1 4569 119 MYELOID-SPECIFIC INACTIVATION OF P15INK4B RESULTS IN MONOCYTOSIS AND PREDISPOSITION TO MYELOID LEUKEMIA. INACTIVATION OF P15INK4B, AN INHIBITOR OF CYCLIN-DEPENDENT KINASES, THROUGH DNA METHYLATION IS ONE OF THE MOST COMMON EPIGENETIC ABNORMALITIES IN MYELOID LEUKEMIA. ALTHOUGH THIS SUGGESTS A KEY ROLE FOR THIS PROTEIN IN MYELOID DISEASE SUPPRESSION, EXPERIMENTAL EVIDENCE TO SUPPORT THIS HAS NOT BEEN REPORTED. TO ADDRESS WHETHER THIS EVENT IS CRITICAL FOR PREMALIGNANT MYELOID DISORDERS AND LEUKEMIA DEVELOPMENT, MICE WERE GENERATED THAT HAVE LOSS OF P15INK4B SPECIFICALLY IN MYELOID CELLS. THE P15INK4B(FL/FL)-LYSMCRE MICE DEVELOP NONREACTIVE MONOCYTOSIS IN THE PERIPHERAL BLOOD ACCOMPANIED BY INCREASED NUMBERS OF MYELOID AND MONOCYTIC CELLS IN THE BONE MARROW RESEMBLING THE MYELOPROLIFERATIVE FORM OF CHRONIC MYELOMONOCYTIC LEUKEMIA. SPONTANEOUS PROGRESSION FROM CHRONIC DISEASE TO ACUTE LEUKEMIA WAS NOT OBSERVED. NEVERTHELESS, MOL4070LTR RETROVIRUS INTEGRATIONS PROVIDED COOPERATIVE GENETIC MUTATIONS RESULTING IN A HIGH FREQUENCY OF MYELOID LEUKEMIA IN KNOCKOUT MICE. TWO COMMON RETROVIRUS INSERTION SITES NEAR C-MYB AND SOX4 GENES WERE IDENTIFIED, AND THEIR TRANSCRIPT UP-REGULATED IN LEUKEMIA, SUGGESTING A COLLABORATIVE ROLE OF THEIR PROTEIN PRODUCTS WITH P15INK4B-DEFICIENCY IN PROMOTING MALIGNANT DISEASE. THIS NEW ANIMAL MODEL DEMONSTRATES EXPERIMENTALLY THAT P15INK4B IS A TUMOR SUPPRESSOR FOR MYELOID LEUKEMIA, AND ITS LOSS MAY PLAY AN ACTIVE ROLE IN THE ESTABLISHMENT OF PRELEUKEMIC CONDITIONS. 2010 2 1674 34 DRIVER MUTATIONS IN LEUKEMIA PROMOTE DISEASE PATHOGENESIS THROUGH A COMBINATION OF CELL-AUTONOMOUS AND NICHE MODULATION. STUDIES OF PATIENTS WITH ACUTE MYELOID LEUKEMIA (AML) HAVE LED TO THE IDENTIFICATION OF MUTATIONS THAT AFFECT DIFFERENT CELLULAR PATHWAYS. SOME OF THESE HAVE BEEN CLASSIFIED AS PRELEUKEMIC, AND A STEPWISE EVOLUTION PROGRAM WHEREBY CELLS ACQUIRE ADDITIONAL MUTATIONS HAS BEEN PROPOSED IN THE DEVELOPMENT OF AML. HOW THE TIMING OF ACQUISITION OF THESE MUTATIONS AND THEIR IMPACT ON TRANSFORMATION AND THE BONE MARROW (BM) MICROENVIRONMENT OCCURS HAS ONLY RECENTLY BEGUN TO BE INVESTIGATED. WE SHOW THAT CONSTITUTIVE AND EARLY LOSS OF THE EPIGENETIC REGULATOR, TET2, WHEN COMBINED WITH CONSTITUTIVE ACTIVATION OF FLT3, RESULTS IN TRANSFORMATION OF CHRONIC MYELOMONOCYTIC LEUKEMIA-LIKE OR MYELOPROLIFERATIVE NEOPLASM-LIKE PHENOTYPE TO AML, WHICH IS MORE PRONOUNCED IN DOUBLE-MUTANT MICE RELATIVE TO MICE CARRYING MUTATIONS IN SINGLE GENES. FURTHERMORE, WE SHOW THAT IN PRELEUKEMIC AND LEUKEMIC MICE THERE ARE ALTERATIONS IN THE BM NICHE AND SECRETED CYTOKINES, WHICH CREATES A PERMISSIVE ENVIRONMENT FOR THE GROWTH OF MUTATION-BEARING CELLS RELATIVE TO NORMAL CELLS. 2020 3 825 28 CHARACTERIZATION OF FUNCTIONAL TRANSPOSABLE ELEMENT ENHANCERS IN ACUTE MYELOID LEUKEMIA. TRANSPOSABLE ELEMENTS (TES) HAVE BEEN SHOWN TO HAVE IMPORTANT GENE REGULATORY FUNCTIONS AND THEIR ALTERATION COULD LEAD TO DISEASE PHENOTYPES. ACUTE MYELOID LEUKEMIA (AML) DEVELOPS AS A CONSEQUENCE OF A SERIES OF GENETIC CHANGES IN HEMATOPOIETIC PRECURSOR CELLS, INCLUDING MUTATIONS IN EPIGENETIC FACTORS. HERE, WE SET OUT TO STUDY THE GENE REGULATORY ROLE OF TES IN AML. WE FIRST EXPLORED THE EPIGENETIC LANDSCAPE OF TES IN AML PATIENTS USING ATAC-SEQ DATA. WE SHOW THAT A LARGE NUMBER OF TES IN GENERAL, AND MORE SPECIFICALLY MAMMALIAN-WIDE INTERSPERSED REPEATS (MIRS), ARE MORE ENRICHED IN AML CELLS THAN IN NORMAL BLOOD CELLS. WE OBTAINED A SIMILAR FINDING WHEN ANALYZING HISTONE MODIFICATION DATA IN AML PATIENTS. GENE ONTOLOGY ENRICHMENT ANALYSIS SHOWED THAT GENES NEAR MIRS IN OPEN CHROMATIN REGIONS ARE INVOLVED IN LEUKEMOGENESIS. TO FUNCTIONALLY VALIDATE THEIR REGULATORY ROLE, WE SELECTED 19 MIR REGIONS IN AML CELLS, AND TESTED THEM FOR ENHANCER ACTIVITY IN AN AML CELL LINE (KASUMI-1) AND A CHRONIC MYELOID LEUKEMIA (CML) CELL LINE (K562); THE RESULTS REVEALED SEVERAL MIRS TO BE FUNCTIONAL ENHANCERS. TAKEN TOGETHER, OUR RESULTS SUGGEST THAT TES ARE POTENTIALLY INVOLVED IN MYELOID LEUKEMOGENESIS AND HIGHLIGHT THESE SEQUENCES AS POTENTIAL CANDIDATES HARBORING AML-ASSOCIATED VARIATION. 2020 4 1542 34 DNA METHYLATION IN HAEMATOLOGICAL MALIGNANCIES: THE ROLE OF DECITABINE. NORMAL CELL DEVELOPMENT AND FUNCTION IS DEPENDENT UPON CONTROLLED GENE EXPRESSION. DNA METHYLATION IS AN EPIGENETIC MODIFICATION THAT CAN PLAY AN IMPORTANT ROLE IN THE CONTROL OF GENE EXPRESSION. DNA METHYLATION AT CYTOSINE RESIDUES IN GENE PROMOTER CPG SEQUENCES IS KNOWN TO INHIBIT GENE TRANSCRIPTION. INAPPROPRIATE INHIBITION OF THE TRANSCRIPTION OF TUMOUR SUPPRESSOR GENES, GENES THAT INHIBIT ANGIOGENESIS AND METASTASIS AND GENES INVOLVED IN DNA REPAIR BY UNCONTROLLED METHYLATION, CAN LEAD TO UNREGULATED GROWTH AND PROLIFERATION OF A CELL AND CARCINOGENESIS. PROMOTER HYPERMETHYLATION AFFECTING THE P16 GENE, RESULTING IN GENE SILENCING, HAS BEEN SHOWN TO OCCUR IN MANY HUMAN SOLID TUMOURS AND A 'HYPERMETHYLATION PROFILE' IN SOME LEUKAEMIAS HAS BEEN DEFINED. THE MOLECULAR MECHANISMS BY WHICH ABERRANT DNA METHYLATION TAKES PLACE DURING CARCINOGENESIS ARE STILL NOT CLEAR. HOWEVER, THE LARGE NUMBER OF TARGET GENES (INVOLVED IN TUMORIGENESIS) THAT ARE SILENCED BY ABERRANT METHYLATION SUGGESTS THAT INHIBITION OF THIS PROCESS MAY HAVE POTENTIAL AS CANCER THERAPY. DECITABINE (NSC-127716, DACOGEN; SUPERGEN) IS A POTENT AND SPECIFIC HYPOMETHYLATING AGENT AND AN INHIBITOR OF THE DNA METHYLTRANSFERASE ACTIVITY THAT MEDIATES DNA METHYLATION. DECITABINE HAS BEEN SHOWN TO HAVE A BROAD RANGE OF ANTINEOPLASTIC ACTIVITY IN PRECLINICAL STUDIES. THIS AGENT HAS EXHIBITED SIGNIFICANT ACTIVITY IN THE TREATMENT OF PATIENTS WITH MYELODYSPLASTIC SYNDROME, CHRONIC MYELOID LEUKAEMIA AND ACUTE MYELOID LEUKAEMIA, ALTHOUGH CLINICAL PHASE I AND II STUDIES WITH SOLID TUMOURS HAVE NOT BEEN VERY PROMISING. PHASE II AND III STUDIES ARE CURRENTLY ONGOING TO EVALUATE DECITABINE, BOTH ALONE AND IN COMBINATION, IN VARIOUS STAGES OF THESE HAEMATOLOGICAL MALIGNANCIES. 2003 5 160 31 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 6 2781 28 EZH2 IN MYELOID MALIGNANCIES. OUR UNDERSTANDING OF THE SIGNIFICANCE OF EPIGENETIC DYSREGULATION IN THE PATHOGENESIS OF MYELOID MALIGNANCIES HAS GREATLY ADVANCED IN THE PAST DECADE. ENHANCER OF ZESTE HOMOLOG 2 (EZH2) IS THE CATALYTIC CORE COMPONENT OF THE POLYCOMB REPRESSIVE COMPLEX 2 (PRC2), WHICH IS RESPONSIBLE FOR GENE SILENCING THROUGH TRIMETHYLATION OF H3K27. EZH2 DYSREGULATION IS HIGHLY TUMORIGENIC AND HAS BEEN OBSERVED IN VARIOUS CANCERS, WITH EZH2 ACTING AS AN ONCOGENE OR A TUMOR-SUPPRESSOR DEPENDING ON CELLULAR CONTEXT. WHILE LOSS-OF-FUNCTION MUTATIONS OF EZH2 FREQUENTLY AFFECT PATIENTS WITH MYELODYSPLASTIC/MYELOPROLIFERATIVE NEOPLASMS, MYELODYSPLASTIC SYNDROME AND MYELOFIBROSIS, CASES OF CHRONIC MYELOID LEUKEMIA (CML) SEEM TO BE LARGELY CHARACTERIZED BY EZH2 OVEREXPRESSION. A VARIETY OF OTHER FACTORS FREQUENTLY ABERRANT IN MYELOID LEUKEMIA CAN AFFECT PRC2 FUNCTION AND DISEASE PATHOGENESIS, INCLUDING ADDITIONAL SEX COMBS LIKE 1 (ASXL1) AND SPLICING GENE MUTATIONS. AS THE GENETIC BACKGROUND OF MYELOID MALIGNANCIES IS LARGELY HETEROGENEOUS, IT IS NOT SURPRISING THAT EZH2 MUTATIONS ACT IN CONJUNCTION WITH OTHER ABERRATIONS. SINCE EZH2 MUTATIONS ARE CONSIDERED TO BE EARLY EVENTS IN DISEASE PATHOGENESIS, THEY ARE OF THERAPEUTIC INTEREST TO RESEARCHERS, THOUGH TARGETING OF EZH2 LOSS-OF-FUNCTION DOES PRESENT UNIQUE CHALLENGES. PRELIMINARY RESEARCH INDICATES THAT COMBINED TYROSINE KINASE INHIBITOR (TKI) AND EZH2 INHIBITOR THERAPY MAY PROVIDE A STRATEGY TO ELIMINATE THE RESIDUAL DISEASE BURDEN IN CML TO ALLOW PATIENTS TO REMAIN IN TREATMENT-FREE REMISSION. 2020 7 2237 37 EPIGENETIC MODIFIERS IN MYELOID MALIGNANCIES: THE ROLE OF HISTONE DEACETYLASE INHIBITORS. MYELOID HEMATOLOGICAL MALIGNANCIES ARE CLONAL BONE MARROW NEOPLASMS, COMPRISING OF ACUTE MYELOID LEUKEMIA (AML), THE MYELODYSPLASTIC SYNDROMES (MDS), CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML), THE MYELOPROLIFERATIVE NEOPLASMS (MPN) AND SYSTEMIC MASTOCYTOSIS (SM). THE FIELD OF EPIGENETIC REGULATION OF NORMAL AND MALIGNANT HEMATOPOIESIS IS RAPIDLY GROWING. IN RECENT YEARS, HETEROZYGOUS SOMATIC MUTATIONS IN GENES ENCODING EPIGENETIC REGULATORS HAVE BEEN FOUND IN ALL SUBTYPES OF MYELOID MALIGNANCIES, SUPPORTING THE RATIONALE FOR TREATMENT WITH EPIGENETIC MODIFIERS. HISTONE DEACETYLASE INHIBITORS (HDACI) ARE EPIGENETIC MODIFIERS THAT, IN VITRO, HAVE BEEN SHOWN TO INDUCE GROWTH ARREST, APOPTOTIC OR AUTOPHAGIC CELL DEATH, AND TERMINAL DIFFERENTIATION OF MYELOID TUMOR CELLS. THESE EFFECTS WERE OBSERVED BOTH AT THE BULK TUMOR LEVEL AND IN THE MOST IMMATURE CD34(+)38(-) CELL COMPARTMENTS CONTAINING THE LEUKEMIC STEM CELLS. THUS, THERE IS A STRONG RATIONALE SUPPORTING HDACI THERAPY IN MYELOID MALIGNANCIES. HOWEVER, DESPITE INITIAL PROMISING RESULTS IN PHASE I TRIALS, HDACI IN MONOTHERAPY AS WELL AS IN COMBINATION WITH OTHER DRUGS, HAVE FAILED TO IMPROVE RESPONSES OR SURVIVAL. THIS REVIEW PROVIDES AN OVERVIEW OF THE RATIONALE FOR HDACI IN MYELOID MALIGNANCIES, CLINICAL RESULTS AND SPECULATIONS ON WHY CLINICAL TRIALS HAVE THUS FAR NOT MET THE EXPECTATIONS, AND HOW THIS MAY BE IMPROVED IN THE FUTURE. 2018 8 5687 30 SIGNIFICANCE OF INACTIVATED GENES IN LEUKEMIA: PATHOGENESIS AND PROGNOSIS. EPIGENETIC AND GENETIC ALTERATIONS ARE TWO MECHANISMS PARTICIPATING IN LEUKEMIA, WHICH CAN INACTIVATE GENES INVOLVED IN LEUKEMIA PATHOGENESIS OR PROGRESSION. THE PURPOSE OF THIS REVIEW WAS TO INTRODUCE VARIOUS INACTIVATED GENES AND EVALUATE THEIR POSSIBLE ROLE IN LEUKEMIA PATHOGENESIS AND PROGNOSIS. BY SEARCHING THE MESH WORDS "GENE, SILENCING AND LEUKEMIA" IN PUBMED WEBSITE, RELEVANT ENGLISH ARTICLES DEALT WITH HUMAN SUBJECTS AS OF 2000 WERE INCLUDED IN THIS STUDY. GENE INACTIVATION IN LEUKEMIA IS LARGELY MEDIATED BY PROMOTER'S HYPERMETHYLATION OF GENE INVOLVING IN CELLULAR FUNCTIONS SUCH AS CELL CYCLE, APOPTOSIS, AND GENE TRANSCRIPTION. INACTIVATED GENES, SUCH AS ASPP1, TP53, IKZF1 AND P15, MAY CORRELATE WITH POOR PROGNOSIS IN ACUTE LYMPHOID LEUKEMIA (ALL), CHRONIC LYMPHOID LEUKEMIA (CLL), CHRONIC MYELOGENOUS LEUKEMIA (CML) AND ACUTE MYELOID LEUKEMIA (AML), RESPECTIVELY. GENE INACTIVATION MAY PLAY A CONSIDERABLE ROLE IN LEUKEMIA PATHOGENESIS AND PROGNOSIS, WHICH CAN BE CONSIDERED AS COMPLEMENTARY DIAGNOSTIC TESTS TO DIFFERENTIATE DIFFERENT LEUKEMIA TYPES, DETERMINE LEUKEMIA PROGNOSIS, AND ALSO DETECT RESPONSE TO THERAPY. IN GENERAL, THIS REVIEW SHOWED SOME GENES INACTIVATED ONLY IN LEUKEMIA (WITH DIFFERENCES BETWEEN B-ALL, T-ALL, CLL, AML AND CML). THESE DIFFERENCES COULD BE OF INTEREST AS AN ADDITIONAL TOOL TO BETTER CATEGORIZE LEUKEMIA TYPES. FURTHERMORE; BASED ON INACTIVATED GENES, A DIVERSE CLASSIFICATION OF LEUKEMIAS COULD REPRESENT A POWERFUL METHOD TO ADDRESS A TARGETED THERAPY OF THE PATIENTS, IN ORDER TO MINIMIZE SIDE EFFECTS OF CONVENTIONAL THERAPIES AND TO ENHANCE NEW DRUG STRATEGIES. 2017 9 535 33 ASXL1 MUTATION CORRECTION BY CRISPR/CAS9 RESTORES GENE FUNCTION IN LEUKEMIA CELLS AND INCREASES SURVIVAL IN MOUSE XENOGRAFTS. RECURRENT SOMATIC MUTATIONS OF THE EPIGENETIC MODIFIER AND TUMOR SUPPRESSOR ASXL1 ARE COMMON IN MYELOID MALIGNANCIES, INCLUDING CHRONIC MYELOID LEUKEMIA (CML), AND ARE ASSOCIATED WITH POOR CLINICAL OUTCOME. CRISPR/CAS9 HAS RECENTLY EMERGED AS A POWERFUL AND VERSATILE GENOME EDITING TOOL FOR GENOME ENGINEERING IN VARIOUS SPECIES. WE HAVE USED THE CRISPR/CAS9 SYSTEM TO CORRECT THE ASXL1 HOMOZYGOUS NONSENSE MUTATION PRESENT IN THE CML CELL LINE KBM5, WHICH LACKS ASXL1 PROTEIN EXPRESSION. CRISPR/CAS9-MEDIATED ASXL1 HOMOZYGOUS CORRECTION RESULTED IN PROTEIN RE-EXPRESSION WITH RESTORED NORMAL FUNCTION, INCLUDING DOWN-REGULATION OF POLYCOMB REPRESSIVE COMPLEX 2 TARGET GENES. SIGNIFICANTLY REDUCED CELL GROWTH AND INCREASED MYELOID DIFFERENTIATION WERE OBSERVED IN ASXL1 MUTATION-CORRECTED CELLS, PROVIDING NEW INSIGHTS INTO THE ROLE OF ASXL1 IN HUMAN MYELOID CELL DIFFERENTIATION. MICE XENOGRAFTED WITH MUTATION-CORRECTED KBM5 CELLS SHOWED SIGNIFICANTLY LONGER SURVIVAL THAN UNCORRECTED XENOGRAFTS. THESE RESULTS SHOW THAT THE SOLE CORRECTION OF A DRIVER MUTATION IN LEUKEMIA CELLS INCREASES SURVIVAL IN VIVO IN MICE. THIS STUDY PROVIDES PROOF-OF-CONCEPT FOR DRIVER GENE MUTATION CORRECTION VIA CRISPR/CAS9 TECHNOLOGY IN HUMAN LEUKEMIA CELLS AND PRESENTS A STRATEGY TO ILLUMINATE THE IMPACT OF ONCOGENIC MUTATIONS ON CELLULAR FUNCTION AND SURVIVAL. 2015 10 3532 32 IMATINIB INDEPENDENT ABERRANT METHYLATION OF NOV/CCN3 IN CHRONIC MYELOGENOUS LEUKEMIA PATIENTS: A MECHANISM UPSTREAM OF BCR-ABL1 FUNCTION? BACKGROUND: THE NOV GENE PRODUCT, CCN3, HAS BEEN REPORTED IN A DIVERSE RANGE OF TUMORS TO SERVE AS A NEGATIVE GROWTH REGULATOR, WHILE ACTING AS A TUMOR SUPPRESSOR IN CHRONIC MYELOGENOUS LEUKEMIA (CML). HOWEVER, THE PRECISE MECHANISM OF ITS SILENCING IN CML IS POORLY UNDERSTOOD. IN THE CURRENT STUDY, WE AIMED TO QUERY IF THE GENE REGULATION OF CCN3 IS MEDIATED BY THE PROMOTER METHYLATION IN THE PATIENTS WITH CML. IN ADDITION, TO CLARIFY WHETHER THE EPIGENETIC SILENCING IS AFFECTED BY BCR-ABL1 INHIBITION, WE ASSESSED THE METHYLATION STATUS IN THE PATIENTS AT DIFFERENT TIME INTERVALS FOLLOWING THE TYROSINE KINASE INHIBITION USING IMATINIB THERAPY, AS THE FIRST-LINE TREATMENT FOR THIS TYPE OF LEUKEMIA. METHODS: TO ADDRESS THIS ISSUE, WE APPLIED BISULFITE-SEQUENCING TECHNIQUE AS A HIGH-RESOLUTION METHOD TO STUDY THE REGULATORY SEGMENT OF THE CCN3 GENE. THE RESULTS WERE ANALYZED IN NEWLY DIAGNOSED CML PATIENTS AS WELL AS FOLLOWING IMATINIB THERAPY. WE ALSO EVALUATED THE CORRELATION OF CCN3 PROMOTER METHYLATION WITH BCR-ABL1 LEVELS. RESULTS: OUR FINDINGS REVEALED THAT THE METHYLATION OCCURS FREQUENTLY IN THE PROMOTER REGION OF CML PATIENTS SHOWING A SIGNIFICANT INCREASE OF THE METHYLATED PERCENTAGE AT THE CPG SITES COMPARED TO NORMAL INDIVIDUALS. INTERESTINGLY, THIS HYPERMETHYLATION WAS INDICATED TO BE INDEPENDENT OF BCR-ABL1 TITERS IN BOTH GROUPS, WHICH MIGHT SUGGEST A MECHANISM BEYOND THE BCR-ABL1 FUNCTION. CONCLUSION: DESPITE SUGGESTING THAT THE CCN3 HYPERMETHYLATION ACTS AS A MOLECULAR MECHANISM INDEPENDENT OF BCR-ABL1 FUNCTION IN CML PATIENTS, THIS SCENARIO REQUIRES FURTHER VALIDATION BY COMPLEMENTARY EXPERIMENTS. IN THE CASE OF ACTING UPSTREAM OF BCR-ABL1 SIGNALING, THE METHYLATION MARKER CAN PROVIDE EARLY DETECTION AND A NOVEL PLATFORM FOR TARGETED EPIGENETIC MODIFIERS FOR EFFICIENT TREATMENT IN IMATINIB RESISTANT PATIENTS. 2019 11 5259 38 PROGRESSIVE DE NOVO DNA METHYLATION AT THE BCR-ABL LOCUS IN THE COURSE OF CHRONIC MYELOGENOUS LEUKEMIA. DE NOVO METHYLATION OF CPG ISLANDS IS A RARE EVENT IN MAMMALIAN CELLS. IT HAS BEEN OBSERVED IN THE COURSE OF DEVELOPMENTAL PROCESSES, SUCH AS X CHROMOSOME INACTIVATION AND GENOMIC IMPRINTING. THE METHYLATION OF DNA, AN IMPORTANT FACTOR IN THE EPIGENETIC CONTROL OF GENE EXPRESSION, MAY ALSO BE INVOLVED IN TUMORIGENESIS. AFTER THE T(9;22) CHROMOSOMAL TRANSLOCATION AND GENERATION OF THE PHILADELPHIA CHROMOSOME, THE INITIATING EVENT IN CHRONIC MYELOGENOUS LEUKEMIA (CML), MOST OF THE ABL CODING SEQUENCE IS FUSED TO THE 5' REGION OF THE BCR GENE. EXPRESSION OF THE HYBRID BCR-ABL GENE IS, THEREFORE, REGULATED BY THE BCR PROMOTER. IN MOST CASES OF CML, ONE OF THE TWO ABL PROMOTERS (PA) IS NESTED WITHIN THE BCR-ABL TRANSCRIPTIONAL UNIT AND SHOULD BE ABLE TO TRANSCRIBE THE TYPE IA 6-KB NORMAL ABL MRNA FROM THE PHILADELPHIA CHROMOSOME. HOWEVER, WE HAVE FOUND THAT THE 6-KB TRANSCRIPT IS PRESENT ONLY IN CML CELL LINES CONTAINING A NORMAL ABL ALLELE AND THAT THE APPARENT INACTIVATION OF THE NESTED PA PROMOTER IS ASSOCIATED WITH ALLELE-SPECIFIC METHYLATION. FURTHERMORE, WE HAVE NOTICED THAT THE PA PROMOTER IS CONTAINED WITHIN A CPG ISLAND AND UNDERGOES PROGRESSIVE DE NOVO METHYLATION IN THE COURSE OF THE DISEASE. THIS IS ATTESTED TO BY THE FACT THAT DNA SAMPLES FROM CML PATIENTS THAT ARE METHYLATION-FREE AT THE TIME OF DIAGNOSIS INVARIABLY BECOME METHYLATED IN ADVANCED CML. SINCE TUMOR PROGRESSION IN CML CANNOT ALWAYS BE INFERRED FROM THE CLINICAL PRESENTATION, ASSESSMENT OF DE NOVO CPG METHYLATION MAY PROVE TO BE OF CRITICAL VALUE IN MANAGEMENT OF THE DISEASE. IT COULD HERALD BLASTIC TRANSFORMATION AT A STAGE WHEN BONE MARROW TRANSPLANTATION, THE ONLY POTENTIALLY CURATIVE THERAPEUTIC PROCEDURE IN CML, IS STILL EFFECTIVE. 1994 12 6773 25 [ADVANCES OF RESEARCH ON DEMETHYLATION THERAPY FOR HEMATOLOGIC MALIGNANCIES]. DNA METHYLATION IS AN IMPORTANT AND REVERSIBLE EPIGENETIC MODIFICATION WHICH REGULATES GENOMIC STABILITY. METHYLATION IS ESSENTIAL FOR MAMMALIAN DEVELOPMENT. GENERALLY, GENE EXPRESSION LEVEL AND DNA METHYLATION ARE NEGATIVE CORRELATION. TRANSCRIPTIONAL SILENCING VIA METHYLATION OF CPG ISLANDS IN THE PROMOTER IS IMPORTANT FOR CELL GROWTH AND DIFFERENTIATION AND PLAYS A KEY ROLE IN TUMORIGENESIS. DEMETHYLATION DRUG CAN MODIFY CHROMATIN AND RESTORE THE ABILITY OF ANTI-ONCOGENE. DEMETHYLATION THERAPY AS A NEW THERAPY MAY TREAT EFFICIENTLY HEMATOLOGICAL MALIGNANCIES WITH RESISTANCE AND RELAPSE. IN THIS REVIEW, DNA METHYLATION MECHANISM, RELATIONSHIP BETWEEN ABERRANT METHYLATION AND HEMATOLOGIC MALIGNANCIES, MECHANISM OF DEMETHYLATION THERAPY, THE ADVANCE OF RESEARCH ON THE DEMETHYLATION THERAPY OF HEMATOLOGICAL MALIGNANCIES, SUCH AS ACUTE AND CHRONIC LEUKEMIA, LYMPHOMA, MYELODYSPLASTIC SYNDROME WERE SUMMARIZED. 2009 13 3234 25 HEMATOPOIETIC AND CHRONIC MYELOID LEUKEMIA STEM CELLS: MULTI-STABILITY VERSUS LINEAGE RESTRICTION. THERE IS COMPELLING EVIDENCE TO SUPPORT THE VIEW THAT THE CELL-OF-ORIGIN FOR CHRONIC MYELOID LEUKEMIA IS A HEMATOPOIETIC STEM CELL. UNLIKE NORMAL HEMATOPOIETIC STEM CELLS, THE PROGENY OF THE LEUKEMIA STEM CELLS ARE PREDOMINANTLY NEUTROPHILS DURING THE DISEASE CHRONIC PHASE AND THERE IS A MILD ANEMIA. THE HALLMARK ONCOGENE FOR CHRONIC MYELOID LEUKEMIA IS THE BCR-ABLP210 FUSION GENE. VARIOUS STUDIES HAVE EXCLUDED A ROLE FOR BCR-ABLP210 EXPRESSION IN MAINTAINING THE POPULATION OF LEUKEMIA STEM CELLS. STUDIES OF BCR-ABLP210 EXPRESSION IN EMBRYONAL STEM CELLS THAT WERE DIFFERENTIATED INTO HEMATOPOIETIC STEM CELLS AND OF THE EXPRESSION IN TRANSGENIC MICE HAVE REVEALED THAT BCR-ABLP210 IS ABLE TO VEER HEMATOPOIETIC STEM AND PROGENITOR CELLS TOWARDS A MYELOID FATE. FOR THE TRANSGENIC MICE, GLOBAL CHANGES TO THE EPIGENETIC LANDSCAPE WERE OBSERVED. IN CHRONIC MYELOID LEUKEMIA, THE ABILITY OF THE LEUKEMIA STEM CELLS TO CHOOSE FROM THE MANY FATES THAT ARE AVAILABLE TO NORMAL HEMATOPOIETIC STEM CELLS APPEARS TO BE DEREGULATED BY BCR-ABLP210 AND CHANGES TO THE EPIGENOME ARE ALSO IMPORTANT. EVEN SO, WE STILL DO NOT HAVE A PRECISE PICTURE AS TO WHY NEUTROPHILS ARE ABUNDANTLY PRODUCED IN CHRONIC MYELOID LEUKEMIA. 2022 14 1465 27 DISSECTING THE ROLE OF ABERRANT DNA METHYLATION IN HUMAN LEUKAEMIA. CHRONIC MYELOID LEUKAEMIA (CML) IS A MYELOPROLIFERATIVE DISORDER CHARACTERIZED BY THE GENETIC TRANSLOCATION T(9;22)(Q34;Q11.2) ENCODING FOR THE BCR-ABL FUSION ONCOGENE. HOWEVER, MANY MOLECULAR MECHANISMS OF THE DISEASE PROGRESSION STILL REMAIN POORLY UNDERSTOOD. A GROWING BODY OF EVIDENCE SUGGESTS THAT THE EPIGENETIC ABNORMALITIES ARE INVOLVED IN TYROSINE KINASE RESISTANCE IN CML, LEADING TO LEUKAEMIC CLONE ESCAPE AND DISEASE PROPAGATION. HERE WE SHOW THAT, BY APPLYING CELLULAR REPROGRAMMING TO PRIMARY CML CELLS, ABERRANT DNA METHYLATION CONTRIBUTES TO THE DISEASE EVOLUTION. IMPORTANTLY, USING A BCR-ABL INDUCIBLE MURINE MODEL, WE DEMONSTRATE THAT A SINGLE ONCOGENIC LESION TRIGGERS DNA METHYLATION CHANGES, WHICH IN TURN ACT AS A PRECIPITATING EVENT IN LEUKAEMIA PROGRESSION. 2015 15 358 36 ALTERNATIVE SPLICING IN CHRONIC MYELOID LEUKEMIA (CML): A NOVEL THERAPEUTIC TARGET? ALTHOUGH THE IMATINIB BASED THERAPY OF CHRONIC MYELOID LEUKEMIA (CML) REPRESENTS A TRIUMPH OF MEDICINE, NOT ALL PATIENTS WITH CML BENEFIT FROM THIS DRUG DUE TO THE DEVELOPMENT OF RESISTANCE AND INTOLERANCE. THE INTERRUPTION OF IMATINIB TREATMENT IS OFTEN FOLLOWED BY CLINICAL RELAPSE, SUGGESTING A FAILURE IN THE KILLING OF RESIDUAL LEUKAEMIC STEM CELLS. THERE IS NEED TO IDENTIFY ALTERNATIVE SELECTIVE MOLECULAR TARGETS FOR THIS DISEASE AND DEVELOP MORE EFFECTIVE THERAPEUTIC APPROACHES. ALTERNATIVE PRE-MRNA SPLICING (AS) IS AN EPIGENETIC PROCESS THAT GREATLY DIVERSIFIES THE REPERTOIRE OF THE TRANSCRIPTOME. AS ORCHESTRATES INTERACTIONS BETWEEN VARIOUS TYPES OF PROTEINS AND BETWEEN PROTEINS AND NUCLEIC ACIDS. CHANGES CAUSED BY INDIVIDUAL SPLICING EVENTS IN THE CELLS ARE SMALL, HOWEVER, "SPLICING PROGRAMS" TYPICALLY REACT TO THESE INDIVIDUAL CHANGES WITH CONSIDERABLE EFFECTS IN CELL PROLIFERATION, CELL SURVIVAL, AND APOPTOSIS. CURRENT EVIDENCE SUGGESTS A PIVOTAL ROLE OF AS IN LEUKEMIAS, PARTICULARLY IN MYELODISPLASTIC SYNDROME (MDS) AND CHRONIC LYMPHOCYTE LEUKEMIA (CLL). FROM THESE STUDIES AND STUDIES IN OTHER MALIGNANCES, IT IS CLEAR THAT SPLICING ABNORMALITIES PLAY A SIGNIFICANT ROLE IN MALIGNANT TRANSFORMATION. EVALUATION OF AS EVENTS IN CML CAN BE USED TO IDENTIFY NOVEL DISEASE MARKERS AND DRUGSENSITIVE TARGETS TO OVERCOME THE LIMITS OF THE SMALL MOLECULE INHIBITORS CURRENTLY USED FOR TREATING PATIENTS WITH CML. THE USE OF ABERRANT SPLICE VARIANTS AS DISEASE MARKERS HAS BEEN REPORTED, HOWEVER, LITTLE IS KNOWN ABOUT THE USE OF SPLICING ABNORMALITIES AS DRUG TARGETS IN CML. HEREIN WE DISCUSS POTENTIAL THERAPEUTIC APPROACHES THAT CAN BE USED TO TARGET SPLICING ABNORMALITIES IN CML. 2013 16 1976 30 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 17 2911 33 GENE EXPRESSION PROFILING OF LOSS OF TET2 AND/OR JAK2V617F MUTANT HEMATOPOIETIC STEM CELLS FROM MOUSE MODELS OF MYELOPROLIFERATIVE NEOPLASMS. MYELOPROLIFERATIVE NEOPLASMS (MPNS) ARE CLINICALLY CHARACTERIZED BY THE CHRONIC OVERPRODUCTION OF DIFFERENTIATED PERIPHERAL BLOOD CELLS AND THE GRADUAL EXPANSION OF MALIGNANT INTRAMEDULLARY/EXTRAMEDULLARY HEMATOPOIESIS. IN MPNS MUTATIONS IN JAK2 MPL OR CALR ARE DETECTED MUTUALLY EXCLUSIVE IN MORE THAN 90% OF CASES [1,2]. MUTATIONS IN THEM LEAD TO THE ABNORMAL ACTIVATION OF JAK/STAT SIGNALING AND THE AUTONOMOUS GROWTH OF DIFFERENTIATED CELLS THEREFORE THEY ARE CONSIDERED AS "DRIVER" GENE MUTATIONS. IN ADDITION TO THE ABOVE DRIVER GENE MUTATIONS MUTATIONS IN EPIGENETIC REGULATORS SUCH AS TET2 DNMT3A ASXL1 EZH2 OR IDH1/2 ARE DETECTED IN ABOUT 5%-30% OF CASES RESPECTIVELY [3]. MUTATIONS IN TET2 DNMT3A EZH2 OR IDH1/2 COMMONLY CONFER THE INCREASED SELF-RENEWAL CAPACITY ON NORMAL HEMATOPOIETIC STEM CELLS (HSCS) BUT THEY DO NOT LEAD TO THE AUTONOMOUS GROWTH OF DIFFERENTIATED CELLS AND ONLY EXHIBIT SUBTLE CLINICAL PHENOTYPES [4,6-8,5]. IT WAS UNCLEAR HOW MUTATIONS IN SUCH EPIGENETIC REGULATORS INFLUENCED ABNORMAL HSCS WITH DRIVER GENE MUTATIONS HOW THEY INFLUENCED THE DISEASE PHENOTYPE OR WHETHER A SINGLE DRIVER GENE MUTATION WAS SUFFICIENT FOR THE INITIATION OF HUMAN MPNS. THEREFORE WE FOCUSED ON JAK2V617F AND LOSS OF TET2-THE FORMER AS A REPRESENTATIVE OF DRIVER GENE MUTATIONS AND THE LATTER AS A REPRESENTATIVE OF MUTATIONS IN EPIGENETIC REGULATORS-AND EXAMINED THE INFLUENCE OF SINGLE OR DOUBLE MUTATIONS ON HSCS (LINEAGE(-)SCA-1(+)C-KIT(+) CELLS (LSKS)) BY FUNCTIONAL ANALYSES AND MICROARRAY WHOLE-GENOME EXPRESSION ANALYSES [9]. GENE EXPRESSION PROFILING SHOWED THAT THE HSC FINGERPRINT GENES [10] WAS STATISTICALLY EQUALLY ENRICHED IN TET2-KNOCKDOWN-LSKS BUT NEGATIVELY ENRICHED IN JAK2V617F-LSKS COMPARED TO THAT IN WILD-TYPE-LSKS. DOUBLE-MUTANT-LSKS SHOWED THE SAME TENDENCY AS JAK2V617F-LSKS IN TERMS OF THEIR HSC FINGERPRINT GENES BUT THE EXPRESSION OF INDIVIDUAL GENES DIFFERED BETWEEN THE TWO GROUPS. AMONG 245 HSC FINGERPRINT GENES 100 WERE MORE HIGHLY EXPRESSED IN DOUBLE-MUTANT-LSKS THAN IN JAK2V617F-LSKS. THESE ALTERED GENE EXPRESSIONS MIGHT PARTLY EXPLAIN THE MECHANISMS OF INITIATION AND PROGRESSION OF MPNS WHICH WAS OBSERVED IN THE FUNCTIONAL ANALYSES [9]. HERE WE DESCRIBE GENE EXPRESSION PROFILES DEPOSITED AT THE GENE EXPRESSION OMNIBUS (GEO) UNDER THE ACCESSION NUMBER GSE62302 INCLUDING EXPERIMENTAL METHODS AND QUALITY CONTROL ANALYSES. 2015 18 59 33 A GENOME-WIDE SCREEN IDENTIFIES FREQUENTLY METHYLATED GENES IN HAEMATOLOGICAL AND EPITHELIAL CANCERS. BACKGROUND: GENETIC AS WELL AS EPIGENETIC ALTERATIONS ARE A HALLMARK OF BOTH EPITHELIAL AND HAEMATOLOGICAL MALIGNANCIES. HIGH THROUGHPUT SCREENS ARE REQUIRED TO IDENTIFY EPIGENETIC MARKERS THAT CAN BE USEFUL FOR DIAGNOSTIC AND PROGNOSTIC PURPOSES ACROSS MALIGNANCIES. RESULTS: HERE WE REPORT FOR THE FIRST TIME THE USE OF THE MIRA ASSAY (METHYLATED CPG ISLAND RECOVERY ASSAY) IN COMBINATION WITH GENOME-WIDE CPG ISLAND ARRAYS TO IDENTIFY EPIGENETIC MOLECULAR MARKERS IN CHILDHOOD ACUTE LYMPHOBLASTIC LEUKEMIA (ALL) ON A GENOME-WIDE SCALE. WE IDENTIFIED 30 GENES DEMONSTRATING METHYLATION FREQUENCIES OF > OR =25% IN CHILDHOOD ALL, NINE GENES SHOWED SIGNIFICANTLY DIFFERENT METHYLATION FREQUENCIES IN B VS T-ALL. FOR MAJORITY OF THE GENES EXPRESSION COULD BE RESTORED IN METHYLATED LEUKEMIA LINES AFTER TREATMENT WITH 5-AZADC. FORTY-FOUR PERCENT OF THE GENES REPRESENT TARGETS OF THE POLYCOMB COMPLEX. IN CHRONIC MYELOID LEUKEMIA (CML) TWO OF THE GENES, (TFAP2A AND EBF2), DEMONSTRATED INCREASED METHYLATION IN BLAST CRISIS COMPARED TO CHRONIC PHASE (P < 0.05). FURTHERMORE HYPERMETHYLATION OF AN AUTOPHAGY RELATED GENE ATG16L2 WAS ASSOCIATED WITH POORER PROGNOSIS IN TERMS OF MOLECULAR RESPONSE TO IMATINIB TREATMENT. LASTLY WE DEMONSTRATED THAT TEN OF THESE GENES WERE ALSO FREQUENTLY METHYLATED IN COMMON EPITHELIAL CANCERS. CONCLUSION: IN SUMMARY WE HAVE IDENTIFIED A LARGE NUMBER OF GENES SHOWING FREQUENT METHYLATION IN CHILDHOOD ALL, METHYLATION STATUS OF TWO OF THESE GENES IS ASSOCIATED WITH ADVANCED DISEASE IN CML AND METHYLATION STATUS OF ANOTHER GENE IS ASSOCIATED WITH PROGNOSIS. IN ADDITION A SUBSET OF THESE GENES MAY ACT AS EPIGENETIC MARKERS ACROSS HEMATOLOGICAL MALIGNANCIES AS WELL AS COMMON EPITHELIAL CANCERS. 2010 19 151 29 ABERRANT METHYLATION AND IMPAIRED EXPRESSION OF THE P15(INK4B) CELL CYCLE REGULATORY GENE IN CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML). THE IMPORTANT CELL CYCLE REGULATORY GENE P15(INK4B) HAS BEEN SHOWN TO BE INACTIVATED IN ACUTE MYELOID LEUKEMIA AND MYELODYSPLASTIC SYNDROME. LITTLE IS KNOWN ABOUT THE EXPRESSION AND EPIGENETIC MODIFICATION OF THIS GENE IN CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML) THAT BELONGS TO THE MYELODYSPLASTIC/MYELOPROLIFERATIVE DISORDERS (MDS/MPD) WITH A HIGH PROPORTION OF BLASTIC TRANSFORMATION. ANALYSIS OF BONE MARROW TREPHINES IN A SERIES OF 33 CMML CASES SHOWED AN ABERRANT P15(INK4B) GENE METHYLATION IN UP TO 58% OF CASES. METHYLATION WAS ANALYZED EMPLOYING DIFFERENT METHYLATION-SPECIFIC PCR AND GENOMIC SEQUENCING PROTOCOLS. IT TURNED OUT TO BE SPREAD OVER A BROAD AREA OF THE 5' REGION AND EXHIBITED SUBSTANTIAL HETEROGENEITY BETWEEN CASES AND EVEN IN INDIVIDUAL PATIENTS. THE DEGREE OF ABERRANT METHYLATION WAS CORRELATED WITH A REDUCED MRNA AS WELL AS REDUCED PROTEIN EXPRESSION, AND WAS ASSOCIATED WITH A HIGHER EXPRESSION OF DNA METHYLTRANSFERASE DNMT 3A. WE CONCLUDE THAT ABERRANT GENE METHYLATION IS A FREQUENT EVENT IN CMML THAT MIGHT CONTRIBUTE TO THE PATHOGENESIS OF THIS MDS/MPD. 2003 20 4547 28 MUTATION ALLELE BURDEN REMAINS UNCHANGED IN CHRONIC MYELOMONOCYTIC LEUKAEMIA RESPONDING TO HYPOMETHYLATING AGENTS. THE CYTIDINE ANALOGUES AZACYTIDINE AND 5-AZA-2'-DEOXYCYTIDINE (DECITABINE) ARE COMMONLY USED TO TREAT MYELODYSPLASTIC SYNDROMES, WITH OR WITHOUT A MYELOPROLIFERATIVE COMPONENT. IT REMAINS UNCLEAR WHETHER THE RESPONSE TO THESE HYPOMETHYLATING AGENTS RESULTS FROM A CYTOTOXIC OR AN EPIGENETIC EFFECT. IN THIS STUDY, WE ADDRESS THIS QUESTION IN CHRONIC MYELOMONOCYTIC LEUKAEMIA. WE DESCRIBE A COMPREHENSIVE ANALYSIS OF THE MUTATIONAL LANDSCAPE OF THESE TUMOURS, COMBINING WHOLE-EXOME AND WHOLE-GENOME SEQUENCING. WE IDENTIFY AN AVERAGE OF 14+/-5 SOMATIC MUTATIONS IN CODING SEQUENCES OF SORTED MONOCYTE DNA AND THE SIGNATURES OF THREE MUTATIONAL PROCESSES. SERIAL SEQUENCING DEMONSTRATES THAT THE RESPONSE TO HYPOMETHYLATING AGENTS IS ASSOCIATED WITH CHANGES IN DNA METHYLATION AND GENE EXPRESSION, WITHOUT ANY DECREASE IN THE MUTATION ALLELE BURDEN, NOR PREVENTION OF NEW GENETIC ALTERATION OCCURENCE. OUR FINDINGS INDICATE THAT CYTOSINE ANALOGUES RESTORE A BALANCED HAEMATOPOIESIS WITHOUT DECREASING THE SIZE OF THE MUTATED CLONE, ARGUING FOR A PREDOMINANTLY EPIGENETIC EFFECT. 2016