Epigenetics, Environment and Cancer: Articles of Note @PharmaceuticalIntelligence.com
Author and Curator: Larry H. Bernstein, MD, FCAP and Curator: Aviva Lev-Ari, PhD, RN
Introduction
Author: Larry H. Bernstein, MD, FCAP
The following discussions are presented in two series. The first set of discussions is mainly concerned with the role of genomics in the rapidly emerging research domain of genomics and medicine. The recent advances in genomic research at the end of the 20th century brought into the new millennium a seminal accomplishment because of the mapping of the human genome. This development required advances in technology that touches on biochemistry, organic chemistry, physical chemistry, mathematics and computational sciences that have been followed by a surge of innovation for the last 15 years. This was an accomplishment of basic science research that can be ascribed to substantial leadership from the National Institutes of Health, and to a diversity of research centers within the United States, England, France, and Germany, and Israel among others.
In looking back at this development, it might appear to be weighted heavily in a concentrated work on the genetic code. This was predated by the discovery of genetic inborn errors of metabolism that was at least a half century precedent. Thus a model was constructed for the accounting for many human conditions that are expressed in-utero, perinatal, postnatal, and at critical life stages. However, even allowing for over-simplification of a model of life reduced to the expression of a genetic code, this has led to the genesis of a concept of genetic clarification of life “maladies”, diagnostic, therapeutic, and prognostic implications. The concept of a “personalized medicine” emerges from such a construct.
I have already ceded considerable ground in an argument of what occurs in life, illness, and death at the cellular, organ, and organ system level. There are indeed gene amplifications and downregulation of genes that are expressed or have an “on-off” nature in transcription, which becomes a major driver of metabolic control. In this respect, the classic model of gene-RNA-protein has been superseded by a much more complicated model, but still in the realm of personalized medicine. The classic model of metabolism is tied to anabolic and catabolic pathways, glycolytic and mitochondrial substrates, amino acids, proteins and 3D-protein aggregates that have functional roles, and that is controlled by allosteric interactions, ion transport, membrane affinity, signaling pathways, and hydrophilic and hydrophobic effects. This leads to the second part of the discussion about epigenetics and environmental impacts on cellular function. It is by no means irrelevant because the evolution of organisms from sea to land, and the existence of living forms in mountainous and desert regions imposed restrictions that required adaptation. A full understanding of these factors is required in the immersion in personalized medicine.
Genetics Impact on Physiology
A Perspective on Personalized Medicine
Curator: Larry H. Bernstein, MD, FCAP
Precision Medicine for Future of Genomics Medicine is The New Era
Demet Sag, PhD, CRA, GCP
Reporter: Aviva Lev-Ari, PhD, RN
A Reconstructed View of Personalized Medicine
Author: Larry H. Bernstein, MD, FCAP
Signaling and Signaling Pathways
Curator: Larry H. Bernstein, MD, FCAP
Gene Amplification and Activation of the Hedgehog Pathway
Curator: Larry H Bernstein, MD, FCAP
Pancreatic Cancer and Crossing Roads of Metabolism
Curator: Demet Sag, PhD
Reviewer and Curator: Larry H. Bernsteag, MD, FCAP
Acetylation and Deacetylation of non-Histone Proteins
Author and Curator: Larry H Bernstein, MD, FCAP
Author and Curator, Larry H. Bernstein, MD, FCAP
Epilogue: Envisioning New Insights in Cancer Translational Biology
Author and Curator: Larry H Bernstein, MD, FCAP
Directions for Genomics in Personalized Medicine
Author: Larry H. Bernstein, MD, FCAP
What is the Future for Genomics in Clinical Medicine?
Author and Curator: Larry H Bernstein, MD, FCAP
Environmental Factors Impacting Genetic Mutations
Curator: Larry H. Bernstein, MD, FCAP
The Underappreciated EpiGenome
Author: Demet Sag, PhD
Curator: Larry H Bernstein, MD, FCAP
The Metabolic View of Epigenetic Expression
Writer and Curator: Larry H Bernstein, MD, FCAP
Somatic, germ-cell, and whole sequence DNA in cell lineage and disease profiling
Curator: Larry H Bernstein, MD, FCAP
RNA and the transcription the genetic code
Curator: Larry H. Bernstein, MD, FCAP
Introduction – The Evolution of Cancer Therapy and Cancer Research: How We Got Here?
Author and Curator: Larry H Bernstein, MD, FCAP
Genomics and Epigenetics: Genetic Errors and Methodologies – Cancer and Other Diseases
Writer and Curator: Larry H Bernstein, MD, FCAP
BET Proteins Connect Diabetes and Cancer
Author and Curator: Larry H. Bernstein, MD, FCAP
Author: Tilda Barliya PhD
Curator and Writer: Stephen J. Williams, Ph.D.
Immuno therapy at MassBio, 3/31 and 4/1/2016.
Reporter: Aviva Lev-Ari, PhD, RN
Summary
Larry H. Bernstein, MD, FCAP
The preceding chapters have provided a substantial insight into the growth and acceleration of work related to translational medicine and personalized medicine. I make note of the fact that a substantial knowledge has been from basic research using animal models, including C. Eligans. The amount of knowledge is quite impressive. Let me review some major points gained from these presentations.
- Non-coding areas of our DNA are far from being without function. But the ensuing work with RNAs is captivating. Whether regulating gene expression and transcription, or providing protein attachment sites, this once-dismissed part of the genome is vital for all life.
There are two basic categories of nitrogenous bases: the purines (adenine [A] and guanine [G]), each with two fused rings, and the pyrimidines (cytosine [C], thymine [T], and uracil [U]), each with a single ring. Furthermore, it is now widely accepted that RNA contains only A, G, C, and U (no T), whereas DNA contains only A, G, C, and T (no U).
There is no uncertainty about the importance of “Junk DNA”. It is both an evolutionary remnant, and it has a role in cell regulation. Further, the role of histones in their relationship the oligonucleotide sequences is not understood. We now have a large output of research on noncoding RNA, including siRNA, miRNA, and others with roles other than transcription. This requires major revision of our model of cell regulatory processes. The classic model is solely transcriptional.
- DNA-> RNA-> Amino Acid in a protein.
Redrawn we have
- DNA-> RNA-> DNA and
- DNA->RNA-> protein-> DNA.
DNA is involved mainly with genetic information storage, while RNA molecules—mRNA, rRNA, tRNA, miRNA, and others—are engaged in diverse structural, catalytic, and regulatory activities, in addition to translating genes into proteins. RNA’s multitasking prowess, at the heart of the RNA World hypothesis implicating RNA as the first molecule of life, likely spurred the evolution of numerous modified nucleotides. This enabled the diversified complementarity and secondary structures that allow RNA species to specifically interact with other components of the cellular machinery such as DNA and proteins. The alphabet of RNA consists of at least 140 alternative nucleotide forms.
Among the 140 modified RNA nucleotide variants identified, methylation of adenosine at the N6 position (m6A) is the most prevalent epigenetic mark in eukaryotic mRNA. Identified in bacterial rRNAs and tRNAs as early as the 1950s, this type of methylation was subsequently found in other RNA molecules, including mRNA, in animal and plant cells as well. In 1984, researchers identified a site that was specifically methylated—the 3′ untranslated region (UTR) of bovine prolactin mRNA.1 As more sites of m6A modification were identified, a consistent pattern emerged: the methylated A is preceded by A or G and followed by C (A/G—methylated A—C).
Although the identification of m6A in RNA is 40 years old, until recently researchers lacked efficient molecular mapping and quantification methods to fully understand the functional implications of the modification. In 2012, we (D.D. and G.R.) combined the power of next-generation sequencing (NGS) with traditional antibody-mediated capture techniques to perform high-resolution transcriptome-wide mapping of m6A, an approach we termed m6A-seq.2 Briefly, the transcriptome is randomly fragmented and an anti-m6A antibody is used to fish out the methylated RNA fragments; the m6A-containing fragments are then sequenced and aligned to the genome, thus allowing us to locate the positions of methylation marks.
- The work of Warburg and Meyerhoff, followed by that of Krebs, Kaplan, Chance, and others built a solid foundation in the knowledge of enzymes, coenzymes, adenine and pyridine nucleotides, and metabolic pathways, not to mention the importance of Fe3+, Cu2+, Zn2+, and other metal cofactors.
Of huge importance was the work of Jacob, Monod and Changeux, and the effects of cooperativity in allosteric systems and of repulsion in tertiary structure of proteins related to hydrophobic and hydrophilic interactions, which involves the effect of one ligand on the binding or catalysis of another, demonstrated by the end-product inhibition of the enzyme, L-threonine deaminase (Changeux 1961), L-isoleucine, which differs sterically from the reactant, L-threonine whereby the former could inhibit the enzyme without competing with the latter. The current view based on a variety of measurements (e.g., NMR, FRET, and single molecule studies) is a ‘‘dynamic’’ proposal by Cooper and Dryden (1984) that the distribution around the average structure changes in allostery affects the subsequent (binding) affinity at a distant site.
Present day applications of computational methods to biomolecular systems, combined with structural, thermodynamic, and kinetic studies, make possible an approach to that question, so as to provide a deeper understanding of the requirements for allostery. The current view is that a variety of measurements (e.g., NMR, FRET, and single molecule studies) are providing additional data beyond that available previously from structural, thermodynamic, and kinetic results. These should serve to continue to improve our understanding of the molecular mechanism of allostery
- Metal-mediated formation of free radicals causes various modifications to DNA bases, enhanced lipid peroxidation, and altered calcium and sulfhydryl homeostasis. The measurement of free radicals has increased awareness of radical-induced impairment of the oxidative/antioxidative balance, essential for an understanding of disease progression. Metal-mediated formation of free radicals causes various modifications to DNA bases, enhanced lipid peroxidation, and altered calcium and sulfhydryl homeostasis. Lipid peroxides, formed by the attack of radicals on polyunsaturated fatty acid residues of phospholipids, can further react with redox metals finally producing mutagenic and carcinogenic malondialdehyde, 4-hydroxynonenal and other exocyclic DNA adducts (etheno and/or propano adducts). The unifying factor in determining toxicity and carcinogenicity for all these metals is the generation of reactive oxygen and nitrogen species. Various studies have confirmed that metals activate signaling pathways and the carcinogenic effect of metals has been related to activation of mainly redox sensitive transcription factors, involving NF-kappaB, AP-1 and p53.
- There is heterogeneity in the immediate interstices between cancer cells, which may seem surprising, but it should not be. This refers to the complexity of the cells arranged as tissues and to their immediate environment, which I shall elaborate on. Integration with genome-wide profiling data identified losses of specific genes on 4p14 and 5q13 that were enriched in grade 3 tumors with high microenvironmental diversity that also substratified patients into poor prognostic groups.
IDH1 mutations have been identified at the Arg132 codon. Mutations in IDH2 have been identified at the Arg140 codon, as well as at Arg172, which is aligned with IDH1 Arg132. IDH1 and IDH2 mutations are heterozygous in cancer, and they catalyze the production of α-2-hydroxyglutarate. The study found human IDH1 transitions between an inactive open, an inactive semi-open, and a catalytically active closed conformation. In the inactive open conformation, Asp279 occupies the position where the isocitrate substrate normally forms hydrogen bonds with Ser94. This steric hindrance by Asp279 to isocitrate binding is relieved in the active closed conformation.
There are allelic variations that underlie common diseases and complete genome sequencing for many individuals with and without disease is required. However, there are advantages and disadvantages as we can carry out partial surveys of the genome by genotyping large numbers of common SNPs in genome-wide association studies but there are problems such as computing the data efficiently and sharing the information without tempering privacy.
Since the first report of p53 as a non-histone target of a histone acetyltransferase (HAT), there has been a rapid proliferation in the description of new non-histone targets of HATs. Of these,
- transcription factors comprise the largest class of new targets.
The substrates for HATs extend to
- cytoskeletal proteins,
- molecular chaperones and
- nuclear import factors.
- Deacetylation of these non-histone proteins by histone deacetylases (HDACs) opens yet another exciting new field of discovery in
- the role of the dynamic acetylation and deacetylation on cellular function.
We capture the dynamic interactions between the systems under stress that are elicited by cytokine-driven hormonal responses, long thought to be circulatory and multisystem, that affect the major compartments of fat and lean body mass, and are as much the drivers of metabolic pathway changes that emerge as epigenetics, without disregarding primary genetic diseases.
The greatest difficulty in organizing such a work is in whether it is to be merely a compilation of cancer expression organized by organ systems, or whether it is to capture developing concepts of underlying stem cell expressed changes that were once referred to as “dedifferentiation”. In proceeding through the stages of neoplastic transformation, there occur adaptive local changes in cellular utilization of anabolic and catabolic pathways, and a retention or partial retention of functional specificities.
This effectively results in the same cancer types not all fitting into the same “shoe”. There is a sequential loss of identity associated with cell migration, cell-cell interactions with underlying stroma, and metastasis., but cells may still retain identifying “signatures” in microRNA combinatorial patterns. The story is still incomplete, with gaps in our knowledge that challenge the imagination.
What we have laid out is a map with substructural ordered concepts forming subsets within the structural maps. There are the traditional energy pathways with terms aerobic and anaerobic glycolysis, gluconeogenesis, triose phosphate branch chains, pentose shunt, and TCA cycle vs the Lynen cycle, the Cori cycle, glycogenolysis, lipid peroxidation, oxidative stress, autosomy and mitosomy, and genetic transcription, cell degradation and repair, muscle contraction, nerve transmission, and their involved anatomic structures (cytoskeleton, cytoplasm, mitochondria, liposomes and phagosomes, contractile apparatus, synapse.
We are a magnificent “magical” experience in evolutionary time, functioning in a bioenvironment, put rogether like a truly complex machine, and with interacting parts. What are those parts – organelles, a genetic message that may be constrained and it may be modified based on chemical structure, feedback, crosstalk, and signaling pathways. This brings in diet as a source of essential nutrients, exercise as a method for delay of structural loss (not in excess), stress oxidation, repair mechanisms, and an entirely unexpected impact of this knowledge on pharmacotherapy.
Despite what we have learned, the strength of inter-molecular interactions, strong and weak chemical bonds, essential for 3-D folding, we know little about the importance of trace metals that have key roles in catalysis and because of their orbital structures, are essential for organic-inorganic interplay. This will not be coming soon because we know almost nothing about the intracellular, interstitial, and intravesicular distributions and how they affect the metabolic – truly metabolic events.
- We must translate the sequence information from genomics locus of the genes to function with related polymorphism of these genes so that possible patterns of the gene expression and disease traits can be matched. Then, we may develop precision technologies for:
- Diagnostics
- Targeted Drugs and Treatments
- Biomarkers to modulate cells for correct functions
With the knowledge of:
- gene expression variations
- insight in the genetic contribution to clinical endpoints ofcomplex disease and
- their biological risk factors,
- share etiologic pathways
which requires an understanding of both:
- the structure and
- the biology of the genome.
- A new paradigm is summarized in a sequence of six steps:
“(1) A pathogenic stimulus (biological or chemical) leads at first to a normal reaction seen in wound healing, namely, inflammation. When the inflammatory stimulus is too great or too prolonged, the healing process is unsuccessful, and that results in
(2) chronic inflammation.
“That’s just the beginning. When chronic inflammation persists,
(3) fibrosis [thickening and scarring of the connective tissue,] develops. The fibrosis, with its ongoing alteration of the cellular microenvironment is different and creates
(4) a precancerous niche, resulting in a chronically stressed cellular matrix. In such a situation, the organism deploys
(5) a chronic stress escape strategy. But if this attempt fails to resolve the precancerous state, then
(6) a normal cell is transformed into a cancerous cell.”
Keep in mind:
- Nutritional resources that have been available and made plentiful over generations are not abundant in some climates.
- Despite the huge impact that genomics has had on biological progress over the last century, there is a huge contribution not to be overlooked in epigenetics, metabolomics, and pathways analysis.
I have provided mechanisms explanatory for regulation of the cell that go beyond the classic model of metabolic pathways associated with the cytoplasm, mitochondria, endoplasmic reticulum, and lysosome, such as, the cell death pathways, expressed in apoptosis and repair. Nevertheless, there is still a missing part of this discussion that considers the time and space interactions of the cell, cellular cytoskeleton and extracellular and intracellular substrate interactions in the immediate environment.
- Signal transduction occurs when an extracellular signaling[1] molecule activates a specific receptor located on the cell surface or inside the cell. In turn, this receptor triggers a biochemical chain of events inside the cell, creating a response.[2] Depending on the cell, the response alters the cell’s metabolism, shape, gene expression, or ability to divide.[3] The signal can be amplified at any step. Thus, one signaling molecule can cause many responses.[4]
In 1970, Martin Rodbell examined the effects of glucagon on a rat’s liver cell membrane receptor. He noted that guanosine triphosphate disassociated glucagon from this receptor and stimulated the G-protein, which strongly influenced the cell’s metabolism. Thus, he deduced that the G-protein is a transducer that accepts glucagon molecules and affects the cell.[5] For this, he shared the 1994 Nobel Prize in Physiology or Medicine with Alfred G. Gilman.
Signal transduction involves the binding of extracellular signaling molecules and ligands to cell-surface receptors that trigger events inside the cell. The combination of messenger with receptor causes a change in the conformation of the receptor, known as receptor activation. This activation is always the initial step (the cause) leading to the cell’s ultimate responses (effect) to the messenger. Despite the myriad of these ultimate responses, they are all directly due to changes in particular cell proteins. Intracellular signaling cascades can be started through cell-substratum interactions; examples are the integrin that binds ligands in the extracellular matrix and steroids.[13] Most steroid hormones have receptors within the cytoplasm and act by stimulating the binding of their receptors to the promoter region of steroid-responsive genes.[14] Examples of signaling molecules include the hormone melatonin,[15] the neurotransmitter acetylcholine[16] and the cytokine interferon γ.[17]
Various environmental stimuli exist that initiate signal transmission processes in multicellular organisms; examples include photons hitting cells in the retina of the eye,[20] and odorants binding to odorant receptors in the nasal epithelium.[21] Certain microbial molecules, such as viral nucleotides and protein antigens, can elicit an immune system response against invading pathogens mediated by signal transduction processes. This may occur independent of signal transduction stimulation by other molecules, as is the case for the toll-like receptor. It may occur with help from stimulatory molecules located at the cell surface of other cells, as with T-cell receptor signaling.
Unraveling the multitude of
- nutrigenomic,
- proteomic, and
- metabolomic patterns
that arise from the ingestion of foods or their
- bioactive food components
will not be simple but is likely to provide insights into a tailored approach to diet and health. The use of new and innovative technologies, such as
- microarrays,
- RNA interference, and
- nanotechnologies,
will provide needed insights into molecular targets for specific bioactive food components and
- how they harmonize to influence individual phenotypes(1).
- Oct4 has a critical role in committing pluripotent cells into the somatic cellular pathway. When embryonic stem cells overexpress Oct4, they undergo rapid differentiation and then lose their ability for pluripotency. Other studies have shown that Oct4 expression in somatic cells reprograms them for transformation into a particular germ cell layer and also gives rise to induced pluripotent stem cells (iPSCs) under specific culture conditions.
Oct4 is the gatekeeper into and out of the reprogramming expressway. By modifying experimental conditions, Oct4 plus additional factors can induce formation of iPSCs, epiblast stem cells, neural cells, or cardiac cells. Dr. Schöler suggests that Oct4 a potentially key factor not only for inducing iPSCs but also for transdifferention. “Therapeutic applications might eventually focus less on pluripotency and more on multipotency,
- Epigenetics is getting a big attention recently to understand genomics and provide better results. However, this field is studied for many years under functional genomics and developmental biology for cellular and molecular biology. Stem cells have a free drive that we have not figured out yet. So genomics must be studied essentially with people training in developmental biology and comparative molecular genetics knowledge to make heads and tail for translational medicine.
There are three main routes of epigenetic modifications one
- histone modifications via acetylation and methylation and the other is
- DNA methylation, which are two classical mechanisms in epigenetics.
The third factor is
- non-coding RNAs that are usually underestimated even not included.
In 1993, Kavai group showed brain development assays of mice showed that only 0.7% genome has tissue and cellular specificity, and 1.7% of genome was able to turn on and off. This conclusion is relevant to genome sequencing data. Also, previous studies in genome and RNA biology presented that RNA directed DNA modifications lead into splicing and transcriptional silencing for gene regulation in Arapsidosis, mice, and Drosophila. (Borge, F. and. Martiensse, R.A. 2013; Di Croce L, Raker VA, Corsaro M, et al. 2002; Piferrer, F, 2013; Jun Kawai1 et al. 1993)
The environment creates the epigenerators including temperature, differentiation signals and metabolites that trigger the cell membrane proteins for development of signal transduction within the cell to activate gene(s) and to create cellular response. These changes can be modulated but they are not necessary for modulation. The second step involves epigenetic initiators that require precise coordination to recognize specific sequences on a chromatin in response to epigenerator signals. These molecules are
- DNA binding proteins and
- non coding RNAs.
After they are involved they are on for life and controlled by autoregulatory mechanisms, like Sxl (sex lethal) RNA binding protein in somatic sex determination and ovo DNA binding protein in germline sex determination of fruit fly. Both have autoregulation mechanisms, cross talks, differential signals and cross reacting genes since after the final update made the soma has to maintain the decision to stay healthy and develop correctly. Then, this brings the third level mechanism called epigenetic maintainers that are DNA methylating enzymes, histone modifying enzymes and histone variants. The good news is they can be reversed. As a result the phonotype establishes either a
- short term phenotype, transient for transcription,
- DNA replication and repair or
- long term phenotype outcomes that are chromatin conformation and heritable markers.
Early in development things are short term and stop after the development seized but be able to maintain the short term phenotype during wound healing, coagulation, trauma, disease and immune responses.
The metabolome for each organism is unique, but from an evolutionary perspective has metabolic pathways in common, and expressed in concert with the environment that these living creatures exist. The metabolome of each has adaptive accommodation with suppression and activation of pathways that are functional and necessary in balance, for its existence.
Most interesting is a recent report from Johns Hopkins in Mar 28, PNAS on breast cancer and stem cell physiology. “Aggressive cancers contain regions where the cancer cells are starved for oxygen and die off, yet patients with these tumors generally have the worst outcome,” Semenza said in a release. “Our new findings tell us that low oxygen conditions actually encourage certain cancer stem cells to multiply through the same mechanism used by embryonic stem cells.”
One of the genes responsible for initiating a stem cell fate under low oxygen conditions is called NANOG. This gene is one of many turned on in oxygen-poor conditions by proteins called hypoxia-inducible factors, or HIFs. NANOG in turn instructs cells to become stem cells to resist the poor conditions and help survival.
NANOG levels can be artificially lowered in embryonic stem cells by experimentally methylating the respective mRNA transcript at the sixth position of its adenine nucleotide. Since this methylation is otherwise thought to stabilize the transcript from degradation, this may help NANOG abandon its proposed stem cell fate for the cell.
In addition to the basic essential nutrients and their metabolic utilization, they are under cellular metabolic regulation that is tied to signaling pathways. In addition, the genetic expression of the organism is under regulatory control by the interaction of RNAs that interact with the chromatin genetic framework, with exosomes, and with protein modulators. This is referred to as epigenetics, but there are also drivers of metabolism that are shaped by the interactions between enzymes and substrates, and are related to the tertiary structure of a protein. The framework for diseases in and Pharmaceutical interventions that are designed to modulate specific metabolic targets are addressed as the pathways are unfolded.
Personalized Medicine is here now
Two years ago AJP was found to have a positive test for BRCA1, carrying an 87 percent risk for breast cancer and a 50 percent risk for ovarian cancer. At that time she had a preventive mastectomy. The decision was not easy, but it also brought into consideration that her mother and grandmother both died of breast cancer. She did not have an oophorectomy at that time because on considering the advice of medical experts, she would have been left with no estrogen support. She wanted to delay her early vegetative senescence. She has reached the age of 39 years and on the advice of medical expert opinion, she proceeded with salpingo-oophorectomy, at age 39 years, a decade before her mother had developed cancer. But her delay was to allow her to recover and adjust emotionally to her ongoing situation, with a remaining risk for ovarian cancer.
in a report in Carcinogenesis back in 2005[3] Lorena Losi, Benedicte Baisse, Hanifa Bouzourene and Jean Benhatter had shown some similar results in colorectal cancer as their abstract described:
“In primary colorectal cancers (CRCs), intratumoral genetic heterogeneity was more often observed in early than in advanced stages, at 90 and 67%, respectively. All but one of the advanced CRCs were composed of one predominant clone and other minor clones, whereas no predominant clone has been identified in half of the early cancers. A reduction of the intratumoral genetic heterogeneity for point mutations and a relative stability of the heterogeneity for allelic losses indicate that, during the progression of CRC, clonal selection and chromosome instability continue, while an increase cannot be proven.”
An article written by Drs. Andrei Krivtsov and Scott Armstrong entitled “Can One Cell Influence Cancer Heterogeneity”[4] commented on a study by Friedman-Morvinski[5] in Inder Verma’s laboratory discussed how genetic lesions can revert differentiated neurons and glial cells to an undifferentiated state [an important phenotype in development of glioblastoma multiforme].
In particular it is discussed that epigenetic state of the transformed cell may contribute to the heterogeneity of the resultant tumor. Indeed many investigators (initially discovered and proposed by Dr. Beatrice Mintz of the Institute for Cancer Research, later to be named the Fox Chase Cancer Center) show the cellular microenvironment influences transformation and tumor development [6-8].
The mechanism by which tissue microecology influences invasion and metastasis is largely unknown. Recent studies have indicated differences in the molecular architecture of the metastatic lesion compared to the primary tumor, however, systemic analysis of the alterations within the activated protein signaling network has not been described. Using laser capture microdissection, protein microarray technology, and a unique specimen collection of 34 matched primary colorectal cancers (CRC) and synchronous hepatic metastasis, the quantitative measurement of the total and activated/phosphorylated levels of 86 key signaling proteins was performed. Activation of the EGFR-PDGFR-cKIT network, in addition to PI3K/AKT pathway, was found uniquely activated in the hepatic metastatic lesions compared to the matched primary tumors. If validated in larger study sets, these findings may have potential clinical relevance since many of these activated signaling proteins are current targets for molecularly targeted therapeutics. Thus, these findings could lead to liver metastasis specific molecular therapies for CRC.
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