1 6616 165 UNCOVERING THE DNA METHYLOME IN CHRONIC LYMPHOCYTIC LEUKEMIA. OVER THE PAST TWO DECADES, ABERRANT DNA METHYLATION HAS EMERGED AS A KEY PLAYER IN THE PATHOGENESIS OF CHRONIC LYMPHOCYTIC LEUKEMIA (CLL), AND KNOWLEDGE REGARDING ITS BIOLOGICAL AND CLINICAL CONSEQUENCES IN THIS DISEASE HAS EVOLVED RAPIDLY. SINCE THE INITIAL STUDIES RELATING DNA HYPOMETHYLATION TO GENOMIC INSTABILITY IN CLL, A PLETHORA OF REPORTS HAVE FOLLOWED SHOWING THE IMPACT OF DNA HYPERMETHYLATION IN SILENCING VITAL SINGLE GENE PROMOTERS AND THE REVERSIBLE NATURE OF DNA METHYLATION THROUGH INHIBITOR DRUGS. WITH THE RECOGNITION THAT DNA HYPERMETHYLATION EVENTS COULD POTENTIALLY ACT AS NOVEL PROGNOSTIC AND TREATMENT TARGETS IN CLL, THE SEARCH FOR ABERRANTLY METHYLATED GENES, GENE FAMILIES AND PATHWAYS HAS ENSUED. SUBSEQUENTLY, THE ADVENT OF MICROARRAY AND NEXT-GENERATION SEQUENCING TECHNOLOGIES HAS SUPPORTED THE HUNT FOR SUCH TARGETS, ALLOWING EXPLORATION OF THE METHYLATION LANDSCAPE IN CLL AT AN UNPRECEDENTED SCALE. IN LIGHT OF THESE ANALYSES, WE NOW UNDERSTAND THAT DIFFERENT CLL PROGNOSTIC SUBGROUPS ARE CHARACTERIZED BY DIFFERENTIAL METHYLATION PROFILES; WE RECOGNIZE DNA METHYLATION OF A NUMBER OF SIGNALING PATHWAYS GENES TO BE ALTERED IN CLL, AND ACKNOWLEDGE THE ROLE OF DNA METHYLATION OUTSIDE OF TRADITIONAL CPG ISLAND PROMOTERS AS FUNDAMENTAL PLAYERS IN THE REGULATION OF GENE EXPRESSION. TODAY, THE SIGNIFICANCE AND TIMING OF ALTERED DNA METHYLATION WITHIN THE COMPLEX EPIGENETIC NETWORK OF CONCOMITANT EPIGENETIC MESSENGERS SUCH AS HISTONES AND MIRNAS IS AN INTENSIVE AREA OF RESEARCH. IN CLL, IT APPEARS THAT DNA METHYLATION IS A RATHER STABLE EPIGENETIC MARK OCCURRING RATHER EARLY IN THE DISEASE PATHOGENESIS. HOWEVER, OTHER CONSEQUENCES, SUCH AS HOW AND WHY ABERRANT METHYLATION MARKS OCCUR, ARE LESS EXPLORED. IN THIS REVIEW, WE WILL NOT ONLY PROVIDE A COMPREHENSIVE SUMMARY OF THE CURRENT LITERATURE WITHIN THE EPIGENETICS FIELD OF CLL, BUT ALSO HIGHLIGHT SOME OF THE NOVEL FINDINGS RELATING TO WHEN, WHERE, WHY AND HOW ALTERED DNA METHYLATION MATERIALIZES IN CLL. 2013 2 2074 61 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 3 3768 44 INTEGRATIVE EPIGENOMICS IN CHRONIC LYMPHOCYTIC LEUKAEMIA: BIOLOGICAL INSIGHTS AND CLINICAL APPLICATIONS. CHRONIC LYMPHOCYTIC LEUKAEMIA (CLL) IS NOT ONLY CHARACTERISED BY DRIVER GENETIC ALTERATIONS BUT BY EXTENSIVE EPIGENETIC CHANGES. OVER THE LAST DECADE, EPIGENOMIC STUDIES HAVE DESCRIBED THE DNA METHYLOME, CHROMATIN ACCESSIBILITY, HISTONE MODIFICATIONS AND THE THREE-DIMENSIONAL (3D) GENOME ARCHITECTURE OF CLL. BEYOND ITS REGULATORY ROLE, THE DNA METHYLOME CONTAINS IMPRINTS OF THE CELLULAR ORIGIN AND PROLIFERATIVE HISTORY OF CLL CELLS. THESE TWO ASPECTS ARE STRONG INDEPENDENT PROGNOSTIC FACTORS. INTEGRATIVE ANALYSES OF CHROMATIN MARKS HAVE UNCOVERED NOVEL REGULATORY ELEMENTS AND ALTERED TRANSCRIPTION FACTOR NETWORKS AS NON-GENETIC MEANS MEDIATING GENE DEREGULATION IN CLL. ADDITIONALLY, CLL CELLS DISPLAY A DISEASE-SPECIFIC PATTERN OF 3D GENOME INTERACTIONS. FROM THE TECHNOLOGICAL PERSPECTIVE, WE ARE CURRENTLY WITNESSING A TRANSITION FROM BULK OMICS TO SINGLE-CELL ANALYSES. THIS REVIEW AIMS AT SUMMARISING THE MAJOR FINDINGS FROM THE EPIGENOMICS FIELD AS WELL AS PROVIDING A PROSPECT OF THE PRESENT AND FUTURE OF SINGLE-CELL ANALYSES IN CLL. 2023 4 2535 37 EPIGENETICS IN CHRONIC LYMPHOCYTIC LEUKEMIA. ENORMOUS EVIDENCE HAS ACCUMULATED IN THE PAST DECADES THAT ESTABLISHES THE IMPORTANCE OF EPIGENETIC MODIFICATIONS IN CANCER AND HAS RESULTED IN SHIFTING THE FOCUS FROM ENTIRELY GENETIC-BASED STUDIES TO INTEGRATED STUDIES INVOLVING BOTH GENETIC AND EPIGENETIC ALTERATIONS. CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) IS ONE SUCH EXAMPLE WHERE STUDIES INVOLVING EPIGENETIC ABERRATIONS HAVE ACCELERATED THE SEARCH FOR AFFECTED GENES, WHICH WAS INITIALLY RESTRICTED TO COMMONLY DELETED CHROMOSOMAL REGIONS. MANY NOVEL GENES THAT ARE EPIGENETICALLY SILENCED IN CLL HAVE BEEN IDENTIFIED. ADVANCES IN THE UNDERSTANDING OF POST-TRANSLATIONAL HISTONE MODIFICATIONS AND DNA METHYLATION IN NORMAL AND IN CLL CELLS HAVE PROVEN TO BE EXTREMELY BENEFICIAL IN FINDING POWERFUL DIAGNOSTIC MARKERS, AS WELL AS IN EXPLORING NOVEL THERAPIES. AT PRESENT, THE FIELD OF EPIGENETICS IS AT AN EVOLVING STAGE, BUT THERE IS NO DOUBT THAT FURTHER UNRAVELING OF ITS CAUSE AND EFFECTS IN TRANSFORMED CELLS WILL BRING A NEW REVOLUTION IN CANCER THERAPEUTICS. 2006 5 3089 36 GENOMIC AND EPIGENOMIC ALTERATIONS IN CHRONIC LYMPHOCYTIC LEUKEMIA. CHRONIC LYMPHOCYTIC LEUKEMIA IS A COMMON DISEASE IN WESTERN COUNTRIES AND HAS HETEROGENEOUS CLINICAL BEHAVIOR. THE RELEVANCE OF THE GENETIC BASIS OF THE DISEASE HAS COME TO THE FOREFRONT RECENTLY, WITH GENOME-WIDE STUDIES THAT HAVE PROVIDED A COMPREHENSIVE VIEW OF STRUCTURAL VARIANTS, SOMATIC MUTATIONS, AND DIFFERENT LAYERS OF EPIGENETIC CHANGES. THE MUTATIONAL LANDSCAPE IS CHARACTERIZED BY RELATIVELY COMMON COPY NUMBER ALTERATIONS, A FEW MUTATED GENES OCCURRING IN 10-15% OF CASES, AND A LARGE NUMBER OF GENES MUTATED IN A SMALL NUMBER OF CASES. THE EPIGENOMIC PROFILE HAS REVEALED A MARKED REPROGRAMMING OF REGULATORY REGIONS IN TUMOR CELLS COMPARED WITH NORMAL B CELLS. ALL OF THESE ALTERATIONS ARE DIFFERENTIALLY DISTRIBUTED IN CLINICAL AND BIOLOGICAL SUBSETS OF THE DISEASE, INDICATING THAT THEY MAY UNDERLIE THE HETEROGENEOUS EVOLUTION OF THE DISEASE. THESE GLOBAL STUDIES ARE REVEALING THE MOLECULAR COMPLEXITY OF CHRONIC LYMPHOCYTIC LEUKEMIA AND PROVIDE NEW PERSPECTIVES THAT HAVE HELPED TO UNDERSTAND ITS PATHOGENIC MECHANISMS AND IMPROVE THE CLINICAL MANAGEMENT OF PATIENTS. 2020 6 606 45 BEYOND GENETICS--THE EMERGING ROLE OF EPIGENETIC CHANGES IN HEMATOPOIETIC MALIGNANCIES. THE TERM EPIGENETIC REFERS TO A HERITABLE CHANGE IN GENE EXPRESSION THAT IS MEDIATED BY MECHANISMS OTHER THAN ALTERATIONS IN THE PRIMARY NUCLEOTIDE SEQUENCE. DNA METHYLATION AT CYTOSINE BASES THAT ARE LOCATED 5' TO GUANOSINE WITHIN A CPG DINUCLEOTIDE IS THE MAIN EPIGENETIC MODIFICATION IN HUMANS. PATTERNS OF DNA METHYLATION ARE PROFOUNDLY DERANGED IN HUMAN CANCER AND COMPRISE GENOME-WIDE LOSSES AS WELL AS REGIONAL GAINS IN DNA METHYLATION. HYPERMETHYLATION OF CPG ISLANDS WITHIN GENE PROMOTER REGIONS IS ASSOCIATED WITH TRANSCRIPTIONAL INACTIVATION AND REPRESENTS, IN ADDITION TO GENETIC ABERRATIONS, AN IMPORTANT MECHANISM OF GENE SILENCING IN THE PATHOGENESIS OF HEMATOPOIETIC MALIGNANCIES. THIS EPIGENETIC PHENOMENON ACTS AS AN ALTERNATIVE TO MUTATIONS AND DELETIONS TO DISRUPT TUMOR SUPPRESSOR GENE FUNCTION. A LARGE NUMBER OF GENES INVOLVING FUNDAMENTAL CELLULAR PATHWAYS MAY BE AFFECTED IN VIRTUALLY ALL TYPES OF HUMAN CANCER BY ABERRANT CPG ISLAND METHYLATION IN ASSOCIATION WITH TRANSCRIPTIONAL SILENCING. ALTERED METHYLATION PATTERNS CAN BE USED AS BIOMARKERS FOR CANCER DETECTION, ASSESSMENT OF PROGNOSIS, AND PREDICTION OF RESPONSE TO ANTITUMOR TREATMENT. FURTHERMORE, CLINICAL TRIALS USING EPIGENETICALLY TARGETED THERAPIES HAVE YIELDED PROMISING RESULTS FOR ACUTE AND CHRONIC LEUKEMIAS AS WELL AS FOR MYELODYSPLASTIC SYNDROMES. THE EXPLORATION OF OUR GROWING KNOWLEDGE ABOUT EPIGENETIC ABERRATIONS MAY HELP DEVELOP NOVEL STRATEGIES FOR THE DIAGNOSIS AND TREATMENT OF HEMATOPOIETIC MALIGNANCIES IN THE FUTURE. 2004 7 2944 49 GENETIC AND EPIGENETIC BASIS OF CHRONIC LYMPHOCYTIC LEUKEMIA. PURPOSE OF REVIEW: NEXT-GENERATION SEQUENCING OF WHOLE GENOMES, EXOMES AND DNA METHYLOMES IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) HAS PROVIDED THE FIRST COMPREHENSIVE VIEW OF SOMATIC MUTATIONS AND METHYLATION CHANGES IN THIS DISEASE. THIS REVIEW SUMMARIZES THE RECENT FINDINGS IN THIS FIELD AND THEIR IMPACT ON OUR CURRENT UNDERSTANDING OF THIS NEOPLASM. RECENT FINDINGS: GENOMIC STUDIES HAVE REVEALED A REMARKABLE MOLECULAR HETEROGENEITY OF THE DISEASE, WITH ONLY FEW GENES MUTATED IN UP TO 10-15% OF THE PATIENTS AND A RELATIVELY LARGE NUMBER OF GENES RECURRENTLY MUTATED AT LOW FREQUENCY. THE MUTATED GENES TEND TO CLUSTER IN DIFFERENT PATHWAYS THAT INCLUDE NOTCH1 SIGNALING, RNA SPLICING, PROCESSING AND TRANSPORT MACHINERY, INNATE INFLAMMATORY RESPONSE, AND DNA DAMAGE AND CELL CYCLE CONTROL, AMONG OTHERS. NOTCH1 AND SF3B1 MUTATIONS ARE EMERGING AS NEW DRIVERS OF AGGRESSIVE FORMS OF THE DISEASE. GENOME-WIDE METHYLATION STUDIES HAVE SHOWN THAT CLL TRANSFORMATION IS ASSOCIATED WITH A MASSIVE HYPOMETHYLATION PHENOMENON FREQUENTLY AFFECTING THE ENHANCER REGIONS. THIS EPIGENETIC REPROGRAMMING MAINTAINS AN IMPRINT OF THE PUTATIVE CELL OF ORIGIN FROM NAIVE AND MEMORY B-CELLS. SUMMARY: GENOMIC AND EPIGENOMIC STUDIES OF CLL ARE RESHAPING OUR UNDERSTANDING OF THE DISEASE AND PROVIDE NEW PERSPECTIVE FOR A MORE INDIVIDUALIZED DIAGNOSIS AND NEW POTENTIAL THERAPEUTIC TARGETS. 2013 8 6854 32 [NEW ADVANCES OF EPIGENETIC STUDY IN TUMORS OF LYMPHATIC SYSTEM---REVIEW]. EPIGENETICS IS AIMED TO STUDY THE HERITABLE CHANGES IN GENE EXPRESSION PATTERNS INDEPENDENT OF ALTERATIONS IN GENOMIC DNA SEQUENCE STRUCTURE, AND THE MECHANISMS OF TRANSLATION FROM GENOTYPE TO PHENOTYPE. IN RECENT YEARS, COMPELLING EVIDENCE GATHERED SUPPORTS A ROLE OF EPIGENETIC ALTERATIONS IN THE PATHOGENESIS OF LYMPHATIC SYSTEM TUMORS. FOR EXAMPLE, RECENT DATA FROM MULTIPLE LABORATORIES INDICATE THAT SEVERAL HUNDRED GENES, INVOLVING DOZENS OF CRITICAL MOLECULAR PATHWAYS, ARE EPIGENETICALLY SUPPRESSED IN ACUTE LYMPHOCYTIC LEUKEMIA; A PANEL OF METHYLATION MARKERS CAN BE USED FOR ADDITIONAL RISK STRATIFICATION OF CHRONIC LYMPHOCYTIC LEUKEMIA PATIENTS; BASED ON THE EPIGENETIC PROFILES, THE CLASS PREDICTION MODELS IN GRAY ZONE LYMPHOMA CAN BE ESTABLISHED; THE EPIGENETIC SILENCING OF MICRORNAS IN MULTIPLE MYELOMA GENERALLY APPEARS TO HAVE INTACT P53 FUNCTION; EPIGENETIC THERAPIES HAVE BROADER IMPLICATION AND HIGH POTENTIAL FOR THE DEVELOPMENT OF IMMUNOTHERAPEUTIC STRATEGIES AND SO ON. IN THIS REVIEW, THE LATEST ADVANCES OF EPIGENETIC STUDY AND THE PROSPECT OF EPIGENETIC THERAPY FOR TUMORS IN LYMPHATIC SYSTEM ARE SUMMARIZED. 2012 9 1562 47 DNA METHYLATION OF ENHANCER ELEMENTS IN MYELOID NEOPLASMS: THINK OUTSIDE THE PROMOTERS? GENE REGULATION THROUGH DNA METHYLATION IS A WELL DESCRIBED PHENOMENON THAT HAS A PROMINENT ROLE IN PHYSIOLOGICAL AND PATHOLOGICAL CELL-STATES. THIS EPIGENETIC MODIFICATION IS USUALLY GROUPED IN REGIONS DENOMINATED CPG ISLANDS, WHICH FREQUENTLY CO-LOCALIZE WITH GENE PROMOTERS, SILENCING THE TRANSCRIPTION OF THOSE GENES. RECENT GENOME-WIDE DNA METHYLATION STUDIES HAVE CHALLENGED THIS PARADIGM, DEMONSTRATING THAT DNA METHYLATION OF REGULATORY REGIONS OUTSIDE PROMOTERS IS ABLE TO INFLUENCE CELL-TYPE SPECIFIC GENE EXPRESSION PROGRAMS UNDER PHYSIOLOGIC OR PATHOLOGIC CONDITIONS. COUPLING GENOME-WIDE DNA METHYLATION ASSAYS WITH HISTONE MARK ANNOTATION HAS ALLOWED FOR THE IDENTIFICATION OF SPECIFIC EPIGENOMIC CHANGES THAT AFFECT ENHANCER REGULATORY REGIONS, REVEALING AN ADDITIONAL LAYER OF COMPLEXITY TO THE EPIGENETIC REGULATION OF GENE EXPRESSION. IN THIS REVIEW, WE SUMMARIZE THE NOVEL EVIDENCE FOR THE MOLECULAR AND BIOLOGICAL REGULATION OF DNA METHYLATION IN ENHANCER REGIONS AND THE DYNAMISM OF THESE CHANGES CONTRIBUTING TO THE FINE-TUNING OF GENE EXPRESSION. WE ALSO ANALYZE THE CONTRIBUTION OF ENHANCER DNA METHYLATION ON THE EXPRESSION OF RELEVANT GENES IN ACUTE MYELOID LEUKEMIA AND CHRONIC MYELOPROLIFERATIVE NEOPLASMS. THE CHARACTERIZATION OF THE ABERRANT ENHANCER DNA METHYLATION PROVIDES NOT ONLY A NOVEL PATHOGENIC MECHANISM FOR DIFFERENT TUMORS BUT ALSO HIGHLIGHTS NOVEL POTENTIAL THERAPEUTIC TARGETS FOR MYELOID DERIVED NEOPLASMS. 2019 10 4228 27 METHYLATION OF INFLAMMATORY CELLS IN LUNG DISEASES. THIS CHAPTER OVERVIEWS ROLES OF DNA METHYLATION IN INFLAMMATORY CELL BIOLOGY WITH THE FOCUSES ON LYMPHOCYTES AND MACROPHAGES/MONOCYTES IN LUNG DISEASES, ALTHOUGH THE MOLECULAR MECHANISMS BY WHICH TARGET GENES ARE METHYLATED AND REGULATED IN LUNG DISEASES REMAIN UNCLEAR. MOST OF EPIGENETIC STUDIES ON DNA METHYLATION OF TARGET GENES IN LUNG DISEASES MAINLY DEMONSTRATED THE CORRELATION OF DNA METHYLATION OF TARGET GENES WITH THE LEVELS OF OTHER CORRESPONDING FACTORS, WITH THE SPECIFICITY OF CLINICAL PHENOMES, AND WITH THE SEVERITY OF LUNG DISEASES. THERE IS AN URGENT NEED TO IDENTIFY AND VALIDATE THE SPECIFICITY AND REGULATORY MECHANISMS OF INFLAMMATORY CELL EPIGENETICS IN DEPTH. THE EPIGENETIC HETEROGENEITY AMONG DIFFERENT SUBSETS OF T CELLS AND AMONG PROMOTERS OR NON-PROMOTERS OF TARGET GENES SHOULD BE FURTHERMORE CLARIFIED IN ACUTE OR CHRONIC LUNG DISEASES AND CANCERS. THE HYPER/HYPO-METHYLATION AND MODIFICATIONS OF CHROMOSOL AND EXTRACHROMOSOMAL DNA MAY RESULT IN ALTERNATIONS IN PROTEINS WITHIN INFLAMMATORY CELLS, WHICH CAN BE IDENTIFIED AS DISEASE-SPECIFIC BIOMARKERS AND THERAPEUTIC TARGETS. 2020 11 4481 36 MOLECULAR PROFILING OF CHRONIC LYMPHOCYTIC LEUKAEMIA: GENETICS MEETS EPIGENETICS TO IDENTIFY PREDISPOSING GENES. MOLECULAR PROFILING MAY LEAD TO A BETTER UNDERSTANDING OF A DISEASE. THIS KNOWLEDGE IS ESPECIALLY IMPORTANT IN MALIGNANCIES, WHERE MULTIPLE ALTERATIONS ARE REQUIRED DURING THE PROGRESSION FROM PREMALIGNANT TO MALIGNANT STAGES. SUCH INFORMATION CAN BE USEFUL FOR THE DEVELOPMENT OF NOVEL BIOMARKERS THAT ALLOW THE PREDICTION OF A CLINICAL COURSE, RESPONSE TO TREATMENT OR EARLY DETECTION. MOLECULAR DATA IS ALSO UTILIZED TO DEVELOP TARGETED THERAPIES. MOREOVER, GENE DEFECTS IDENTIFIED IN PROFILING STUDIES WILL HELP TO UNDERSTAND THE MOLECULAR PATHWAYS DISRUPTED IN THE DISEASE. THIS REVIEW PROVIDES AN OVERVIEW OF MOLECULAR PROFILING APPROACHES IN CHRONIC LYMPHOCYTIC LEUKAEMIA (CLL). WE WILL DESCRIBE OUR CURRENT UNDERSTANDING OF GENETIC ALTERATIONS IN CLL, THE USE OF FAMILIAL CLL FOR THE IDENTIFICATION OF PREDISPOSING MUTATIONS, AND THE SEARCH FOR EPIGENETIC ALTERATIONS IN CLL. 2007 12 2494 36 EPIGENETICS AND CHRONIC LYMPHOCYTIC LEUKEMIA. THE DNA METHYLATION LEVEL IN PATIENTS WITH CHRONIC LYMPHOCYTIC LEUKEMIA IS GENERALLY LOWER THAN HEALTHY INDIVIDUALS. ALTHOUGH DNA METHYLATION IS GLOBALLY DECREASED, REGIONAL HYPERMETHYLATION OF GENE PROMOTERS LEADS TO GENE SILENCING. MANY OF THESE GENES HAVE TUMOR SUPPRESSOR PHENOTYPES. UNLIKE MUTATIONS OR DELETIONS, HYPERMETHYLATION IS POTENTIALLY REVERSIBLE AFTER INHIBITION WITH DNA METHYLATION MODULATORS. MYELODYSPLASTIC SYNDROME HAS BEEN A MODEL DISEASE IN WHICH TREATMENT OF PATIENTS RESULTS IN DEMETHYLATION OF SPECIFIC GENES. THE STORY IN PATIENTS WITH CHRONIC LYMPHOCYTIC LEUKEMIA IS SLOWLY UNRAVELING AS EPIGENETIC MODIFICATIONS LIKELY ALSO PLAY AN IMPORTANT ROLE. ONGOING CLINICAL TRIALS CORRELATING CLINICAL RESPONSE TO GENE EXPRESSION AFTER TREATMENT WITH DNA METHYLATION INHIBITORS WILL ULTIMATELY ALLOW US TO BETTER RISK STRATIFY AND PREDICT THE SUBGROUP OF PATIENTS WHO WILL BENEFIT FROM TREATMENT WITH THIS CLASS OF DRUGS. 2006 13 160 45 ABERRANT PROMOTER HYPOMETHYLATION IN CLL: DOES IT MATTER FOR DISEASE DEVELOPMENT? OVER THE LAST 30 YEARS, STUDIES OF ABERRANT DNA METHYLATION IN HEMATOLOGIC MALIGNANCIES HAVE BEEN DOMINATED BY THE PRIMARY FOCUS OF UNDERSTANDING PROMOTER HYPERMETHYLATION. THESE EFFORTS NOT ONLY RESULTED IN A BETTER UNDERSTANDING OF THE BASIS OF EPIGENETIC SILENCING OF TUMOR SUPPRESSOR GENES BUT ALSO RESULTED IN APPROVAL OF HYPOMETHYLATING AGENTS FOR THE TREATMENT OF SEVERAL MALIGNANCIES, SUCH AS MYELODYSPLASTIC SYNDROME AND ACUTE MYELOID LEUKEMIA. RECENT ADVANCES IN GLOBAL METHYLATION PROFILING COUPLED WITH THE USE OF MOUSE MODELS SUGGEST THAT ABERRANT PROMOTER HYPOMETHYLATION IS ALSO A FREQUENT EVENT IN HEMATOLOGIC MALIGNANCIES, PARTICULARLY IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL). PROMOTER HYPOMETHYLATION AFFECTS GENE EXPRESSION AND, THEREFORE, MAY PLAY AN IMPORTANT ROLE IN DISEASE PATHOGENESIS. HERE, WE REVIEW RECENT FINDINGS AND DISCUSS THE POTENTIAL INVOLVEMENT OF ABERRANT PROMOTER HYPOMETHYLATION IN CLL. 2016 14 6771 37 [ACQUIRED DISORDERS AND EPIGENETICS]. EPIGENETIC MODIFICATIONS, INVOLVING DNA METHYLATION AND HISTONE MODIFICATIONS, ARE MAINTAINED UPON SOMATIC CELL REPLICATION, AND ARE FUNDAMENTAL MECHANISMS FOR CELLULAR MEMORY. DNA METHYLATION OF PROMOTER CPG ISLANDS OF TUMOR-SUPPRESSOR GENES CAN SILENCE THEIR DOWNSTREAM GENES, AND CAN BE CAUSALLY INVOLVED IN CANCER DEVELOPMENT AND PROGRESSION. SINCE THIS EFFECT IS THE SAME WITH THAT OF INACTIVATING MUTATIONS, THE NATURES OF DNA METHYLATION WERE ONCE CONSIDERED TO BE SIMILAR TO MUTATIONS. HOWEVER, RECENTLY, IT WAS REVEALED THAT A LARGE NUMBER OF EPIGENETIC ALTERATIONS ARE PRESENT IN A SINGLE CANCER CELL, THAT A LARGE NUMBER OF CELLS HAVE AN EPIGENETIC ALTERATION OF A SPECIFIC GENE IN NON-CANCEROUS, THUS POLYCLONAL, TISSUES, THAT GENE SPECIFICITY IN METHYLATION INDUCTION IS PRESENT ACCORDING TO TISSUE TYPES AND INDUCERS, AND THAT CHRONIC INFLAMMATION IS DEEPLY INVOLVED IN METHYLATION INDUCTION. THESE FACTS SUGGEST THAT EPIGENETIC ALTERATIONS OF KEY GENES INVOLVED IN ACQUIRED CHRONIC DISORDERS CAN BE PRESENT IN A SIGNIFICANT FRACTION OF CELLS IN A TISSUE, AND THUS CAN IMPAIR THE FUNCTION OF THE TISSUE. ASSOCIATIONS BETWEEN EPIGENETIC ALTERATIONS AND BEHAVIOR, MEMORY, MENTAL DISORDERS, NEUROLOGICAL DISORDERS, METABOLIC DISORDERS, ALLERGY, AUTOIMMUNE DISORDERS, AND OTHER DISORDERS HAVE BEEN REPORTED. FURTHER RESEARCH IN THE FIELD IS NECESSARY TO CLARIFY THE CAUSAL ROLES OF THESE EPIGENETIC ALTERATIONS IN DISEASE DEVELOPMENT, AND TO APPLY THE FINDINGS TO NEW STRATEGIES OF DISEASE PREVENTION, DIAGNOSIS, AND TREATMENT. 2010 15 4320 30 MICRORNAS IN CHRONIC LYMPHOCYTIC LEUKEMIA: AN OLD DISEASE WITH NEW GENETIC INSIGHTS. CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) IS THE MOST COMMON LEUKEMIA AMONG ADULT POPULATION IN WESTERN COUNTRY. IN THE LAST DECADE, SEVERAL FINDINGS HAVE SUBSTANTIALLY REVOLUTIONIZED THE OLD CONCEPT THAT CLL IS A DISEASE ORIGINATING FROM MATURE, NOT-DIVIDING CELL WITH INDOLENT CLINICAL COURSE. NOTABLY, NEXT GENERATION SEQUENCING (NGS) HAS CONTRIBUTED TO DEEPEN THE KNOWLEDGE OF THE CELLULAR NETWORKS THAT IMPLY THE ONSET AND THE PROGRESSION OF CLL. AMONG GENETIC ABERRATIONS THAT ARE RECURRENTLY OBSERVED IN B-CELLS FROM PATIENTS WITH CLL, MICRORNA DEREGULATION REPRESENTED THE FIRST EPIGENETIC MECHANISM THAT HAS BEEN IDENTIFIED. THROUGH EPIGENETIC MECHANISM THEY CAN MODULATE GENE EXPRESSION AND INTERFERE WITH CELLULAR PATHWAYS THAT ARE INVOLVED IN CELL CYCLE, APOPTOSIS AND B-CELL RECEPTOR (BCR) ACTIVATION. ALTHOUGH FEW STUDIES HAVE SHOWN THE PROGNOSTIC AND PREDICTIVE VALUE OF MICRORNA EXPRESSION LEVELS, THEIR VALIDATION WITHIN PROSPECTIVE CLINICAL TRIALS IS WARRANTED. 2016 16 3015 34 GENETICS AND EPIGENETICS OF CLL. CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) HAS A HETEROGENEOUS BIOLOGICAL BEHAVIOR, WHICH IS HIGHLY INFLUENCED BY ITS IMMUNOGENETIC, EPIGENETIC, AND GENOMIC PROPERTIES. THE REMARKABLY VARIABLE CLINICAL COURSE OF THE DISEASE HAS BEEN ASSOCIATED WITH GENETIC FEATURES SUCH AS CHROMOSOMAL ABNORMALITIES, THE PRESENCE OF EITHER HIGH OR LOW NUMBERS OF SOMATIC HYPERMUTATIONS (SHM) IN THE VARIABLE REGION OF THE IMMUNOGLOBULIN HEAVY CHAIN LOCUS (IGHV), AND SOMATIC MUTATIONS OF SEVERAL SPECIFIC DRIVER GENES. NEXT-GENERATION SEQUENCING (NGS) TECHNOLOGIES HAVE PROVIDED A COMPREHENSIVE CHARACTERIZATION OF THE GENOMIC AND EPIGENOMIC LANDSCAPE IN CLL, ELUCIDATING IMPORTANT UNDERLYING MECHANISMS OF THE DISEASE'S BIOLOGY. THE SCOPE OF THIS REVIEW IS TO SUMMARIZE THE MOST RECENT DISCOVERIES ABOUT NOVEL GENETIC AND EPIGENETIC ALTERATIONS, DISCUSSING THEIR IMPACT ON CLINICAL OUTCOMES AND RESPONSE TO CURRENTLY AVAILABLE THERAPY. 2023 17 2033 39 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 18 1518 36 DNA METHYLATION AS AN EPIGENETIC MECHANISM IN THE DEVELOPMENT OF MULTIPLE SCLEROSIS. THE EPIGENETIC MECHANISMS OF GENE EXPRESSION REGULATION ARE A GROUP OF THE KEY CELLULAR AND MOLECULAR PATHWAYS THAT LEAD TO INHERITED ALTERATIONS IN GENES' ACTIVITY WITHOUT CHANGING THEIR CODING SEQUENCE. DNA METHYLATION AT THE C5 POSITION OF CYTOSINE IN CPG DINUCLEOTIDES IS AMONGST THE CENTRAL EPIGENETIC MECHANISMS. CURRENTLY, THE NUMBER OF STUDIES THAT ARE DEVOTED TO THE IDENTIFICATION OF METHYLATION PATTERNS SPECIFIC TO MULTIPLE SCLEROSIS (MS), A SEVERE CHRONIC AUTOIMMUNE DISEASE OF THE CENTRAL NERVOUS SYSTEM, IS ON A RAPID RISE. HOWEVER, THE ISSUE OF THE CONTRIBUTION OF DNA METHYLATION TO THE DEVELOPMENT OF THE DIFFERENT CLINICAL PHENOTYPES OF THIS HIGHLY HETEROGENEOUS DISEASE HAS ONLY BEGUN TO ATTRACT THE ATTENTION OF RESEARCHERS. THIS REVIEW SUMMARIZES THE DATA ON THE MOLECULAR MECHANISMS UNDERLYING DNA METHYLATION AND THE MS RISK FACTORS THAT CAN AFFECT THE DNA METHYLATION PROFILE AND, THEREBY, MODULATE THE EXPRESSION OF THE GENES INVOLVED IN THE DISEASE'S PATHOGENESIS. THE FOCUS OF OUR ATTENTION IS CENTERED ON THE ANALYSIS OF THE PUBLISHED DATA ON THE DIFFERENTIAL METHYLATION OF DNA FROM VARIOUS BIOLOGICAL SAMPLES OF MS PATIENTS OBTAINED USING BOTH THE CANDIDATE GENE APPROACH AND HIGH-THROUGHPUT METHODS. 2021 19 3686 34 INFLAMMATION-RELATED ABERRANT PATTERNS OF DNA METHYLATION: DETECTION AND ROLE IN EPIGENETIC DEREGULATION OF CANCER CELL TRANSCRIPTOME. IT IS NOW APPARENT THAT EPIGENETIC ABNORMALITIES, IN PARTICULAR ALTERED DNA METHYLATION, PLAY A CRUCIAL ROLE IN THE DEVELOPMENT AND PROGRESSION OF HUMAN CANCERS. DNA HYPERMETHYLATION AT PROMOTER CPG ISLANDS IS NOW RECOGNIZED AS A THIRD MECHANISM BY WHICH INACTIVATION OF TUMOR SUPPRESSOR GENES OCCURS. ABERRANT CPG ISLAND HYPERMETHYLATION IS ALSO FREQUENTLY OBSERVED IN CHRONIC INFLAMMATION AND PRECANCEROUS LESIONS, WHICH SUGGESTS THAT IT IS AN EARLY EVENT IN TUMORIGENESIS THAT COULD SERVE AS A USEFUL TUMOR MARKER. A VARIETY OF SCREENING TECHNIQUES HAVE BEEN DEVELOPED FOR GENOME-WIDE SCREENING OF METHYLATION STATUS. OF THOSE, TRANSCRIPTOME ANALYSIS COUPLED WITH PHARMACOLOGICAL UNMASKING HAS EMERGED AS A POWERFUL TOOL FOR REVEALING DNA METHYLATION PATTERNS IN CANCER CELLS AND IDENTIFYING NEW TUMOR MARKER CANDIDATES. 2009 20 3822 32 INVESTIGATING EPIGENETIC EFFECTS OF ACTIVATION-INDUCED DEAMINASE IN CHRONIC LYMPHOCYTIC LEUKEMIA. ACTIVATION INDUCED DEAMINASE (AID) HAS TWO DISTINCT AND WELL DEFINED ROLES, BOTH RELYING ON ITS DEOXYCYTIDINE (DC) DEAMINATING FUNCTION: ONE AS A DNA MUTATOR AND ANOTHER IN DNA DEMETHYLATION. IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL), AID WAS PREVIOUSLY SHOWN TO BE AN INDEPENDENT NEGATIVE PROGNOSTIC FACTOR. WHILE THERE IS SUBSTANTIAL IMPACT ON DNA MUTATIONS, EFFECTS OF AID ON GENE EXPRESSION BY PROMOTER DEMETHYLATION OF DISEASE RELATED TARGET GENES IN LEUKEMIA HAS NOT BEEN ADDRESSED. TO SHED LIGHT ON THIS QUESTION, WE AIMED AT DETERMINING GENOME WIDE METHYLATION CHANGES AS WELL AS GENE EXPRESSION CHANGES IN RESPONSE TO AID EXPRESSION IN CLL. ALTHOUGH WE FOUND MINOR DIFFERENCES IN INDIVIDUAL METHYLATION VARIABLE POSITIONS FOLLOWING AID EXPRESSION, WE COULD NOT FIND RECURRENT METHYLATION CHANGES OF SPECIFIC TARGET SITES OR CHANGES IN GLOBAL METHYLATION. 2018