1 6571 113 TRANSPOSABLE ELEMENTS CROSS KINGDOM BOUNDARIES AND CONTRIBUTE TO INFLAMMATION AND AGEING: SOMATIC ACQUISITION OF FOREIGN TRANSPOSABLE ELEMENTS AS A CATALYST OF GENOME INSTABILITY, EPIGENETIC DYSREGULATION, INFLAMMATION, SENESCENCE, AND AGEING. THE DE-REPRESSION OF TRANSPOSABLE ELEMENTS (TES) IN MAMMALIAN GENOMES IS THOUGHT TO CONTRIBUTE TO GENOME INSTABILITY, INFLAMMATION, AND AGEING, YET IS VIEWED AS A CELL-AUTONOMOUS EVENT. IN CONTRAST TO MAMMALIAN CELLS, PROKARYOTES CONSTANTLY EXCHANGE GENETIC MATERIAL THROUGH TES, CROSSING BOTH CELL AND SPECIES BARRIERS, CONTRIBUTING TO RAPID MICROBIAL EVOLUTION AND DIVERSITY IN COMPLEX COMMUNITIES SUCH AS THE MAMMALIAN GUT. HERE, IT IS PROPOSED THAT TES RELEASED FROM PROKARYOTES IN THE MICROBIOME OR FROM PATHOGENIC INFECTIONS REGULARLY CROSS THE KINGDOM BARRIER TO THE SOMATIC CELLS OF THEIR EUKARYOTIC HOSTS. IT IS PROPOSED THIS HORIZONTAL TRANSFER OF TES FROM MICROBE TO HOST IS A STOCHASTIC, ONGOING CATALYST OF GENOME DESTABILIZATION, RESULTING IN STRUCTURAL AND EPIGENETIC VARIATIONS, AND ACTIVATION OF WELL-EVOLVED HOST DEFENSE MECHANISMS CONTRIBUTING TO INFLAMMATION, SENESCENCE, AND BIOLOGICAL AGEING. IT IS PROPOSED THAT INNATE IMMUNITY PATHWAYS DEFEND AGAINST THE HORIZONTAL ACQUISITION OF MICROBIAL TES, AND THAT ACTIVATION OF THIS PATHWAY DURING HORIZONTAL TRANSPOSON TRANSFER PROMOTES CHRONIC INFLAMMATION DURING AGEING. FINALLY, IT IS SUGGESTED THAT HORIZONTAL ACQUISITION OF PROKARYOTIC TES INTO MAMMALIAN GENOMES HAS BEEN MASKED AND SUBSEQUENTLY UNDER-REPORTED DUE TO FLAWS IN CURRENT SEQUENCING PIPELINES, AND NEW STRATEGIES TO UNCOVER THESE EVENTS ARE PROPOSED. 2020 2 5942 30 TARGETING OF CELLULAR REDOX METABOLISM FOR MITIGATION OF RADIATION INJURY. ACCIDENTAL EXPOSURE TO IONIZING RADIATION IS A SERIOUS CONCERN TO HUMAN LIFE. STUDIES ON THE MITIGATION OF SIDE EFFECTS FOLLOWING EXPOSURE TO ACCIDENTAL RADIATION EVENTS ARE ONGOING. RECENT STUDIES HAVE SHOWN THAT RADIATION CAN ACTIVATE SEVERAL SIGNALING PATHWAYS, LEADING TO CHANGES IN THE METABOLISM OF FREE RADICALS INCLUDING REACTIVE OXYGEN SPECIES (ROS) AND NITRIC OXIDE (NO). CELLULAR AND MOLECULAR MECHANISMS SHOW THAT RADIATION CAN CAUSE DISRUPTION OF NORMAL REDUCTION/OXIDATION (REDOX) SYSTEM. MITOCHONDRIA MALFUNCTION FOLLOWING EXPOSURE TO RADIATION AND MUTATIONS IN MITOCHONDRIA DNA (MTDNA) HAVE A KEY ROLE IN CHRONIC OXIDATIVE STRESS. FURTHERMORE, EXPOSURE TO RADIATION LEADS TO INFILTRATION OF INFLAMMATORY CELLS SUCH AS MACROPHAGES, LYMPHOCYTES AND MAST CELLS, WHICH ARE IMPORTANT SOURCES OF ROS AND NO. THESE CELLS GENERATE FREE RADICALS VIA UPREGULATION OF SOME PRO-OXIDANT ENZYMES SUCH AS NADPH OXIDASES, INDUCIBLE NITRIC OXIDE SYNTHASE (INOS) AND CYCLOOXYGENASE-2 (COX-2). EPIGENETIC CHANGES ALSO HAVE A KEY ROLE IN A SIMILAR WAY. OTHER MEDIATORS SUCH AS MAMMALIAN TARGET OF RAPAMYCIN (MTOR) AND PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR (PPAR), WHICH ARE INVOLVED IN THE NORMAL METABOLISM OF CELLS HAVE ALSO BEEN SHOWN TO REGULATE CELL DEATH FOLLOWING EXPOSURE TO RADIATION. THESE MECHANISMS ARE TISSUE SPECIFIC. INHIBITION OR ACTIVATION OF EACH OF THESE TARGETS CAN BE SUGGESTED FOR MITIGATION OF RADIATION INJURY IN A SPECIFIC TISSUE. IN THE CURRENT PAPER, WE REVIEW THE CELLULAR AND MOLECULAR CHANGES IN THE METABOLISM OF CELLS AND ROS/NO FOLLOWING EXPOSURE TO RADIATION. FURTHERMORE, THE POSSIBLE STRATEGIES FOR MITIGATION OF RADIATION INJURY THROUGH MODULATION OF CELLULAR METABOLISM IN IRRADIATED ORGANS WILL BE DISCUSSED. 2020 3 5252 26 PROGRAMMING AND REGULATION OF METABOLIC HOMEOSTASIS. EVIDENCE IS PRESENTED THAT THE RATE AND EQUILIBRIUM CONSTANTS IN MITOCHONDRIAL OXIDATIVE PHOSPHORYLATION SET AND MAINTAIN METABOLIC HOMEOSTASIS IN EUKARYOTIC CELLS. THESE INTERNAL CONSTANTS DETERMINE THE ENERGY STATE ([ATP]/[ADP][PI]), AND THE ENERGY STATE MAINTAINS HOMEOSTASIS THROUGH A BIDIRECTIONAL SENSORY/SIGNALING CONTROL NETWORK THAT REACHES EVERY ASPECT OF CELLULAR METABOLISM. THE ENERGY STATE IS MAINTAINED WITH HIGH PRECISION (TO APPROXIMATELY 1 PART IN 10(10)), AND THE CONTROL SYSTEM CAN RESPOND TO TRANSIENT CHANGES IN ENERGY DEMAND (ATP UTILIZATION) OF MORE THAN 100 TIMES THE RESTING RATE. EPIGENETIC AND ENVIRONMENTAL FACTORS ARE ABLE TO "FINE-TUNE" THE PROGRAMMED SET POINT OVER A NARROW RANGE TO MEET THE SPECIAL NEEDS ASSOCIATED WITH CELL DIFFERENTIATION AND CHRONIC CHANGES IN METABOLIC REQUIREMENTS. THE RESULT IS ROBUST ACROSS-PLATFORM CONTROL OF METABOLISM, WHICH IS ESSENTIAL TO CELLULAR DIFFERENTIATION AND THE EVOLUTION OF COMPLEX ORGANISMS. A MODEL OF OXIDATIVE PHOSPHORYLATION IS PRESENTED, FOR WHICH THE STEADY-STATE RATE EXPRESSION HAS BEEN DERIVED AND COMPUTER PROGRAMMED. THE BEHAVIOR OF OXIDATIVE PHOSPHORYLATION PREDICTED BY THE MODEL IS SHOWN TO FIT THE EXPERIMENTAL DATA AVAILABLE FOR ISOLATED MITOCHONDRIA AS WELL AS FOR CELLS AND TISSUES. THIS INCLUDES MEASUREMENTS FROM SEVERAL DIFFERENT MAMMALIAN TISSUES AS WELL AS FROM INSECT FLIGHT MUSCLE AND PLANTS. THE RESPIRATORY CHAIN AND OXIDATIVE PHOSPHORYLATION IS REMARKABLY SIMILAR FOR ALL HIGHER PLANTS AND ANIMALS. THIS IS CONSISTENT WITH THE EFFICIENT SYNTHESIS OF ATP AND PRECISE CONTROL OF METABOLIC HOMEOSTASIS PROVIDED BY OXIDATIVE PHOSPHORYLATION BEING A KEY TO CELLULAR DIFFERENTIATION AND THE EVOLUTION OF STRUCTURES WITH SPECIALIZED FUNCTION. 2015 4 2614 25 EPIGENETICS: NEW QUESTIONS ON THE RESPONSE TO HYPOXIA. REDUCTION IN OXYGEN LEVELS BELOW NORMAL CONCENTRATIONS PLAYS IMPORTANT ROLES IN DIFFERENT NORMAL AND PATHOLOGICAL CONDITIONS, SUCH AS DEVELOPMENT, TUMORIGENESIS, CHRONIC KIDNEY DISEASE AND STROKE. ORGANISMS EXPOSED TO HYPOXIA TRIGGER CHANGES AT BOTH CELLULAR AND SYSTEMIC LEVELS TO RECOVER OXYGEN HOMEOSTASIS. MOST OF THESE PROCESSES ARE MEDIATED BY HYPOXIA INDUCIBLE FACTORS, HIFS, A FAMILY OF TRANSCRIPTION FACTORS THAT DIRECTLY INDUCE THE EXPRESSION OF SEVERAL HUNDRED GENES IN MAMMALIAN CELLS. ALTHOUGH DIFFERENT ASPECTS OF HIF REGULATION ARE WELL KNOWN, IT IS STILL UNCLEAR BY WHICH PRECISE MECHANISM HIFS ACTIVATE TRANSCRIPTION OF THEIR TARGET GENES. CONCOMITANTLY, HYPOXIA PROVOKES A DRAMATIC DECREASE OF GENERAL TRANSCRIPTION THAT SEEMS TO RELY IN PART ON EPIGENETIC CHANGES THROUGH A POORLY UNDERSTOOD MECHANISM. IN THIS REVIEW WE DISCUSS THE CURRENT KNOWLEDGE ON CHROMATIN CHANGES INVOLVED IN HIF DEPENDENT GENE ACTIVATION, AS WELL AS ON OTHER EPIGENETIC CHANGES, NOT NECESSARILY LINKED TO HIF THAT TAKE PLACE UNDER HYPOXIC CONDITIONS. 2011 5 474 19 ARSENIC BIOTRANSFORMATION AS A CANCER PROMOTING FACTOR BY INDUCING DNA DAMAGE AND DISRUPTION OF REPAIR MECHANISMS. CHRONIC EXPOSURE TO ARSENIC IN DRINKING WATER POSES A MAJOR GLOBAL HEALTH CONCERN. POPULATIONS EXPOSED TO HIGH CONCENTRATIONS OF ARSENIC-CONTAMINATED DRINKING WATER SUFFER SERIOUS HEALTH CONSEQUENCES, INCLUDING ALARMING CANCER INCIDENCE AND DEATH RATES. ARSENIC IS BIOTRANSFORMED THROUGH SEQUENTIAL ADDITION OF METHYL GROUPS, ACQUIRED FROM S-ADENOSYLMETHIONINE (SAM). METABOLISM OF ARSENIC GENERATES A VARIETY OF GENOTOXIC AND CYTOTOXIC SPECIES, DAMAGING DNA DIRECTLY AND INDIRECTLY, THROUGH THE GENERATION OF REACTIVE OXIDATIVE SPECIES AND INDUCTION OF DNA ADDUCTS, STRAND BREAKS AND CROSS LINKS, AND INHIBITION OF THE DNA REPAIR PROCESS ITSELF. SINCE SAM IS THE METHYL GROUP DONOR USED BY DNA METHYLTRANSFERASES TO MAINTAIN NORMAL EPIGENETIC PATTERNS IN ALL HUMAN CELLS, ARSENIC IS ALSO POSTULATED TO AFFECT MAINTENANCE OF NORMAL DNA METHYLATION PATTERNS, CHROMATIN STRUCTURE, AND GENOMIC STABILITY. THE BIOLOGICAL PROCESSES UNDERLYING THE CANCER PROMOTING FACTORS OF ARSENIC METABOLISM, RELATED TO DNA DAMAGE AND REPAIR, WILL BE DISCUSSED HERE. 2011 6 5416 17 REGULATION OF CELLULAR METABOLISM: PROGRAMMING AND MAINTAINING METABOLIC HOMEOSTASIS. MITOCHONDRIAL OXIDATIVE PHOSPHORYLATION IS PROGRAMMED TO SET AND MAINTAIN METABOLIC HOMEOSTASIS. THIS IS ACCOMPLISHED THROUGH AN INTRINSIC PROGRAM THAT DETERMINES THE METABOLIC [ATP]/[ADP]/[PI], WHERE [PI] IS THE CONCENTRATION OF INORGANIC PHOSPHATE (ENERGY STATE) AND MAINTAINS IT THROUGH A BIDIRECTIONAL SENSORY/SIGNALING CONTROL NETWORK THAT REACHES EVERY ASPECT OF CELLULAR METABOLISM. THE PROGRAM SETS THE ENERGY STATE WITH HIGH PRECISION (TO BETTER THAN ONE PART IN 10(9)) AND CAN RESPOND TO TRANSIENT CHANGES IN ENERGY DEMAND (ATP USE) TO MORE THAN 100 TIMES THE RESTING RATE. EPIGENETIC AND ENVIRONMENTAL FACTORS ARE ABLE TO "FINE TUNE" THE PROGRAMMED SET POINT OVER A NARROW RANGE TO MEET THE SPECIAL NEEDS ASSOCIATED WITH CELL DIFFERENTIATION AND CHRONIC CHANGES IN METABOLIC REQUIREMENTS. THE RESULT IS ROBUST, ACROSS PLATFORM CONTROL OF METABOLISM, ESSENTIAL TO CELLULAR DIFFERENTIATION AND THE EVOLUTION OF COMPLEX ORGANISMS. 2013 7 6855 21 [NEW APPROACH TO THE INVESTIGATION OF DOHAD USING X-INACTIVATION GENE EXPRESSION SYSTEM]. X-CHROMOSOME INACTIVATION (XCI) OCCURS DURING THE GESTATION PERIOD TO COMPENSATE FOR THE DOSAGE OF X-LINKED GENES IN FEMALE MAMMALS. XIST RNA IS A LONG NONCODING RNA WITH A GLOBAL EPIGENETIC FUNCTION AND IS INDISPENSABLE FOR XCI FROM THE INITIATION TO ESTABLISHMENT AND MAINTENANCE PHASES. THE X CHROMOSOME CONTAINS OVER 1,000 GENES THAT ARE ESSENTIAL FOR PROPER DEVELOPMENT, ESPECIALLY THAT OF THE BRAIN, IMMUNE SYSTEM, METABOLISM AND REPRODUCTIVE FUNCTIONS. WE FOUND THAT EXPOSURE TO BISPHENOL A OR FOLATE DEFICIENCY DURING THE FETAL PERIOD CHANGES THE EXPRESSIONS OF XIST, TSIX (THE ANTISENSE REPRESSOR OF XIST), AND MANY X CHROMOSOME LINKED GENES WIDELY IN NEWBORN MICE. THIS FINDING SUGGESTS THAT THIS X-CHROMOSOME MEDIATED EFFECT IS CONSIDERED ONE OF THE MECHANISMS OF VARIOUS PROBLEMS ENCOUNTERED IN THE FETAL ENVIRONMENT. THE DEVELOPMENTAL ORIGINS OF HEALTH AND DISEASE (DOHAD) HYPOTHESIS STATES THAT NUTRITION AND OTHER ENVIRONMENTAL STIMULI DURING CRITICAL PERIODS AFFECT DEVELOPMENTAL PATHWAYS WITH EPIGENETICS AND INDUCE METABOLISM AND CHRONIC DISEASE SUSCEPTIBILITY. THE XCI PROCESS HAS SOME SIMILARITIES TO THIS HYPOTHESIS AND IT MAY BECOME ONE OF THE APPROACHES TO REVEAL THE DOHAD MECHANISMS. 2018 8 1300 24 DEDIFFERENTIATION AND IN VIVO REPROGRAMMING OF COMMITTED CELLS IN WOUND REPAIR (REVIEW). ACCUMULATING EVIDENCE HAS SHOWN THAT CELL DEDIFFERENTIATION OR REPROGRAMMING IS A PIVOTAL PROCEDURE FOR ANIMALS TO DEAL WITH INJURY AND PROMOTE ENDOGENOUS TISSUE REPAIR. TISSUE DAMAGE IS A CRITICAL FACTOR THAT TRIGGERS CELL DEDIFFERENTIATION OR REPROGRAMMING IN VIVO. BY CONTRAST, MICROENVIRONMENTAL CHANGES, INCLUDING THE LOSS OF STEM CELLS, HYPOXIA, CELL SENESCENCE, INFLAMMATION AND IMMUNITY, CAUSED BY TISSUE DAMAGE CAN RETURN CELLS TO AN UNSTABLE STATE. IF THE WOUND PERSISTS IN THE LONG?TERM DUE TO CHRONIC DAMAGE, THEN DEDIFFERENTIATION OR REPROGRAMMING OF THE SURROUNDING CELLS MAY LEAD TO CARCINOGENESIS. IN RECENT YEARS, EXTENSIVE RESEARCH HAS BEEN PERFORMED INVESTIGATING CELL DEDIFFERENTIATION OR REPROGRAMMING IN VIVO, WHICH CAN HAVE SIGNIFICANT IMPLICATIONS FOR WOUND REPAIR, TREATMENT AND PREVENTION OF CANCER IN THE FUTURE. THE CURRENT REVIEW SUMMARIZES THE MOLECULAR EVENTS THAT ARE KNOWN TO DRIVE CELL DEDIFFERENTIATION DIRECTLY FOLLOWING TISSUE INJURY AND THE EFFECTS OF EPIGENETIC MODIFICATION ON DEDIFFERENTIATION OR REPROGRAMMING IN VIVO. IN ADDITION, THE PRESENT REVIEW EXPLORES THE INTRACELLULAR MECHANISM OF ENDOGENOUS TISSUE REPAIR AND ITS RELATIONSHIP WITH CANCER, WHICH IS ESSENTIAL FOR BALANCING THE RISK BETWEEN TISSUE REPAIR AND MALIGNANT TRANSFORMATION AFTER INJURY. 2022 9 3287 28 HIERARCHICAL AND CYBERNETIC NATURE OF BIOLOGIC SYSTEMS AND THEIR RELEVANCE TO HOMEOSTATIC ADAPTATION TO LOW-LEVEL EXPOSURES TO OXIDATIVE STRESS-INDUCING AGENTS. DURING EVOLUTION IN AN AEROBIC ENVIRONMENT, MULTICELLULAR ORGANISMS SURVIVED BY ADAPTIVE RESPONSES TO BOTH THE ENDOGENOUS OXIDATIVE METABOLISM IN THE CELLS OF THE ORGANISM AND THE CHEMICALS AND LOW-LEVEL RADIATION TO WHICH THEY HAD BEEN EXPOSED. THE DEFENSE REPERTOIRE EXISTS AT ALL LEVELS OF THE BIOLOGICAL HIERARCHY--FROM THE MOLECULAR AND BIOCHEMICAL LEVEL TO THE CELLULAR AND TISSUE LEVEL TO THE ORGAN AND ORGAN SYSTEM LEVEL. CELLS CONTAIN PREVENTIVE ANTIOXIDANTS TO SUPPRESS OXIDATIVE DAMAGE TO MEMBRANES. CELLS ALSO CONTAIN PROTEINS AND DNA; BUILT-IN REDUNDANCIES FOR DAMAGED MOLECULES AND ORGANELLES; TIGHTLY COUPLED REDOX SYSTEMS; POOLS OF REDUCTANTS; ANTIOXIDANTS; DNA REPAIR MECHANISMS AND SENSITIVE SENSOR MOLECULES SUCH AS NUCLEAR FACTOR KAPPA BETA; AND SIGNAL TRANSDUCTION MECHANISMS AFFECTING BOTH TRANSCRIPTION AND POST-TRANSLATIONAL MODIFICATION OF PROTEINS NEEDED TO COPE WITH OXIDATIVE STRESS. THE BIOLOGIC CONSEQUENCES OF THE LOW-LEVEL RADIATION THAT EXCEEDS THE BACKGROUND LEVEL OF OXIDATIVE DAMAGE COULD BE NECROSIS OR APOPTOSIS, CELL PROLIFERATION, OR CELL DIFFERENTIATION. THESE EFFECTS ARE TRIGGERED BY OXIDATIVE STRESS-INDUCED SIGNAL TRANSDUCTION MECHANISMS--AN EPIGENETIC, NOT GENOTOXIC, PROCESS. IF THE END POINTS OF CELL PROLIFERATION, DIFFERENTIATION, OR CELL DEATH ARE NOT SEEN AT FREQUENCIES ABOVE BACKGROUND LEVELS IN AN ORGANISM, IT IS UNLIKELY THAT LOW-LEVEL RADIATION WOULD PLAY A ROLE IN THE MULTISTEP PROCESSES OF CHRONIC DISEASES SUCH AS CANCER. THE MECHANISM LINKED TO HOMEOSTATIC REGULATION OF PROLIFERATION AND ADAPTIVE FUNCTIONS IN A MULTICELLULAR ORGANISM COULD PROVIDE PROTECTION OF ANY ONE CELL RECEIVING DEPOSITED ENERGY BY THE RADIATION TRACT THROUGH THE SHARING OF REDUCTANTS AND BY TRIGGERING APOPTOSIS OF TARGET STEM CELLS. EXAMPLES OF THE ROLE OF GAP JUNCTIONAL INTERCELLULAR COMMUNICATION IN THE ADAPTIVE RESPONSE OF CELLS AND THE BYSTANDER EFFECT ILLUSTRATE HOW THE INTERACTION OF CELLS CAN MODULATE THE EFFECT OF RADIATION ON THE SINGLE CELL. 1998 10 2111 15 EPIGENETIC FUNCTION OF TET FAMILY, 5-METHYLCYTOSINE, AND 5-HYDROXYMETHYLCYTOSINE IN HEMATOLOGIC MALIGNANCIES. DNA METHYLATION PLAYS SIGNIFICANT ROLES IN A VARIETY OF BIOLOGICAL AND PATHOLOGICAL PROCESSES INCLUDING MAMMALIAN DEVELOPMENT, GENOMIC IMPRINTING, RETROTRANSPOSON SILENCING, AND X-CHROMOSOME INACTIVATION. RECENT DISCOVERIES INDICATED THAT TEN-ELEVEN TRANSLOCATION (TET) FAMILY OF DIOXYGENASES CAN CONVERT 5-METHYLCYTOSINE (5-MC) INTO 5-HYDROXYMETHYLCYTOSINE (5-HMC). THE TET FAMILY INCLUDES THREE MEMBERS: TET1, TET2, AND TET3. WITH INCREASING EVIDENCE, MORE AND MORE BIOLOGICAL AND PATHOLOGICAL PROCESSES IN WHICH 5-HMC AND TET FAMILY SERVE UNPARALLELED BIOLOGICAL ROLES ARE NOTICED, FOR EXAMPLE, DNA DEMETHYLATION AND TRANSCRIPTIONAL REGULATION OF DIFFERENT TARGET GENES, WHICH ARE INVOLVED IN MANY HUMAN DISEASES, ESPECIALLY HEMATOLOGIC MALIGNANCIES, RESEMBLING CHRONIC MYELOMONOCYTIC LEUKEMIA, MYELODYSPLASTIC SYNDROMES, AND SO ON. IN THIS REVIEW, WE FOCUS ON THE DIVERSE FUNCTIONS OF TET FAMILY AND THE NOVEL EPIGENETIC MARKS, 5-MC AND 5-HMC, IN HEMATOLOGIC MALIGNANCIES. THIS REVIEW WILL PROVIDE VALUABLE INSIGHTS INTO THE POTENTIAL TARGETS OF HEMATOLOGIC MALIGNANCIES. FURTHER UNDERSTANDING OF THE NORMAL AND PATHOLOGICAL FUNCTIONS OF TET FAMILY MAY PROVIDE NEW METHODS TO DEVELOP NOVEL EPIGENETIC THERAPIES FOR TREATING HEMATOLOGIC MALIGNANCIES. 2019 11 2184 23 EPIGENETIC MECHANISMS THAT UNDERPIN METABOLIC AND CARDIOVASCULAR DISEASES. CELLULAR COMMITMENT TO A SPECIFIC LINEAGE IS CONTROLLED BY DIFFERENTIAL SILENCING OF GENES, WHICH IN TURN DEPENDS ON EPIGENETIC PROCESSES SUCH AS DNA METHYLATION AND HISTONE MODIFICATION. DURING EARLY EMBRYOGENESIS, THE MAMMALIAN GENOME IS 'WIPED CLEAN' OF MOST EPIGENETIC MODIFICATIONS, WHICH ARE PROGRESSIVELY RE-ESTABLISHED DURING EMBRYONIC DEVELOPMENT. THUS, THE EPIGENOME OF EACH MATURE CELLULAR LINEAGE CARRIES THE RECORD OF ITS DEVELOPMENTAL HISTORY. THE SUBSEQUENT TRAJECTORY AND PATTERN OF DEVELOPMENT ARE ALSO RESPONSIVE TO ENVIRONMENTAL INFLUENCES, AND SUCH PLASTICITY IS LIKELY TO HAVE AN EPIGENETIC BASIS. EPIGENETIC MARKS MAY BE TRANSMITTED ACROSS GENERATIONS, EITHER DIRECTLY BY PERSISTING THROUGH MEIOSIS OR INDIRECTLY THROUGH REPLICATION IN THE NEXT GENERATION OF THE CONDITIONS IN WHICH THE EPIGENETIC CHANGE OCCURRED. DEVELOPMENTAL PLASTICITY EVOLVED TO MATCH AN ORGANISM TO ITS ENVIRONMENT, AND A MISMATCH BETWEEN THE PHENOTYPIC OUTCOME OF ADAPTIVE PLASTICITY AND THE CURRENT ENVIRONMENT INCREASES THE RISK OF METABOLIC AND CARDIOVASCULAR DISEASE. THESE CONSIDERATIONS POINT TO EPIGENETIC PROCESSES AS A KEY MECHANISM THAT UNDERPINS THE DEVELOPMENTAL ORIGINS OF CHRONIC NONCOMMUNICABLE DISEASE. HERE, WE REVIEW THE EVIDENCE THAT ENVIRONMENTAL INFLUENCES DURING MAMMALIAN DEVELOPMENT LEAD TO STABLE CHANGES IN THE EPIGENOME THAT ALTER THE INDIVIDUAL'S SUSCEPTIBILITY TO CHRONIC METABOLIC AND CARDIOVASCULAR DISEASE, AND DISCUSS THE CLINICAL IMPLICATIONS. 2009 12 5816 22 STRESS AND STEM CELLS. THE UNIQUE PROPERTIES AND FUNCTIONS OF STEM CELLS MAKE THEM PARTICULARLY SUSCEPTIBLE TO STRESSES AND ALSO LEAD TO THEIR REGULATION BY STRESS. STEM CELL DIVISION MUST RESPOND TO THE DEMAND TO REPLENISH CELLS DURING NORMAL TISSUE TURNOVER AS WELL AS IN RESPONSE TO DAMAGE. OXIDATIVE STRESS, MECHANICAL STRESS, GROWTH FACTORS, AND CYTOKINES SIGNAL STEM CELL DIVISION AND DIFFERENTIATION. MANY OF THE CONSERVED PATHWAYS REGULATING STEM CELL SELF-RENEWAL AND DIFFERENTIATION ARE ALSO STRESS-RESPONSE PATHWAYS. THE LONG LIFE SPAN AND DIVISION POTENTIAL OF STEM CELLS CREATE A PROPENSITY FOR TRANSFORMATION (CANCER) AND SPECIFIC STRESS RESPONSES SUCH AS APOPTOSIS AND SENESCENCE ACT AS ANTITUMOR MECHANISMS. QUIESCENCE REGULATED BY CDK INHIBITORS AND A HYPOXIC NICHE REGULATED BY FOXO TRANSCRIPTION FACTOR FUNCTION TO REDUCE STRESS FOR SEVERAL TYPES OF STEM CELLS TO FACILITATE LONG-TERM MAINTENANCE. AGING IS A PARTICULARLY RELEVANT STRESS FOR STEM CELLS, BECAUSE REPEATED DEMANDS ON STEM CELL FUNCTION OVER THE LIFE SPAN CAN HAVE CUMULATIVE CELL-AUTONOMOUS EFFECTS INCLUDING EPIGENETIC DYSREGULATION, MUTATIONS, AND TELOMERE EROSION. IN ADDITION, AGING OF THE ORGANISM IMPAIRS FUNCTION OF THE STEM CELL NICHE AND SYSTEMIC SIGNALS, INCLUDING CHRONIC INFLAMMATION AND OXIDATIVE STRESS. 2012 13 2541 20 EPIGENETICS IN KIDNEY DEVELOPMENT AND RENAL DISEASE. THE STUDY OF EPIGENETICS IS INTIMATELY LINKED AND INSEPARABLE FROM DEVELOPMENTAL BIOLOGY. MANY OF THE GENES THAT IMPRINT EPIGENETIC INFORMATION ON CHROMATIN FUNCTION DURING THE SPECIFICATION OF CELL LINEAGES IN THE DEVELOPING EMBRYO. THESE INCLUDE THE HISTONE METHYLTRANSFERASES AND THEIR COFACTORS OF THE POLYCOMB AND TRITHORAX GENE FAMILIES. HOW HISTONE METHYLATION IS ESTABLISHED AND WHAT REGULATES THE TISSUE AND LOCUS SPECIFICITY OF HISTONE METHYLATION IS AN EMERGING AREA OF RESEARCH. THE EMBRYONIC KIDNEY IS USED AS A MODEL TO UNDERSTAND HOW DNA-BINDING PROTEINS CAN SPECIFY CELL LINEAGES AND HOW SUCH PROTEINS INTERACT DIRECTLY WITH THE HISTONE METHYLATION MACHINERY TO GENERATE A UNIQUE EPIGENOME FOR PARTICULAR TISSUES AND CELL TYPES. IN ADULT TISSUES, HISTONE METHYLATION MARKS MUST BE MAINTAINED FOR NORMAL GENE EXPRESSION PATTERNS. IN CHRONIC AND ACUTE RENAL DISEASE, EPIGENETIC MARKS ARE BEING CHARACTERIZED AND CORRELATED WITH THE ESTABLISHMENT OF METABOLIC MEMORY, IN PART TO EXPLAIN THE PERSISTENCE OF PATHOLOGIES EVEN WHEN OPTIMAL TREATMENT MODALITIES ARE USED. THUS, THE STATE OF THE EPIGENOME IN ADULT CELLS MUST BE CONSIDERED WHEN ATTEMPTING TO ALLEVIATE OR ALTER GENE EXPRESSION PATTERNS IN DISEASE. 2015 14 860 23 CHROMATIN MODIFICATIONS DURING REPAIR OF ENVIRONMENTAL EXPOSURE-INDUCED DNA DAMAGE: A POTENTIAL MECHANISM FOR STABLE EPIGENETIC ALTERATIONS. EXPOSURES TO ENVIRONMENTAL TOXICANTS AND TOXINS CAUSE EPIGENETIC CHANGES THAT LIKELY PLAY A ROLE IN THE DEVELOPMENT OF DISEASES ASSOCIATED WITH EXPOSURE. THE MECHANISM BEHIND THESE EXPOSURE-INDUCED EPIGENETIC CHANGES IS CURRENTLY UNKNOWN. ONE COMMONALITY BETWEEN MOST ENVIRONMENTAL EXPOSURES IS THAT THEY CAUSE DNA DAMAGE EITHER DIRECTLY OR THROUGH CAUSING AN INCREASE IN REACTIVE OXYGEN SPECIES, WHICH CAN DAMAGE DNA. LIKE TRANSCRIPTION, DNA DAMAGE REPAIR MUST OCCUR IN THE CONTEXT OF CHROMATIN REQUIRING BOTH HISTONE MODIFICATIONS AND ATP-DEPENDENT CHROMATIN REMODELING. THESE CHROMATIN CHANGES AID IN DNA DAMAGE ACCESSIBILITY AND SIGNALING. SEVERAL PROTEINS AND COMPLEXES INVOLVED IN EPIGENETIC SILENCING DURING BOTH DEVELOPMENT AND CANCER HAVE BEEN FOUND TO BE LOCALIZED TO SITES OF DNA DAMAGE. THE CHROMATIN-BASED RESPONSE TO DNA DAMAGE IS CONSIDERED A TRANSIENT EVENT, WITH CHROMATIN BEING RESTORED TO NORMAL AS DNA DAMAGE REPAIR IS COMPLETED. HOWEVER, IN INDIVIDUALS CHRONICALLY EXPOSED TO ENVIRONMENTAL TOXICANTS OR WITH CHRONIC INFLAMMATORY DISEASE, REPEATED DNA DAMAGE-INDUCED CHROMATIN REARRANGEMENT MAY ULTIMATELY LEAD TO PERMANENT EPIGENETIC ALTERATIONS. UNDERSTANDING THE MECHANISM BEHIND EXPOSURE-INDUCED EPIGENETIC CHANGES WILL ALLOW US TO DEVELOP STRATEGIES TO PREVENT OR REVERSE THESE CHANGES. THIS REVIEW FOCUSES ON EPIGENETIC CHANGES AND DNA DAMAGE INDUCED BY ENVIRONMENTAL EXPOSURES, THE CHROMATIN CHANGES THAT OCCUR AROUND SITES OF DNA DAMAGE, AND HOW THESE TRANSIENT CHROMATIN CHANGES MAY LEAD TO HERITABLE EPIGENETIC ALTERATIONS AT SITES OF CHRONIC EXPOSURE. 2014 15 3837 24 IONIZING RADIATION-INDUCED OXIDATIVE STRESS, EPIGENETIC CHANGES AND GENOMIC INSTABILITY: THE PIVOTAL ROLE OF MITOCHONDRIA. PURPOSE: TO REVIEW THE DATA CONCERNING THE ROLE OF ENDOGENOUSLY GENERATED REACTIVE OXYGEN SPECIES (ROS) IN THE NON-TARGETED IONIZING RADIATION (IR) EFFECTS AND IN DETERMINATION OF THE CELL POPULATION'S FATE, BOTH EARLY AFTER EXPOSURE AND AFTER MANY GENERATIONS. CONCLUSIONS: THE SHORT-TERM AS WELL AS CHRONIC OXIDATIVE STRESS RESPONSES MAINLY ARE PRODUCED DUE TO ROS GENERATION BY THE ELECTRON TRANSPORT CHAIN (ETC) OF THE MITOCHONDRIA AND BY THE CYTOPLASMIC NADPH OXIDASES. WHETHER THE INDUCTION OF THE OXIDATIVE STRESS AND ITS CONSEQUENCES OCCUR OR ARE HAMPERED IN A SINGLE CELL LARGELY DEPENDS ON THE INTERACTION BETWEEN THE NUCLEUS AND THE CELLULAR POPULATION OF SEVERAL HUNDRED OR THOUSANDS OF MITOCHONDRIA THAT ARE GENETICALLY HETEROGENEOUS. HIGH INTRA-MITOCHONDRIAL ROS LEVEL IS DAMAGING THE MITOCHONDRIAL (MT) DNA AND ITS MUTATIONS AFFECT THE EPIGENETIC CONTROL MECHANISMS OF THE NUCLEAR (N) DNA, BY DECREASING THE ACTIVITY OF METHYLTRANSFERASES AND THUS, CAUSING GLOBAL DNA HYPOMETHYLATION. THESE CHANGES ARE TRANSMITTED TO THE PROGENY OF THE IRRADIATED CELLS. THE CHRONIC OXIDATIVE STRESS IS THE MAIN CAUSE OF THE LATE POST-RADIATION EFFECTS, INCLUDING CANCER, AND THIS MAKES IT AN IMPORTANT ADVERSE EFFECT OF EXPOSURE TO IR AND A TARGET FOR RADIOLOGICAL PROTECTION. 2015 16 1929 23 ENVIRONMENTAL EXPOSURE, DNA METHYLATION, AND GENE REGULATION: LESSONS FROM DIETHYLSTILBESTEROL-INDUCED CANCERS. DNA METHYLATION IS AN EPIGENETIC MECHANISM THAT REGULATES CHROMOSOMAL STABILITY AND GENE EXPRESSION. ABNORMAL DNA METHYLATION PATTERNS HAVE BEEN OBSERVED IN MANY TYPES OF HUMAN TUMORS, INCLUDING THOSE OF THE BREAST, PROSTATE, COLON, THYROID, STOMACH, UTERUS, AND CERVIX. WE AND OTHERS HAVE SHOWN THAT EXPOSURE TO A WIDE VARIETY OF XENOBIOTICS DURING CRITICAL PERIODS OF MAMMALIAN DEVELOPMENT CAN PERSISTENTLY ALTER THE PATTERN OF DNA METHYLATION, RESULTING IN POTENTIALLY ADVERSE BIOLOGICAL EFFECTS SUCH AS ABERRANT GENE EXPRESSION. THUS, THIS EPIGENETIC MECHANISM MAY UNDERLIE THE OBSERVED INCREASED RISK IN ADULTHOOD OF SEVERAL CHRONIC DISEASES, INCLUDING CANCER, IN RESPONSE TO XENOBIOTIC EXPOSURES EARLY IN LIFE. WE PRESENT HERE THE LESSONS LEARNED FROM STUDIES ON THE EFFECTS OF PERINATAL DIETHYLSTILBESTEROL (DES) EXPOSURE ON THE METHYLATION PATTERN OF THE PROMOTERS OF SEVERAL ESTROGEN-RESPONSIVE GENES ASSOCIATED WITH THE DEVELOPMENT OF REPRODUCTIVE ORGANS. PERINATAL DES EXPOSURE, WHICH INDUCES EPITHELIAL TUMORS OF THE UTERUS IN MICE AND IS ASSOCIATED WITH SEVERAL REPRODUCTIVE TRACT ABNORMALITIES AND INCREASED VAGINAL AND CERVICAL CANCER RISK IN WOMEN, PROVIDES A CLEAR EXAMPLE OF HOW ESTROGENIC XENOBIOTIC EXPOSURE DURING A CRITICAL PERIOD OF DEVELOPMENT CAN ABNORMALLY DEMETHYLATE DNA SEQUENCES DURING ORGAN DEVELOPMENT AND POSSIBLY INCREASE CANCER RISK LATER IN LIFE. IN ADDITION, NUTRITIONAL FACTORS AND STRESS MAY ALSO ALTER DNA METHYLATION DURING EARLY LIFE AND MODULATE THE RISK OF CANCER AND OTHER CHRONIC DISEASES IN ADULTHOOD. WE SUGGEST THAT DNA METHYLATION STATUS MAY BE INFLUENCED BY ENVIRONMENTAL EXPOSURES IN EARLY LIFE, LEADING TO INCREASED RISK OF CANCER IN ADULTHOOD. 2003 17 3403 22 HOW EPIGENETIC MODIFICATIONS DRIVE THE EXPRESSION AND MEDIATE THE ACTION OF PGC-1ALPHA IN THE REGULATION OF METABOLISM. EPIGENETIC CHANGES ARE A HALLMARK OF SHORT- AND LONG-TERM TRANSCRIPTIONAL REGULATION, AND HENCE INSTRUMENTAL IN THE CONTROL OF CELLULAR IDENTITY AND PLASTICITY. EPIGENETIC MECHANISMS LEADING TO CHANGES IN CHROMATIN STRUCTURE, ACCESSIBILITY FOR RECRUITMENT OF TRANSCRIPTIONAL COMPLEXES, AND INTERACTION OF ENHANCERS AND PROMOTERS ALL CONTRIBUTE TO ACUTE AND CHRONIC ADAPTATIONS OF CELLS, TISSUES AND ORGANS TO INTERNAL AND EXTERNAL PERTURBATIONS. SIMILARLY, THE PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR GAMMA COACTIVATOR 1ALPHA (PGC-1ALPHA) IS ACTIVATED BY STIMULI THAT ALTER THE CELLULAR ENERGETIC DEMAND, AND SUBSEQUENTLY CONTROLS COMPLEX TRANSCRIPTIONAL NETWORKS RESPONSIBLE FOR CELLULAR PLASTICITY. IT THUS IS OF NO SURPRISE THAT PGC-1ALPHA IS UNDER THE CONTROL OF EPIGENETIC MECHANISMS, AND CONSTITUTES A MEDIATOR OF EPIGENETIC CHANGES IN VARIOUS TISSUES AND CONTEXTS. IN THIS REVIEW, WE SUMMARIZE THE CURRENT KNOWLEDGE OF THE LINK BETWEEN EPIGENETICS AND PGC-1ALPHA IN HEALTH AND DISEASE. 2019 18 712 25 CADMIUM AND ITS EPIGENETIC EFFECTS. CADMIUM (CD) IS A TOXIC, NONESSENTIAL TRANSITION METAL AND CONTRIBUTES A HEALTH RISK TO HUMANS, INCLUDING VARIOUS CANCERS AND CARDIOVASCULAR DISEASES; HOWEVER, UNDERLYING MOLECULAR MECHANISMS REMAIN LARGELY UNKNOWN. CELLS TRANSMIT INFORMATION TO THE NEXT GENERATION VIA TWO DISTINCT WAYS: GENETIC AND EPIGENETIC. CHEMICAL MODIFICATIONS TO DNA OR HISTONE THAT ALTERS THE STRUCTURE OF CHROMATIN WITHOUT CHANGE OF DNA NUCLEOTIDE SEQUENCE ARE KNOWN AS EPIGENETICS. THESE HERITABLE EPIGENETIC CHANGES INCLUDE DNA METHYLATION, POST-TRANSLATIONAL MODIFICATIONS OF HISTONE TAILS (ACETYLATION, METHYLATION, PHOSPHORYLATION, ETC), AND HIGHER ORDER PACKAGING OF DNA AROUND NUCLEOSOMES. APART FROM DNA METHYLTRANSFERASES, HISTONE MODIFICATION ENZYMES SUCH AS HISTONE ACETYLTRANSFERASE, HISTONE DEACETYLASE, AND METHYLTRANSFERASE, AND MICRORNAS (MIRNAS) ALL INVOLVE IN THESE EPIGENETIC CHANGES. RECENT STUDIES INDICATE THAT CD IS ABLE TO INDUCE VARIOUS EPIGENETIC CHANGES IN PLANT AND MAMMALIAN CELLS IN VITRO AND IN VIVO. SINCE ABERRANT EPIGENETICS PLAYS A CRITICAL ROLE IN THE DEVELOPMENT OF VARIOUS CANCERS AND CHRONIC DISEASES, CD MAY CAUSE THE ABOVE-MENTIONED PATHOGENIC RISKS VIA EPIGENETIC MECHANISMS. HERE WE REVIEW THE IN VITRO AND IN VIVO EVIDENCE OF EPIGENETIC EFFECTS OF CD. THE AVAILABLE FINDINGS INDICATE THAT EPIGENETICS OCCURRED IN ASSOCIATION WITH CD INDUCTION OF MALIGNANT TRANSFORMATION OF CELLS AND PATHOLOGICAL PROLIFERATION OF TISSUES, SUGGESTING THAT EPIGENETIC EFFECTS MAY PLAY A ROLE IN CD TOXIC, PARTICULARLY CARCINOGENIC EFFECTS. THE FUTURE OF ENVIRONMENTAL EPIGENOMIC RESEARCH ON CD SHOULD INCLUDE THE ROLE OF EPIGENETICS IN DETERMINING LONG-TERM AND LATE-ONSET HEALTH EFFECTS FOLLOWING CD EXPOSURE. 2012 19 4683 27 NEW PERSPECTIVES ON FOLATE TRANSPORT IN RELATION TO ALCOHOLISM-INDUCED FOLATE MALABSORPTION--ASSOCIATION WITH EPIGENOME STABILITY AND CANCER DEVELOPMENT. FOLATES ARE MEMBERS OF THE B-CLASS OF VITAMINS, WHICH ARE REQUIRED FOR THE SYNTHESIS OF PURINES AND PYRIMIDINES, AND FOR THE METHYLATION OF ESSENTIAL BIOLOGICAL SUBSTANCES, INCLUDING PHOSPHOLIPIDS, DNA, AND NEUROTRANSMITTERS. FOLATES CANNOT BE SYNTHESIZED DE NOVO BY MAMMALS; HENCE, AN EFFICIENT INTESTINAL ABSORPTION PROCESS IS REQUIRED. INTESTINAL FOLATE TRANSPORT IS CARRIER-MEDIATED, PH-DEPENDENT AND ELECTRONEUTRAL, WITH SIMILAR AFFINITY FOR OXIDIZED AND REDUCED FOLIC ACID DERIVATIVES. THE VARIOUS TRANSPORTERS, I.E. REDUCED FOLATE CARRIER, PROTON-COUPLED FOLATE TRANSPORTER, FOLATE-BINDING PROTEIN, AND ORGANIC ANION TRANSPORTERS, ARE INVOLVED IN THE FOLATE TRANSPORT PROCESS IN VARIOUS TISSUES. ANY IMPAIRMENT IN UPTAKE OF FOLATE CAN LEAD TO A STATE OF FOLATE DEFICIENCY, THE MOST PREVALENT VITAMIN DEFICIENCY IN WORLD, AFFECTING 10% OF THE POPULATION IN THE USA. SUCH IMPAIRMENTS IN FOLATE TRANSPORT OCCUR IN A VARIETY OF CONDITIONS, INCLUDING CHRONIC USE OF ETHANOL, SOME INBORN HEREDITARY DISORDERS, AND CERTAIN DISEASES. AMONG THESE, ETHANOL INGESTION HAS BEEN THE MAJOR CONTRIBUTOR TO FOLATE DEFICIENCY. ETHANOL-ASSOCIATED FOLATE DEFICIENCY CAN DEVELOP BECAUSE OF DIETARY INADEQUACY, INTESTINAL MALABSORPTION, ALTERED HEPATOBILIARY METABOLISM, ENHANCED COLONIC METABOLISM, AND INCREASED RENAL EXCRETION. ETHANOL REDUCES THE INTESTINAL AND RENAL UPTAKE OF FOLATE BY ALTERING THE BINDING AND TRANSPORT KINETICS OF FOLATE TRANSPORT SYSTEMS. ALSO, ETHANOL REDUCES THE EXPRESSION OF FOLATE TRANSPORTERS IN BOTH INTESTINE AND KIDNEY, AND THIS MIGHT BE A CONTRIBUTING FACTOR FOR FOLATE MALABSORPTION, LEADING TO FOLATE DEFICIENCY. THE MAINTENANCE OF INTRACELLULAR FOLATE HOMEOSTASIS IS ESSENTIAL FOR THE ONE-CARBON TRANSFER REACTIONS NECESSARY FOR DNA SYNTHESIS AND BIOLOGICAL METHYLATION REACTIONS. DNA METHYLATION IS AN IMPORTANT EPIGENETIC DETERMINANT IN GENE EXPRESSION, IN THE MAINTENANCE OF DNA INTEGRITY AND STABILITY, IN CHROMOSOMAL MODIFICATIONS, AND IN THE DEVELOPMENT OF MUTATIONS. ETHANOL, A TOXIN THAT IS CONSUMED REGULARLY, HAS BEEN FOUND TO AFFECT THE METHYLATION OF DNA. IN ADDITION TO ITS EFFECT ON DNA METHYLATION DUE TO FOLATE DEFICIENCY, ETHANOL COULD DIRECTLY EXERT ITS EFFECT THROUGH ITS INTERACTION WITH ONE-CARBON METABOLISM, IMPAIRMENT OF METHYL GROUP SYNTHESIS, AND AFFECTING THE ENZYMES REGULATING THE SYNTHESIS OF S-ADENOSYLMETHIONINE, THE PRIMARY METHYL GROUP DONOR FOR MOST BIOLOGICAL METHYLATION REACTIONS. THUS, ETHANOL PLAYS AN IMPORTANT ROLE IN THE PATHOGENESIS OF SEVERAL DISEASES THROUGH ITS POTENTIAL ABILITY TO MODULATE THE METHYLATION OF BIOLOGICAL MOLECULES. THIS REVIEW DISCUSSES THE UNDERLYING MECHANISM OF FOLATE MALABSORPTION IN ALCOHOLISM, THE MECHANISM OF METHYLATION-ASSOCIATED SILENCING OF GENES, AND HOW THE INTERACTION BETWEEN ETHANOL AND FOLATE DEFICIENCY AFFECTS THE METHYLATION OF GENES, THEREBY MODULATING EPIGENOME STABILITY AND THE RISK OF CANCER. 2009 20 2033 27 EPIGENETIC CHANGES IN SOLID AND HEMATOPOIETIC TUMORS. THERE ARE THREE CONNECTED MOLECULAR MECHANISMS OF EPIGENETIC CELLULAR MEMORY IN MAMMALIAN CELLS: DNA METHYLATION, HISTONE MODIFICATIONS, AND RNA INTERFERENCE. THE FIRST TWO HAVE NOW BEEN FIRMLY LINKED TO NEOPLASTIC TRANSFORMATION. HYPERMETHYLATION OF CPG-RICH PROMOTERS TRIGGERS LOCAL HISTONE CODE MODIFICATIONS RESULTING IN A CELLULAR CAMOUFLAGE MECHANISM THAT SEQUESTERS GENE PROMOTERS AWAY FROM TRANSCRIPTION FACTORS AND RESULTS IN STABLE SILENCING. THIS NORMALLY RESTRICTED MECHANISM IS UBIQUITOUSLY USED IN CANCER TO SILENCE HUNDREDS OF GENES, AMONG WHICH SOME CRITICALLY CONTRIBUTE TO THE NEOPLASTIC PHENOTYPE. VIRTUALLY EVERY PATHWAY IMPORTANT TO CANCER FORMATION IS AFFECTED BY THIS PROCESS. METHYLATION PROFILING OF HUMAN CANCERS REVEALS TISSUE-SPECIFIC EPIGENETIC SIGNATURES, AS WELL AS TUMOR-SPECIFIC SIGNATURES, REFLECTING IN PARTICULAR THE PRESENCE OF EPIGENETIC INSTABILITY IN A SUBSET OF CANCERS AFFECTED BY THE CPG ISLAND METHYLATOR PHENOTYPE. GENERALLY, METHYLATION PATTERNS CAN BE TRACED TO A TISSUE-SPECIFIC, PROLIFERATION-DEPENDENT ACCUMULATION OF ABERRANT PROMOTER METHYLATION IN AGING TISSUES, A PROCESS THAT CAN BE ACCELERATED BY CHRONIC INFLAMMATION AND LESS WELL-DEFINED MECHANISMS INCLUDING, POSSIBLY, DIET AND GENETIC PREDISPOSITION. THE EPIGENETIC MACHINERY CAN ALSO BE ALTERED IN CANCER BY SPECIFIC LESIONS IN EPIGENETIC EFFECTOR GENES, OR BY ABERRANT RECRUITMENT OF THESE GENES BY MUTANT TRANSCRIPTION FACTORS AND COACTIVATORS. EPIGENETIC PATTERNS ARE PROVING CLINICALLY USEFUL IN HUMAN ONCOLOGY VIA RISK ASSESSMENT, EARLY DETECTION, AND PROGNOSTIC CLASSIFICATION. PHARMACOLOGIC MANIPULATION OF THESE PATTERNS-EPIGENETIC THERAPY-IS ALSO POISED TO CHANGE THE WAY WE TREAT CANCER IN THE CLINIC. 2005