challenged the classical view on the metastatic cascade, for example the establishment of a “premetastatic niche”, the requirement of stem cell-like properties, the role of the tumor stroma and paracrine interactions of the tumor with cells in distant anatomical sites. A better understanding of the molecular processes underlying metastasis will conceivably present us with novel targets for therapeutic intervention.

Axis of evil: molecular mechanisms of cancer metastasis Thomas Bogenrieder1 and Meenhard Herlyn1
Oncogene (2003) 22, 6524–6536.
http://dx.doi.org:/doi:10.1038/sj.onc.1206757

Although the genetic basis of tumorigenesis may vary greatly between different cancer types, the cellular and molecular steps required for metastasis are similar for all cancer cells. Not surprisingly, the molecular mechanisms that propel invasive growth and metastasis are also found in embryonic development, and to a less perpetual extent, in adult tissue repair processes. It is increasingly apparent that the stromal microenvironment, in which neoplastic cells develop, profoundly influences many steps of cancer progression, including the ability of tumor cells to metastasize. In carcinomas, the influences of the microenvironment are mediated, in large part, by bidirectional interactions (adhesion, survival, proteolysis, migration, immune escape mechanisms lymph-/angiogenesis, and homing on target organs) between epithelial tumor cells and neighboring stromal cells, such as fibroblasts as well as endothelial and immune cells. In this review, we summarize recent advances in understanding the molecular mechanisms that govern this frequently lethal metastatic progression along an axis from primary tumor to regional lymph nodes to distant organ sites. Affected proteins include growth factor signaling molecules, chemokines, cell–cell adhesion molecules (cadherins, integrins) as well as extracellular proteases (matrix metalloproteinases). We then discuss promising new therapeutic approaches targeting the microenvironment. We note, however, that there is still too little knowledge of how the many events are coordinated and integrated by the cancer cell, with conspiratorial help by the stromal component of the host. Before drug development can proceed with a legitimate chance of success, significant gaps in basic knowledge need to be filled.

Metastases to regional lymph nodes are detected at diagnosis and surgery in approximately one-third of breast, colorectal, uterine cervix, and oral cavity and pharynx cancer patients, and one-quarter of esophageal, lung pancreas, gastric and bladder cancer patients (Greenlee et al., 2001). The high mortality rates associated with cancer are caused by the metastatic spread of tumor cells from the site of their origin. In fact, metastases are the cause of 90% of cancer deaths (Hanahan and Weinberg, 2000). The prognosis for a patient who is diagnosed with advanced invasive or metastatic disease remains little better than it was decades ago (Sporn, 1997). Tumor cells invade either the blood or lymphatic vessels to access the general circulation and then establish themselves in other (visceral) tissues. Ultimately, they become surgically unresectable, with pharmacological or radiological long-term control being uncommon (Stacker et al., 2002).

Although the genetic basis of tumorigenesis may vary greatly between different cancer types, the cellular and molecular steps required for metastasis are generally similar for all solid tumor cells (Woodhouse et al., 1997Liotta and Kohn, 2003). Not surprisingly, the molecular mechanisms that propel invasive growth and metastasis are also found in embryonic development, and, however to a less perpetual/chronic/aggressive/quantitatively different extent, in adult tissue maintenance (e.g. involving stem cell differentiation) and repair processes (‘tumors are wounds that do not heal’) (Dvorak, 1986). We now view cancer as a complex tissue resulting from disrupted organ homeostasis, rather than focusing on the cancer cell, and the genes within it, alone (Hanahan and Weinberg, 2000;Bissell and Radisky, 2001Bogenrieder and Herlyn, 2002Wiseman and Werb, 2002). Normal tissue homeostasis is maintained between epithelial cells and their microenvironment, such as fibroblasts, endothelial and immunocompetent cells, and the extracellular matrix (ECM). Similarly, during malignant transformation and progression, there are (however deregulated) reciprocal and conspirational interactions between the neoplastic cells and the adjacent stromal cells (Hsu et al., 2002). A series of recent investigations have shown that aberrations in the stroma can both precede and stimulate the development of cancers (reviewed in Bissell and Radisky, 2001Wiseman and Werb, 2002).

The process of metastasis involves an intricate interplay between altered cell adhesion, survival, proteolysis, migration, lymph-/angiogenesis (see articles in this issue by R Kerbel and P Campochiaro, pp. NNN–NNN), immune escape mechanisms, and homing on target organs (Table 1). However, there is still very little knowledge of how these events are coordinated by the cancer cell, with conspirational help by the stromal component (microenvironment) of the host (Clark, 1991Hsu et al., 2002). This process is usually said to be ‘uncontrolled’. As we shall see, however, it is by no means purely stochastic, but rather a finely tuned molecular machinery with active tumor cell–host collaboration. Thus, all explanations of ‘success’ of the metastatic axis contain a strong element of determinism. Whereas the early steps in the metastastic campaign are completed very efficiently, metastasis is an inefficient process in its later steps, especially the regulation of cancer cell growth at the secondary sites (Luzzi et al., 1998Cameron et al., 2000Chambers et al., 2002). Given that spread of the tumor to distant organs is usually lethal, more intense studies of these molecular mechanisms assume general importance to develop more effective anticancer strategies. In the following discussion of specific molecular mechanisms, we have often chosen to draw mainly from examples that pertain to melanoma progression, although similar processes are most likely also operating during oncogenesis of a wide range of cancers.

The classical metastatic cascade encompasses intravasation by tumor cells, their circulation in lymph and blood vascular systems, arrest in distant organs, extravasation, and growth into metastatic foci (Herlyn and Malkowicz, 1991;Woodhouse et al., 1997). Ann Chambers et al. (2001),(2002) have demonstrated in murine models that the limiting factor for metastasis formation is growth after extravasation (Figure 1a). Recently, this extravasation model has been challenged by Ruth Muschel and co-workers (Al-Mehdi et al., 2000Wong et al., 2002), who showed that tumor cells can readily proliferate after arrest in blood vessels, suggesting that extravasation is not a prerequisite for metastatic growth (Figure 1b). In a separate series of experiments, Mary Hendrix and co-workers described that tumor cells can even have endothelial cell-like functions and form channels that allow fluid flow (Maniotis et al., 1999Folberg et al., 2000) (Figure 1c). The group has identified some of the players, such as EphA2 and VE-cadherin, on aggressive melanoma cells that are shared with endothelial cells and that are likely involved in ‘vasculogenic mimicry’. Vasculogenic mimicry is the ability of aggressive cancer cells to form de novo vessel-like networks in vitro in the absence of endothelial cells or fibroblasts, concomitant with their expression of vascular-associated cellular marker (Sood et al., 2001,2002). Tumor cell plasticity is demonstrated by the ability of tumor cells to adopt a variety of phenotypes, including an endothelial phenotype (Sood et al., 2001, 2002). These exciting new findings underscore the plasticity of malignant cells from advanced tumor progression stages, and they require from tumor biologists a more dynamic view of the metastatic cascade. If the biological phenotype of metastasis must be portrayed flexibly, then we need a new ‘yardstick,’ a normal cell, to better characterize and understand the many faces of metastasis. We need to understand how the malignant cells exert cooperation from the normal cells. Our central hypothesis is that both normal and malignant cells utilize the same molecules for invasion, but that differences in downstream signaling events allow the tumor cells to dominate over normal cells in the microenvironment. This ‘dominant plasticity’ model of cancer metastasis takes into account the flexible response of malignant cells to microenvironmental pressures while maintaining dominance over the normal parenchymal and stromal cells.

Models of metastasis

Models of metastasis

http://www.nature.com/onc/journal/v22/n42/images/1206757f1.jpg

Models of metastasis. (a) According to Chambers and co-workers, only a very small population of injected cells (2%) form micrometastases, although over 87% are arrested in the liver. Furthermore, not all of the micrometastases persist, and the progressively growing metastases that kill the mice arise only from a small subset (0.02%) of the injected cells. (b) Muschel and co-workers recently proposed a new model for pulmonary metastasis in which endothelium-attached tumor cells that survived the initial apoptotic stimuli proliferate intravascularly. Thus, a principal tenet of this new model is that the extravasation of tumor cells is not a prerequisite for metastatic colony formation and that the initial proliferation takes place within the blood vessels. (c) The unique ability of aggressive tumor cells to generate patterned networks, similar to the patterned networks during embryonic vasculogenesis, and concomitantly to express vascular markers associated with endothelial cells, their precursors and other vascular cells has been termed ‘vasculogenic mimicry’ by Hendrix and co-workers

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Introduction – The Evolution of Cancer Therapy and Cancer Research: How We Got Here?


Introduction – The Evolution of Cancer Therapy and Cancer Research: How We Got Here?

Author and Curator: Larry H Bernstein, MD, FCAP

The evolution of progress we have achieved in cancer research, diagnosis, and therapeutics has  originated from an emergence of scientific disciplines and the focus on cancer has been recent. We can imagine this from a historical perspective with respect to two observations. The first is that the oldest concepts of medicine lie with the anatomic dissection of animals and the repeated recurrence of war, pestilence, and plague throughout the middle ages, and including the renaissance.  In the awakening, architecture, arts, music, math, architecture and science that accompanied the invention of printing blossomed, a unique collaboration of individuals working in disparate disciplines occurred, and those who were privileged received an education, which led to exploration, and with it, colonialism.  This also led to the need to increasingly, if not without reprisal, questioning long-held church doctrines.

It was in Vienna that Rokitansky developed the discipline of pathology, and his student Semelweis identified an association between then unknown infection and childbirth fever. The extraordinary accomplishments of John Hunter in anatomy and surgery came during the twelve years war, and his student, Edward Jenner, observed the association between cowpox and smallpox resistance. The development of a nursing profession is associated with the work of Florence Nightengale during the Crimean War (at the same time as Leo Tolstoy). These events preceded the work of Pasteur, Metchnikoff, and Koch in developing a germ theory, although Semelweis had committed suicide by infecting himself with syphilis. The first decade of the Nobel Prize was dominated by discoveries in infectious disease and public health (Ronald Ross, Walter Reed) and we know that the Civil War in America saw an epidemic of Yellow Fever, and the Armed Services Medical Museum was endowed with a large repository of osteomyelitis specimens. We also recall that the Russian physician and playwriter, Anton Checkov, wrote about the conditions in prison camps.

But the pharmacopeia was about to open with the discoveries of insulin, antibiotics, vitamins, thyroid action (Mayo brothers pioneered thyroid surgery in the thyroid iodine-deficient midwest), and pitutitary and sex hormones (isolatation, crystal structure, and synthesis years later), and Karl Landsteiner’s discovery of red cell antigenic groups (but he also pioneered in discoveries in meningitis and poliomyelitis, and conceived of the term hapten) with the introduction of transfusion therapy that would lead to transplantation medicine.  The next phase would be heralded by the discovery of cancer, which was highlighted by the identification of leukemia by Rudolph Virchow, who cautioned about the limitations of microscopy. This period is highlighted by the classic work – “Microbe Hunters”.

John Hunter

John Hunter

Walter Reed

Walter Reed

Robert Koch

Robert Koch

goldberger 1916 Pellagra

goldberger 1916 Pellagra

Louis Pasteur

Louis Pasteur

A multidisciplinary approach has led us to a unique multidisciplinary or systems view of cancer, with different fields of study offering their unique expertise, contributions, and viewpoints on the etiology of cancer.  Diverse fields in immunology, biology, biochemistry, toxicology, molecular biology, virology, mathematics, social activism and policy, and engineering have made such important contributions to our understanding of cancer, that without cooperation among these diverse fields our knowledge of cancer would never had evolved as it has. In a series of posts “Heroes in Medical Research:” the work of researchers are highlighted as examples of how disparate scientific disciplines converged to produce seminal discoveries which propelled the cancer field, although, at the time, they seemed like serendipitous findings.  In the post Heroes in Medical Research: Barnett Rosenberg and the Discovery of Cisplatin (Translating Basic Research to the Clinic) discusses the seminal yet serendipitous discoveries by bacteriologist Dr. Barnett Rosenberg, which eventually led to the development of cisplatin, a staple of many chemotherapeutic regimens. Molecular biologist Dr. Robert Ting, working with soon-to-be Nobel Laureate virologist Dr. James Gallo on AIDS research and the associated Karposi’s sarcoma identified one of the first retroviral oncogenes, revolutionizing previous held misconceptions of the origins of cancer (described in Heroes in Medical Research: Dr. Robert Ting, Ph.D. and Retrovirus in AIDS and Cancer).   Located here will be a MONTAGE of PHOTOS of PEOPLE who made seminal discoveries and contributions in every field to cancer   Each of these paths of discovery in cancer research have led to the unique strategies of cancer therapeutics and detection for the purpose of reducing the burden of human cancer.  However, we must recall that this work has come at great cost, while it is indeed cause for celebration. The current failure rate of clinical trials at over 70 percent, has been a cause for disappointment, and has led to serious reconsideration of how we can proceed with greater success. The result of the evolution of the cancer field is evident in the many parts and chapters of this ebook.  Volume 4 contains chapters that are in a predetermined order:

  1. The concepts of neoplasm, malignancy, carcinogenesis,  and metastatic potential, which encompass:

(a)     How cancer cells bathed in an oxygen rich environment rely on anaerobic glycolysis for energy, and the secondary consequences of cachexia and sarcopenia associated with progression

invasion

invasion

ARTS protein and cancer

ARTS protein and cancer

Glycolysis

Glycolysis

Krebs cycle

Krebs cycle

Metabolic control analysis of respiration in human cancer tissue

Metabolic control analysis of respiration in human cancer tissue

akip1-expression-modulates-mitochondrial-function

akip1-expression-modulates-mitochondrial-function

(b)     How advances in genetic analysis, molecular and cellular biology, metabolomics have expanded our basic knowledge of the mechanisms which are involved in cellular transformation to the cancerous state.

nucleotides

nucleotides

Methylation of adenine

Methylation of adenine

ampk-and-ampk-related-kinase-ark-family-

ampk-and-ampk-related-kinase-ark-family-

ubiquitylation

ubiquitylation

(c)  How molecular techniques continue to advance our understanding  of how genetics, epigenetics, and alterations in cellular metabolism contribute to cancer and afford new pathways for therapeutic intervention.

 genomic effects

genomic effects

LKB1AMPK pathway

LKB1AMPK pathway

mutation-frequencies-across-12-cancer-types

mutation-frequencies-across-12-cancer-types

AMPK-activating drugs metformin or phenformin might provide protection against cancer

AMPK-activating drugs metformin or phenformin might provide protection against cancer

pim2-phosphorylates-pkm2-and-promotes-glycolysis-in-cancer-cells

pim2-phosphorylates-pkm2-and-promotes-glycolysis-in-cancer-cells

pim2-phosphorylates-pkm2-and-promotes-glycolysis-in-cancer-cells

pim2-phosphorylates-pkm2-and-promotes-glycolysis-in-cancer-cells

2. The distinct features of cancers of specific tissue sites of origin

3.  The diagnosis of cancer by

(a)     Clinical presentation

(b)     Age of onset and stage of life

(c)     Biomarker features

hairy cell leukemia

hairy cell leukemia

lymphoma leukemia

lymphoma leukemia

(d)     Radiological and ultrasound imaging

  1. Treatments
  2. Prognostic differences within and between cancer types

We have introduced the emergence of a disease of great complexity that has been clouded in more questions than answers until the emergence of molecular biology in the mid 20th century, and then had to await further discoveries going into the 21st century.  What gave the research impetus was the revelation of

1     the mechanism of transcription of the DNA into amino acid sequences

Proteins in Disease

Proteins in Disease

2     the identification of stresses imposed on cellular function

NO beneficial effects

NO beneficial effects

3     the elucidation of the substructure of the cell – cell membrane, mitochondria, ribosomes, lysosomes – and their functions, respectively

pone.0080815.g006  AKIP1 Expression Modulates Mitochondrial Function

AKIP1 Expression Modulates Mitochondrial Function

4     the elucidation of oligonucleotide sequences

nucleotides

nucleotides

dna-replication-unwinding

dna-replication-unwinding

dna-replication-ligation

dna-replication-ligation

dna-replication-primer-removal

dna-replication-primer-removal

dna-replication-leading-strand

dna-replication-leading-strand

dna-replication-lagging-strand

dna-replication-lagging-strand

dna-replication-primer-synthesis

dna-replication-primer-synthesis

dna-replication-termination

dna-replication-termination

5     the further elucidation of functionally relevant noncoding lncDNA

lncRNA-s   A summary of the various functions described for lncRNA

6     the technology to synthesis mRNA and siRNA sequences

RNAi_Q4 Primary research objectives

Figure. RNAi and gene silencing

7     the repeated discovery of isoforms of critical enzymes and their pleiotropic properties

8.     the regulatory pathways involved in signaling

signaling pathjways map

Figure. Signaling Pathways Map

This is a brief outline of the modern progression of advances in our understanding of cancer.  Let us go back to the beginning and check out a sequence of  Nobel Prizes awarded and related discoveries that have a historical relationship to what we know.  The first discovery was the finding by Louis Pasteur that fungi that grew in an oxygen poor environment did not put down filaments.  They did not utilize oxygen and they produced used energy by fermentation.  This was the basis for Otto Warburg sixty years later to make the comparison to cancer cells that grew in the presence of oxygen, but relied on anaerobic glycolysis. He used a manometer to measure respiration in tissue one cell layer thick to measure CO2 production in an adiabatic system.

video width=”1280″ height=”720″ caption=”1741-7007-11-65-s1 Macromolecular juggling by ubiquitylation enzymes.” mp4=”https://pharmaceuticalintelligence.files.wordpress.com/2014/04/1741-7007-11-65-s1-macromolecular-juggling-by-ubiquitylation-enzymes.mp4“][/video]

An Introduction to the Warburg Apparatus

http://www.youtube.com/watch?v=M-HYbZwN43o

Lavoisier Antoine-Laurent and Laplace Pierre-Simon (1783) Memoir on heat. Mémoirs de l’Académie des sciences. Translated by Guerlac H, Neale Watson Academic Publications, New York, 1982.

Instrumental background 200 years later:   Gnaiger E (1983) The twin-flow microrespirometer and simultaneous calorimetry. In Gnaiger E, Forstner H, eds. Polarographic Oxygen Sensors. Springer, Heidelberg, Berlin, New York: 134-166.

otto_heinrich_warburg

otto_heinrich_warburg

Warburg apparatus

The Warburg apparatus is a manometric respirometer which was used for decades in biochemistry for measuring oxygen consumption of tissue homogenates or tissue slices.

The Warburg apparatus has its name from the German biochemist Otto Heinrich Warburg (1883-1970) who was awarded the Nobel Prize in physiology or medicine in 1931 for his “discovery of the nature and mode of action of the respiratory enzyme” [1].

The aqueous phase is vigorously shaken to equilibrate with a gas phase, from which oxygen is consumed while the evolved carbon dioxide is trapped, such that the pressure in the constant-volume gas phase drops proportional to oxygen consumption. The Warburg apparatus was introduced to study cell respiration, i.e. the uptake of molecular oxygen and the production of carbon dioxide by cells or tissues. Its applications were extended to the study of fermentation, when gas exchange takes place in the absence of oxygen. Thus the Warburg apparatus became established as an instrument for both aerobic and anaerobic biochemical studies [2, 3].

The respiration chamber was a detachable glass flask (F) equipped with one or more sidearms (S) for additions of chemicals and an open connection to a manometer (M; pressure gauge). A constant temperature was provided by immersion of the Warburg chamber in a constant temperature water bath. At thermal mass transfer equilibrium, an initial reading is obtained on the manometer, and the volume of gas produced or absorbed is determined at specific time intervals. A limited number of ‘titrations’ can be performed by adding the liquid contained in a side arm into the main reaction chamber. A Warburg apparatus may be equipped with more than 10 respiration chambers shaking in a common water bath.   Since temperature has to be controlled very precisely in a manometric approach, the early studies on mammalian tissue respiration were generally carried out at a physiological temperature of 37 °C.

The Warburg apparatus has been replaced by polarographic instruments introduced by Britton Chance in the 1950s. Since Chance and Williams (1955) measured respiration of isolated mitochondria simultaneously with the spectrophotometric determination of cytochrome redox states, a water chacket could not be used, and measurements were carried out at room temperature (or 25 °C). Thus most later studies on isolated mitochondria were shifted to the artifical temperature of 25 °C.

Today, the importance of investigating mitochondrial performance at in vivo temperatures is recognized again in mitochondrial physiology.  Incubation times of 1 hour were typical in experiments with the Warburg apparatus, but were reduced to a few or up to 20 min, following Chance and Williams, due to rapid oxygen depletion in closed, aqueous phase oxygraphs with high sample concentrations.  Today, incubation times of 1 hour are typical again in high-resolution respirometry, with low sample concentrations and the option of reoxygenations.

“The Nobel Prize in Physiology or Medicine 1931”. Nobelprize.org. 27 Dec 2011 www.nobelprize.org/nobel_prizes/medicine/laureates/1931/

  1. Oesper P (1964) The history of the Warburg apparatus: Some reminiscences on its use. J Chem Educ 41: 294.
  2. Koppenol WH, Bounds PL, Dang CV (2011) Otto Warburg’s contributions to current concepts of cancer metabolism. Nature Reviews Cancer 11: 325-337.
  3. Gnaiger E, Kemp RB (1990) Anaerobic metabolism in aerobic mammalian cells: information from the ratio of calorimetric heat flux and respirometric oxygen flux. Biochim Biophys Acta 1016: 328-332. – “At high fructose concen­trations, respiration is inhibited while glycolytic end products accumulate, a phenomenon known as the Crabtree effect. It is commonly believed that this effect is restric­ted to microbial and tumour cells with uniquely high glycolytic capaci­ties (Sussman et al, 1980). How­ever, inhibition of respiration and increase of lactate production are observed under aerobic condi­tions in beating rat heart cell cultures (Frelin et al, 1974) and in isolated rat lung cells (Ayuso-Parrilla et al, 1978). Thus, the same general mechanisms respon­sible for the integra­tion of respiration and glycolysis in tumour cells (Sussman et al, 1980) appear to be operating to some extent in several isolated mammalian cells.”

Mitochondria are sometimes described as “cellular power plants” because they generate most of the cell’s supply of adenosine triphosphate (ATP), used as a source of chemical energy.[2] In addition to supplying cellular energy, mitochondria are involved in other tasks such as signalingcellular differentiationcell death, as well as the control of the cell cycle and cell growth.[3]   The organelle is composed of compartments that carry out specialized functions. These compartments or regions include the outer membrane, the intermembrane space, the inner membrane, and the cristae and matrix. Mitochondrial proteins vary depending on the tissue and the species. In humans, 615 distinct types of proteins have been identified from cardiac mitochondria,[9   Leonor Michaelis discovered that Janus green can be used as a supravital stain for mitochondria in 1900.  Benjamin F. Kingsbury, in 1912, first related them with cell respiration, but almost exclusively based on morphological observations.[13] In 1913 particles from extracts of guinea-pig liver were linked to respiration by Otto Heinrich Warburg, which he called “grana”. Warburg and Heinrich Otto Wieland, who had also postulated a similar particle mechanism, disagreed on the chemical nature of the respiration. It was not until 1925 when David Keilin discovered cytochromes that the respiratory chain was described.[13]    

The Clark Oxygen Sensor

Dr. Leland Clark – inventor of the “Clark Oxygen Sensor” (1954); the Clark type polarographic oxygen sensor remains the gold standard for measuring dissolved oxygen in biomedical, environmental and industrial applications .   ‘The convenience and simplicity of the polarographic ‘oxygen electrode’ technique for measuring rapid changes in the rate of oxygen utilization by cellular and subcellular systems is now leading to its more general application in many laboratories. The types and design of oxygen electrodes vary, depending on the investigator’s ingenuity and specific requirements of the system under investigation.’Estabrook R (1967) Mitochondrial respiratory control and the polarographic measurement of ADP:O ratios. Methods Enzymol. 10: 41-47.   “one approach that is underutilized in whole-cell bioenergetics, and that is accessible as long as cells can be obtained in suspension, is the oxygen electrode, which can obtain more precise information on the bioenergetic status of the in situ mitochondria than more ‘high-tech’ approaches such as fluorescent monitoring of Δψm.” Nicholls DG, Ferguson S (2002) Bioenergetics 3. Academic Press, London.

Great Figures in Cancer

Dr. Elizabeth Blackburn,

Dr. Elizabeth Blackburn,

j_michael_bishop onogene

j_michael_bishop onogene

Harold Varmus

Harold Varmus

Potts and Habener (PTH mRNA, Harvard MIT)  JCI

Potts and Habener (PTH mRNA, Harvard MIT) JCI

JCI Fuller Albright and hPTH AA sequence

JCI Fuller Albright and hPTH AA sequence

Dr. E. Donnall Thomas  Bone Marrow Transplants

Dr. E. Donnall Thomas Bone Marrow Transplants

Dr Haraldzur Hausen  EBV HPV

Dr Haraldzur Hausen EBV HPV

Dr. Craig Mello

Dr. Craig Mello

Dorothy Hodgkin  protein crystallography

Lee Hartwell - Hutchinson Cancer Res Center

Lee Hartwell – Hutchinson Cancer Res Center

Judah Folkman, MD

Judah Folkman, MD

Gertrude B. Elien (1918-1999)

Gertrude B. Elien (1918-1999)

The Nobel Prize in Physiology or Medicine 1922   

Archibald V. Hill, Otto Meyerhof

AV Hill –

“the production of heat in the muscle” Hill started his research work in 1909. It was due to J.N. Langley, Head of the Department of Physiology at that time that Hill took up the study on the nature of muscular contraction. Langley drew his attention to the important (later to become classic) work carried out by Fletcher and Hopkins on the problem of lactic acid in muscle, particularly in relation to the effect of oxygen upon its removal in recovery. In 1919 he took up again his study of the physiology of muscle, and came into close contact with Meyerhof of Kiel who, approaching the problem differently, arrived at results closely analogous to his study. In 1919 Hill’s friend W. Hartree, mathematician and engineer, joined in the myothermic investigations – a cooperation which had rewarding results.

Otto Meyerhof

otto-fritz-meyerhof

otto-fritz-meyerhof

lactic acid production in muscle contraction Under the influence of Otto Warburg, then at Heidelberg, Meyerhof became more and more interested in cell physiology.  In 1923 he was offered a Professorship of Biochemistry in the United States, but Germany was unwilling to lose him.  In 1929 he was he was placed in charge of the newly founded Kaiser Wilhelm Institute for Medical Research at Heidelberg.  From 1938 to 1940 he was Director of Research at the Institut de Biologie physico-chimique at Paris, but in 1940 he moved to the United States, where the post of Research Professor of Physiological Chemistry had been created for him by the University of Pennsylvania and the Rockefeller Foundation.  Meyerhof’s own account states that he was occupied chiefly with oxidation mechanisms in cells and with extending methods of gas analysis through the calorimetric measurement of heat production, and especially the respiratory processes of nitrifying bacteria. The physico-chemical analogy between oxygen respiration and alcoholic fermentation caused him to study both these processes in the same subject, namely, yeast extract. By this work he discovered a co-enzyme of respiration, which could be found in all the cells and tissues up till then investigated. At the same time he also found a co-enzyme of alcoholic fermentation. He also discovered the capacity of the SH-group to transfer oxygen; after Hopkins had isolated from cells the SH bodies concerned, Meyerhof showed that the unsaturated fatty acids in the cell are oxidized with the help of the sulfhydryl group. After studying closer the respiration of muscle, Meyerhof investigated the energy changes in muscle. Considerable progress had been achieved by the English scientists Fletcher and Hopkins by their recognition of the fact that lactic acid formation in the muscle is closely connected with the contraction process. These investigations were the first to throw light upon the highly paradoxical fact, already established by the physiologist Hermann, that the muscle can perform a considerable part of its external function in the complete absence of oxygen.

But it was indisputable that in the last resort the energy for muscle activity comes from oxidation, so the connection between activity and combustion must be an indirect one, and observed that in the absence of oxygen in the muscle, lactic acid appears, slowly in the relaxed state and rapidly in the active state, disappearing in the presence of oxygen. Obviously, then, oxygen is involved when muscle is in the relaxed state. http://upload.wikimedia.org/wikipedia/commons/e/e1/Glycolysis.jpg

The Nobel Prize committee had been receiving nominations intermittently for the previous 14 years (for Eijkman, Funk, Goldberger, Grijns, Hopkins and Suzuki but, strangely, not for McCollum in this period). Tthe Committee for the 1929 awards apparently agreed that it was high time to honor the discoverer(s) of vitamins; but who were they? There was a clear case for Grijns, but he had not been re-nominated for that particular year, and it could be said that he was just taking the relatively obvious next steps along the new trail that had been laid down by Eijkman, who was also now an old man in poor health, but there was no doubt that he had taken the first steps in the use of an animal model to investigate the nutritional basis of a clinical disorder affecting millions. Goldberger had been another important contributor, but his recent death put him out of consideration. The clearest evidence for lack of an unknown “something” in a mammalian diet was presented by Gowland Hopkins in 1912. This Cambridge biochemist was already well known for having isolated the amino acid tryptophan from a protein and demonstrated its essential nature. He fed young rats on an experimental diet, half of them receiving a daily milk supplement, and only those receiving milk grew well, Hopkins suggested that this was analogous to human diseases related to diet, as he had suggested already in a lecture published in 1906. Hopkins, the leader of the “dynamic biochemistry” school in Britain and an influential advocate for the importance of vitamins, was awarded the prize jointly with Eijkman. A door was opened. Recognition of work on the fat-soluble vitamins begun by McCollum. The next award related to vitamins was given in 1934 to George WhippleGeorge Minot and William Murphy “for their discoveries concerning liver therapy in cases of [then incurable pernicious] anemia,” The essential liver factor (cobalamin, or vitamin B12) was isolated in 1948, and Vitamin B12  was absent from plant foods. But William Castle in 1928 had demonstrated that the stomachs of pernicious anemia patients were abnormal in failing to secrete an “intrinsic factor”.

1937   Albert von Szent-Györgyi Nagyrápolt

” the biological combustion processes, with special reference to vitamin C and the catalysis of fumaric acid”

http://www.biocheminfo.org/klotho/html/fumarate.html

structure of fumarate

Szent-Györgyi was a Hungarian biochemist who had worked with Otto Warburg and had a special interest in oxidation-reduction mechanisms. He was invited to Cambridge in England in 1927 after detecting an antioxidant compound in the adrenal cortex, and there, he isolated a compound that he named hexuronic acid. Charles Glen King of the University of Pittsburgh reported success In isolating the anti-scorbutic factor in 1932, and added that his crystals had all the properties reported by Szent-Györgyi for hexuronic acid. But his work on oxidation reactions was also important. Fumarate is an intermediate in the citric acid cycle used by cells to produce energy in the form of adenosine triphosphate (ATP) from food. It is formed by the oxidation of succinate by the enzyme succinate dehydrogenase. Fumarate is then converted by the enzyme fumarase to malate. An enzyme adds water to the fumarate molecule to form malate. The malate is created by adding one hydrogen atom to a carbon atom and then adding a hydroxyl group to a carbon next to a terminal carbonyl group.

In the same year, Norman Haworth from the University of Birmingham in England received a Nobel prize from the Chemistry Committee for having advanced carbohydrate chemistry and, specifically, for having worked out the structure of Szent-Györgyi’s crystals, and then been able to synthesize the vitamin. This was a considerable achievement. The Nobel Prize in Chemistry was shared with the Swiss organic chemist Paul Karrer, cited for his work on the structures of riboflavin and vitamins A and E as well as other biologically interesting compounds. This was followed in 1938 by a further Chemistry award to the German biochemist Richard Kuhn, who had also worked on carotenoids and B-vitamins, including riboflavin and pyridoxine. But Karrer was not permitted to leave Germany at that time by the Nazi regime. However, the American work with radioisotopes at Lawrence Livermore Laboratory, UC Berkeley, was already ushering in a new era of biochemistry that would enrich our studies of metabolic pathways. The importance of work involving vitamins was acknowledged in at least ten awards in the 20th century.

1.   Carpenter, K.J., Beriberi, White Rice and Vitamin B, University of California Press, Berkeley (2000).

2.  Weatherall, M.W. and Kamminga, H., The making of a biochemist: the construction of Frederick Gowland Hopkins’ reputation. Medical History vol.40, pp. 415-436 (1996).

3.  Becker, S.L., Will milk make them grow? An episode in the discovery of the vitamins. In Chemistry and Modern Society (J. Parascandela, editor) pp. 61-83, American Chemical Society,

Washington, D.C. (1983).

4.  Carpenter, K.J., The History of Scurvy and Vitamin C, Cambridge University Press, New York (1986).

Transport and metabolism of exogenous fumarate and 3-phosphoglycerate in vascular smooth muscle.

D R FinderC D Hardin

Molecular and Cellular Biochemistry (Impact Factor: 2.33). 05/1999; 195(1-2):113-21.  http://dx.doi.org/10.1023/A:1006976432578

The keto (linear) form of exogenous fructose 1,6-bisphosphate, a highly charged glycolytic intermediate, may utilize a dicarboxylate transporter to cross the cell membrane, support glycolysis, and produce ATP anaerobically. We tested the hypothesis that fumarate, a dicarboxylate, and 3-phosphoglycerate (3-PG), an intermediate structurally similar to a dicarboxylate, can support contraction in vascular smooth muscle during hypoxia. 3-PG improved maintenance of force (p < 0.05) during the 30-80 min period of hypoxia. Fumarate decreased peak isometric force development by 9.5% (p = 0.008) but modestly improved maintenance of force (p < 0.05) throughout the first 80 min of hypoxia. 13C-NMR on tissue extracts and superfusates revealed 1,2,3,4-(13)C-fumarate (5 mM) metabolism to 1,2,3,4-(13)C-malate under oxygenated and hypoxic conditions suggesting uptake and metabolism of fumarate. In conclusion, exogenous fumarate and 3-PG readily enter vascular smooth muscle cells, presumably by a dicarboxylate transporter, and support energetically important pathways.

Comparison of endogenous and exogenous sources of ATP in fueling Ca2+ uptake in smooth muscle plasma membrane vesicles.

C D HardinL RaeymaekersR J Paul

The Journal of General Physiology (Impact Factor: 4.73). 12/1991; 99(1):21-40.   http://dx.doi.org:/10.1085/jgp.99.1.21

A smooth muscle plasma membrane vesicular fraction (PMV) purified for the (Ca2+/Mg2+)-ATPase has endogenous glycolytic enzyme activity. In the presence of glycolytic substrate (fructose 1,6-diphosphate) and cofactors, PMV produced ATP and lactate and supported calcium uptake. The endogenous glycolytic cascade supports calcium uptake independent of bath [ATP]. A 10-fold dilution of PMV, with the resultant 10-fold dilution of glycolytically produced bath [ATP] did not change glycolytically fueled calcium uptake (nanomoles per milligram protein). Furthermore, the calcium uptake fueled by the endogenous glycolytic cascade persisted in the presence of a hexokinase-based ATP trap which eliminated calcium uptake fueled by exogenously added ATP. Thus, it appears that the endogenous glycolytic cascade fuels calcium uptake in PMV via a membrane-associated pool of ATP and not via an exchange of ATP with the bulk solution. To determine whether ATP produced endogenously was utilized preferentially by the calcium pump, the ATP production rates of the endogenous creatine kinase and pyruvate kinase were matched to that of glycolysis and the calcium uptake fueled by the endogenous sources was compared with that fueled by exogenous ATP added at the same rate. The rate of calcium uptake fueled by endogenous sources of ATP was approximately twice that supported by exogenously added ATP, indicating that the calcium pump preferentially utilizes ATP produced by membrane-bound enzymes.

Evidence for succinate production by reduction of fumarate during hypoxia in isolated adult rat heart cells.

C HohlR OestreichP RösenR WiesnerM Grieshaber

Archives of Biochemistry and Biophysics (Impact Factor: 3.37). 01/1988; 259(2):527-35. http://dx.doi.org:/10.1016/0003-9861(87)90519-4   It has been demonstrated that perfusion of myocardium with glutamic acid or tricarboxylic acid cycle intermediates during hypoxia or ischemia, improves cardiac function, increases ATP levels, and stimulates succinate production. In this study isolated adult rat heart cells were used to investigate the mechanism of anaerobic succinate formation and examine beneficial effects attributed to ATP generated by this pathway. Myocytes incubated for 60 min under hypoxic conditions showed a slight loss of ATP from an initial value of 21 +/- 1 nmol/mg protein, a decline of CP from 42 to 17 nmol/mg protein and a fourfold increase in lactic acid production to 1.8 +/- 0.2 mumol/mg protein/h. These metabolite contents were not altered by the addition of malate and 2-oxoglutarate to the incubation medium nor were differences in cell viability observed; however, succinate release was substantially accelerated to 241 +/- 53 nmol/mg protein. Incubation of cells with [U-14C]malate or [2-U-14C]oxoglutarate indicates that succinate is formed directly from malate but not from 2-oxoglutarate. Moreover, anaerobic succinate formation was rotenone sensitive.

We conclude that malate reduction to succinate occurs via the reverse action of succinate dehydrogenase in a coupled reaction where NADH is oxidized (and FAD reduced) and ADP is phosphorylated. Furthermore, by transaminating with aspartate to produce oxaloacetate, 2-oxoglutarate stimulates cytosolic malic dehydrogenase activity, whereby malate is formed and NADH is oxidized.

In the form of malate, reducing equivalents and substrate are transported into the mitochondria where they are utilized for succinate synthesis.

1953 Hans Adolf Krebs –

 ” discovery of the citric acid cycle” and In the course of the 1920’s and 1930’s great progress was made in the study of the intermediary reactions by which sugar is anaerobically fermented to lactic acid or to ethanol and carbon dioxide. The success was mainly due to the joint efforts of the schools of Meyerhof, Embden, Parnas, von Euler, Warburg and the Coris, who built on the pioneer work of Harden and of Neuberg. This work brought to light the main intermediary steps of anaerobic fermentations.

In contrast, very little was known in the earlier 1930’s about the intermediary stages through which sugar is oxidized in living cells. When, in 1930, I left the laboratory of Otto Warburg (under whose guidance I had worked since 1926 and from whom I have learnt more than from any other single teacher), I was confronted with the question of selecting a major field of study and I felt greatly attracted by the problem of the intermediary pathway of oxidations.

These reactions represent the main energy source in higher organisms, and in view of the importance of energy production to living organisms (whose activities all depend on a continuous supply of energy) the problem seemed well worthwhile studying.   http://www.johnkyrk.com/krebs.html

Interactive Krebs cycle

There are different points where metabolites enter the Krebs’ cycle. Most of the products of protein, carbohydrates and fat metabolism are reduced to the molecule acetyl coenzyme A that enters the Krebs’ cycle. Glucose, the primary fuel in the body, is first metabolized into pyruvic acid and then into acetyl coenzyme A. The breakdown of the glucose molecule forms two molecules of ATP for energy in the Embden Meyerhof pathway process of glycolysis.

On the other hand, amino acids and some chained fatty acids can be metabolized into Krebs intermediates and enter the cycle at several points. When oxygen is unavailable or the Krebs’ cycle is inhibited, the body shifts its energy production from the Krebs’ cycle to the Embden Meyerhof pathway of glycolysis, a very inefficient way of making energy.  

Fritz Albert Lipmann –

 “discovery of co-enzyme A and its importance for intermediary metabolism”.

In my development, the recognition of facts and the rationalization of these facts into a unified picture, have interplayed continuously. After my apprenticeship with Otto Meyerhof, a first interest on my own became the phenomenon we call the Pasteur effect, this peculiar depression of the wasteful fermentation in the respiring cell. By looking for a chemical explanation of this economy measure on the cellular level, I was prompted into a study of the mechanism of pyruvic acid oxidation, since it is at the pyruvic stage where respiration branches off from fermentation.

For this study I chose as a promising system a relatively simple looking pyruvic acid oxidation enzyme in a certain strain of Lactobacillus delbrueckii1.   In 1939, experiments using minced muscle cells demonstrated that one oxygen atom can form two adenosine triphosphate molecules, and, in 1941, the concept of phosphate bonds being a form of energy in cellular metabolism was developed by Fritz Albert Lipmann.

In the following years, the mechanism behind cellular respiration was further elaborated, although its link to the mitochondria was not known.[13]The introduction of tissue fractionation by Albert Claude allowed mitochondria to be isolated from other cell fractions and biochemical analysis to be conducted on them alone. In 1946, he concluded that cytochrome oxidase and other enzymes responsible for the respiratory chain were isolated to the mitchondria. Over time, the fractionation method was tweaked, improving the quality of the mitochondria isolated, and other elements of cell respiration were determined to occur in the mitochondria.[13]

The most important event during this whole period, I now feel, was the accidental observation that in the L. delbrueckii system, pyruvic acid oxidation was completely dependent on the presence of inorganic phosphate. This observation was made in the course of attempts to replace oxygen by methylene blue. To measure the methylene blue reduction manometrically, I had to switch to a bicarbonate buffer instead of the otherwise routinely used phosphate. In bicarbonate, pyruvate oxidation was very slow, but the addition of a little phosphate caused a remarkable increase in rate. The phosphate effect was removed by washing with a phosphate free acetate buffer. Then it appeared that the reaction was really fully dependent on phosphate.

A coupling of this pyruvate oxidation with adenylic acid phosphorylation was attempted. Addition of adenylic acid to the pyruvic oxidation system brought out a net disappearance of inorganic phosphate, accounted for as adenosine triphosphate.   The acetic acid subunit of acetyl CoA is combined with oxaloacetate to form a molecule of citrate. Acetyl coenzyme A acts only as a transporter of acetic acid from one enzyme to another. After Step 1, the coenzyme is released by hydrolysis to combine with another acetic acid molecule and begin the Krebs’ Cycle again.

Hugo Theorell

the nature and effects of oxidation enzymes”

From 1933 until 1935 Theorell held a Rockefeller Fellowship and worked with Otto Warburg at Berlin-Dahlem, and here he became interested in oxidation enzymes. At Berlin-Dahlem he produced, for the first time, the oxidation enzyme called «the yellow ferment» and he succeeded in splitting it reversibly into a coenzyme part, which was found to be flavin mononucleotide, and a colourless protein part. On return to Sweden, he was appointed Head of the newly established Biochemical Department of the Nobel Medical Institute, which was opened in 1937.

Succinate is oxidized by a molecule of FAD (Flavin Adenine Dinucleotide). The FAD removes two hydrogen atoms from the succinate and forms a double bond between the two carbon atoms to create fumarate.

1953

double-stranded-dna

double-stranded-dna

crick-watson-with-their-dna-model.

crick-watson-with-their-dna-model.

Watson & Crick double helix model 

A landmark in this journey

They followed the path that became clear from intense collaborative work in California by George Beadle, by Avery and McCarthy, Max Delbruck, TH Morgan, Max Delbruck and by Chargaff that indicated that genetics would be important.

1965

François Jacob, André Lwoff and Jacques Monod  –

” genetic control of enzyme and virus synthesis”.

In 1958 the remarkable analogy revealed by genetic analysis of lysogeny and that of the induced biosynthesis of ß-galactosidase led François Jacob, with Jacques Monod, to study the mechanisms responsible for the transfer of genetic information as well as the regulatory pathways which, in the bacterial cell, adjust the activity and synthesis of macromolecules. Following this analysis, Jacob and Monod proposed a series of new concepts, those of messenger RNA, regulator genes, operons and allosteric proteins.

Francois Jacob

Having determined the constants of growth in the presence of different carbohydrates, it occurred to me that it would be interesting to determine the same constants in paired mixtures of carbohydrates. From the first experiment on, I noticed that, whereas the growth was kinetically normal in the presence of certain mixtures (that is, it exhibited a single exponential phase), two complete growth cycles could be observed in other carbohydrate mixtures, these cycles consisting of two exponential phases separated by a-complete cessation of growth.

Lwoff, after considering this strange result for a moment, said to me, “That could have something to do with enzyme adaptation.”

“Enzyme adaptation? Never heard of it!” I said.

Lwoff’s only reply was to give me a copy of the then recent work of Marjorie Stephenson, in which a chapter summarized with great insight the still few studies concerning this phenomenon, which had been discovered by Duclaux at the end of the last century.  Studied by Dienert and by Went as early as 1901 and then by Euler and Josephson, it was more or less rediscovered by Karström, who should be credited with giving it a name and attracting attention to its existence.

Lwoff’s intuition was correct. The phenomenon of “diauxy” that I had discovered was indeed closely related to enzyme adaptation, as my experiments, included in the second part of my doctoral dissertation, soon convinced me. It was actually a case of the “glucose effect” discovered by Dienert as early as 1900.   That agents that uncouple oxidative phosphorylation, such as 2,4-dinitrophenol, completely inhibit adaptation to lactose or other carbohydrates suggested that “adaptation” implied an expenditure of chemical potential and therefore probably involved the true synthesis of an enzyme.

With Alice Audureau, I sought to discover the still quite obscure relations between this phenomenon and the one Massini, Lewis, and others had discovered: the appearance and selection of “spontaneous” mutants.   We showed that an apparently spontaneous mutation was allowing these originally “lactose-negative” bacteria to become “lactose-positive”. However, we proved that the original strain (Lac-) and the mutant strain (Lac+) did not differ from each other by the presence of a specific enzyme system, but rather by the ability to produce this system in the presence of lactose.  This mutation involved the selective control of an enzyme by a gene, and the conditions necessary for its expression seemed directly linked to the chemical activity of the system.

1974

Albert Claude, Christian de Duve and George E. Palade –

” the structural and functional organization of the cell”.

I returned to Louvain in March 1947 after a period of working with Theorell in Sweden, the Cori’s, and E Southerland in St. Louis, fortunate in the choice of my mentors, all sticklers for technical excellence and intellectual rigor, those prerequisites of good scientific work. Insulin, together with glucagon which I had helped rediscover, was still my main focus of interest, and our first investigations were accordingly directed on certain enzymatic aspects of carbohydrate metabolism in liver, which were expected to throw light on the broader problem of insulin action. But I became distracted by an accidental finding related to acid phosphatase, drawing most of my collaborators along with me. The studies led to the discovery of the lysosome, and later of the peroxisome.

In 1962, I was appointed a professor at the Rockefeller Institute in New York, now the Rockefeller University, the institution where Albert Claude had made his pioneering studies between 1929 and 1949, and where George Palade had been working since 1946.  In New York, I was able to develop a second flourishing group, which follows the same general lines of research as the Belgian group, but with a program of its own.

1968

Robert W. Holley, Har Gobind Khorana and Marshall W. Nirenberg –

“interpretation of the genetic code and its function in protein synthesis”.

1969

Max Delbrück, Alfred D. Hershey and Salvador E. Luria –

” the replication mechanism and the genetic structure of viruses”.

1975 David Baltimore, Renato Dulbecco and Howard Martin Temin –

” the interaction between tumor viruses and the genetic material of the cell”.

1976

Baruch S. Blumberg and D. Carleton Gajdusek –

” new mechanisms for the origin and dissemination of infectious diseases” The editors of the Nobelprize.org website of the Nobel Foundation have asked me to provide a supplement to the autobiography that I wrote in 1976 and to recount the events that happened after the award. Much of what I will have to say relates to the scientific developments since the last essay. These are described in greater detail in a scientific memoir first published in 2002 (Blumberg, B. S., Hepatitis B. The Hunt for a Killer Virus, Princeton University Press, 2002, 2004).

1980

Baruj Benacerraf, Jean Dausset and George D. Snell 

” genetically determined structures on the cell surface that regulate immunological reactions”.

1992

Edmond H. Fischer and Edwin G. Krebs 

“for their discoveries concerning reversible protein phosphorylation as a biological regulatory mechanism”

1994

Alfred G. Gilman and Martin Rodbell –

“G-proteins and the role of these proteins in signal transduction in cells”

2011

Bruce A. Beutler and Jules A. Hoffmann –

the activation of innate immunity and the other half to Ralph M. Steinman – “the dendritic cell and its role in adaptive immunity”.

Renato L. Baserga, M.D.

Kimmel Cancer Center and Keck School of Medicine

Dr. Baserga’s research focuses on the multiple roles of the type 1 insulin-like growth factor receptor (IGF-IR) in the proliferation of mammalian cells. The IGF-IR activated by its ligands is mitogenic, is required for the establishment and the maintenance of the transformed phenotype, and protects tumor cells from apoptosis. It, therefore, serves as an excellent target for therapeutic interventions aimed at inhibiting abnormal growth. In basic investigations, this group is presently studying the effects that the number of IGF-IRs and specific mutations in the receptor itself have on its ability to protect cells from apoptosis.

This investigation is strictly correlated with IGF-IR signaling, and part of this work tries to elucidate the pathways originating from the IGF-IR that are important for its functional effects. Baserga’s group has recently discovered a new signaling pathway used by the IGF-IR to protect cells from apoptosis, a unique pathway that is not used by other growth factor receptors. This pathway depends on the integrity of serines 1280-1283 in the C-terminus of the receptor, which bind 14.3.3 and cause the mitochondrial translocation of Raf-1.

Another recent discovery of this group has been the identification of a mechanism by which the IGF-IR can actually induce differentiation in certain types of cells. When cells have IRS-1 (a major substrate of the IGF-IR), the IGF-IR sends a proliferative signal; in the absence of IRS-1, the receptor induces cell differentiation. The extinction of IRS-1 expression is usually achieved by DNA methylation.

Janardan Reddy, MD

Northwestern University

The central effort of our research has been on a detailed analysis at the cellular and molecular levels of the pleiotropic responses in liver induced by structurally diverse classes of chemicals that include fibrate class of hypolipidemic drugs, and phthalate ester plasticizers, which we designated hepatic peroxisome proliferators. Our work has been central to the establishment of several principles, namely that hepatic peroxisome proliferation is associated with increases in fatty acid oxidation systems in liver, and that peroxisome proliferators, as a class, are novel nongenotoxic hepatocarcinogens.

We introduced the concept that sustained generation of reactive oxygen species leads to oxidative stress and serves as the basis for peroxisome proliferator-induced liver cancer development. Furthermore, based on the tissue/cell specificity of pleiotropic responses and the coordinated transcriptional regulation of fatty acid oxidation system genes, we postulated that peroxisome proliferators exert their action by a receptor-mediated mechanism. This receptor concept laid the foundation for the discovery of

  • a three member peroxisome proliferator-activated receptor (PPARalpha-, ß-, and gamma) subfamily of nuclear receptors.
  •  PPARalpha is responsible for peroxisome proliferator-induced pleiotropic responses, including
    • hepatocarcinogenesis and energy combustion as it serves as a fatty acid sensor and regulates fatty acid oxidation.

Our current work focuses on the molecular mechanisms responsible for PPAR action and generation of fatty acid oxidation deficient mouse knockout models. Transcription of specific genes by nuclear receptors is a complex process involving the participation of multiprotein complexes composed of transcription coactivators.  

Jose Delgado de Salles Roselino, Ph.D.

Leloir Institute, Brazil

Warburg effect, in reality “Pasteur-effect” was the first example of metabolic regulation described. A decrease in the carbon flux originated at the sugar molecule towards the end metabolic products, ethanol and carbon dioxide that was observed when yeast cells were transferred from anaerobic environmental condition to an aerobic one. In Pasteur´s works, sugar metabolism was measured mainly by the decrease of sugar concentration in the yeast growth media observed after a measured period of time. The decrease of the sugar concentration in the media occurs at great speed in yeast grown in anaerobiosis condition and its speed was greatly reduced by the transfer of the yeast culture to an aerobic condition. This finding was very important for the wine industry of France in Pasteur time, since most of the undesirable outcomes in the industrial use of yeast were perceived when yeasts cells took very long time to create a rather selective anaerobic condition. This selective culture media was led by the carbon dioxide higher levels produced by fast growing yeast cells and by a great alcohol content in the yeast culture media. This finding was required to understand Lavoisier’s results indicating that chemical and biological oxidation of sugars produced the same calorimetric results. This observation requires a control mechanism (metabolic regulation) to avoid burning living cells by fast heat released by the sugar biological oxidative processes (metabolism). In addition, Lavoisier´s results were the first indications that both processes happened inside similar thermodynamics limits.

In much resumed form, these observations indicates the major reasons that led Warburg to test failure in control mechanisms in cancer cells in comparison with the ones observed in normal cells. Biology inside classical thermo dynamics poses some challenges to scientists. For instance, all classical thermodynamics must be measured in reversible thermodynamic conditions. In an isolated system, increase in P (pressure) leads to decrease in V (volume) all this in a condition in which infinitesimal changes in one affects in the same way the other, a continuum response. Not even a quantic amount of energy will stand beyond those parameters. In a reversible system, a decrease in V, under same condition, will led to an increase in P.

In biochemistry, reversible usually indicates a reaction that easily goes from A to B or B to A. This observation confirms the important contribution of E Schrodinger in his What´s Life: “This little book arose from a course of public lectures, delivered by a theoretical physicist to an audience of about four hundred which did not substantially dwindle, though warned at the outset that the subject-matter was a difficult one and that the lectures could not be termed popular, even though the physicist’s most dreaded weapon, mathematical deduction, would hardly be utilized. The reason for this was not that the subject was simple enough to be explained without mathematics, but rather that it was much too involved to be fully accessible to mathematics.”

Hans Krebs describes the cyclic nature of the citrate metabolism. Two major research lines search to understand the mechanism of energy transfer that explains how ADP is converted into ATP. One followed the organic chemistry line of reasoning and therefore, searched how the breakdown of carbon-carbon link could have its energy transferred to ATP synthesis. A major leader of this research line was B. Chance who tried to account for two carbon atoms of acetyl released as carbon dioxide in the series of Krebs cycle reactions. The intermediary could store in a phosphorylated amino acid the energy of carbon-carbon bond breakdown. This activated amino acid could transfer its phosphate group to ADP producing ATP. Alternatively, under the possible influence of the excellent results of Hodgkin and Huxley a second line of research appears.

The work of Hodgkin & Huxley indicated the storage of electrical potential energy in transmembrane ionic asymmetries and presented the explanation for the change from resting to action potential in excitable cells. This second line of research, under the leadership of P Mitchell postulated a mechanism for the transfer of oxide/reductive power of organic molecules oxidation through electron transfer as the key for energetic transfer mechanism required for ATP synthesis. Paul Boyer could present how the energy was transduced by a molecular machine that changes in conformation in a series of 3 steps while rotating in one direction in order to produce ATP and in opposite direction in order to produce ADP plus Pi from ATP (reversibility). Nonetheless, a victorious Peter Mitchell obtained the correct result in the conceptual dispute, over the B. Chance point of view, after he used E. Coli mutants to show H gradients in membrane and its use as energy source.

However, this should not detract from the important work of Chance. B. Chance got the simple and rapid polarographic assay method of oxidative phosphorylation and the idea of control of energy metabolism that bring us back to Pasteur. This second result seems to have been neglected in searching for a single molecular mechanism required for the understanding of the buildup of chemical reserve in our body. In respiring mitochondria the rate of electron transport, and thus the rate of ATP production, is determined primarily by the relative concentrations of ADP, ATP and phosphate in the external media (cytosol) and not by the concentration of respiratory substrate as pyruvate. Therefore, when the yield of ATP is high as is in aerobiosis and the cellular use of ATP is not changed, the oxidation of pyruvate and therefore of glycolysis is quickly (without change in gene expression), throttled down to the resting state. The dependence of respiratory rate on ADP concentration is also seen in intact cells. A muscle at rest and using no ATP has very low respiratory rate.

I have had an ongoing discussion with Jose Eduardo de Salles Roselino, inBrazil. He has made important points that need to be noted.

  1. The constancy of composition which animals maintain in the environment surrounding their cells is one of the dominant features of their physiology. Although this phenomenon, homeostasis, has held the interest of biologists over a long period of time, the elucidation of the molecular basis for complex processes such as temperature control and the maintenance of various substances at constant levels in the blood has not yet been achieved. By comparison, metabolic regulation in microorganisms is much better understood, in part because the microbial physiologist has focused his attention on enzyme-catalyzed reactions and their control, as these are among the few activities of microorganisms amenable to quantitative study. Furthermore, bacteria are characterized by their ability to make rapid and efficient adjustments to extensive variations in most parameters of their environment; therefore, they exhibit a surprising lack of rigid requirements for their environment, and appears to influence it only as an incidental result of their metabolism. Animal cells on the other hand have only a limited capacity for adjustment and therefore require a constant milieu. Maintenance of such constancy appears to be a major goal in their physiology (Regulation of Biosynthetic Pathways H.S. Moyed and H EUmbarger Phys Rev,42 444 (1962)).
  2. A living cell consists in a large part of a concentrated mixture of hundreds of different enzymes, each a highly effective catalyst for one or more chemical reactions involving other components of the cell. The paradox of intense and highly diverse chemical activity on the one hand and strongly poised chemical stability (biological homeostasis) on the other is one of the most challenging problems of biology (Biological feedback Control at the molecular Level D.E. Atkinson Science vol. 150: 851, 1965). Almost nothing is known concerning the actual molecular basis for modulation of an enzyme`s kinetic behavior by interaction with a small molecule. (Biological feedback Control at the molecular Level D.E. Atkinson Science vol. 150: 851, 1965). In the same article, since the core of Atkinson´s thinking seems to be strongly linked with Adenylates as regulatory effectors, the previous phrases seems to indicate a first step towards the conversion of homeostasis to an intracellular phenomenon and therefore, one that contrary to Umbarger´s consideration could be also studied in microorganisms.
  3.  Most biochemical studies using bacteria, were made before the end of the third upper part of log growth phase. Therefore, they could be considered as time-independent as S Luria presented biochemistry in Life an Unfinished Experiment. The sole ingredient on the missing side of the events that led us into the molecular biology construction was to consider that proteins, a macromolecule, would never be affected by small molecules translational kinetic energy. This, despite the fact that in a catalytic environment and its biological implications S Grisolia incorporated A K Balls observation indicating that the word proteins could be related to Proteus an old sea god that changed its form whenever he was subjected to inquiry (Phys Rev v 4,657 (1964).
  1. In D.E. Atkinson´s work (Science vol 150 p 851, 1965), changes in protein synthesis acting together with factors that interfere with enzyme activity will lead to “fine-tuned” regulation better than enzymatic activity regulation alone. Comparison of glycemic regulation in granivorous and carnivorous birds indicate that when no important nutritional source of glucose is available, glycemic levels can be kept constant in fasted and fed birds. The same was found in rats and cats fed on high protein diets. Gluconeogenesis is controlled by pyruvate kinase inhibition. Therefore, the fact that it can discriminate between fasting alone and fasting plus exercise (carbachol) requirement of gluconeogenic activity (correspondent level of pyruvate kinase inhibition) the control of enzyme activity can be made fast and efficient without need for changes in genetic expression (20 minute after stimulus) ( Migliorini,R.H. et al Am J. Physiol.257 (Endocrinol. Met. 20): E486, 1989). Regrettably, this was not discussed in the quoted work. So, when the control is not affected by the absorption of nutritional glucose it can be very fast, less energy intensive and very sensitive mechanism of control despite its action being made in the extracellular medium (homeostasis).

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Larry H. Bernstein, MD, FCAP, Reviewer and Curator

http://pharmaceuticalinnovation.com/2012-12-09/larryhbern/Silencing Cancers with Synthetic siRNAs

The challenge of cancer drug development has been marker by less than a century of development of major insights into the know of biochemical pathways and the changes in those pathways in a dramatic shift in enrgy utilization and organ development, and the changes in those pathways with the development of malignant neoplasia.  The first notable change is the Warburg Effect (attributed to the 1860 obsevation by Pasteur that yeast cells use glycolysis under anaerobic conditions).  Warburg also referred to earlier work by Meyerhoff, in a ratio of CO2 release to O2 consumption, a Meyerhoff ratio.  Much more was elucidated after the discovery of the pyridine nucleotides, which gave understanding of glycolysis and lactate production with a key two enzyme separation at the forward LDH reaction and the back reentry to the TCA cycle.  But the TCA cycle could be used for oxidative energy utilization in the mitochondria by oxidative phosphorylation elucidated by Peter Mitchell, or it can alternatively be used for syntheses, like proteins and lipid membrane structures.

A brilliant student in Leloir’s laboratory in Brazil undertook a study of isoenzyme structure in 1971, at a time that I was working under Nathan O. Kaplan on the mechanism of inhibition of mitochondrial malate dehydrogenase. In his descripton, taking into account the effect of substrates upon protein stability (FEBS) could be, in a prebiotic system, the form required in order to select protein and RNA in parallel or in tandem in a way that generates the genetic code (3 bases for one amino acid). Later, other proteins like reverse transcriptase, could transcribe it into the more stable DNA. Leloir had just finished ( a few years before 1971 but, not published by these days yet) a somehow similar reasoning about metabolic regions rich in A or in C or .. G or T.  He later spent time in London to study the early events in the transition of growing cells linked to ion fluxes, which he was attracted to by the idea that life is so strongly associated with the K (potassium) and Na (sodium) asymmetry.   Moreover, he notes that while DNA is the same no matter the cell is dead or alive,  and therefore,  it is a huge mistake to call DNA the molecule of life. In all life forms, you will find K reach inside and Na rich outside its membrane. On his return to Brazil, he accepted a request to collaborate with the Surgery department in energetic metabolism of tissues submitted to ischemia and reperfusion. This led me back to Pasteur and Warburg effects and like in Leloir´s time, he worked with a dimorphic yeast/mold that was considered a morphogenetic presentation of the Pasteur Effect.  His findings were as follows. In absence of glucose, a condition that prevents the yeast like cell morphology, which led to the study of an enzyme “half reaction”. The reaction that on the half, “seen in our experimental conditions did not followed classical thermodynamics” (According to Collowick & Kaplan (of your personal knowledge) vol. I See Utter and Kurahashi in it). This somehow contributed to a way of seeing biochemistry with modesty. The second and more strongly related to the Pasteur Effect was the use an entirely designed and produced in our Medical School Coulometer spirometer that measures oxygen consumption in a condition of constant oxygen supply. At variance with Warburg apparatus and Clark´s electrode, this oxymeters uses decrease in partial oxygen pressure and decrease electrical signal of oxygen polarography to measure it (Leite, J.V.P. Research in Physiol. Kao, Koissumi, Vassali eds Aulo Gaggi Bologna, 673-80-1971). “With this, I was able to measure the same mycelium in low and high “cell density” inside the same culture media. The result shows, high density one stops mitochondrial function while low density continues to consume oxygen (the internal increase or decrease in glycogen levels shows which one does or does not do it). Translation for today: The same genome in the same chemical environment behave differently mostly likely by its interaction differences. This previous experience fits well with what  I have to read by that time of my work with surgeons.  Submitted to total ischemia tissues mitochondrial function is stopped when they already have enough oxyhemoglobin (1) Epstein, Balaban and Ross Am J Physiol.243, F356-63 (1982) 2) Bashford , C. L, Biological membranes a practical approach Oxford Was. P 219-239 (1987).”

Of course, the world of medical and pharmaceutical engagement with this problem, though changed in focus, has benefitted hugely from “The Human Genome Project”, and the events since the millenium, because of technology advances in instrumental analysis, and in bioinformatics and computational biology.  This has lead to recent advances in regenerative biology with stem cell “models”, to advances in resorbable matrices, and so on.  We proceed to an interesting work that applies synthetic work with nucleic acid signaling to pharmacotherapy of cancer.

Synthetic RNAs Designed to Fight Cancer

Fri, 12/06/2013 Biosci Technology
Xiaowei Wang and his colleagues have designed synthetic molecules that combine the advantages of two experimental RNA therapies against cancer. (Source: WUSTL/Robert J. Boston)In search of better cancer treatments, researchers at Washington University School of Medicine in St. Louis have designed synthetic molecules that combine the advantages of two experimental RNA therapies.  The study appears in the December issue of the journal RNA.
 RNAs play an important role in how genes are turned on and off in the body. Both siRNAs and microRNAs are snippets of RNA known to modulate a gene’s signal or shut it down entirely. Separately, siRNA and microRNA treatment strategies are in early clinical trials against cancer, but few groups have attempted to marry the two.   “These are preliminary findings, but we have shown that the concept is worth pursuing,” said Xiaowei Wang, assistant professor of radiation oncology at the School of Medicine and a member of the Siteman Cancer Center. “We are trying to merge two largely separate fields of RNA research and harness the advantages of both.”
 “We designed an artificial RNA that is a combination of siRNA and microRNA, The showed that the artificial RNA combines the functions of the two separate molecules, simultaneously inhibiting both cell migration and proliferation. They designed and assembled small interfering” RNAs, or siRNAs,  made to shut down– or interfere with– a single specific gene that drives cancer.  The siRNA molecules work extremely well at silencing a gene target because the siRNA sequence is made to perfectly complement the target sequence, thereby
  • silencing a gene’s expression.
Though siRNAs are great at turning off the gene target, they also have potentially dangerous side effects:
  • siRNAs inadvertently can shut down other genes that need to be expressed to carry out tasks that keep the body healthy.
 According to Wang and his colleagues, siRNAs interfere with off-target genes that closely complement their “seed region,” a short but important
  • section of the siRNA sequence that governs binding to a gene target.
 “We can never predict all of the toxic side effects that we might see with a particular siRNA,” said Wang. “In the past, we tried to block the seed region in an attempt to reduce the side effects. Until now,
  • we never tried to replace the seed region completely.”
 Wang and his colleagues asked whether
  • they could replace the siRNA’s seed region with the seed region from microRNA.
Unlike siRNA, microRNA is a natural part of the body’s gene expression. And it can also shut down genes. As such, the microRNA seed region (with its natural targets) might reduce
  • the toxic side effects caused by the artificial siRNA seed region. Plus,
  • the microRNA seed region would add a new tool to shut down other genes that also may be driving cancer.
 Wang’s group started with a bioinformatics approach, using a computer algorithm to design
  • siRNA sequences against a common driver of cancer,
  • a gene called AKT1 that encourages uncontrolled cell division.
They used the program to select siRNAs against AKT1 that also had a seed region highly similar to the seed region of a microRNA known to inhibit a cell’s ability to move, thus
  • potentially reducing the cancer’s ability to spread.
In theory, replacing the siRNA seed region with the microRNA seed region also would combine their functions
  • reducing cell division and
  • movement with a single RNA molecule.
 Of more than 1,000 siRNAs that can target AKT1,
  • they found only three that each had a seed region remarkably similar to the seed region of the microRNA that reduces cell movement.
 They then took the microRNA seed region and
  • used it to replace the seed region in the three siRNAs that target AKT1.
The close similarity between the two seed regions is required because
  • changing the original siRNA sequence too much would make it less effective at shutting down AKT1.
 They dubbed the resulting combination RNA molecule “artificial interfering” RNA, or aiRNA. Once they arrived at these three sequences using computer models,
  1. they assembled the aiRNAs and
  2. tested them in cancer cells.
 One of the three artificial RNAs that they built in the lab
  • combined the advantages of the original siRNA and the microRNA seed region that was transplanted into it.
This aiRNA greatly reduced both
  1. cell division (like the siRNA) and
  2. movement (like the microRNA).
And to further show proof-of-concept, they also did the reverse, designing an aiRNA that
  1. both resists chemotherapy and
  2. promotes movement of the cancer cells.
 “Obviously, we would not increase cell survival and movement for cancer therapy, but we wanted to show how flexible this technology can be, potentially expanding it to treat diseases other than cancer,” Wang said.
Source: WUSTL

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