1 1516 156 DNA METHYLATION AS A BIOMARKER OF AGING IN EPIDEMIOLOGIC STUDIES. CANCER IS LARGELY AN AGING DISEASE. ACCELERATED BIOLOGICAL AGING MAY BE THE STRONGEST PREDICTOR OF CANCER AND OTHER CHRONIC DISEASE RISKS. IN THE ABSENCE OF RELIABLE AND QUANTIFIABLE BIOMARKERS OF AGING TO DATE, IT HAS LONG BEEN OBSERVED THAT TUMORIGENESIS SHARES DISTINCT EPIGENETIC ALTERATIONS WITH THE AGING PROCESS. RECENTLY, EPIGENETIC AGE ESTIMATES HAVE BEEN DEVELOPED BASED ON THE AVAILABILITY OF GENOME-WIDE DNA METHYLATION PROFILES, BY APPLYING IN THE PREDICTION FORMULA THE METHYLATION LEVEL AT A SUBSET OF HIGHLY PREDICTIVE METHYLATION SITES, CALLED EPIGENETIC CLOCK. THESE DNA METHYLATION AGE ESTIMATES HAVE PRODUCED REMARKABLY STRONG CORRELATIONS WITH CHRONOLOGICAL AGE, WITH A SMALL DEVIATION AND HIGH REPRODUCIBILITY ACROSS DIFFERENT AGE GROUPS AND STUDY POPULATIONS. MOREOVER, AN INCREASING NUMBER OF EPIDEMIOLOGIC STUDIES HAVE DEMONSTRATED AN INDEPENDENT ASSOCIATION OF DNA METHYLATION AGE OR THE EXTENT OF ACCELERATION WITH MORTALITY AND VARIOUS AGING-RELATED CONDITIONS, EVEN AFTER ACCOUNTING FOR DIFFERENCES IN CHRONOLOGICAL AGE AND OTHER RISK FACTORS. ALTHOUGH EPIGENETIC PROFILES ARE KNOWN TO BE TISSUE-SPECIFIC, BOTH TARGET TISSUE- AND MULTIPLE TISSUE-DERIVED ESTIMATES APPEAR TO PERFORM WELL TO CAPTURE WHAT IS THOUGHT TO BE THE CUMULATIVE EPIGENETIC DRIFT THAT REPRESENTS A MULTIFACTORIAL DEGENERATIVE PROCESS ACROSS TISSUES AND ORGANISMS. FURTHER REFINEMENT OF THE EPIGENETIC AGE ESTIMATES IS ANTICIPATED OVER TIME TO ACCOMMODATE A BETTER TECHNOLOGICAL COVERAGE OF THE METHYLOME AND A BETTER UNDERSTANDING OF THE BIOLOGY UNDERLYING PREDICTIVE REGIONS. EPIDEMIOLOGIC PRINCIPLES WILL REMAIN CRITICAL FOR THE EVALUATION OF RESEARCH FINDINGS INVOLVING, FOR EXAMPLE, DIFFERENT STUDY POPULATIONS, DESIGN, FOLLOW-UP TIME, AND QUALITY OF COVARIATE DATA. OVERALL, THE EPIGENETIC AGE ESTIMATES ARE AN EXCITING DEVELOPMENT WITH USEFUL IMPLICATIONS FOR BIOMEDICAL RESEARCH OF HEALTHY AGING AND DISEASE PREVENTION AND CONTROL. 2018 2 1585 36 DNA METHYLATION PROFILING IDENTIFIES EPIGENETIC DIFFERENCES BETWEEN DIABETES PATIENTS WITH ESRD AND DIABETES PATIENTS WITHOUT NEPHROPATHY. WE IDENTIFIED POTENTIAL EPIGENETIC BIOMARKERS FOR CHRONIC KIDNEY DISEASE PROGRESSION BY COMPARING SITE-SPECIFIC DNA METHYLATION LEVELS IN MORE THAN 14,000 GENES BETWEEN AFRICAN AMERICAN AND HISPANIC DIABETES PATIENTS WITH END STAGE RENAL DISEASE (ESRD) AND DIABETES PATIENTS WITHOUT NEPHROPATHY. WE IDENTIFIED 187 GENES THAT ARE DIFFERENTIALLY METHYLATED BETWEEN THE TWO GROUPS ON AT LEAST TWO CPG SITES IN EACH GENE IN DNA EXTRACTED FROM SALIVA. OF THE 187 GENES WHOSE MEAN METHYLATION LEVELS DIFFERED BETWEEN THE TWO GROUPS, 39 GENES, OR CLOSELY RELATED GENE FAMILY MEMBERS, HAVE BEEN REPORTED TO BE INVOLVED IN KIDNEY DEVELOPMENT OR DIABETIC NEPHROPATHY, PER SE, OR HAVE BEEN ASSOCIATED WITH DIALYSIS-INDUCED CHANGES IN GENE EXPRESSION IN PERIPHERAL BLOOD CELLS. THE FACT THAT SUCH A SUBSTANTIAL FRACTION (21%) OF THE 187 CANDIDATE GENES HAVE BEEN IMPLICATED PREVIOUSLY THROUGH GENOME ASSOCIATION OR TRANSCRIPTION PROFILING STUDIES SUGGESTS STRONGLY THAT THE DNA METHYLATION DIFFERENCES WE OBSERVE ARE ASSOCIATED WITH DISEASE PREDISPOSITION AND/OR TREATMENT. THE FACT THAT THESE NEPHROPATHY AND/OR DIALYSIS-ASSOCIATED DIFFERENCES BETWEEN PATIENTS WERE IDENTIFIED IN DNA EXTRACTED FROM SALIVA OFFERS PROOF-OF-PRINCIPLE THAT INTER-INDIVIDUAL EPIGENETIC DIFFERENCES MAY PROVE USEFUL AS PREDICTIVE BIOMARKERS OF DISEASE SUSCEPTIBILITY. 2011 3 70 37 A METHOD TO DETECT DIFFERENTIALLY METHYLATED LOCI WITH NEXT-GENERATION SEQUENCING. EPIGENETIC CHANGES, ESPECIALLY DNA METHYLATION AT CPG LOCI HAVE IMPORTANT IMPLICATIONS IN CANCER AND OTHER COMPLEX DISEASES. WITH THE DEVELOPMENT OF NEXT-GENERATION SEQUENCING (NGS), IT IS FEASIBLE TO GENERATE DATA TO INTERROGATE THE DIFFERENCE IN METHYLATION STATUS FOR GENOME-WIDE LOCI USING CASE-CONTROL DESIGN. HOWEVER, A PROPER AND EFFICIENT STATISTICAL TEST IS LACKING. THERE ARE SEVERAL CHALLENGES. FIRST, UNLIKE METHYLATION EXPERIMENTS USING MICROARRAYS, WHERE THERE IS ONE MEASURE OF METHYLATION FOR ONE INDIVIDUAL AT A PARTICULAR CPG SITE, HERE WE HAVE THE COUNTS OF METHYLATION ALLELE AND UNMETHYLATION ALLELE FOR EACH INDIVIDUAL. SECOND, DUE TO THE NATURE OF SAMPLE PREPARATION, THE MEASURED METHYLATION REFLECTS THE METHYLATION STATUS OF A MIXTURE OF CELLS INVOLVED IN SAMPLE PREPARATION. THEREFORE, THE UNDERLYING DISTRIBUTION OF THE MEASURED METHYLATION LEVEL IS UNKNOWN, AND A ROBUST TEST IS MORE DESIRABLE THAN PARAMETRIC APPROACH. THIRD, CURRENTLY NGS MEASURES METHYLATION AT OVER 2 MILLION CPG SITES. ANY STATISTICAL TESTS HAVE TO BE COMPUTATIONALLY EFFICIENT IN ORDER TO BE APPLIED TO THE NGS DATA. TAKING THESE CHALLENGES INTO ACCOUNT, WE PROPOSE A TEST FOR DIFFERENTIAL METHYLATION BASED ON CLUSTERED DATA ANALYSIS BY MODELING THE METHYLATION COUNTS. WE PERFORMED SIMULATIONS TO SHOW THAT IT IS ROBUST UNDER SEVERAL DISTRIBUTIONS FOR THE MEASURED METHYLATION LEVELS. IT HAS GOOD POWER AND IS COMPUTATIONALLY EFFICIENT. FINALLY, WE APPLY THE TEST TO OUR NGS DATA ON CHRONIC LYMPHOCYTIC LEUKEMIA. THE RESULTS INDICATE THAT IT IS A PROMISING AND PRACTICAL TEST. 2013 4 2106 37 EPIGENETIC EVOLUTION AND LINEAGE HISTORIES OF CHRONIC LYMPHOCYTIC LEUKAEMIA. GENETIC AND EPIGENETIC INTRA-TUMORAL HETEROGENEITY COOPERATE TO SHAPE THE EVOLUTIONARY COURSE OF CANCER(1). CHRONIC LYMPHOCYTIC LEUKAEMIA (CLL) IS A HIGHLY INFORMATIVE MODEL FOR CANCER EVOLUTION AS IT UNDERGOES SUBSTANTIAL GENETIC DIVERSIFICATION AND EVOLUTION AFTER THERAPY(2,3). THE CLL EPIGENOME IS ALSO AN IMPORTANT DISEASE-DEFINING FEATURE(4,5), AND GROWING POPULATIONS OF CELLS IN CLL DIVERSIFY BY STOCHASTIC CHANGES IN DNA METHYLATION KNOWN AS EPIMUTATIONS(6). HOWEVER, PREVIOUS STUDIES USING BULK SEQUENCING METHODS TO ANALYSE THE PATTERNS OF DNA METHYLATION WERE UNABLE TO DETERMINE WHETHER EPIMUTATIONS AFFECT CLL POPULATIONS HOMOGENEOUSLY. HERE, TO MEASURE THE EPIMUTATION RATE AT SINGLE-CELL RESOLUTION, WE APPLIED MULTIPLEXED SINGLE-CELL REDUCED-REPRESENTATION BISULFITE SEQUENCING TO B CELLS FROM HEALTHY DONORS AND PATIENTS WITH CLL. WE OBSERVED THAT THE COMMON CLONAL ORIGIN OF CLL RESULTS IN A CONSISTENTLY INCREASED EPIMUTATION RATE, WITH LOW VARIABILITY IN THE CELL-TO-CELL EPIMUTATION RATE. BY CONTRAST, VARIABLE EPIMUTATION RATES ACROSS HEALTHY B CELLS REFLECT DIVERSE EVOLUTIONARY AGES ACROSS THE TRAJECTORY OF B CELL DIFFERENTIATION, CONSISTENT WITH EPIMUTATIONS SERVING AS A MOLECULAR CLOCK. HERITABLE EPIMUTATION INFORMATION ALLOWED US TO RECONSTRUCT LINEAGES AT HIGH-RESOLUTION WITH SINGLE-CELL DATA, AND TO APPLY THIS DIRECTLY TO PATIENT SAMPLES. THE CLL LINEAGE TREE SHAPE REVEALED EARLIER BRANCHING AND LONGER BRANCH LENGTHS THAN IN NORMAL B CELLS, REFLECTING RAPID DRIFT AFTER THE INITIAL MALIGNANT TRANSFORMATION AND A GREATER PROLIFERATIVE HISTORY. INTEGRATION OF SINGLE-CELL BISULFITE SEQUENCING ANALYSIS WITH SINGLE-CELL TRANSCRIPTOMES AND GENOTYPING CONFIRMED THAT GENETIC SUBCLONES MAPPED TO DISTINCT CLADES, AS INFERRED SOLELY ON THE BASIS OF EPIMUTATION INFORMATION. FINALLY, TO EXAMINE POTENTIAL LINEAGE BIASES DURING THERAPY, WE PROFILED SERIAL SAMPLES DURING IBRUTINIB-ASSOCIATED LYMPHOCYTOSIS, AND IDENTIFIED CLADES OF CELLS THAT WERE PREFERENTIALLY EXPELLED FROM THE LYMPH NODE AFTER TREATMENT, MARKED BY DISTINCT TRANSCRIPTIONAL PROFILES. THE SINGLE-CELL INTEGRATION OF GENETIC, EPIGENETIC AND TRANSCRIPTIONAL INFORMATION THUS CHARTS THE LINEAGE HISTORY OF CLL AND ITS EVOLUTION WITH THERAPY. 2019 5 3309 32 HIGHER GENE EXPRESSION VARIABILITY IN THE MORE AGGRESSIVE SUBTYPE OF CHRONIC LYMPHOCYTIC LEUKEMIA. BACKGROUND: CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) PRESENTS TWO SUBTYPES WHICH HAVE DRASTICALLY DIFFERENT CLINICAL OUTCOMES, IGVH MUTATED (M-CLL) AND IGVH UNMUTATED (U-CLL). SO FAR, THESE TWO SUBTYPES ARE NOT ASSOCIATED TO CLEAR DIFFERENCES IN GENE EXPRESSION PROFILES. INTERESTINGLY, RECENT RESULTS HAVE HIGHLIGHTED IMPORTANT ROLES FOR HETEROGENEITY, BOTH AT THE GENETIC AND AT THE EPIGENETIC LEVEL IN CLL PROGRESSION. METHODS: WE ANALYZED GENE EXPRESSION DATA OF TWO LARGE COHORTS OF CLL PATIENTS AND QUANTIFIED EXPRESSION VARIABILITY ACROSS INDIVIDUALS TO INVESTIGATE DIFFERENCES BETWEEN THE TWO SUBTYPES USING DIFFERENT MEASURES AND STATISTICAL TESTS. FUNCTIONAL SIGNIFICANCE WAS EXPLORED BY PATHWAY ENRICHMENT AND NETWORK ANALYSES. FURTHERMORE, WE IMPLEMENTED A RANDOM FOREST APPROACH BASED ON EXPRESSION VARIABILITY TO CLASSIFY PATIENTS INTO DISEASE SUBTYPES. RESULTS: WE FOUND THAT U-CLL, THE MORE AGGRESSIVE TYPE OF THE DISEASE, SHOWS SIGNIFICANTLY INCREASED VARIABILITY OF GENE EXPRESSION ACROSS PATIENTS AND THAT, OVERALL, GENES THAT SHOW HIGHER VARIABILITY IN THE AGGRESSIVE SUBTYPE ARE RELATED TO CELL CYCLE, DEVELOPMENT AND INTER-CELLULAR COMMUNICATION. THESE FUNCTIONS INDICATE A POTENTIAL RELATION BETWEEN GENE EXPRESSION VARIABILITY AND THE FASTER PROGRESSION OF THIS CLL SUBTYPE. FINALLY, A CLASSIFIER BASED ON GENE EXPRESSION VARIABILITY WAS ABLE TO CORRECTLY PREDICT THE DISEASE SUBTYPE OF CLL PATIENTS. CONCLUSIONS: THERE ARE STRONG RELATIONS BETWEEN GENE EXPRESSION VARIABILITY AND DISEASE SUBTYPE LINKING SIGNIFICANTLY INCREASED EXPRESSION VARIABILITY TO PHENOTYPES SUCH AS AGGRESSIVENESS AND RESISTANCE TO THERAPY IN CLL. 2015 6 1599 40 DNA METHYLATION SIGNATURE OF CHILDHOOD CHRONIC PHYSICAL AGGRESSION IN T CELLS OF BOTH MEN AND WOMEN. BACKGROUND: HIGH FREQUENCY OF PHYSICAL AGGRESSION IS THE CENTRAL FEATURE OF SEVERE CONDUCT DISORDER AND IS ASSOCIATED WITH A WIDE RANGE OF SOCIAL, MENTAL AND PHYSICAL HEALTH PROBLEMS. WE HAVE PREVIOUSLY TESTED THE HYPOTHESIS THAT DIFFERENTIAL DNA METHYLATION SIGNATURES IN PERIPHERAL T CELLS ARE ASSOCIATED WITH A CHRONIC AGGRESSION TRAJECTORY IN MALES. DESPITE THE FACT THAT SEX DIFFERENCES APPEAR TO PLAY A PIVOTAL ROLE IN DETERMINING THE DEVELOPMENT, MAGNITUDE AND FREQUENCY OF AGGRESSION, MOST OF PREVIOUS STUDIES FOCUSED ON MALES, SO LITTLE IS KNOWN ABOUT FEMALE CHRONIC PHYSICAL AGGRESSION. WE THEREFORE TESTED HERE WHETHER OR NOT THERE IS A SIGNATURE OF PHYSICAL AGGRESSION IN FEMALE DNA METHYLATION AND, IF THERE IS, HOW IT RELATES TO THE SIGNATURE OBSERVED IN MALES. METHODOLOGY/PRINCIPAL FINDINGS: METHYLATION PROFILES WERE CREATED USING THE METHOD OF METHYLATED DNA IMMUNOPRECIPITATION (MEDIP) FOLLOWED BY MICROARRAY HYBRIDIZATION AND STATISTICAL AND BIOINFORMATIC ANALYSES ON T CELL DNA OBTAINED FROM ADULT WOMEN WHO WERE FOUND TO BE ON A CHRONIC PHYSICAL AGGRESSION TRAJECTORY (CPA) BETWEEN 6 AND 12 YEARS OF AGE COMPARED TO WOMEN WHO FOLLOWED A NORMAL PHYSICAL AGGRESSION TRAJECTORY. WE CONFIRMED THE EXISTENCE OF A WELL-DEFINED, GENOME-WIDE SIGNATURE OF DNA METHYLATION ASSOCIATED WITH CHRONIC PHYSICAL AGGRESSION IN THE PERIPHERAL T CELLS OF ADULT FEMALES THAT INCLUDES MANY OF THE GENES SIMILARLY ASSOCIATED WITH PHYSICAL AGGRESSION IN THE SAME CELL TYPES OF ADULT MALES. CONCLUSIONS: THIS STUDY IN A SMALL NUMBER OF WOMEN PRESENTS PRELIMINARY EVIDENCE FOR A GENOME-WIDE VARIATION IN PROMOTER DNA METHYLATION THAT ASSOCIATES WITH CPA IN WOMEN THAT WARRANT LARGER STUDIES FOR FURTHER VERIFICATION. A SIGNIFICANT PROPORTION OF THESE ASSOCIATIONS WERE PREVIOUSLY OBSERVED IN MEN WITH CPA SUPPORTING THE HYPOTHESIS THAT THE EPIGENETIC SIGNATURE OF EARLY LIFE AGGRESSION IN FEMALES IS COMPOSED OF A COMPONENT SPECIFIC TO FEMALES AND ANOTHER COMMON TO BOTH MALES AND FEMALES. 2014 7 6539 34 TRANSCRIPTIONAL VARIATIONS IN THE WIDER PERITUMORAL TISSUE ENVIRONMENT OF PANCREATIC CANCER. TRANSCRIPTIONAL PROFILING WAS PERFORMED ON 452 RNA PREPARATIONS ISOLATED FROM VARIOUS TYPES OF PANCREATIC TISSUE FROM TUMOUR PATIENTS AND HEALTHY DONORS, WITH A PARTICULAR FOCUS ON PERITUMORAL SAMPLES. PANCREATIC DUCTAL ADENOCARCINOMAS (PDAC) AND CYSTIC TUMOURS WERE MOST DIFFERENT IN THESE NON-TUMOROUS TISSUES SURROUNDING THEM, WHEREAS THE ACTUAL TUMOURS EXHIBITED RATHER SIMILAR TRANSCRIPT PATTERNS. THE ENVIRONMENT OF CYSTIC TUMOURS WAS TRANSCRIPTIONALLY NEARLY IDENTICAL TO NORMAL PANCREAS TISSUE. IN CONTRAST, THE TISSUE AROUND PDAC BEHAVED A LOT LIKE THE TUMOUR, INDICATING SOME KIND OF FIELD DEFECT, WHILE SHOWING FAR LESS MOLECULAR RESEMBLANCE TO BOTH CHRONIC PANCREATITIS AND HEALTHY TISSUE. THIS SUGGESTS THAT THE MAJOR PATHOGENIC DIFFERENCE BETWEEN CYSTIC AND DUCTAL TUMOURS MAY BE DUE TO THEIR CELLULAR ENVIRONMENT RATHER THAN THE FEW VARIATIONS BETWEEN THE TUMOURS. LACK OF CORRELATION BETWEEN DNA METHYLATION AND TRANSCRIPT LEVELS MAKES IT UNLIKELY THAT THE OBSERVED FIELD DEFECT IN THE PERITUMORAL TISSUE OF PDAC IS CONTROLLED TO A LARGE EXTENT BY SUCH EPIGENETIC REGULATION. FUNCTIONALLY, A STRIKINGLY LARGE NUMBER OF AUTOPHAGY-RELATED TRANSCRIPTS WAS CHANGED IN BOTH PDAC AND ITS PERITUMORAL TISSUE, BUT NOT IN OTHER PANCREATIC TUMOURS. A TRANSCRIPTION SIGNATURE OF 15 AUTOPHAGY-RELATED GENES WAS ESTABLISHED THAT PERMITS A PROGNOSIS OF SURVIVAL WITH HIGH ACCURACY AND INDICATES THE ROLE OF AUTOPHAGY IN TUMOUR BIOLOGY. 2018 8 311 40 ALCOHOL AND THE METHYLOME: DESIGN AND ANALYSIS CONSIDERATIONS FOR RESEARCH USING HUMAN SAMPLES. BACKGROUND: A GROWING NUMBER OF STUDIES IN HUMAN SAMPLES HAVE SOUGHT TO DETERMINE WHETHER CHRONIC ALCOHOL USE AND ALCOHOL USE DISORDERS (AUDS) MAY BE ASSOCIATED WITH EPIGENETIC FACTORS, SUCH AS DNA METHYLATION. WE REVIEW THE EXTANT LITERATURE IN LIGHT OF SOME OF THE CHALLENGES THAT CURRENTLY AFFECT THE DESIGN AND INTERPRETATION OF EPIGENETIC RESEARCH IN HUMAN SAMPLES. METHOD: A LITERATURE SEARCH WAS USED TO IDENTIFY STUDIES THAT HAVE EXAMINED DNA METHYLATION IN RELATION TO ALCOHOL USE OR AUDS IN HUMAN SAMPLES (THROUGH JULY 2013). A TOTAL OF 22 STUDIES WERE IDENTIFIED. RESULTS: ASSOCIATIONS WITH QUANTITATIVE OR DIAGNOSTIC PHENOTYPES OF ALCOHOL USE OR AUDS HAVE BEEN REPORTED FOR SEVERAL GENES. HOWEVER, ALL STUDIES TO DATE HAVE RELIED ON RELATIVELY SMALL SAMPLES AND CROSS-SECTIONAL STUDY DESIGNS. ADDITIONALLY, ATTEMPTS TO REPLICATE RESULTS HAVE BEEN RARE. MORE GENERALLY, RESEARCH PROGRESS IS HAMPERED BY SEVERAL ISSUES, INCLUDING LIMITATIONS OF THE TECHNOLOGIES USED TO ASSESS DNA METHYLATION, TISSUE- AND CELL-SPECIFICITY OF METHYLATION PATTERNS, THE DIFFICULTIES OF RELATING OBSERVED METHYLATION DIFFERENCES AT A GIVEN LOCUS TO A FUNCTIONAL EFFECT, AND LIMITED KNOWLEDGE ABOUT THE MOLECULAR MECHANISMS UNDERLYING THE EFFECTS OF ALCOHOL ON DNA METHYLATION. CONCLUSIONS: ALTHOUGH WE SHARE THE OPTIMISM THAT EPIGENETICS MAY LEAD TO NEW INSIGHTS INTO THE ETIOLOGY AND PATHOPHYSIOLOGY OF AUDS, THE METHODOLOGICAL AND SCIENTIFIC CHALLENGES ASSOCIATED WITH CONDUCTING METHYLOMIC RESEARCH IN HUMAN SAMPLES NEED TO BE CAREFULLY CONSIDERED WHEN DESIGNING AND EVALUATING SUCH STUDIES. 2013 9 2920 43 GENE-SET ANALYSIS IS SEVERELY BIASED WHEN APPLIED TO GENOME-WIDE METHYLATION DATA. MOTIVATION: DNA METHYLATION IS AN EPIGENETIC MARK THAT CAN STABLY REPRESS GENE EXPRESSION. BECAUSE OF ITS BIOLOGICAL AND CLINICAL SIGNIFICANCE, SEVERAL METHODS HAVE BEEN DEVELOPED TO COMPARE GENOME-WIDE PATTERNS OF METHYLATION BETWEEN GROUPS OF SAMPLES. THE APPLICATION OF GENE SET ANALYSIS TO IDENTIFY RELEVANT GROUPS OF GENES THAT ARE ENRICHED FOR DIFFERENTIALLY METHYLATED GENES IS OFTEN A MAJOR COMPONENT OF THE ANALYSIS OF THESE DATA. THIS CAN BE USED, FOR EXAMPLE, TO IDENTIFY PROCESSES OR PATHWAYS THAT ARE PERTURBED IN DISEASE DEVELOPMENT. WE SHOW THAT GENE-SET ANALYSIS, AS IT IS TYPICALLY APPLIED TO GENOME-WIDE METHYLATION ASSAYS, IS SEVERELY BIASED AS A RESULT OF DIFFERENCES IN THE NUMBERS OF CPG SITES ASSOCIATED WITH DIFFERENT CLASSES OF GENES AND GENE PROMOTERS. RESULTS: WE DEMONSTRATE THIS BIAS USING PUBLISHED DATA FROM A STUDY OF DIFFERENTIAL CPG ISLAND METHYLATION IN LUNG CANCER AND A DATASET WE GENERATED TO STUDY METHYLATION CHANGES IN PATIENTS WITH LONG-STANDING ULCERATIVE COLITIS. WE SHOW THAT SEVERAL OF THE GENE SETS THAT SEEM ENRICHED WOULD ALSO BE IDENTIFIED WITH RANDOMIZED DATA. WE SUGGEST TWO EXISTING APPROACHES THAT CAN BE ADAPTED TO CORRECT THE BIAS. ACCOUNTING FOR THE BIAS IN THE LUNG CANCER AND ULCERATIVE COLITIS DATASETS PROVIDES NOVEL BIOLOGICAL INSIGHTS INTO THE ROLE OF METHYLATION IN CANCER DEVELOPMENT AND CHRONIC INFLAMMATION, RESPECTIVELY. OUR RESULTS HAVE SIGNIFICANT IMPLICATIONS FOR MANY PREVIOUS GENOME-WIDE METHYLATION STUDIES THAT HAVE DRAWN CONCLUSIONS ON THE BASIS OF SUCH STRONGLY BIASED ANALYSIS. CONTACT: CATHAL.SEOIGHE@NUIGALWAY.IE SUPPLEMENTARY INFORMATION: SUPPLEMENTARY DATA ARE AVAILABLE AT BIOINFORMATICS ONLINE. 2013 10 5685 42 SHOULD WE INVEST IN BIOLOGICAL AGE PREDICTORS TO TREAT COLORECTAL CANCER IN OLDER ADULTS? COLORECTAL CANCER (CRC) IS A CHRONIC DISEASE OF THE OLD POPULATION WITH SLOW DEVELOPMENT PROGRESSING INTO CLINICAL SIGNS AND SYMPTOMS. BIOLOGICAL AGING IS CHARACTERIZED BY E.G. MITOCHONDRIAL DYSFUNCTION AND EPIGENETIC ALTERATIONS (E.G. METHYLATION) - MECHANISMS THAT ARE ALSO IMPORTANT IN CANCER DEVELOPMENT. FOR CRC, SPECIFIC TYPES OF TUMORS ARE DISTINGUISHABLE BY THEIR METHYLATION PATTERNS AND SEVERAL DETECTION METHODS USING DIFFERENT EPIGENETIC MARKS HAVE BEEN DEVELOPED AS SIGNATURES FOR THE DISEASE. BIOLOGICAL AGE ASSESSED BY DNA METHYLATION PATTERNS FROM BLOOD, I.E. THE EPIGENETIC CLOCK, IS HIGHER IN CRC PATIENTS COMPARED TO CONTROLS, AND MAY BE A TOOL FOR IDENTIFYING INDIVIDUALS AT INCREASED RISK FOR CRC. OTHER TYPES OF BIOMARKERS OF AGING ARE USEFUL TO CALCULATE BIOLOGICAL AGE, SUCH AS METABOLITES, PROTEIN LEVELS, INFLAMMATORY MARKERS AND CLINICAL BIOMARKERS, WHERE COMPOSITE SCORES OF BIOMARKERS HAVE BEEN USED TO ASSESS THE RISK OF CRC AND COLORECTAL ADENOMAS. CLINICAL ASSESSMENTS OF BIOLOGICAL AGING INCLUDES FRAILTY, WHICH IS A GERIATRIC SYNDROME CHARACTERIZED BY INCREASED VULNERABILITY TO ADVERSE OUTCOMES. MORE THAN HALF OF THE CRC PATIENTS ARE ESTIMATED TO BE FRAIL OR PRE-FRAIL, AND THESE INDIVIDUALS ARE AT INCREASED RISK OF POSTOPERATIVE COMPLICATIONS, POORER PROGNOSIS, TREATMENT INTOLERANCE AND DEATH. HENCE, CONSIDERING FRAILTY AS PART OF BIOLOGICAL AGE IN CRC PATIENTS MAY HELP IDENTIFYING THOSE AT NEED OF CLOSE MONITORING. IN SUMMARY, FUTURE SCREENING PROGRAMS FOR CRC MAY MAKE USE OF BIOLOGICAL AGE ASSESSMENTS, E.G. BY EPIGENETIC CLOCK OR COMPOSITE SCORES. MONITORING DISEASE RELAPSE AND TREATMENT RESPONSE SHOULD BE ENHANCED IN FRAIL INDIVIDUALS FOR BETTER PROGNOSIS. 2020 11 3803 39 INTESTINAL METAPLASIA OF THE STOMACH. A STATUS REPORT. INTESTINAL METAPLASIA IN THE STOMACH INCREASES THE RISK OF GASTRIC CANCER, AND THE INCREASED RISK IS PROPORTIONAL TO THE EXTENT OF THE METAPLASIA. THIS RISK COULD BE GENERATED BY ONE OR MORE MECHANISMS: (1) THE METAPLASTIC TISSUE IS AN EARLY STEP IN A MULTISTEP INDUCTION PROCESS; (2) THE METAPLASTIC TISSUE IS AN EPIGENETIC CHANGE THAT RAISES THE PH OF GASTRIC JUICE BY REPLACING OXYNTIC MUCOSA, FAVORING THE GROWTH OF A BACTERIA CAPABLE OF GENERATING ENDOGENOUS MUTAGENS; AND/OR (3) THE METAPLASIA IS ONLY A MARKER FOR CHRONIC GASTRITIS DUE TO H. PYLORI INFECTION OR PERNICIOUS ANEMIA. WITH THE LAST MECHANISM, THE INFLAMMATORY RESPONSE FAVORS INTRAMURAL MUTAGENESIS THAT MIGHT RESULT IN METAPLASIA OR NEOPLASIA AS INDEPENDENT EVENTS. FINDING GENE REARRANGEMENTS COMMON TO BOTH METAPLASTIC AND NEOPLASTIC TISSUE MAY ESTABLISH A DIRECT LINK BETWEEN THEM, BUT TOO FEW HAVE BEEN IDENTIFIED TO ACCOUNT FOR THE LARGE NUMBER OF STOMACH CANCERS THAT DEVELOP IN HIGH RISK POPULATIONS. HISTOCHEMICAL AND IMMUNOCHEMICAL STAINS THAT IDENTIFY ENZYMES OR MUCOSUBSTANCES MAY SUGGEST THAT METAPLASTIC EPITHELIAL CELLS RESEMBLE SMALL OR LARGE INTESTINAL CELLS, BUT THEY ARE DISTINCTLY DIFFERENT FROM BOTH. MOREOVER, THESE STAINS DO NOT INDICATE WHETHER A GIVEN CYTOLOGIC CHANGE IS GENETIC OR EPIGENETIC; THEREFORE, THEY CANNOT BE USED TO DEFINE THE RELATIONSHIP BETWEEN METAPLASIA AND NEOPLASIA. IT IS UNNECESSARY FOR PRACTICING PHYSICIANS TO AWAIT RESOLUTION OF THIS QUESTION. IT CAN BE ASSUMED THAT ANY PERSON WITH EXTENSIVE METAPLASIA IS AT HIGH RISK FOR GASTRIC CANCER AND SHOULD BE SUBJECT TO PERIODIC SCREENING. THE EXTENT OF THE METAPLASTIC PROCESS IS PROBABLY MORE IMPORTANT THAN THE METAPLASTIC SUBTYPE. 1994 12 287 31 AGING AND CHRONIC SUN EXPOSURE CAUSE DISTINCT EPIGENETIC CHANGES IN HUMAN SKIN. EPIGENETIC CHANGES ARE WIDELY CONSIDERED TO PLAY AN IMPORTANT ROLE IN AGING, BUT EXPERIMENTAL EVIDENCE TO SUPPORT THIS HYPOTHESIS HAS BEEN SCARCE. WE HAVE USED ARRAY-BASED ANALYSIS TO DETERMINE GENOME-SCALE DNA METHYLATION PATTERNS FROM HUMAN SKIN SAMPLES AND TO INVESTIGATE THE EFFECTS OF AGING, CHRONIC SUN EXPOSURE, AND TISSUE VARIATION. OUR RESULTS REVEAL A HIGH DEGREE OF TISSUE SPECIFICITY IN THE METHYLATION PATTERNS AND ALSO SHOWED VERY LITTLE INTERINDIVIDUAL VARIATION WITHIN TISSUES. DATA STRATIFICATION BY AGE REVEALED THAT DNA FROM OLDER INDIVIDUALS WAS CHARACTERIZED BY A SPECIFIC HYPERMETHYLATION PATTERN AFFECTING LESS THAN 1% OF THE MARKERS ANALYZED. INTERESTINGLY, STRATIFICATION BY SUN EXPOSURE PRODUCED A FUNDAMENTALLY DIFFERENT PATTERN WITH A SIGNIFICANT TREND TOWARDS HYPOMETHYLATION. OUR RESULTS THUS IDENTIFY DEFINED AGE-RELATED DNA METHYLATION CHANGES AND SUGGEST THAT THESE ALTERATIONS MIGHT CONTRIBUTE TO THE PHENOTYPIC CHANGES ASSOCIATED WITH SKIN AGING. 2010 13 228 37 ADAPTATION OF THE HUMAN POPULATION TO THE ENVIRONMENT: CURRENT KNOWLEDGE, CLUES FROM CZECH CYTOGENETIC AND "OMICS" BIOMONITORING STUDIES AND POSSIBLE MECHANISMS. THE HUMAN POPULATION IS CONTINUALLY EXPOSED TO NUMEROUS HARMFUL ENVIRONMENTAL STRESSORS, CAUSING NEGATIVE HEALTH EFFECTS AND/OR DEREGULATION OF BIOMARKER LEVELS. HOWEVER, STUDIES REPORTING NO OR EVEN POSITIVE IMPACTS OF SOME STRESSORS ON HUMANS ARE ALSO SOMETIMES PUBLISHED. THE MAIN AIM OF THIS REVIEW IS TO PROVIDE A COMPREHENSIVE OVERVIEW OF THE LAST DECADE OF CZECH BIOMONITORING RESEARCH, CONCERNING THE EFFECT OF VARIOUS LEVELS OF AIR POLLUTION (BENZO[A]PYRENE) AND RADIATION (URANIUM, X-RAY EXAMINATION AND NATURAL RADON BACKGROUND), ON THE DIFFERENTLY EXPOSED POPULATION GROUPS. BECAUSE SOME RESULTS OBTAINED FROM CYTOGENETIC STUDIES WERE OPPOSITE THAN HYPOTHESIZED, WE HAVE SEARCHED FOR A MEANINGFUL INTERPRETATION IN GENOMIC/EPIGENETIC STUDIES. A DETAILED ANALYSIS OF OUR DATA SUPPORTED BY THE STUDIES OF OTHERS AND CURRENT EPIGENETIC KNOWLEDGE, LEADS TO A HYPOTHESIS OF THE VERSATILE MECHANISM OF ADAPTATION TO ENVIRONMENTAL STRESSORS VIA DNA METHYLATION SETTINGS WHICH MAY EVEN ORIGINATE IN PRENATAL DEVELOPMENT, AND HELP TO REDUCE THE RESULTING DNA DAMAGE LEVELS. THIS HYPOTHESIS IS FULLY IN AGREEMENT WITH UNEXPECTED DATA FROM OUR STUDIES (E.G. LOWER LEVELS OF DNA DAMAGE IN SUBJECTS FROM HIGHLY POLLUTED REGIONS THAN IN CONTROLS OR IN SUBJECTS EXPOSED REPEATEDLY TO A POLLUTANT THAN IN THOSE WITHOUT PREVIOUS EXPOSURE), AND IS ALSO SUPPORTED BY DIFFERENCES IN DNA METHYLATION PATTERNS IN GROUPS FROM REGIONS WITH VARIOUS LEVELS OF POLLUTION. IN LIGHT OF THE ADAPTATION HYPOTHESIS, THE FOLLOWING POINTS MAY BE SUGGESTED FOR FUTURE RESEARCH: (I) THE CHRONIC AND ACUTE EXPOSURE OF STUDY SUBJECTS SHOULD BE DISTINGUISHED; (II) THE EXPOSURE HISTORY SHOULD BE MAPPED INCLUDING PLACE OF RESIDENCE DURING THE LIFE AND PRENATAL DEVELOPMENT; (III) CHANGES OF EPIGENETIC MARKERS SHOULD BE MONITORED OVER TIME. IN SUMMARY, INVESTIGATION OF HUMAN ADAPTATION TO THE ENVIRONMENT, ONE OF THE MOST IMPORTANT PROCESSES OF SURVIVAL, IS A NEW CHALLENGE FOR FUTURE RESEARCH IN THE FIELD OF HUMAN BIOMONITORING THAT MAY CHANGE OUR VIEW ON THE RESULTS OF BIOMARKER ANALYSES AND POTENTIAL NEGATIVE HEALTH IMPACTS OF THE ENVIRONMENT. 2017 14 822 39 CHARACTERIZATION OF BLOOD SURROGATE IMMUNE-METHYLATION BIOMARKERS FOR IMMUNE CELL INFILTRATION IN CHRONIC INFLAMMAGING DISORDERS. ALZHEIMER'S DISEASE (AD) AND ATHEROSCLEROSIS ARE BOTH CHRONIC AGE- AND INFLAMMATION-DEPENDENT DISEASES. IN ADDITION, ATHEROSCLEROSIS IS FREQUENTLY OBSERVED IN AD PATIENTS INDICATING COMMON INVOLVEMENT OF VASCULAR COMPONENTS IN BOTH DISEASE ETIOLOGIES. RECENTLY, EPIGENOME-WIDE ASSOCIATION STUDIES HAVE IDENTIFIED EPIGENETIC ALTERATIONS, AND IN PARTICULARLY DNA METHYLATION CHANGES FOR BOTH DISORDERS. WE HYPOTHESIZED THE EXISTENCE OF A COMMON DNA METHYLATION PROFILE IN ATHEROSCLEROSIS AND AD WHICH MAY BE VALUABLE AS A BLOOD-BASED DNA METHYLATION INFLAMMAGING BIOMARKER. USING PUBLICLY AVAILABLE 450K ILLUMINA METHYLATION DATASETS, WE IDENTIFIED A CO-METHYLATION NETWORK ASSOCIATED WITH BOTH ATHEROSCLEROSIS AND AD IN WHOLE BLOOD SAMPLES. THIS METHYLATION PROFILE APPEARED TO INDICATE SHIFTS IN BLOOD IMMUNE CELL TYPE DISTRIBUTION. REMARKABLY, SIMILAR METHYLATION CHANGES WERE ALSO DETECTED IN DISEASE TISSUES, INCLUDING AD BRAIN TISSUES, ATHEROSCLEROTIC PLAQUES, AND TUMORS AND WERE FOUND TO CORRELATE WITH IMMUNE CELL INFILTRATION. IN ADDITION, THIS IMMUNE-RELATED METHYLATION PROFILE COULD ALSO BE DETECTED IN OTHER INFLAMMAGING DISEASES, INCLUDING PARKINSON'S DISEASE AND OBESITY, BUT NOT IN MULTIPLE SCLEROSIS, SCHIZOPHRENIA, AND OSTEOPOROSIS. IN CONCLUSION, WE IDENTIFIED A BLOOD-BASED IMMUNE-RELATED DNA METHYLATION SIGNATURE IN MULTIPLE INFLAMMAGING DISEASES ASSOCIATED WITH CHANGES IN BLOOD IMMUNE CELL COUNTS AND PREDICTIVE FOR IMMUNE CELL INFILTRATION IN DISEASED TISSUES. IN ADDITION TO EPIGENETIC CLOCK MEASUREMENTS, THIS IMMUNE-METHYLATION SIGNATURE MAY BECOME A VALUABLE BLOOD-BASED BIOMARKER TO PREVENT CHRONIC INFLAMMATORY DISEASE DEVELOPMENT OR MONITOR LIFESTYLE INTERVENTION STRATEGIES WHICH PROMOTE HEALTHY AGING. 2019 15 1068 30 CLL INTRACLONAL FRACTIONS EXHIBIT ESTABLISHED AND RECENTLY ACQUIRED PATTERNS OF DNA METHYLATION. INTRACLONAL SUBPOPULATIONS OF CIRCULATING CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) CELLS WITH DIFFERENT PROLIFERATIVE HISTORIES AND RECIPROCAL SURFACE EXPRESSION OF CXCR4 AND CD5 HAVE BEEN OBSERVED IN THE PERIPHERAL BLOOD OF CLL PATIENTS AND NAMED PROLIFERATIVE (PF), INTERMEDIATE (IF), AND RESTING (RF) CELLULAR FRACTIONS. HERE, WE FOUND THAT THESE INTRACLONAL CIRCULATING FRACTIONS SHARE PERSISTENT DNA METHYLATION SIGNATURES LARGELY ASSOCIATED WITH THE MUTATION STATUS OF THE IMMUNOGLOBULIN HEAVY CHAIN LOCUS (IGHV) AND THEIR ORIGINS FROM DISTINCT STAGES OF DIFFERENTIATION OF ANTIGEN-EXPERIENCED B CELLS. INCREASED LEUKEMIC BIRTH RATE, HOWEVER, SHOWED A VERY LIMITED IMPACT ON DNA METHYLATION OF CIRCULATING CLL FRACTIONS INDEPENDENT OF IGHV MUTATION STATUS. ADDITIONALLY, DNA METHYLATION HETEROGENEITY INCREASED AS LEUKEMIC CELLS ADVANCED FROM PF TO RF IN THE PERIPHERAL BLOOD. THIS FREQUENTLY CO-OCCURRED WITH HETEROCHROMATIN HYPOMETHYLATION AND HYPERMETHYLATION OF POLYCOMB-REPRESSED REGIONS IN THE PF, SUGGESTING ACCUMULATION OF LONGEVITY-ASSOCIATED EPIGENETIC FEATURES IN RECENTLY BORN CELLS. ON THE OTHER HAND, TRANSCRIPTIONAL DIFFERENCES BETWEEN PAIRED INTRACLONAL FRACTIONS CONFIRMED THEIR PROLIFERATIVE EXPERIENCE AND FURTHER SUPPORTED A LINEAR ADVANCEMENT FROM PF TO RF IN THE PERIPHERAL BLOOD. SEVERAL OF THESE DIFFERENTIALLY EXPRESSED GENES SHOWED UNIQUE ASSOCIATIONS WITH CLINICAL OUTCOME NOT EVIDENT IN THE BULK CLONE, SUPPORTING THE PATHOLOGICAL AND THERAPEUTIC RELEVANCE OF STUDYING INTRACLONAL CLL FRACTIONS. WE CONCLUDE THAT INDEPENDENT METHYLATION AND TRANSCRIPTIONAL LANDSCAPES REFLECT BOTH PREEXISTING CELL-OF-ORIGIN FINGERPRINTS AND MORE RECENTLY ACQUIRED HALLMARKS ASSOCIATED WITH THE LIFE CYCLE OF CIRCULATING CLL CELLS. 2020 16 3934 47 LIVER TUMOR INDUCTION. THE SIGNIFICANCE OF THE DEVELOPMENT OF NODULAR LIVER LESIONS IN RODENTS FOLLOWING THE ADMINISTRATION OF TEST AGENTS RAISES SEVERAL QUESTIONS WHICH COULD BE PLACED IN ONE OF TWO GENERAL CATEGORIES: DIAGNOSTIC AND INTERPRETATIONAL. FROM A DIAGNOSTIC POINT OF VIEW, THE PROPER CLASSIFICATION OF LIVER TUMORS INTO A BENIGN AND MALIGNANT CATEGORY HAS TO BE BASED ON THE DIRECT CORRELATION BETWEEN THE MORPHOLOGY AND THE BIOLOGIC BEHAVIOR OF THE LESIONS. THEREFORE, EXTREME CARE SHOULD BE TAKEN TO SEPARATE THE MALIGNANT TUMORS FROM THE BENIGN AND THE BENIGN NEOPLASIA FROM THE HYPERPLASIA. THE SUBSTITUTION OF THE TERM "NEOPLASTIC NODULE" FOR HYPERPLASTIC NODULE IN RATS IS MISLEADING. MOST OF THESE NODULES, WHEN INDUCED UNDER SPECIAL EXPERIMENTAL CONDITIONS, MAY REGRESS OR REMODEL AND THUS THEY ARE NOT NEOPLASTIC IN NATURE. CHRONIC CARCINOGENICITY BIOASSAYS SHOULD INCLUDE "STOP" TYPE OF TREATMENT LEAVING ENOUGH OF THE OBSERVATIONAL TIME TO ESTABLISH THE FATE OF INDUCED NODULAR LESIONS. THE INDUCTION OF HISTOCHEMICALLY CHANGED FOCI CAN SERVE ONLY AS AN INDICATION OF POTENTIAL HEPATOCARCINOGENICITY AND SHOULD NOT BE EQUATED WITH THE INDUCTION OF BONA FIDE CANCER. THE BIOLOGIC INTERPRETATION OF NODULAR LIVER LESIONS, ESPECIALLY IN MICE, NEEDS FURTHER SCRUTINY BECAUSE THESE LESIONS HAVE A TENDENCY TO DEVELOP SPONTANEOUSLY WITH HIGH INCIDENCE IN SOME STRAINS. THIS CHARACTERISTIC THEN RAISES THE QUESTION AS TO THE MECHANISM BY WHICH VARIOUS AGENTS AUGMENT AND/OR ACCELERATE THE DEVELOPMENT OF SUCH TUMORS. IS THIS ACTION PRIMARILY PROMOTING OR INITIATING IN NATURE OR DOES IT REPRESENT THE INDUCTION OF TUMORS DE NOVO? THE ANSWER TO THIS DILEMMA MAY HAVE A DECISIVE BEARING ON CARCINOGENIC RISK ASSESSMENT AND THE TYPE OF REGULATORY ACTION, SINCE THE PROMOTING AGENTS POSSESS A THRESHOLD EFFECT AND THE PROMOTED CHANGES MAY REGRESS FOLLOWING WITHDRAWAL OF TREATMENT. THE INTERPRETATION OF HEPATOCARCINOGENESIS IS FURTHER COMPLICATED BY THE FACT THAT SEVERAL FACTORS, SUCH AS SEX HORMONAL ENVIRONMENT, INCREASED MITOTIC ACTIVITY FOLLOWING AN EXCESSIVE LOSS OF PARENCHYMAL CELLS, DEGREE OF CALORIC INTAKE, ENZYMATIC COMPLEMENT, AND ANIMALS' AGE AT THE TIME OF THE EXPOSURE TO A TEST AGENT, MAY INFLUENCE THE OUTCOME OF LIVER TUMOR DEVELOPMENT BY MODULATING "INITIATION" AND/OR "PROMOTION" OF CARCINOGENESIS. BROAD FLUCTUATION IN THE HISTORIC INCIDENCE OF LIVER TUMORS FURTHER COMPOUNDS THE COMPLEXITY OF THE PROPER BIOASSAY INTERPRETATION. THE SPECIFICALLY DESIGNED EXPERIMENTS MAY HAVE THE OBJECTIVE TO EXPLORE PREDOMINANTLY THE INITIATING OR PROMOTING EFFECTS OF THE AGENT. SUCH PROTOCOLS SHOULD BE USED WHENEVER NECESSARY TO DIFFERENTIATE BETWEEN THESE TWO MECHANISMS OF ACTION. IN THE CAUCASIANS, THE "SPONTANEOUS" DEVELOPMENT OF THE PRIMARY HEPATOCELLULAR TUMORS IS RARE. THE MAJORITY OF THESE TUMORS ARE MALIGNANT AND RAPIDLY FATAL. ACCORDING TO SOME HUMAN PATHOLOGISTS, THE BENIGN VARIETY OF LIVER TUMORS IS RARE AND IT DOES NOT REPRESENT NECESSARILY A PREMALIGNANT STAGE IN TUMOR DEVELOPMENT. CARCINOMA OF THE LIVER MAY OCCUR IN INFANCY, ESPECIALLY IN MALES BEFORE THE AGE OF 2 YEARS. THIS SUGGESTS A GENETIC CAUSATION OR CARCINOGENIC EXPOSURE IN UTERO. ONE OF THE GEOGRAPHIC FACTORS WHICH SIGNIFICANTLY ENHANCES THE INCIDENCE OF HEPATOCELLULAR CARCINOMA IN HUMANS IS EXPOSURE TO AFLATOXIN B(1) WHICH IS APPARENTLY POTENTIATED BY CONCURRENT LIVER CIRRHOSIS. BECAUSE MANY MORE AGENTS HAVE BEEN FOUND TO BE HEPATOCARCINOGENIC IN MICE AND RATS THAN IN MEN, A QUESTION ARISES AS TO THE DIRECT RELEVANCE OF RODENT STUDIES TO HUMANS. A BALANCED ASSESSMENT OF THE CARCINOGENICITY OF THE AGENT COULD ONLY BE REACHED IN CONSIDERING BOTH THE PHARMACOKINETICS AND THE DEVELOPMENT OF MALIGNANT NEOPLASIA IN OTHER ORGANS. IN THE CASE OF POSITIVE CARCINOGENICITY ASSESSMENT, THE OUTCOME OF THE MUTAGENICITY BIOASSAYS CAN SUGGEST GENIC (GENOTOXIC) OR PARAGENIC (EPIGENETIC) MODE OF ACTION IN MAMMALIAN SYSTEMS. 1982 17 4025 30 LUNG CANCER AND CHRONIC OBSTRUCTIVE PULMONARY DISEASE: NEEDS AND OPPORTUNITIES FOR INTEGRATED RESEARCH. LUNG CANCER AND CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) ARE LEADING CAUSES OF MORBIDITY AND MORTALITY IN THE UNITED STATES AND WORLDWIDE. THEY SHARE A COMMON ENVIRONMENTAL RISK FACTOR IN CIGARETTE SMOKE EXPOSURE AND A GENETIC PREDISPOSITION REPRESENTED BY THE INCIDENCE OF THESE DISEASES IN ONLY A FRACTION OF SMOKERS. THE PRESENCE OF COPD INCREASES THE RISK OF LUNG CANCER UP TO 4.5-FOLD. TO INVESTIGATE COMMONALITIES IN DISEASE MECHANISMS AND PERSPECTIVES FOR DISEASE CHEMOPREVENTION, THE NATIONAL HEART, LUNG, AND BLOOD INSTITUTE (NHLBI) AND THE NATIONAL CANCER INSTITUTE (NCI) HELD A WORKSHOP. THE PARTICIPANTS IDENTIFIED FOUR RESEARCH OBJECTIVES: 1) CLARIFY COMMON EPIDEMIOLOGICAL CHARACTERISTICS OF LUNG CANCER AND COPD; 2) IDENTIFY SHARED GENETIC AND EPIGENETIC RISK FACTORS; 3) IDENTIFY AND VALIDATE BIOMARKERS, MOLECULAR SIGNATURES, AND IMAGING-DERIVED MEASUREMENTS OF EACH DISEASE; AND 4) DETERMINE COMMON AND DISPARATE PATHOGENETIC MECHANISMS. THESE OBJECTIVES SHOULD BE REACHED VIA FOUR RESEARCH APPROACHES: 1) IDENTIFY, PUBLICIZE, AND ENABLE THE EVALUATION AND ANALYSIS OF EXISTING DATASETS AND REPOSITORIES OF BIOSPECIMENS; 2) OBTAIN PHENOTYPIC AND OUTCOME DATA AND BIOSPECIMENS FROM LARGE STUDIES OF SUBJECTS WITH AND/OR AT RISK FOR COPD AND LUNG CANCER; 3) DEVELOP AND USE ANIMAL AND OTHER PRECLINICAL MODELS TO INVESTIGATE PATHOGENETIC LINKS BETWEEN THE DISEASES; AND 4) CONDUCT EARLY-PHASE CLINICAL TRIALS OF POTENTIAL CHEMOPREVENTIVE AGENTS. TO FOSTER MUCH NEEDED RESEARCH INTERACTIONS, TWO FINAL RECOMMENDATIONS WERE MADE BY THE PARTICIPANTS: 1) INCORPORATE BASELINE PHENOTYPING AND OUTCOME MEASURES FOR BOTH DISEASES IN FUTURE LONGITUDINAL STUDIES OF EACH DISEASE AND 2) EXPAND COLLABORATIVE EFFORTS BETWEEN THE NCI AND NHLBI. 2009 18 1705 40 DYNAMICS OF SMOKING-INDUCED GENOME-WIDE METHYLATION CHANGES WITH TIME SINCE SMOKING CESSATION. SEVERAL STUDIES HAVE RECENTLY IDENTIFIED STRONG EPIGENETIC SIGNALS RELATED TO TOBACCO SMOKING. HOWEVER, AN ASPECT THAT DID NOT RECEIVE MUCH ATTENTION IS THE EVOLUTION OF EPIGENETIC CHANGES WITH TIME SINCE SMOKING CESSATION. WE CONDUCTED A SERIES OF EPIGENOME-WIDE ASSOCIATION STUDIES TO CAPTURE THE DYNAMICS OF SMOKING-INDUCED EPIGENETIC CHANGES AFTER SMOKING CESSATION, USING GENOME-WIDE METHYLATION PROFILES OBTAINED FROM BLOOD SAMPLES IN 745 WOMEN FROM 2 EUROPEAN POPULATIONS. TWO DISTINCT CLASSES OF CPG SITES WERE IDENTIFIED: SITES WHOSE METHYLATION REVERTS TO LEVELS TYPICAL OF NEVER SMOKERS WITHIN DECADES AFTER SMOKING CESSATION, AND SITES REMAINING DIFFERENTIALLY METHYLATED, EVEN MORE THAN 35 YEARS AFTER SMOKING CESSATION. OUR RESULTS SUGGEST THAT THE DYNAMICS OF METHYLATION CHANGES FOLLOWING SMOKING CESSATION ARE DRIVEN BY A DIFFERENTIAL AND SITE-SPECIFIC MAGNITUDE OF THE SMOKING-INDUCED ALTERATIONS (WITH PERSISTENT SITES BEING MOST AFFECTED) IRRESPECTIVE OF THE INTENSITY AND DURATION OF SMOKING. ANALYSES OF THE LINK BETWEEN METHYLATION AND EXPRESSION LEVELS REVEALED THAT METHYLATION PREDOMINANTLY AND REMOTELY DOWN-REGULATES GENE EXPRESSION. AMONG GENES WHOSE EXPRESSION WAS ASSOCIATED WITH OUR CANDIDATE CPG SITES, LRRN3 APPEARED TO BE PARTICULARLY INTERESTING AS IT WAS ONE OF THE FEW GENES WHOSE METHYLATION AND EXPRESSION WERE DIRECTLY ASSOCIATED, AND THE ONLY GENE IN WHICH BOTH METHYLATION AND GENE EXPRESSION WERE FOUND ASSOCIATED WITH SMOKING. OUR STUDY HIGHLIGHTS PERSISTENT EPIGENETIC MARKERS OF SMOKING, WHICH CAN POTENTIALLY BE DETECTED DECADES AFTER CESSATION. SUCH HISTORICAL SIGNATURES ARE PROMISING BIOMARKERS TO REFINE INDIVIDUAL RISK PROFILING OF SMOKING-INDUCED CHRONIC DISEASE SUCH AS LUNG CANCER. 2015 19 2074 50 EPIGENETIC DEREGULATION IN CHRONIC LYMPHOCYTIC LEUKEMIA: CLINICAL AND BIOLOGICAL IMPACT. DEREGULATED TRANSCRIPTIONAL CONTROL CAUSED BY ABERRANT DNA METHYLATION AND/OR HISTONE MODIFICATIONS IS A HALLMARK OF CANCER CELLS. IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL), THE MOST COMMON ADULT LEUKEMIA, THE EPIGENETIC 'LANDSCAPE' HAS ADDED A NEW LAYER OF COMPLEXITY TO OUR UNDERSTANDING OF THIS CLINICALLY AND BIOLOGICALLY HETEROGENEOUS DISEASE. EARLY STUDIES IDENTIFIED ABERRANT DNA METHYLATION, OFTEN BASED ON SINGLE GENE PROMOTER ANALYSIS WITH BOTH BIOLOGICAL AND CLINICAL IMPACT. SUBSEQUENT GENOME-WIDE PROFILING STUDIES REVEALED DIFFERENTIAL DNA METHYLATION BETWEEN CLLS AND CONTROLS AND IN PROGNOSTICS SUBGROUPS OF THE DISEASE. FROM THESE STUDIES, IT BECAME APPARENT THAT DNA METHYLATION IN REGIONS OUTSIDE OF PROMOTERS, SUCH AS ENHANCERS, IS IMPORTANT FOR THE REGULATION OF CODING GENES AS WELL AS FOR THE REGULATION OF NON-CODING RNAS. ALTHOUGH DNA METHYLATION PROFILES ARE REPORTEDLY STABLE OVER TIME AND IN RELATION TO THERAPY, A HIGHER EPIGENETIC HETEROGENEITY OR 'BURDEN' IS SEEN IN MORE AGGRESSIVE CLL SUBGROUPS, ALBEIT AS NON-RECURRENT 'PASSENGER' EVENTS. MORE RECENTLY, DNA METHYLATION PROFILES IN CLL ANALYZED IN RELATION TO DIFFERENTIATING NORMAL B-CELL POPULATIONS REVEALED THAT THE MAJORITY OF THE CLL EPIGENOME REFLECTS THE EPIGENOMES PRESENT IN THE CELL OF ORIGIN AND THAT ONLY A SMALL FRACTION OF THE EPIGENETIC ALTERATIONS REPRESENTS TRULY CLL-SPECIFIC CHANGES. FURTHERMORE, CLL PATIENTS CAN BE GROUPED INTO AT LEAST THREE CLINICALLY RELEVANT EPIGENETIC SUBGROUPS, POTENTIALLY ORIGINATING FROM DIFFERENT CELLS AT VARIOUS STAGES OF DIFFERENTIATION AND ASSOCIATED WITH DISTINCT OUTCOMES. IN THIS REVIEW, WE SUMMARIZE THE CURRENT UNDERSTANDING OF THE DNA METHYLOME IN CLL, THE ROLE OF HISTONE MODIFYING ENZYMES, HIGHLIGHT INSIGHTS DERIVED FROM ANIMAL MODELS AND ATTEMPTS MADE TO TARGET EPIGENETIC REGULATORS IN CLL ALONG WITH THE FUTURE DIRECTIONS OF THIS RAPIDLY ADVANCING FIELD. 2018 20 1583 38 DNA METHYLATION PROFILES OF BLOOD CELLS ARE DISTINCT BETWEEN EARLY-ONSET OBESE AND CONTROL INDIVIDUALS. OBESITY IS A HIGHLY PREVALENT, CHRONIC DISORDER THAT HAS BEEN INCREASING IN INCIDENCE IN YOUNG PATIENTS. BOTH EPIGENETIC AND GENETIC ABERRATIONS MAY PLAY A ROLE IN THE PATHOGENESIS OF OBESITY. THEREFORE, IN-DEPTH EPIGENOMIC AND GENOMIC ANALYSES WILL ADVANCE OUR UNDERSTANDING OF THE DETAILED MOLECULAR MECHANISMS UNDERLYING OBESITY AND AID IN THE SELECTION OF POTENTIAL BIOMARKERS FOR OBESITY IN YOUTH. HERE, WE PERFORMED MICROARRAY-BASED DNA METHYLATION AND GENE EXPRESSION PROFILING OF PERIPHERAL WHITE BLOOD CELLS OBTAINED FROM SIX YOUNG, OBESE INDIVIDUALS AND SIX HEALTHY CONTROLS. WE OBSERVED THAT THE HIERARCHICAL CLUSTERING OF DNA METHYLATION, BUT NOT GENE EXPRESSION, CLEARLY SEGREGATES THE OBESE INDIVIDUALS FROM THE CONTROLS, SUGGESTING THAT THE METABOLIC DISTURBANCE THAT OCCURS AS A RESULT OF OBESITY AT A YOUNG AGE MAY AFFECT THE DNA METHYLATION OF PERIPHERAL BLOOD CELLS WITHOUT ACCOMPANYING TRANSCRIPTIONAL CHANGES. TO EXAMINE THE GENOME-WIDE DIFFERENCES IN THE DNA METHYLATION PROFILES OF YOUNG OBESE AND CONTROL INDIVIDUALS, WE IDENTIFIED DIFFERENTIALLY METHYLATED CPG SITES AND INVESTIGATED THEIR GENOMIC AND EPIGENOMIC CONTEXTS. THE ABERRANT DNA METHYLATION PATTERNS IN OBESE INDIVIDUALS CAN BE SUMMARIZED AS RELATIVE GAINS AND LOSSES OF DNA METHYLATION IN GENE PROMOTERS AND GENE BODIES, RESPECTIVELY. WE ALSO OBSERVED THAT THE CPG ISLANDS OF OBESE INDIVIDUALS ARE MORE SUSCEPTIBLE TO DNA METHYLATION COMPARED TO CONTROLS. OUR PILOT STUDY SUGGESTS THAT THE GENOME-WIDE ABERRANT DNA METHYLATION PATTERNS OF OBESE INDIVIDUALS MAY ADVANCE NOT ONLY OUR UNDERSTANDING OF THE EPIGENOMIC PATHOGENESIS BUT ALSO EARLY SCREENING OF OBESITY IN YOUTH. 2017