1 66 117 A KEY ROLE FOR EZH2 IN EPIGENETIC SILENCING OF HOX GENES IN MANTLE CELL LYMPHOMA. THE CHROMATIN MODIFIER EZH2 IS OVEREXPRESSED AND ASSOCIATED WITH INFERIOR OUTCOME IN MANTLE CELL LYMPHOMA (MCL). RECENTLY, WE DEMONSTRATED PREFERENTIAL DNA METHYLATION OF HOX GENES IN MCL COMPARED WITH CHRONIC LYMPHOCYTIC LEUKEMIA (CLL), DESPITE THESE GENES NOT BEING EXPRESSED IN EITHER ENTITY. SINCE EZH2 HAS BEEN SHOWN TO REGULATE HOX GENE EXPRESSION, TO GAIN FURTHER INSIGHT INTO ITS POSSIBLE ROLE IN DIFFERENTIAL SILENCING OF HOX GENES IN MCL VS. CLL, WE PERFORMED DETAILED EPIGENETIC CHARACTERIZATION USING REPRESENTATIVE CELL LINES AND PRIMARY SAMPLES. WE OBSERVED SIGNIFICANT OVEREXPRESSION OF EZH2 IN MCL VS. CLL. CHROMATIN IMMUNE PRECIPITATION (CHIP) ASSAYS REVEALED THAT EZH2 CATALYZED REPRESSIVE H3 LYSINE 27 TRIMETHYLATION (H3K27ME3), WHICH WAS SUFFICIENT TO SILENCE HOX GENES IN CLL, WHEREAS IN MCL H3K27ME3 IS ACCOMPANIED BY DNA METHYLATION FOR A MORE STABLE REPRESSION. MORE IMPORTANTLY, HYPERMETHYLATION OF THE HOX GENES IN MCL RESULTED FROM EZH2 OVEREXPRESSION AND SUBSEQUENT RECRUITMENT OF THE DNA METHYLATION MACHINERY ONTO HOX GENE PROMOTERS. THE IMPORTANCE OF EZH2 UPREGULATION IN THIS PROCESS WAS FURTHER UNDERSCORED BY SIRNA TRANSFECTION AND EZH2 INHIBITOR EXPERIMENTS. ALTOGETHER, THESE OBSERVATIONS IMPLICATE EZH2 IN THE LONG-TERM SILENCING OF HOX GENES IN MCL, AND ALLUDE TO ITS POTENTIAL AS A THERAPEUTIC TARGET WITH CLINICAL IMPACT. 2013 2 3918 35 LINKING ABERRANT CHROMATIN FEATURES IN CHRONIC LYMPHOCYTIC LEUKEMIA TO TRANSCRIPTION FACTOR NETWORKS. IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL), A DIVERSE SET OF GENETIC MUTATIONS IS EMBEDDED IN A DEREGULATED EPIGENETIC LANDSCAPE THAT DRIVES CANCEROGENESIS. TO ELUCIDATE THE ROLE OF ABERRANT CHROMATIN FEATURES, WE MAPPED DNA METHYLATION, SEVEN HISTONE MODIFICATIONS, NUCLEOSOME POSITIONS, CHROMATIN ACCESSIBILITY, BINDING OF EBF1 AND CTCF, AS WELL AS THE TRANSCRIPTOME OF B CELLS FROM CLL PATIENTS AND HEALTHY DONORS. A GLOBALLY INCREASED HISTONE DEACETYLASE ACTIVITY WAS DETECTED AND HALF OF THE GENOME COMPRISED TRANSCRIPTIONALLY DOWNREGULATED PARTIALLY DNA METHYLATED DOMAINS DEMARCATED BY CTCF CLL SAMPLES DISPLAYED A H3K4ME3 REDISTRIBUTION AND NUCLEOSOME GAIN AT PROMOTERS AS WELL AS CHANGES OF ENHANCER ACTIVITY AND ENHANCER LINKAGE TO TARGET GENES. A DNA BINDING MOTIF ANALYSIS IDENTIFIED TRANSCRIPTION FACTORS THAT GAINED OR LOST BINDING IN CLL AT SITES WITH ABERRANT CHROMATIN FEATURES. THESE FINDINGS WERE INTEGRATED INTO A GENE REGULATORY ENHANCER CONTAINING NETWORK ENRICHED FOR B-CELL RECEPTOR SIGNALING PATHWAY COMPONENTS. OUR STUDY PREDICTS NOVEL MOLECULAR LINKS TO TARGETS OF CLL THERAPIES AND PROVIDES A VALUABLE RESOURCE FOR FURTHER STUDIES ON THE EPIGENETIC CONTRIBUTION TO THE DISEASE. 2019 3 2771 33 EXTENSIVE PROMOTER DNA HYPERMETHYLATION AND HYPOMETHYLATION IS ASSOCIATED WITH ABERRANT MICRORNA EXPRESSION IN CHRONIC LYMPHOCYTIC LEUKEMIA. DYSREGULATED MICRORNA (MIRNA) EXPRESSION CONTRIBUTES TO THE PATHOGENESIS OF HEMATOPOIETIC MALIGNANCIES, INCLUDING CHRONIC LYMPHOCYTIC LEUKEMIA (CLL). HOWEVER, AN UNDERSTANDING OF THE MECHANISMS THAT CAUSE ABERRANT MIRNA TRANSCRIPTIONAL CONTROL IS LACKING. IN THIS STUDY, WE COMPREHENSIVELY INVESTIGATED THE ROLE AND EXTENT OF MIRNA EPIGENETIC REGULATION IN CLL. GENOME-WIDE PROFILING CONDUCTED ON 24 CLL AND 10 HEALTHY B CELL SAMPLES REVEALED GLOBAL DNA METHYLATION PATTERNS UPSTREAM OF MIRNA SEQUENCES THAT DISTINGUISHED MALIGNANT FROM HEALTHY CELLS AND IDENTIFIED PUTATIVE MIRNA PROMOTERS. INTEGRATION OF DNA METHYLATION AND MIRNA PROMOTER DATA LED TO THE IDENTIFICATION OF 128 RECURRENT MIRNA TARGETS FOR ABERRANT PROMOTER DNA METHYLATION. DNA HYPOMETHYLATION ACCOUNTED FOR MORE THAN 60% OF ALL ABERRANT PROMOTER-ASSOCIATED DNA METHYLATION IN CLL, AND PROMOTER DNA HYPOMETHYLATION WAS RESTRICTED TO WELL-DEFINED REGIONS. INDIVIDUAL HYPER- AND HYPOMETHYLATED PROMOTERS ALLOWED DISCRIMINATION OF CLL SAMPLES FROM HEALTHY CONTROLS. PROMOTER DNA METHYLATION PATTERNS WERE CONFIRMED IN AN INDEPENDENT PATIENT COHORT, WITH 11 MIRNAS CONSISTENTLY SHOWING AN INVERSE CORRELATION BETWEEN DNA METHYLATION STATUS AND EXPRESSION LEVEL. TOGETHER, OUR FINDINGS CHARACTERIZE THE ROLE OF EPIGENETIC CHANGES IN THE REGULATION OF MIRNA TRANSCRIPTION AND CREATE A REPOSITORY OF DISEASE-SPECIFIC PROMOTER REGIONS THAT MAY PROVIDE ADDITIONAL INSIGHTS INTO THE PATHOGENESIS OF CLL. 2012 4 1211 38 CPG ISLAND METHYLATION AND EXPRESSION OF THE SECRETED FRIZZLED-RELATED PROTEIN GENE FAMILY IN CHRONIC LYMPHOCYTIC LEUKEMIA. B-CELL CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) IS CHARACTERIZED BY A CLONAL ACCUMULATION OF MATURE NEOPLASTIC B CELLS INDICATING DISRUPTION OF APOPTOSIS. RESTRICTION LANDMARK GENOME SCANNING WAS DONE TO IDENTIFY NOVEL TARGET GENES SILENCED BY CPG ISLAND METHYLATION IN CLL. SECRETED FRIZZLED-RELATED PROTEIN 4 (SFRP4), A NEGATIVE REGULATOR OF THE WNT SIGNALING PATHWAY, WAS FOUND TO BE FREQUENTLY METHYLATED IN CLL SAMPLES. WNT SIGNALING HAS BEEN SHOWN TO CONTROL NORMAL APOPTOTIC BEHAVIOR AND IS REQUIRED FOR NORMAL B-CELL DEVELOPMENT WHEREAS ABERRANT ACTIVATION OF THIS PATHWAY HAS BEEN OBSERVED IN CLL. WE SHOW ABERRANT DNA METHYLATION AND SILENCING OF SFRP4, AS WELL AS OF ADDITIONAL SFRP FAMILY MEMBERS, IN PRIMARY CLL SAMPLES. INDUCTION OF THEIR EXPRESSION IN A DOSE-DEPENDENT MANNER FOLLOWING TREATMENT WITH A DEMETHYLATING AGENT, 5-AZA-2'-DEOXYCYTIDINE, WAS SHOWN. OF THE FIVE SFRP FAMILY MEMBERS STUDIED IN DETAIL, SFRP1 WAS HYPERMETHYLATED AND DOWN-REGULATED IN ALL CLL PATIENT SAMPLES STUDIED, SUGGESTING THAT THIS EPIGENETIC EVENT IS A CRITICAL STEP DURING LEUKEMOGENESIS. OUR RESULTS SUGGEST THAT SILENCING OF SFRPS BY CPG ISLAND METHYLATION IS ONE POSSIBLE MECHANISM CONTRIBUTING TO ABERRANT ACTIVATION OF WNT SIGNALING PATHWAY IN CLL. 2006 5 3444 33 HYPERMETHYLATION OF E-CADHERIN IN LEUKEMIA. E-CADHERIN GENE IS OFTEN TERMED A "METASTASIS SUPPRESSOR" GENE BECAUSE THE E-CADHERIN PROTEIN CAN SUPPRESS TUMOR CELL INVASION AND METASTASIS. INACTIVATION OF THE E-CADHERIN GENE OCCURS IN UNDIFFERENTIATED SOLID TUMORS BY BOTH GENETIC AND EPIGENETIC MECHANISMS; HOWEVER, THE ROLE OF E-CADHERIN IN HEMATOLOGIC MALIGNANCIES IS ONLY NOW BEING RECOGNIZED. E-CADHERIN EXPRESSION IS ESSENTIAL FOR ERYTHROBLAST AND NORMOBLAST MATURATION, YET EXPRESSION IS REDUCED OR ABSENT IN LEUKEMIC BLAST CELLS. THIS STUDY EXAMINED THE MESSENGER RNA (MRNA) AND PROTEIN EXPRESSION OF THE E-CADHERIN GENE IN BONE MARROW AND BLOOD SAMPLES FROM NORMAL DONORS AND PATIENTS WITH LEUKEMIA. WE FOUND THAT ALL NORMAL DONOR SAMPLES EXPRESSED E-CADHERIN MRNA, WHEREAS BOTH SAMPLES OF ACUTE MYELOGENOUS LEUKEMIA AND CHRONIC LYMPHOCYTIC LEUKEMIA HAD A SIGNIFICANT REDUCTION OR ABSENCE OF EXPRESSION. HOWEVER, NORMAL BLAST COUNTERPARTS EXPRESSED ONLY A LOW LEVEL OF E-CADHERIN SURFACE PROTEIN. SODIUM BISULPHITE GENOMIC SEQUENCING WAS USED TO FULLY CHARACTERIZE THE METHYLATION PATTERNS OF THE CPG ISLAND ASSOCIATED WITH THE E-CADHERIN GENE PROMOTER IN THOSE SAMPLES WITH MATCHED DNA. ALL OF THE NORMAL CONTROL SAMPLES WERE ESSENTIALLY UNMETHYLATED; HOWEVER, 14 OF 18 (78%) OF THE LEUKEMIA SAMPLES HAD ABNORMAL HYPERMETHYLATION OF THE E-CADHERIN CPG ISLAND. IN FACT BOTH ALLELES OF THE E-CADHERIN GENE WERE OFTEN HYPERMETHYLATED. WE CONCLUDE THE E-CADHERIN GENE IS A COMMON TARGET FOR HYPERMETHYLATION IN HEMATOLOGIC MALIGNANCIES. 2000 6 2747 41 EXPRESSION ANALYSIS OF THE EPIGENETIC METHYLTRANSFERASES AND METHYL-CPG BINDING PROTEIN FAMILIES IN THE NORMAL B-CELL AND B-CELL CHRONIC LYMPHOCYTIC LEUKEMIA (CLL). THE IMPORTANCE OF EPIGENETIC MODIFICATIONS IN CARCINOGENESIS HAS BEEN A SOURCE OF CONTROVERSY FOR SOME TIME. THERE IS LITTLE DOUBT THAT CHANGES IN GENOMIC HYPERMETHYLATION CONTRIBUTE TO THE SILENCING OF TUMOR SUPPRESSOR GENES. FURTHERMORE, RECENT STUDIES HAVE ALSO IDENTIFIED THE SIGNIFICANCE OF GENOMIC HYPOMETHYLATION ASSOCIATED WITH CHROMOSOMAL INSTABILITY AND TUMORIGENESIS. ONE OF THE MOST PERPLEXING QUESTIONS REGARDING EPIGENETIC MODIFICATIONS AND LEUKEMOGENESIS IS THE RELATIONSHIP WITH DNA METHYLTRANSFERASES (DNMT'S). THE PRIMARY FUNCTION OF THE DNMT ENZYMES IS TO METHYLATE GENOMIC DNA, WHEREAS THE METHYL-CPG BINDING DOMAIN PROTEINS (MBD) INTERPRET THIS METHYLATION SIGNAL AND REGULATE GENE EXPRESSION AND CHROMATIN BEHAVIOR. IN THIS STUDY WE ANALYSE THESE GENE FAMILIES BY QUANTITATIVE REAL-TIME PCR TO INVESTIGATE WHETHER EXPRESSION LEVELS AND THE B-CELL CHRONIC LYMPHOCYTIC LEUKEMIA (B-CLL) PHENOTYPE ARE ASSOCIATED. FURTHERMORE, GIVEN THE EPIGENETIC CROSSTALK BETWEEN GENOME STABILITY AND THE HISTONE CHROMATIN CODE WE HAVE ANALYSED EUKARYOTIC HISTONE METHYLTRANSFERASE (EU-HMTASEI). SURPRISINGLY, WE DID NOT OBSERVE SIGNIFICANT CHANGES IN DNMT1 EXPRESSION IN B-CLL CASES WHEN COMPARED TO NORMAL LYMPHOCYTES, REGARDLESS OF WHETHER WE NORMALISE AGAINST GAPDH OR PCNA AS REFERENCE STANDARDS. INDEED, EXPRESSION OF THE MAINTENANCE AND DE NOVO METHYLASES WERE INDEPENDENTLY REGULATED. OF PARTICULAR NOTE WAS THE SIGNIFICANT DOWN REGULATION OF DNMT3B. FURTHERMORE, WE OBSERVED A POSITIVE CORRELATION BETWEEN HMTASEI EXPRESSION LEVELS AND STAGE OF LEUKEMIA SUGGESTING THAT CHANGES IN THE METHYLATION PATTERNS IN B-CLL MAY REPRESENT DEREGULATION OF THE EPIGENETIC REPERTOIRE THAT ALSO INCLUDE THE METHYLATION DEPENDENT BINDING PROTEINS, MBD2 AND MECP2. WE ENVISAGE CHANGES IN THE EPIGENETIC PROGRAM ARE MULTIFACTORIAL IN NATURE AND POSTULATE THAT THE PREVALENT GENOMIC METHYLASES JUST ONE COMPONENT OF A LARGER EPIGENETIC REPERTOIRE. 2004 7 206 40 ACTIVATION OF NOTCH AND MYC SIGNALING VIA B-CELL-RESTRICTED DEPLETION OF DNMT3A GENERATES A CONSISTENT MURINE MODEL OF CHRONIC LYMPHOCYTIC LEUKEMIA. CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) IS CHARACTERIZED BY DISORDERED DNA METHYLATION, SUGGESTING THESE EPIGENETIC CHANGES MIGHT PLAY A CRITICAL ROLE IN DISEASE ONSET AND PROGRESSION. THE METHYLTRANSFERASE DNMT3A IS A KEY REGULATOR OF DNA METHYLATION. ALTHOUGH DNMT3A SOMATIC MUTATIONS IN CLL ARE RARE, WE FOUND THAT LOW DNMT3A EXPRESSION IS ASSOCIATED WITH MORE AGGRESSIVE DISEASE. A CONDITIONAL KNOCKOUT MOUSE MODEL SHOWED THAT HOMOZYGOUS DEPLETION OF DNMT3A FROM B CELLS RESULTS IN THE DEVELOPMENT OF CLL WITH 100% PENETRANCE AT A MEDIAN AGE OF ONSET OF 5.3 MONTHS, AND HETEROZYGOUS DNMT3A DEPLETION YIELDS A DISEASE PENETRANCE OF 89% WITH A MEDIAN ONSET AT 18.5 MONTHS, CONFIRMING ITS ROLE AS A HAPLOINSUFFICIENT TUMOR SUPPRESSOR. B1A CELLS WERE CONFIRMED AS THE CELL OF ORIGIN OF DISEASE IN THIS MODEL, AND DNMT3A DEPLETION RESULTED IN FOCAL HYPOMETHYLATION AND ACTIVATION OF NOTCH AND MYC SIGNALING. AMPLIFICATION OF CHROMOSOME 15 CONTAINING THE MYC GENE WAS DETECTED IN ALL CLL MICE TESTED, AND INFILTRATION OF HIGH-MYC-EXPRESSING CLL CELLS IN THE SPLEEN WAS OBSERVED. NOTABLY, HYPERACTIVATION OF NOTCH AND MYC SIGNALING WAS EXCLUSIVELY OBSERVED IN THE DNMT3A CLL MICE, BUT NOT IN THREE OTHER CLL MOUSE MODELS TESTED (SF3B1-ATM, IKZF3, AND MDR), AND DNMT3A-DEPLETED CLL WERE SENSITIVE TO PHARMACOLOGIC INHIBITION OF NOTCH SIGNALING IN VITRO AND IN VIVO. CONSISTENT WITH THESE FINDINGS, HUMAN CLL SAMPLES WITH LOWER DNMT3A EXPRESSION WERE MORE SENSITIVE TO NOTCH INHIBITION THAN THOSE WITH HIGHER DNMT3A EXPRESSION. ALTOGETHER, THESE RESULTS SUGGEST THAT DNMT3A DEPLETION INDUCES CLL THAT IS HIGHLY DEPENDENT ON ACTIVATION OF NOTCH AND MYC SIGNALING. SIGNIFICANCE: LOSS OF DNMT3A EXPRESSION IS A DRIVING EVENT IN CLL AND IS ASSOCIATED WITH AGGRESSIVE DISEASE, ACTIVATION OF NOTCH AND MYC SIGNALING, AND ENHANCED SENSITIVITY TO NOTCH INHIBITION. 2021 8 3415 41 HSP90 INHIBITION INCREASES SOCS3 TRANSCRIPT AND REGULATES MIGRATION AND CELL DEATH IN CHRONIC LYMPHOCYTIC LEUKEMIA. EPIGENETIC OR TRANSCRIPTIONAL SILENCING OF IMPORTANT TUMOR SUPPRESSORS HAS BEEN DESCRIBED TO CONTRIBUTE TO CELL SURVIVAL AND TUMORIGENESIS IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL). USING GENE EXPRESSION MICROARRAY ANALYSIS, WE FOUND THAT THOUSANDS OF GENES ARE REPRESSED MORE THAN 2-FOLD IN CLL COMPARED TO NORMAL B CELLS; HOWEVER THERAPEUTIC APPROACHES TO REVERSE THIS HAVE BEEN LIMITED IN CLL. FOLLOWING TREATMENT WITH THE HSP90 INHIBITOR 17-DMAG, A SIGNIFICANT NUMBER OF THESE REPRESSED GENES WERE SIGNIFICANTLY RE-EXPRESSED. ONE OF THE GENES SIGNIFICANTLY REPRESSED IN CLL AND UP-REGULATED BY 17-DMAG WAS SUPPRESSOR OF CYTOKINE SIGNALING 3, (SOCS3). SOCS3 HAS BEEN SHOWN TO BE SILENCED IN SOLID TUMORS AS WELL AS MYELOID LEUKEMIA; HOWEVER LITTLE IS KNOWN ABOUT THE REGULATION IN CLL. WE FOUND THAT 17-DMAG INDUCES EXPRESSION OF SOCS3 BY VIA THE ACTIVATION OF P38 SIGNALING, AND SUBSEQUENTLY INHIBITS AKT AND STAT3 PHOSPHORYLATION RESULTING IN DOWNSTREAM EFFECTS ON CELL MIGRATION AND SURVIVAL. WE THEREFORE SUGGEST THAT SOCS3 IS AN IMPORTANT SIGNALING PROTEIN IN CLL, AND HSP90 INHIBITORS REPRESENT A NOVEL APPROACH TO TARGET TRANSCRIPTIONAL REPRESSION IN B CELL LYMPHOPROLIFERATIVE DISORDERS WHICH EXHIBIT A SUBSTANTIAL DEGREE OF GENE REPRESSION. 2016 9 2639 27 EPIGENOMIC ANALYSIS DETECTS WIDESPREAD GENE-BODY DNA HYPOMETHYLATION IN CHRONIC LYMPHOCYTIC LEUKEMIA. WE HAVE EXTENSIVELY CHARACTERIZED THE DNA METHYLOMES OF 139 PATIENTS WITH CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) WITH MUTATED OR UNMUTATED IGHV AND OF SEVERAL MATURE B-CELL SUBPOPULATIONS THROUGH THE USE OF WHOLE-GENOME BISULFITE SEQUENCING AND HIGH-DENSITY MICROARRAYS. THE TWO MOLECULAR SUBTYPES OF CLL HAVE DIFFERING DNA METHYLOMES THAT SEEM TO REPRESENT EPIGENETIC IMPRINTS FROM DISTINCT NORMAL B-CELL SUBPOPULATIONS. DNA HYPOMETHYLATION IN THE GENE BODY, TARGETING MOSTLY ENHANCER SITES, WAS THE MOST FREQUENT DIFFERENCE BETWEEN NAIVE AND MEMORY B CELLS AND BETWEEN THE TWO MOLECULAR SUBTYPES OF CLL AND NORMAL B CELLS. ALTHOUGH DNA METHYLATION AND GENE EXPRESSION WERE POORLY CORRELATED, WE IDENTIFIED GENE-BODY CPG DINUCLEOTIDES WHOSE METHYLATION WAS POSITIVELY OR NEGATIVELY ASSOCIATED WITH EXPRESSION. WE HAVE ALSO RECOGNIZED A DNA METHYLATION SIGNATURE THAT DISTINGUISHES NEW CLINICO-BIOLOGICAL SUBTYPES OF CLL. WE PROPOSE AN EPIGENOMIC SCENARIO IN WHICH DIFFERENTIAL METHYLATION IN THE GENE BODY MAY HAVE FUNCTIONAL AND CLINICAL IMPLICATIONS IN LEUKEMOGENESIS. 2012 10 1976 29 EPIGENETIC ALTERATIONS IN A MURINE MODEL FOR CHRONIC LYMPHOCYTIC LEUKEMIA. EARLY STAGES IN THE DEVELOPMENT OF CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) HAVE NOT BEEN EXPLORED MAINLY DUE TO THE INABILITY TO STUDY NORMAL B-CELLS EN ROUTE TO TRANSFORMATION. IN ORDER TO DETERMINE SUCH EARLY EVENTS OF LEUKEMOGENESIS, WE HAVE USED A WELL ESTABLISHED MOUSE MODEL FOR CLL. OVER-EXPRESSION OF HUMAN TCL1, A KNOWN CLL ONCOGENE IN MURINE B-CELLS LEADS TO THE DEVELOPMENT OF MATURE CD19+/CD5+/IGM+ CLONAL LEUKEMIA WITH A DISEASE PHENOTYPE SIMILAR TO THAT SEEN IN HUMAN CLL. HEREIN, WE REVIEW OUR RECENT STUDY USING THIS TCL1-DRIVEN MOUSE MODEL FOR CLL AND CORRESPONDING HUMAN CLL SAMPLES IN A CROSS-SPECIES EPIGENOMICS APPROACH TO ADDRESS THE TIMING AND RELEVANCE OF EPIGENETIC EVENTS OCCURRING DURING LEUKEMOGENESIS. WE DEMONSTRATED THAT THE MOUSE MODEL RECAPITULATES THE EPIGENETIC EVENTS THAT HAVE BEEN REPORTED FOR HUMAN CLL, AFFIRMING THE POWER AND VALIDITY OF THIS MOUSE MODEL TO STUDY EARLY EPIGENETIC EVENTS IN CANCER PROGRESSION. EPIGENETIC ALTERATIONS ARE DETECTED AS EARLY AS THREE MONTHS AFTER BIRTH, FAR BEFORE DISEASE MANIFESTS AT ABOUT 11 MONTHS OF AGE. THESE MICE UNDERGO NFKAPPAB REPRESSOR COMPLEX MEDIATED INACTIVATION OF THE TRANSCRIPTION FACTOR FOXD3, WHOSE TARGETS BECOME ABERRANTLY METHYLATED AND SILENCED IN MOUSE AND HUMAN CLL. OVERALL, OUR DATA SUGGEST THE ACCUMULATED EPIGENETIC ALTERATIONS DURING CLL PATHOGENESIS AS A CONSEQUENCE OF GENE SILENCING THROUGH TCL1 AND NFKAPPAB REPRESSOR COMPLEX, SUGGESTING THE RELEVANCE FOR NFKAPPAB AS A THERAPEUTIC TARGET IN CLL. 2009 11 1620 35 DNA METHYLTRANSFERASE-MEDIATED TRANSCRIPTIONAL SILENCING IN MALIGNANT GLIOMA: A COMBINED WHOLE-GENOME MICROARRAY AND PROMOTER ARRAY ANALYSIS. EPIGENETIC INACTIVATION OF TUMOR SUPPRESSOR GENES IS A COMMON FEATURE IN HUMAN CANCER. PROMOTER HYPERMETHYLATION AND HISTONE DEACETYLATION ARE REVERSIBLE EPIGENETIC MECHANISMS ASSOCIATED WITH TRANSCRIPTIONAL REGULATION. DNA METHYLTRANSFERASES (DNMT1 AND DNMT3B) REGULATE AND MAINTAIN PROMOTER METHYLATION AND ARE OVEREXPRESSED IN HUMAN CANCER. WE PERFORMED WHOLE-GENOME MICROARRAY ANALYSIS TO IDENTIFY GENES WITH ALTERED EXPRESSION AFTER RNAI-INDUCED SUPPRESSION OF DNMT IN A GLIOBLASTOMA MULTIFORME (GBM) CELL LINE. WE THEN IDENTIFIED GENES WITH BOTH DECREASED EXPRESSION AND EVIDENCE OF PROMOTER CPG ISLAND HYPERMETHYLATION IN GBM TISSUE SAMPLES USING A COMBINED WHOLE-GENOME MICROARRAY TRANSCRIPTOME ANALYSIS IN CONJUNCTION WITH A PROMOTER ARRAY ANALYSIS AFTER DNA IMMUNOPRECIPITATION WITH ANTI-5-METHYLCYTIDINE. DNMT1 AND 3B KNOCKDOWN RESULTED IN THE RESTORED EXPRESSION OF 308 GENES THAT ALSO CONTAINED PROMOTER REGION HYPERMETHYLATION. OF THESE, 43 WERE ALSO FOUND TO BE DOWNREGULATED IN GBM TISSUE SAMPLES. THREE DOWNREGULATED GENES WITH HYPERMETHYLATED PROMOTERS AND RESTORED EXPRESSION IN RESPONSE TO ACUTE DNMT SUPPRESSION WERE ASSAYED FOR METHYLATION CHANGES USING BISULFITE SEQUENCE ANALYSIS OF THE PROMOTER REGION AFTER CHRONIC DNMT SUPPRESSION. RESTORATION OF GENE EXPRESSION WAS NOT ASSOCIATED WITH CHANGES IN PROMOTER REGION METHYLATION, BUT RATHER WITH CHANGES IN HISTONE METHYLATION AND CHROMATIN CONFORMATION. TWO OF THE IDENTIFIED GENES EXHIBITED GROWTH SUPPRESSIVE ACTIVITY IN IN VITRO ASSAYS. COMBINING TARGETED GENETIC MANIPULATIONS WITH COMPREHENSIVE GENOMIC AND EXPRESSION ANALYSES PROVIDES A POTENTIALLY POWERFUL NEW APPROACH FOR IDENTIFYING EPIGENETICALLY REGULATED GENES IN GBM. 2009 12 390 35 AN INTEGRATIVE MODEL OF PATHWAY CONVERGENCE IN GENETICALLY HETEROGENEOUS BLAST CRISIS CHRONIC MYELOID LEUKEMIA. TARGETED THERAPIES AGAINST THE BCR-ABL1 KINASE HAVE REVOLUTIONIZED TREATMENT OF CHRONIC PHASE (CP) CHRONIC MYELOID LEUKEMIA (CML). IN CONTRAST, MANAGEMENT OF BLAST CRISIS (BC) CML REMAINS CHALLENGING BECAUSE BC CELLS ACQUIRE COMPLEX MOLECULAR ALTERATIONS THAT CONFER STEMNESS FEATURES TO PROGENITOR POPULATIONS AND RESISTANCE TO BCR-ABL1 TYROSINE KINASE INHIBITORS. COMPREHENSIVE MODELS OF BC TRANSFORMATION HAVE PROVED ELUSIVE BECAUSE OF THE RARITY AND GENETIC HETEROGENEITY OF BC, BUT ARE IMPORTANT FOR DEVELOPING BIOMARKERS PREDICTING BC PROGRESSION AND EFFECTIVE THERAPIES. TO BETTER UNDERSTAND BC, WE PERFORMED AN INTEGRATED MULTIOMICS ANALYSIS OF 74 CP AND BC SAMPLES USING WHOLE-GENOME AND EXOME SEQUENCING, TRANSCRIPTOME AND METHYLOME PROFILING, AND CHROMATIN IMMUNOPRECIPITATION FOLLOWED BY HIGH-THROUGHPUT SEQUENCING. EMPLOYING PATHWAY-BASED ANALYSIS, WE FOUND THE BC GENOME WAS SIGNIFICANTLY ENRICHED FOR MUTATIONS AFFECTING COMPONENTS OF THE POLYCOMB REPRESSIVE COMPLEX (PRC) PATHWAY. WHILE TRANSCRIPTOMICALLY, BC PROGENITORS WERE ENRICHED AND DEPLETED FOR PRC1- AND PRC2-RELATED GENE SETS RESPECTIVELY. BY INTEGRATING OUR DATA SETS, WE DETERMINED THAT BC PROGENITORS UNDERGO PRC-DRIVEN EPIGENETIC REPROGRAMMING TOWARD A CONVERGENT TRANSCRIPTOMIC STATE. SPECIFICALLY, PRC2 DIRECTS BC DNA HYPERMETHYLATION, WHICH IN TURN SILENCES KEY GENES INVOLVED IN MYELOID DIFFERENTIATION AND TUMOR SUPPRESSOR FUNCTION VIA SO-CALLED EPIGENETIC SWITCHING, WHEREAS PRC1 REPRESSES AN OVERLAPPING AND DISTINCT SET OF GENES, INCLUDING NOVEL BC TUMOR SUPPRESSORS. ON THE BASIS OF THESE OBSERVATIONS, WE DEVELOPED AN INTEGRATED MODEL OF BC THAT FACILITATED THE IDENTIFICATION OF COMBINATORIAL THERAPIES CAPABLE OF REVERSING BC REPROGRAMMING (DECITABINE+PRC1 INHIBITORS), NOVEL PRC-SILENCED TUMOR SUPPRESSOR GENES (NR4A2), AND GENE EXPRESSION SIGNATURES PREDICTIVE OF DISEASE PROGRESSION AND DRUG RESISTANCE IN CP. 2020 13 2380 30 EPIGENETIC REGULATION OF WNT SIGNALING IN CHRONIC LYMPHOCYTIC LEUKEMIA. CERTAIN WNT AND WNT NETWORK TARGET GENES ARE EXPRESSED AT HIGHER OR LOWER LEVELS IN CHRONIC LYMPHOCYTIC LEUKEMIA COMPARED WITH NORMAL B-CELLS. THIS INCLUDES UPREGULATION OF NUCLEAR COMPLEX GENES, AS WELL AS GENES FOR CYTOPLASMIC PROTEINS AND WNT LIGANDS AND THEIR COGNATE RECEPTORS. IN ADDITION, EPIGENETIC SILENCING OF SEVERAL NEGATIVE REGULATORS OF THE WNT PATHWAY HAVE BEEN IDENTIFIED. THE BALANCE BETWEEN EPIGENETIC DOWNREGULATION OF NEGATIVE EFFECTOR GENES AND INCREASED EXPRESSION OF POSITIVE EFFECTOR GENES DEMONSTRATE THAT THE EPIGENETIC DOWNREGULATION OF WNT ANTAGONISTS IS ONE MECHANISM, PERHAPS THE MAIN MECHANISM, THAT IS PERMISSIVE TO ACTIVE WNT SIGNALING IN CHRONIC LYMPHOCYTIC LEUKEMIA. MOREOVER, CONSTITUTIVE ACTIVATION OF THE WNT NETWORK AND TARGET GENES IS LIKELY TO IMPACT ON ADDITIONAL INTERACTING SIGNALING PATHWAYS. BASED ON PUBLISHED STUDIES, WE PROPOSE A MODEL OF WNT SIGNALING THAT INVOLVES MAINLY PERMISSIVE EXPRESSION, AND SOMETIMES OVEREXPRESSION, OF POSITIVE EFFECTORS AND DOWNREGULATION OF NEGATIVE REGULATORS IN THE NETWORK. IN THIS MODEL, DNA METHYLATION, HISTONE MODIFICATIONS AND ALTERED EXPRESSION OF MICRORNA MOLECULES INTERACT TO ALLOW CONTINUOUS WNT SIGNALING. 2010 14 3822 28 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 15 160 32 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 16 4254 34 METHYLOME-BASED CELL-OF-ORIGIN MODELING (METHYL-COOM) IDENTIFIES ABERRANT EXPRESSION OF IMMUNE REGULATORY MOLECULES IN CLL. BACKGROUND: IN CANCER, NORMAL EPIGENETIC PATTERNS ARE DISTURBED AND CONTRIBUTE TO GENE EXPRESSION CHANGES, DISEASE ONSET, AND PROGRESSION. THE CANCER EPIGENOME IS COMPOSED OF THE EPIGENETIC PATTERNS PRESENT IN THE TUMOR-INITIATING CELL AT THE TIME OF TRANSFORMATION, AND THE TUMOR-SPECIFIC EPIGENETIC ALTERATIONS THAT ARE ACQUIRED DURING TUMOR INITIATION AND PROGRESSION. THE PRECISE DISSECTION OF THESE TWO COMPONENTS OF THE TUMOR EPIGENOME WILL FACILITATE A BETTER UNDERSTANDING OF THE BIOLOGICAL MECHANISMS UNDERLYING MALIGNANT TRANSFORMATION. CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) ORIGINATES FROM DIFFERENTIATING B CELLS, WHICH UNDERGO EXTENSIVE EPIGENETIC PROGRAMMING. THIS POSES THE CHALLENGE TO PRECISELY DETERMINE THE EPIGENOMIC GROUND STATE OF THE CELL-OF-ORIGIN IN ORDER TO IDENTIFY CLL-SPECIFIC EPIGENETIC ABERRATIONS. METHODS: WE DEVELOPED A LINEAR REGRESSION MODEL, METHYLOME-BASED CELL-OF-ORIGIN MODELING (METHYL-COOM), TO MAP THE CELL-OF-ORIGIN FOR INDIVIDUAL CLL PATIENTS BASED ON THE CONTINUUM OF EPIGENOMIC CHANGES DURING NORMAL B CELL DIFFERENTIATION. RESULTS: METHYL-COOM ACCURATELY MAPS THE CELL-OF-ORIGIN OF CLL AND IDENTIFIES CLL-SPECIFIC ABERRANT DNA METHYLATION EVENTS THAT ARE NOT CONFOUNDED BY PHYSIOLOGIC EPIGENETIC B CELL PROGRAMMING. FURTHERMORE, METHYL-COOM UNMASKS ABNORMAL ACTION OF TRANSCRIPTION FACTORS, ALTERED SUPER-ENHANCER ACTIVITIES, AND ABERRANT TRANSCRIPT EXPRESSION IN CLL. AMONG THE ABERRANTLY REGULATED TRANSCRIPTS WERE MANY GENES THAT HAVE PREVIOUSLY BEEN IMPLICATED IN T CELL BIOLOGY. FLOW CYTOMETRY ANALYSIS OF THESE MARKERS CONFIRMED THEIR ABERRANT EXPRESSION ON MALIGNANT B CELLS AT THE PROTEIN LEVEL. CONCLUSIONS: METHYL-COOM ANALYSIS OF CLL IDENTIFIED DISEASE-SPECIFIC ABERRANT GENE REGULATION. THE ABERRANTLY EXPRESSED GENES IDENTIFIED IN THIS STUDY MIGHT PLAY A ROLE IN IMMUNE-EVASION IN CLL AND MIGHT SERVE AS NOVEL TARGETS FOR IMMUNOTHERAPY APPROACHES. IN SUMMARY, WE PROPOSE A NOVEL FRAMEWORK FOR IN SILICO MODELING OF REFERENCE DNA METHYLOMES AND FOR THE IDENTIFICATION OF CANCER-SPECIFIC EPIGENETIC CHANGES, A CONCEPT THAT CAN BE BROADLY APPLIED TO OTHER HUMAN MALIGNANCIES. 2020 17 6069 41 THE DIOXIN RECEPTOR IS SILENCED BY PROMOTER HYPERMETHYLATION IN HUMAN ACUTE LYMPHOBLASTIC LEUKEMIA THROUGH INHIBITION OF SP1 BINDING. THE TRANSCRIPTION FACTOR ARYL HYDROCARBON RECEPTOR (AHR) HAS RELEVANT FUNCTIONS IN CELL PROLIFERATION. INTERESTINGLY, THE AHR CAN EITHER PROMOTE OR INHIBIT PROLIFERATION DEPENDING ON THE CELL PHENOTYPE. ALTHOUGH RECENT DATA REVEAL POTENTIAL PATHWAYS FOR AHR SIGNALING IN CELL PROLIFERATION, THE MECHANISMS THAT REGULATE ITS ACTIVITY IN TUMOR CELLS REMAIN UNKNOWN. HERE, WE HAVE ANALYZED PROMOTER HYPERMETHYLATION AS A POTENTIAL MECHANISM CONTROLLING AHR EXPRESSION IN HUMAN TUMOR CELLS. AHR PROMOTER CPG METHYLATION WAS SPORADIC IN A PANEL OF 19 TUMOR CELL LINES EXCEPT FOR THE CHRONIC MYELOID LEUKEMIA (CML) K562 AND THE ACUTE LYMPHOBLASTIC LEUKEMIA (ALL) REH. WHEN COMPARED WITH NORMAL LYMPHOCYTES, REH HAD VERY LOW CONSTITUTIVE AHR EXPRESSION THAT COULD BE ATTRIBUTED TO PROMOTER HYPERMETHYLATION SINCE TREATMENT WITH THE DNA DEMETHYLATING AGENT 5-AZA-2'-DEOXYCITIDINE (AZA) SIGNIFICANTLY INCREASED AHR MRNA AND PROTEIN. THESE RESULTS IN LEUKEMIA-DERIVED CELL LINES WERE FURTHER CONFIRMED IN PRIMARY ALL, WHERE 33% OF THE PATIENTS (7/21) HAD AHR PROMOTER HYPERMETHYLATION. CHROMATIN IMMUNOPRECIPITATION (CHIP) SHOWED THAT METHYLATION IMPAIRED BINDING OF THE TRANSCRIPTION FACTOR SP1 TO THE AHR PROMOTER, THUS PROVIDING A MECHANISM FOR AHR DOWNREGULATION IN REH CELLS. THEREFORE, PROMOTER HYPERMETHYLATION REPRESENTS A NOVEL EPIGENETIC MECHANISM DOWNREGULATING AHR ACTIVITY IN HEMATOLOGICAL MALIGNANCIES SUCH AS ALL. 2006 18 2494 32 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 19 4004 32 LOSS OF THE POLYCOMB MARK FROM BIVALENT PROMOTERS LEADS TO ACTIVATION OF CANCER-PROMOTING GENES IN COLORECTAL TUMORS. IN COLON TUMORS, THE TRANSCRIPTION OF MANY GENES BECOMES DEREGULATED BY POORLY DEFINED EPIGENETIC MECHANISMS THAT HAVE BEEN STUDIED MAINLY IN ESTABLISHED CELL LINES. IN THIS STUDY, WE USED FROZEN HUMAN COLON TISSUES TO ANALYZE PATTERNS OF HISTONE MODIFICATION AND DNA CYTOSINE METHYLATION IN CANCER AND MATCHED NORMAL MUCOSA SPECIMENS. DNA METHYLATION IS STRONGLY TARGETED TO BIVALENT H3K4ME3- AND H3K27ME3-ASSOCIATED PROMOTERS, WHICH LOSE BOTH HISTONE MARKS AND ACQUIRE DNA METHYLATION. HOWEVER, WE FOUND THAT LOSS OF THE POLYCOMB MARK H3K27ME3 FROM BIVALENT PROMOTERS WAS ACCOMPANIED OFTEN BY ACTIVATION OF GENES ASSOCIATED WITH CANCER PROGRESSION, INCLUDING NUMEROUS STEM CELL REGULATORS, ONCOGENES, AND PROLIFERATION-ASSOCIATED GENES. INDEED, WE FOUND MANY OF THESE SAME GENES WERE ALSO ACTIVATED IN PATIENTS WITH ULCERATIVE COLITIS WHERE CHRONIC INFLAMMATION PREDISPOSES THEM TO COLON CANCER. BASED ON OUR FINDINGS, WE PROPOSE THAT A LOSS OF POLYCOMB REPRESSION AT BIVALENT GENES COMBINED WITH AN ENSUING SELECTION FOR TUMOR-DRIVING EVENTS PLAYS A MAJOR ROLE IN CANCER PROGRESSION. 2014 20 1212 33 CPG ISLAND METHYLATION OF THE HTERT PROMOTER IS ASSOCIATED WITH LOWER TELOMERASE ACTIVITY IN B-CELL LYMPHOCYTIC LEUKEMIA. OBJECTIVE: EXPRESSION OF THE CATALYTIC SUBUNIT OF THE TELOMERASE ENZYME HTERT IS ESSENTIAL FOR PROLONGING THE REPLICATIVE LIFESPAN AND IS THE RATE-LIMITING STEP IN CELLULAR IMMORTALIZATION AND CARCINOGENESIS. BECAUSE HTERT EXPRESSION IS POSITIVELY CORRELATED WITH TELOMERASE ACTIVITY, ITS REGULATION IS SUGGESTED AS THE MAJOR DETERMINANT OF ENZYMATIC ACTIVITY. THE HTERT PROMOTER REGION CONTAINS TWO CPG ISLANDS, WHICH ARE KNOWN TO BE TARGET SITES FOR DE NOVO DNA METHYLATION. TO ELUCIDATE THE IMPACT OF THIS EPIGENETIC MECHANISM ON TELOMERASE ACTIVITY, WE ANALYZED THE DEGREE OF HTERT PROMOTER METHYLATION IN 30 PATIENTS WITH B-CELL CHRONIC LYMPHOCYTIC LEUKEMIA. MATERIALS AND METHODS: HTERT PROMOTER METHYLATION WAS ASSESSED USING A METHYLATION-SPECIFIC COMPETITIVE POLYMERASE CHAIN REACTION ASSAY. THE ASSAY IS BASED ON DIGESTION OF GENOMIC DNA WITH A METHYLATION-SENSITIVE RESTRICTION ENZYME BEFORE AMPLIFICATION WITH AN INTERNAL STANDARD. RESULTS: PATIENTS EXHIBITING HIGH TELOMERASE ACTIVITY SHOWED SIGNIFICANTLY LESS METHYLATION OF THE HTERT PROMOTER CORE DOMAIN THAN PATIENTS WITH LOW ENZYME ACTIVITY. IN ADDITION, TELOMERASE ACTIVITY WAS SIGNIFICANTLY ASSOCIATED WITH TELOMERE LENGTH AND OVERALL SURVIVAL. CONCLUSIONS: OUR DATA SHOW THAT THE DEGREE OF CPG ISLAND METHYLATION OF THE HTERT PROMOTER EXHIBITS AN IMPACT ON TELOMERASE ACTIVITY IN A SUBGROUP OF PATIENTS WITH B-CELL CHRONIC LYMPHOCYTIC LEUKEMIA AND THEREFORE IS ASSUMED TO PLAY A ROLE IN REGULATING HTERT GENE EXPRESSION IN THESE PATIENTS. 2002