1 1925 76 ENVIRONMENTAL EPIGENETICS IN METAL EXPOSURE. ALTHOUGH IT IS WIDELY ACCEPTED THAT CHRONIC EXPOSURE TO ARSENITE, NICKEL, CHROMIUM AND CADMIUM INCREASES CANCER INCIDENCE IN INDIVIDUALS, THE MOLECULAR MECHANISMS UNDERLYING THEIR ABILITY TO TRANSFORM CELLS REMAIN LARGELY UNKNOWN. CARCINOGENIC METALS ARE TYPICALLY WEAK MUTAGENS, SUGGESTING THAT GENETIC-BASED MECHANISMS MAY NOT BE PRIMARILY RESPONSIBLE FOR METAL-INDUCED CARCINOGENESIS. GROWING EVIDENCE SHOWS THAT ENVIRONMENTAL METAL EXPOSURE INVOLVES CHANGES IN EPIGENETIC MARKS, WHICH MAY LEAD TO A POSSIBLE LINK BETWEEN HERITABLE CHANGES IN GENE EXPRESSION AND DISEASE SUSCEPTIBILITY AND DEVELOPMENT. HERE, WE REVIEW RECENT ADVANCES IN THE UNDERSTANDING OF METAL EXPOSURE AFFECTING EPIGENETIC MARKS AND DISCUSS ESTABLISHMENT OF HERITABLE GENE EXPRESSION IN METAL-INDUCED CARCINOGENESIS. 2011 2 4208 34 METAL CARCINOGEN EXPOSURE INDUCES CANCER STEM CELL-LIKE PROPERTY THROUGH EPIGENETIC REPROGRAMING: A NOVEL MECHANISM OF METAL CARCINOGENESIS. ARSENIC, CADMIUM, NICKEL AND HEXAVALENT CHROMIUM ARE AMONG THE MOST COMMON ENVIRONMENTAL POLLUTANTS AND POTENT CARCINOGENS. CHRONIC EXPOSURE TO THESE METALS CAUSES VARIOUS TYPES OF CANCER IN HUMANS, REPRESENTING A SIGNIFICANT ENVIRONMENTAL HEALTH ISSUE. ALTHOUGH UNDER ACTIVE INVESTIGATION, THE MECHANISMS OF METAL CARCINOGENESIS HAVE NOT BEEN CLEARLY DEFINED. ONE COMMON FEATURE OF THESE METAL CARCINOGENS IS THAT THEY ARE ALL ABLE TO CAUSE VARIOUS EPIGENETIC DYSREGULATIONS, WHICH ARE BELIEVED TO PLAY IMPORTANT ROLES IN THEIR CARCINOGENICITY. HOWEVER, HOW METAL CARCINOGEN-CAUSED EPIGENETIC DYSREGULATION CONTRIBUTES TO METAL CARCINOGENESIS REMAINS LARGELY UNKNOWN. THE EVOLUTION OF CANCER STEM CELL (CSC) THEORY HAS OPENED EXCITING NEW AVENUES FOR STUDYING THE MECHANISM OF METAL CARCINOGENESIS. INCREASING EVIDENCE INDICATES THAT CHRONIC METAL CARCINOGEN EXPOSURE PRODUCES CSC-LIKE CELLS THROUGH DYSREGULATED EPIGENETIC MECHANISMS. THIS REVIEW WILL FIRST PROVIDE SOME BRIEF INTRODUCTIONS ABOUT CSC, EPIGENETICS AND EPIGENETIC REGULATION OF CSCS; THEN SUMMARIZE PROGRESSES IN RECENT STUDIES ON METAL CARCINOGEN-INDUCED CSC-LIKE PROPERTY THROUGH EPIGENETIC REPROGRAMING AS A NOVEL MECHANISM OF METAL CARCINOGENESIS. SOME PERSPECTIVES FOR FUTURE STUDIES IN THIS FIELD ARE ALSO PRESENTED. 2019 3 6370 32 THE ROLE OF MICRORNAS IN METAL CARCINOGEN-INDUCED CELL MALIGNANT TRANSFORMATION AND TUMORIGENESIS. MICRORNAS (MIRNAS), AN IMPORTANT COMPONENT OF EPIGENETIC MECHANISMS OF CARCINOGENESIS, HAVE BEEN SHOWN TO PLAY CRUCIAL ROLES IN CANCER INITIATION, METASTASIS, PROGNOSIS AND RESPONSES TO DRUG TREATMENT AND MAY SERVE AS BIOMARKERS FOR EARLY DIAGNOSIS OF CANCER AND TOOLS FOR CANCER THERAPY. METAL CARCINOGENS, SUCH AS ARSENIC, CADMIUM, HEXAVALENT CHROMIUM AND NICKEL, ARE WELL-ESTABLISHED HUMAN CARCINOGENS CAUSING VARIOUS CANCERS UPON LONG TERM EXPOSURE. HOWEVER, THE MECHANISM OF METAL CARCINOGENESIS HAS NOT BEEN WELL UNDERSTOOD, WHICH LIMITS OUR CAPABILITY TO EFFECTIVELY DIAGNOSE AND TREAT HUMAN CANCERS RESULTING FROM CHRONIC METAL CARCINOGEN EXPOSURE. OVER RECENT YEARS, THE ROLE OF MIRNAS IN METAL CARCINOGENESIS HAS BEEN ACTIVELY EXPLORED AND A GROWING BODY OF EVIDENCE INDICATES THE CRITICAL INVOLVEMENT OF MIRNAS IN METAL CARCINOGENESIS. THIS REVIEW AIMS TO DISCUSS RECENT STUDIES SHOWING THAT MIRNAS PLAY IMPORTANT ROLES IN METAL CARCINOGEN-INDUCED CELL MALIGNANT TRANSFORMATION AND TUMORIGENESIS. SOME THOUGHTS FOR FUTURE FURTHER STUDIES IN THIS FIELD ARE ALSO PRESENTED. 2016 4 3210 23 HEALTH EFFECTS ASSOCIATED WITH PRE- AND PERINATAL EXPOSURE TO ARSENIC. INORGANIC ARSENIC IS A WELL-ESTABLISHED HUMAN CARCINOGEN, ABLE TO INDUCE GENETIC AND EPIGENETIC ALTERATIONS. MORE THAN 200 MILLION PEOPLE WORLDWIDE ARE EXPOSED TO ARSENIC CONCENTRATIONS IN DRINKING WATER EXCEEDING THE RECOMMENDED WHO THRESHOLD (10MUG/L). ADDITIONALLY, CHRONIC EXPOSURE TO LEVELS BELOW THIS THRESHOLD IS KNOWN TO RESULT IN LONG-TERM HEALTH EFFECTS IN HUMANS. THE ARSENIC-RELATED HEALTH EFFECTS IN HUMANS ARE ASSOCIATED WITH ITS BIOTRANSFORMATION PROCESS, WHEREBY THE RESULTING METABOLITES CAN INDUCE MOLECULAR DAMAGE THAT ACCUMULATES OVER TIME. THE EFFECTS DERIVED FROM THESE ALTERATIONS INCLUDE GENOMIC INSTABILITY ASSOCIATED WITH OXIDATIVE DAMAGE, ALTERATION OF GENE EXPRESSION (INCLUDING CODING AND NON-CODING RNAS), GLOBAL AND LOCALIZED EPIGENETIC REPROGRAMMING, AND HISTONE POSTTRANSLATIONAL MODIFICATIONS. THESE ALTERATIONS DIRECTLY AFFECT MOLECULAR PATHWAYS INVOLVED IN THE ONSET AND PROGRESSION OF MANY CONDITIONS THAT CAN ARISE EVEN DECADES AFTER THE EXPOSURE OCCURS. IMPORTANTLY, ARSENIC METABOLITES GENERATED DURING ITS BIOTRANSFORMATION CAN ALSO PASS THROUGH THE PLACENTAL BARRIER, RESULTING IN FETAL EXPOSURE TO THIS CARCINOGEN AT SIMILAR LEVELS TO THOSE OF THE MOTHER. AS SUCH, MORE IMMEDIATE EFFECTS OF THE ARSENIC-INDUCED MOLECULAR DAMAGE CAN BE OBSERVED AS DETRIMENTAL EFFECTS ON FETAL DEVELOPMENT, PREGNANCY, AND BIRTH OUTCOMES. IN THIS REVIEW, WE FOCUS ON THE GENETIC AND EPIGENETIC DAMAGE ASSOCIATED WITH EXPOSURE TO LOW LEVELS OF ARSENIC, PARTICULARLY THOSE AFFECTING EARLY DEVELOPMENTAL STAGES. WE ALSO PRESENT HOW THESE ALTERATIONS OCCURRING DURING EARLY LIFE CAN IMPACT THE DEVELOPMENT OF CERTAIN DISEASES IN ADULT LIFE. 2021 5 712 34 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 6 1970 27 EPIGENETIC ALTERATIONS AND OCCUPATIONAL EXPOSURE TO BENZENE, FIBERS, AND HEAVY METALS ASSOCIATED WITH TUMOR DEVELOPMENT (REVIEW). THE CHRONIC OCCUPATIONAL EXPOSURE TO CONTAMINANTS AND CARCINOGENS LEADS TO THE DEVELOPMENT OF CANCER. OVER THE PAST DECADES, MANY CARCINOGENS HAVE BEEN FOUND IN THE OCCUPATIONAL ENVIRONMENT AND THEIR PRESENCE IS OFTEN ASSOCIATED WITH AN INCREASED INCIDENCE OF CANCER. ACCORDING TO THE INTERNATIONAL AGENCY FOR RESEARCH ON CANCER (IARC), THE MAJORITY OF CARCINOGENS ARE CLASSIFIED AS 'PROBABLE' AND 'POSSIBLE' HUMAN CARCINOGENS, WHILE, DIRECT EVIDENCE OF CARCINOGENICITY IS PROVIDED IN EPIDEMIOLOGICAL AND EXPERIMENTAL STUDIES. ADDITIONALLY, ACCUMULATING EVIDENCE SUGGESTS THAT EPIGENETIC ALTERATIONS MAY BE EARLY INDICATORS OF GENOTOXIC AND NON-GENOTOXIC CARCINOGEN EXPOSURE. IN THE PRESENT REVIEW, THE RELATIONSHIP BETWEEN EXPOSURES TO BENZENE, MINERAL FIBERS, METALS AND EPIGENETIC ALTERATIONS ARE DISCUSSED AS THE MOST IMPORTANT CANCER RISK FACTORS DURING WORK ACTIVITIES. 2017 7 4460 30 MOLECULAR MECHANISMS OF ENVIRONMENTAL EXPOSURES AND HUMAN DISEASE. A SUBSTANTIAL PROPORTION OF DISEASE RISK FOR COMMON COMPLEX DISORDERS IS ATTRIBUTABLE TO ENVIRONMENTAL EXPOSURES AND POLLUTANTS. AN APPRECIATION OF HOW ENVIRONMENTAL POLLUTANTS ACT ON OUR CELLS TO PRODUCE DELETERIOUS HEALTH EFFECTS HAS LED TO ADVANCES IN OUR UNDERSTANDING OF THE MOLECULAR MECHANISMS UNDERLYING THE PATHOGENESIS OF CHRONIC DISEASES, INCLUDING CANCER AND CARDIOVASCULAR, NEURODEGENERATIVE AND RESPIRATORY DISEASES. HERE, WE DISCUSS EMERGING RESEARCH ON THE INTERPLAY OF ENVIRONMENTAL POLLUTANTS WITH THE HUMAN GENOME AND EPIGENOME. WE REVIEW EVIDENCE SHOWING THE ENVIRONMENTAL IMPACT ON GENE EXPRESSION THROUGH EPIGENETIC MODIFICATIONS, INCLUDING DNA METHYLATION, HISTONE MODIFICATION AND NON-CODING RNAS. WE ALSO HIGHLIGHT RECENT STUDIES THAT EVALUATE RECENTLY DISCOVERED MOLECULAR PROCESSES THROUGH WHICH THE ENVIRONMENT CAN EXERT ITS EFFECTS, INCLUDING EXTRACELLULAR VESICLES, THE EPITRANSCRIPTOME AND THE MITOCHONDRIAL GENOME. FINALLY, WE DISCUSS CURRENT CHALLENGES WHEN STUDYING THE EXPOSOME - THE CUMULATIVE MEASURE OF ENVIRONMENTAL INFLUENCES OVER THE LIFESPAN - AND ITS INTEGRATION INTO FUTURE ENVIRONMENTAL HEALTH RESEARCH. 2023 8 4119 29 MECHANISMS OF CADMIUM CARCINOGENICITY IN THE GASTROINTESTINAL TRACT. CANCER, A SERIOUS PUBLIC HEALTH PROBLEM IN WORLDWIDE, RESULTS FROM AN EXCESSIVE AND UNCONTROLLED PROLIFERATION OF THE BODY CELLS WITHOUT OBVIOUS PHYSIOLOGICAL DEMANDS OF ORGANS. THE GASTROINTESTINAL TRACT, INCLUDING THE ESOPHAGUS, STOMACH AND INTESTINE, IS A UNIQUE ORGAN SYSTEM. IT HAS THE HIGHEST CANCER INCIDENCE AND CANCER- RELATED MORTALITY IN THE BODY AND IS INFLUENCEED BY BOTH GENETIC AND ENVIRONMENTAL FACTORS. AMONG THE VARIOUS CHEMICAL ELEMENTS RECOGNIZED IN THE NATURE, SOME OF THEM INCLUDING ZINC, IRON, COBALT, AND COPPER HAVE ESSENTIAL ROLES IN THE VARIOUS BIOCHEMICAL AND PHYSIOLOGICAL PROCESSES, BUT ONLY AT LOW LEVELS AND OTHERS SUCH AS CADMIUM, LEAD, MERCURY, ARSENIC, AND NICKEL ARE CONSIDERED AS THREATS FOR HUMAN HEALTH ESPECIALLY WITH CHRONIC EXPOSURE AT HIGH LEVELS. CADMIUM, AN ENVIRONMENT CONTAMINANT, CANNOT BE DESTROYED IN NATURE. THROUGH IMPAIRMENT OF VITAMIN D METABOLISM IN THE KIDNEY IT CAUSES NEPHROTOXICITY AND SUBSEQUENTLY BONE METABOLISM IMPAIRMENT AND FRAGILITY. THE MAJOR MECHANISMS INVOLVED IN CADMIUM CARCINOGENESIS COULD BE RELATED TO THE SUPPRESSION OF GENE EXPRESSION, INHIBITION OF DNA DAMAGE REPAIR, INHIBITION OF APOPTOSIS, AND INDUCTION OF OXIDATIVE STRESS. IN ADDITION, CADMIUM MAY ACT THROUGH ABERRANT DNA METHYLATION. CADMIUM AFFECTS MULTIPLE CELLULAR PROCESSES, INCLUDING SIGNAL TRANSDUCTION PATHWAYS, CELL PROLIFERATION, DIFFERENTIATION, AND APOPTOSIS. DOWN-REGULATION OF METHYLTRANSFERASES ENZYMES AND REDUCTION OF DNA METHYLATION HAVE BEEN STATED AS EPIGENETIC EFFECTS OF CADMIUM. FURTHERMORE, INCREASING INTRACELLULAR FREE CALCIUM ION LEVELS INDUCES NEURONAL APOPTOSIS IN ADDITION TO OTHER DELETERIOUS INFLUENCE ON THE STABILITY OF THE GENOME. 2015 9 2282 25 EPIGENETIC REGULATION IN EXPOSOME-INDUCED TUMORIGENESIS: EMERGING ROLES OF NCRNAS. ENVIRONMENTAL FACTORS, INCLUDING POLLUTANTS AND LIFESTYLE, CONSTITUTE A SIGNIFICANT ROLE IN SEVERE, CHRONIC PATHOLOGIES WITH AN ESSENTIAL SOCIETAL, ECONOMIC BURDEN. THE MEASUREMENT OF ALL ENVIRONMENTAL EXPOSURES AND ASSESSING THEIR CORRELATION WITH EFFECTS ON INDIVIDUAL HEALTH IS DEFINED AS THE EXPOSOME, WHICH INTERACTS WITH OUR UNIQUE CHARACTERISTICS SUCH AS GENETICS, PHYSIOLOGY, AND EPIGENETICS. EPIGENETICS INVESTIGATES MODIFICATIONS IN THE EXPRESSION OF GENES THAT DO NOT DEPEND ON THE UNDERLYING DNA SEQUENCE. SOME STUDIES HAVE CONFIRMED THAT ENVIRONMENTAL FACTORS MAY PROMOTE DISEASE IN INDIVIDUALS OR SUBSEQUENT PROGENY THROUGH EPIGENETIC ALTERATIONS. VARIATIONS IN THE EPIGENETIC MACHINERY CAUSE A SPECTRUM OF DIFFERENT DISORDERS SINCE THESE MECHANISMS ARE MORE SENSITIVE TO THE ENVIRONMENT THAN THE GENOME, DUE TO THE INHERENT REVERSIBLE NATURE OF THE EPIGENETIC LANDSCAPE. SEVERAL EPIGENETIC MECHANISMS, INCLUDING MODIFICATIONS IN DNA (E.G., METHYLATION), HISTONES, AND NONCODING RNAS CAN CHANGE GENOME EXPRESSION UNDER THE EXOGENOUS INFLUENCE. NOTABLY, THE ROLE OF LONG NONCODING RNAS IN EPIGENETIC PROCESSES HAS NOT BEEN WELL EXPLORED IN THE CONTEXT OF EXPOSOME-INDUCED TUMORIGENESIS. IN THE PRESENT REVIEW, OUR SCOPE IS TO PROVIDE RELEVANT EVIDENCE INDICATING THAT EPIGENETIC ALTERATIONS MEDIATE THOSE DETRIMENTAL EFFECTS CAUSED BY EXPOSURE TO ENVIRONMENTAL TOXICANTS, FOCUSING MAINLY ON A MULTI-STEP REGULATION BY DIVERSE NONCODING RNAS SUBTYPES. 2022 10 1530 31 DNA METHYLATION CHANGES INDUCED BY PRENATAL TOXIC METAL EXPOSURE: AN OVERVIEW OF EPIDEMIOLOGICAL EVIDENCE. ACCUMULATING EVIDENCE SUGGESTS THAT EXPOSURE TO UNFAVORABLE CONDITIONS EARLY IN LIFE CAN SUBSTANTIALLY CONTRIBUTE TO THE RISK OF CHRONIC DISORDERS LATER IN LIFE ('DEVELOPMENTAL PROGRAMMING' PHENOMENON). THE MECHANISTIC BASIS FOR THIS PHENOMENON REMAINS POORLY UNDERSTOOD SO FAR, ALTHOUGH EPIGENETIC MECHANISMS SUCH AS DNA METHYLATION, HISTONE MODIFICATIONS AND MICRORNA-MEDIATED GENE REGULATION APPARENTLY PLAY A CRUCIAL ROLE. THE KEY ROLE OF EPIGENETIC MODIFICATIONS TRIGGERED BY UNFAVORABLE ENVIRONMENTAL CUES DURING SENSITIVE DEVELOPMENTAL PERIODS IN LINKING ADVERSE EARLY-LIFE EVENTS TO LATER-LIFE HEALTH OUTCOMES IS EVIDENT FROM A LARGE BODY OF STUDIES, INCLUDING METHYLOME-WIDE ASSOCIATION STUDIES AND RESEARCH OF CANDIDATE GENES. TOXIC METALS (TMS), SUCH AS HEAVY METALS, INCLUDING LEAD, CHROMIUM, CADMIUM, ARSENIC, MERCURY, ETC., ARE AMONG ENVIRONMENTAL CONTAMINANTS CURRENTLY MOST SIGNIFICANTLY IMPACTING HUMAN HEALTH STATUS. SINCE TMS CAN CROSS THE PLACENTAL BARRIER AND ACCUMULATE IN FETAL TISSUES, EXPOSURE TO HIGH DOSES OF THESE XENOBIOTICS EARLY IN DEVELOPMENT IS CONSIDERED TO BE AMONG IMPORTANT FACTORS CONTRIBUTING TO THE DEVELOPMENTAL PROGRAMMING OF ADULT-LIFE DISEASES IN MODERN SOCIETIES. IN THIS MINI-REVIEW, WE SUMMARIZE EPIDEMIOLOGICAL FINDINGS INDICATING THAT PRENATAL TM EXPOSURE CAN INDUCE EPIGENETIC DYSREGULATION, THEREBY POTENTIALLY AFFECTING ADULT HEALTH OUTCOMES. 2021 11 106 29 A REVIEW OF MOLECULAR EVENTS OF CADMIUM-INDUCED CARCINOGENESIS. CADMIUM (CD) IS A TOXIC, HEAVY INDUSTRIAL METAL THAT POSES SERIOUS ENVIRONMENTAL HEALTH HAZARDS TO BOTH HUMANS AND WILDLIFE. RECENTLY, CD AND CD-CONTAINING COMPOUNDS HAVE BEEN CLASSIFIED AS KNOWN HUMAN CARCINOGENS, AND EPIDEMIOLOGICAL DATA SHOW CAUSAL ASSOCIATIONS WITH PROSTATE, BREAST, AND LUNG CANCER. THE MOLECULAR MECHANISMS INVOLVED IN CD-INDUCED CARCINOGENESIS ARE POORLY UNDERSTOOD AND ARE ONLY NOW BEGINNING TO BE ELUCIDATED. THE EFFECTS OF CHRONIC EXPOSURE TO CD HAVE RECENTLY ATTRACTED GREAT INTEREST DUE TO THE DEVELOPMENT OF MALIGNANCIES IN CD-INDUCED TUMORIGENESIS IN ANIMALS MODELS. BRIEFLY, VARIOUS IN VITRO STUDIES DEMONSTRATE THAT CD CAN ACT AS A MITOGEN, CAN STIMULATE CELL PROLIFERATION AND INHIBIT APOPTOSIS AND DNA REPAIR, AND CAN INDUCE CARCINOGENESIS IN SEVERAL MAMMALIAN TISSUES AND ORGANS. THUS, THE VARIOUS MECHANISMS INVOLVED IN CHRONIC CD EXPOSURE AND MALIGNANT TRANSFORMATIONS WARRANT FURTHER INVESTIGATION. IN THIS REVIEW, WE FOCUS ON RECENT EVIDENCE OF VARIOUS LEADING GENERAL AND TISSUE-SPECIFIC MOLECULAR MECHANISMS THAT FOLLOW CHRONIC EXPOSURE TO CD IN PROSTATE-, BREAST-, AND LUNG-TRANSFORMED MALIGNANCIES. IN ADDITION, IN THIS REVIEW, WE CONSIDER LESS DEFINED MECHANISMS SUCH AS EPIGENETIC MODIFICATION AND AUTOPHAGY, WHICH ARE THOUGHT TO PLAY A ROLE IN THE DEVELOPMENT OF CD-INDUCED MALIGNANT TRANSFORMATION. 2014 12 1917 31 ENVIRONMENTAL ARSENIC EXPOSURE: FROM GENETIC SUSCEPTIBILITY TO PATHOGENESIS. MORE THAN 200 MILLION PEOPLE IN 70 COUNTRIES ARE EXPOSED TO ARSENIC THROUGH DRINKING WATER. CHRONIC EXPOSURE TO THIS METALLOID HAS BEEN ASSOCIATED WITH THE ONSET OF MANY DISEASES, INCLUDING CANCER. EPIDEMIOLOGICAL EVIDENCE SUPPORTS ITS CARCINOGENIC POTENTIAL, HOWEVER, DETAILED MOLECULAR MECHANISMS REMAIN TO BE ELUCIDATED. DESPITE THE GLOBAL MAGNITUDE OF THIS PROBLEM, NOT ALL INDIVIDUALS FACE THE SAME RISK. SUSCEPTIBILITY TO THE TOXIC EFFECTS OF ARSENIC IS INFLUENCED BY ALTERATIONS IN GENES INVOLVED IN ARSENIC METABOLISM, AS WELL AS BIOLOGICAL FACTORS, SUCH AS AGE, GENDER AND NUTRITION. MOREOVER, CHRONIC ARSENIC EXPOSURE RESULTS IN SEVERAL GENOTOXIC AND EPIGENETIC ALTERATIONS TIGHTLY ASSOCIATED WITH THE ARSENIC BIOTRANSFORMATION PROCESS, RESULTING IN AN INCREASED CANCER RISK. IN THIS REVIEW, WE: 1) REVIEW THE ROLES OF INTER-INDIVIDUAL DNA-LEVEL VARIATIONS INFLUENCING THE SUSCEPTIBILITY TO ARSENIC-INDUCED CARCINOGENESIS; 2) DISCUSS THE CONTRIBUTION OF ARSENIC BIOTRANSFORMATION TO CANCER INITIATION; 3) PROVIDE INSIGHTS INTO EMERGING RESEARCH AREAS AND THE CHALLENGES IN THE FIELD; AND 4) COMPILE A RESOURCE OF PUBLICLY AVAILABLE ARSENIC-RELATED DNA-LEVEL VARIATIONS, TRANSCRIPTOME AND METHYLATION DATA. UNDERSTANDING THE MOLECULAR MECHANISMS OF ARSENIC EXPOSURE AND ITS SUBSEQUENT HEALTH EFFECTS WILL SUPPORT EFFORTS TO REDUCE THE WORLDWIDE HEALTH BURDEN AND ENCOURAGE THE DEVELOPMENT OF STRATEGIES FOR MANAGING ARSENIC-RELATED DISEASES IN THE ERA OF PERSONALIZED MEDICINE. 2018 13 738 27 CANCER SUSCEPTIBILITY: EPIGENETIC MANIFESTATION OF ENVIRONMENTAL EXPOSURES. CANCER IS A DISEASE THAT RESULTS FROM BOTH GENETIC AND EPIGENETIC CHANGES. DISCORDANT PHENOTYPES AND VARYING INCIDENCES OF COMPLEX DISEASES SUCH AS CANCER IN MONOZYGOTIC TWINS AS WELL AS GENETICALLY IDENTICAL LABORATORY ANIMALS HAVE LONG BEEN ATTRIBUTED TO DIFFERENCES IN ENVIRONMENTAL EXPOSURES. ACCUMULATING EVIDENCE INDICATES, HOWEVER, THAT DISPARITIES IN GENE EXPRESSION RESULTING FROM VARIABLE MODIFICATIONS IN DNA METHYLATION AND CHROMATIN STRUCTURE IN RESPONSE TO THE ENVIRONMENT ALSO PLAY A ROLE IN DIFFERENTIAL SUSCEPTIBILITY TO DISEASE. DESPITE A GROWING CONSENSUS ON THE IMPORTANCE OF EPIGENETICS IN THE ETIOLOGY OF CHRONIC HUMAN DISEASES, THE GENES MOST PRONE TO EPIGENETIC DYSREGULATION ARE INCOMPLETELY DEFINED. MOREOVER, NEITHER THE ENVIRONMENTAL AGENTS MOST STRONGLY AFFECTING THE EPIGENOME NOR THE CRITICAL WINDOWS OF VULNERABILITY TO ENVIRONMENTALLY INDUCED EPIGENETIC ALTERATIONS ARE ADEQUATELY CHARACTERIZED. THESE MAJOR DEFICITS IN KNOWLEDGE MARKEDLY IMPAIR OUR ABILITY TO UNDERSTAND FULLY THE ETIOLOGY OF CANCER AND THE IMPORTANCE OF THE EPIGENOME IN DIAGNOSING AND PREVENTING THIS DEVASTATING DISEASE. 2007 14 480 29 ARSENIC-INDUCED CARCINOGENESIS: THE IMPACT OF MIRNA DYSREGULATION. ARSENIC IS A TOXIC METALLOID WIDELY PRESENT IN THE EARTH'S CRUST, AND IS A PROVEN HUMAN CARCINOGEN. CHRONIC ARSENIC EXPOSURE MAINLY THROUGH DRINKING WATER CAUSES SKIN, LUNG, AND URINARY BLADDER CANCERS, AND IS ASSOCIATED WITH LIVER, PROSTATE, AND KIDNEY CANCERS, CARDIOVASCULAR AND NEUROLOGICAL DISORDERS, AND DIABETES. SEVERAL MODES OF ACTION HAVE BEEN SUGGESTED IN ARSENIC CARCINOGENESIS. HOWEVER, THE MOLECULAR ETIOLOGY OF ARSENIC-INDUCED CANCER REMAINS UNCLEAR. RECENT EVIDENCE CLEARLY INDICATES THAT GENE EXPRESSION MODIFICATIONS INDUCED BY ARSENIC MAY INVOLVE EPIGENETIC ALTERATIONS, INCLUDING MIRNA DYSREGULATION. MANY MIRNAS HAVE BEEN IMPLICATED IN DIFFERENT HUMAN CANCERS AS A CONSEQUENCE OF LOSSES AND OR GAINS OF MIRNA FUNCTION THAT CONTRIBUTE TO CANCER DEVELOPMENT. PROGRESS IN IDENTIFYING MIRNA DYSREGULATION INDUCED BY ARSENIC HAS BEEN MADE USING DIFFERENT APPROACHES AND MODELS. THE PRESENT REVIEW DISCUSSES THE RECENT DATA REGARDING DYSREGULATED EXPRESSION OF MIRNA IN ARSENIC-INDUCED MALIGNANT TRANSFORMATION IN VITRO, GAPS IN CURRENT UNDERSTANDING AND DEFICIENCIES IN CURRENT MODELS FOR ARSENIC-INDUCED CARCINOGENESIS, AND FUTURE DIRECTIONS OF RESEARCH THAT WOULD IMPROVE OUR KNOWLEDGE REGARDING THE MECHANISMS INVOLVED IN ARSENIC-INDUCED CARCINOGENESIS. 2018 15 6063 23 THE DEVELOPMENTAL ENVIRONMENT, EPIGENETIC BIOMARKERS AND LONG-TERM HEALTH. EVIDENCE FROM BOTH HUMAN AND ANIMAL STUDIES HAS SHOWN THAT THE PRENATAL AND EARLY POSTNATAL ENVIRONMENTS INFLUENCE SUSCEPTIBILITY TO CHRONIC DISEASE IN LATER LIFE AND SUGGESTS THAT EPIGENETIC PROCESSES ARE AN IMPORTANT MECHANISM BY WHICH THE ENVIRONMENT ALTERS LONG-TERM DISEASE RISK. EPIGENETIC PROCESSES, INCLUDING DNA METHYLATION, HISTONE MODIFICATION AND NON-CODING RNAS, PLAY A CENTRAL ROLE IN REGULATING GENE EXPRESSION. THE EPIGENOME IS HIGHLY SENSITIVE TO ENVIRONMENTAL FACTORS IN EARLY LIFE, SUCH AS NUTRITION, STRESS, ENDOCRINE DISRUPTION AND POLLUTION, AND CHANGES IN THE EPIGENOME CAN INDUCE LONG-TERM CHANGES IN GENE EXPRESSION AND PHENOTYPE. IN THIS REVIEW WE FOCUS ON HOW THE EARLY LIFE NUTRITIONAL ENVIRONMENT CAN ALTER THE EPIGENOME LEADING TO AN ALTERED SUSCEPTIBILITY TO DISEASE IN LATER LIFE. 2015 16 860 30 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 17 633 24 BIOLOGICAL EFFECTS AND EPIDEMIOLOGICAL CONSEQUENCES OF ARSENIC EXPOSURE, AND REAGENTS THAT CAN AMELIORATE ARSENIC DAMAGE IN VIVO. THROUGH CONTAMINATED DIET, WATER, AND OTHER FORMS OF ENVIRONMENTAL EXPOSURE, ARSENIC AFFECTS HUMAN HEALTH. THERE ARE MANY U.S. AND WORLDWIDE "HOT SPOTS" WHERE THE ARSENIC LEVEL IN PUBLIC WATER EXCEEDS THE MAXIMUM EXPOSURE LIMIT. THE BIOLOGICAL EFFECTS OF CHRONIC ARSENIC EXPOSURE INCLUDE GENERATION OF REACTIVE OXYGEN SPECIES (ROS), LEADING TO OXIDATIVE STRESS AND DNA DAMAGE, EPIGENETIC DNA MODIFICATION, INDUCTION OF GENOMIC INSTABILITY, AND INFLAMMATION AND IMMUNOMODULATION, ALL OF WHICH CAN INITIATE CARCINOGENESIS. HIGH ARSENIC EXPOSURE IS EPIDEMIOLOGICALLY ASSOCIATED WITH SKIN, LUNG, BLADDER, LIVER, KIDNEY AND PANCREATIC CANCER, AND CARDIOVASCULAR, NEURONAL, AND OTHER DISEASES. THIS REVIEW BRIEFLY SUMMARIZES THE BIOLOGICAL EFFECTS OF ARSENIC EXPOSURE AND EPIDEMIOLOGICAL CANCER STUDIES WORLDWIDE, AND PROVIDES AN OVERVIEW FOR EMERGING RODENT-BASED STUDIES OF REAGENTS THAT CAN AMELIORATE THE EFFECTS OF ARSENIC EXPOSURE IN VIVO. THESE REAGENTS MAY BE TRANSLATED TO HUMAN POPULATIONS FOR DISEASE PREVENTION. WE PROPOSE THE IMPORTANCE OF DEVELOPING A BIOMARKER-BASED PRECISION PREVENTION APPROACH FOR THE HEALTH ISSUES ASSOCIATED WITH ARSENIC EXPOSURE THAT AFFECTS MILLIONS OF PEOPLE WORLDWIDE. 2017 18 2655 33 EPIMUTAGENESIS: A PROSPECTIVE MECHANISM TO REMEDIATE ARSENIC-INDUCED TOXICITY. ARSENIC TOXICITY IS A GLOBAL ISSUE, ADDRESSED BY THE WORLD HEALTH ORGANIZATION AS ONE OF THE MAJOR NATURAL CALAMITIES FACED BY HUMANS. MORE THAN 137 MILLION INDIVIDUALS IN 70 NATIONS ARE AFFECTED BY ARSENIC MAINLY THROUGH DRINKING WATER AND ALSO THROUGH DIET. CHRONIC ARSENIC EXPOSURE LEADS TO VARIOUS TYPES OF PATHO-PHYSIOLOGICAL END POINTS IN HUMANS INCLUDING CANCERS. ARSENIC, A XENOBIOTIC SUBSTANCE, IS BIOTRANSFORMED IN THE BODY TO ITS METHYLATED SPECIES BY USING THE PHYSIOLOGICAL S-ADENOSYL METHIONINE (SAM). SAM DICTATES METHYLATION STATUS OF THE GENOME AND ARSENIC METABOLISM LEADS TO DEPLETION OF SAM LEADING TO AN EPIGENETIC DISEQUILIBRIUM. SINCE EPIGENETICS IS ONE OF THE MAJOR PHENOMENON AT THE INTERFACE BETWEEN THE ENVIRONMENT AND HUMAN HEALTH IMPACT, ITS DISEQUILIBRIUM BY ARSENIC INFLICTS UPON THE CHROMATIN COMPACTION, GENE EXPRESSION, GENOMIC STABILITY AND A HOST OF BIOMOLECULAR INTERACTIONS, THE INTERACTOME WITHIN THE CELL. SINCE ARSENIC IS NOT MUTAGENIC BUT IS CARCINOGENIC IN NATURE, ARSENIC INDUCED EPIMUTAGENESIS HAS COME TO THE FOREFRONT SINCE IT DETERMINES THE TRANSCRIPTIONAL AND GENOMIC INTEGRITY OF THE CELL. ARSENIC TOXICITY BRINGS FORTH SEVERAL PATHOPHYSIOLOGICAL MANIFESTATIONS LIKE DERMATOLOGICAL NON-CANCEROUS, PRE-CANCEROUS AND CANCEROUS LESIONS, PERIPHERAL NEUROPATHY, DNA DAMAGE, RESPIRATORY DISORDERS AND CANCERS OF SEVERAL INTERNAL ORGANS. RECENTLY, SEVERAL DISEASES OF SIMILAR MANIFESTATIONS HAVE BEEN EXPLAINED WITH THE RELEVANT EPIGENETIC PERSPECTIVES REGARDING THE POSSIBLE MOLECULAR MECHANISM FOR THEIR ONSET. HENCE, IN THE CURRENT REVIEW, WE COMPREHENSIVELY TRY TO INTERCALATE THE INFORMATION ON ARSENIC-INDUCED EPIGENETIC ALTERATIONS OF DNA, HISTONES AND MICRORNA SO AS TO UNDERSTAND WHETHER THE ARSENIC-INDUCED TOXIC MANIFESTATIONS ARE BROUGHT ABOUT BY THE EPIGENETIC CHANGES. WE HIGHLIGHT THE NEED TO UNDERSTAND THE ASPECT OF EPIMUTAGENESIS AND SUBSEQUENT ALTERATIONS IN THE CELLULAR INTERACTOME DUE TO ARSENIC-INDUCED MOLECULAR CHANGES, WHICH MAY BE UTILIZED TO DEVELOP PUTATIVE THERAPEUTIC STRATEGIES TARGETING BOTH OXIDATIVE POTENTIAL AND EPIMUTAGENESIS IN HUMANS. 2015 19 396 29 AN UPDATE ON EPIGENETICS AND CHILDHOOD RESPIRATORY DISEASES. EPIGENETIC MECHANISMS, DEFINED AS CHANGES IN PHENOTYPE OR GENE EXPRESSION CAUSED BY MECHANISMS OTHER THAN CHANGES IN THE UNDERLYING DNA SEQUENCE, HAVE BEEN PROPOSED TO CONSTITUTE A LINK BETWEEN GENETIC AND ENVIRONMENTAL FACTORS THAT AFFECT COMPLEX DISEASES. RECENT STUDIES SHOW THAT DNA METHYLATION, ONE OF THE KEY EPIGENETIC MECHANISMS, IS ALTERED IN CHILDREN EXPOSED TO AIR POLLUTANTS AND ENVIRONMENTAL TOBACCO SMOKE EARLY IN LIFE. SEVERAL CANDIDATE GENE STUDIES ON EPIGENETICS HAVE BEEN PUBLISHED TO DATE, BUT IT IS ONLY RECENTLY THAT GLOBAL METHYLATION ANALYSES HAVE BEEN PERFORMED FOR RESPIRATORY DISORDERS SUCH AS ASTHMA AND CHRONIC OBSTRUCTIVE PULMONARY DISEASE. HOWEVER, LARGE-SCALE STUDIES WITH ADEQUATE POWER ARE YET TO BE PRESENTED IN CHILDREN, AND IMPLICATIONS FOR CLINICAL USE REMAIN TO BE EVALUATED. IN THIS REVIEW, WE SUMMARIZE THE RECENT ADVANCES IN EPIGENETICS AND RESPIRATORY DISORDERS IN CHILDREN, WITH A MAIN FOCUS ON METHODOLOGICAL CHALLENGES AND ANALYSES RELATED TO PHENOTYPE AND EXPOSURE USING GLOBAL METHYLATION APPROACHES. 2014 20 6812 27 [EPIGENETICS, INTERFACE BETWEEN ENVIRONMENT AND GENES: ROLE IN COMPLEX DISEASES]. EPIGENETICS IS THE STUDY OF HERITABLE CHANGES IN GENE EXPRESSION OR CELLULAR PHENOTYPE CAUSED BY MECHANISMS OTHER THAN CHANGES IN THE UNDERLYING DNA SEQUENCE. EPIGENETICS IS ONE OF THE MAJOR MECHANISMS EXPLAINING THE "DEVELOPMENTAL ORIGIN OF HEALTH AND DISEASES" (DOHAD). BESIDES GENETIC BACKGROUND INHERITED FROM PARENTS, WHICH CONFERS SUSCEPTIBILITY TO CERTAIN PATHOLOGIES, EPIGENETIC CHANGES CONSTITUTE THE MEMORY OF PREVIOUS EVENTS, EITHER POSITIVE OR NEGATIVE, ALONG THE LIFE CYCLE, INCLUDING AT THE IN UTERO STAGE. THE LATER EXPOSITION TO HOSTILE ENVIRONMENT MAY REVEAL SUCH SUSCEPTIBILITY, WITH THE DEVELOPMENT OF VARIOUS PATHOLOGIES, AMONG THEM NUMEROUS CHRONIC COMPLEX DISEASES. THE DEMONSTRATION OF SUCH A SEQUENCE OF EVENTS HAS BEEN SHOWN FOR METABOLIC DISEASES AS OBESITY, METABOLIC SYNDROME AND TYPE 2 DIABETES, CARDIOVASCULAR DISEASE AND CANCER. IN CONTRAST TO GENETIC PREDISPOSITION, WHICH IS IRREVERSIBLE, EPIGENETIC CHANGES ARE POTENTIALLY REVERSIBLE, THUS GIVING TARGETS NOT ONLY FOR PREVENTION, BUT POSSIBLY ALSO FOR THE TREATMENT OF CERTAIN COMPLEX DISEASES. 2012