1 3641 151 INCREASED GENE EXPRESSION OF HISTONE DEACETYLASES IN PATIENTS WITH PHILADELPHIA-NEGATIVE CHRONIC MYELOPROLIFERATIVE NEOPLASMS. MYELOPROLIFERATION, MYELOACCUMULATION (DECREASED APOPTOSIS), INFLAMMATION, BONE MARROW FIBROSIS AND ANGIOGENESIS ARE CARDINAL FEATURES OF THE PHILADELPHIA-NEGATIVE CHRONIC MYELOPROLIFERATIVE NEOPLASMS: ESSENTIAL THROMBOCYTHEMIA (ET), POLYCYTHEMIA VERA (PV) AND PRIMARY MYELOFIBROSIS (PMF). HISTONE DEACETYLASES (HDACS) HAVE A CRITICAL ROLE IN MODULATING GENE EXPRESSION AND, ACCORDINGLY, IN THE CONTROL OF CELL PATHOBIOLOGY AND CANCER DEVELOPMENT. HDAC INHIBITION HAS BEEN SHOWN TO INHIBIT TUMOR GROWTH (IMPAIRED MYELOPROLIFERATION), TO MODULATE THE BALANCE BETWEEN PRO- AND ANTIAPOPTOTIC PROTEINS IN FAVOR OF APOPTOSIS (ENHANCED APOPTOSIS) AND ALSO TO INHIBIT ANGIOGENESIS. RECENTLY, ENHANCED HDAC ENZYME ACTIVITY HAS BEEN FOUND IN CD34+CELLS FROM PATIENTS WITH PMF, ENZYME ACTIVITY LEVELS HIGHLY EXCEEDING THOSE RECORDED IN OTHER CHRONIC MYELOPROLIFERATIVE NEOPLASMS (CMPNS). THE RAISED LEVELS CORRELATED TO THE DEGREE OF SPLENOMEGALY, SUGGESTING THAT HDAC MIGHT BE RECRUITED AS ET OR PV PROGRESSES INTO MYELOFIBROSIS OR PMF PROGRESSES INTO A MORE ADVANCED STAGE. ACCORDINGLY, HDAC INHIBITION IS AN OBVIOUS NOVEL THERAPEUTIC APPROACH IN THESE NEOPLASMS. USING GLOBAL GENE EXPRESSION PROFILING OF WHOLE BLOOD FROM PATIENTS WITH CMPNS, WE HAVE FOUND A PRONOUNCED DEREGULATION OF HDAC GENES, INVOLVING SIGNIFICANT UP-REGULATION OF THE HDAC GENES 9 AND 11, WITH THE HIGHEST EXPRESSION LEVELS BEING FOUND IN PATIENTS WITH ET (HDAC9 AND 11), PMF (HDAC9) AND CMPNS (BOTH HDAC9 AND HDAC11). FURTHERMORE, WE HAVE IDENTIFIED THAT THE HDAC6 GENE IS PROGRESSIVELY EXPRESSED IN PATIENTS WITH ET, PV AND PMF, REFLECTING A STEADY ACCUMULATION OF ABNORMALLY EXPRESSED HDAC6 DURING DISEASE EVOLUTION. OUR RESULTS LEND FURTHER SUPPORT TO HDACS AS IMPORTANT EPIGENETIC TARGETS IN THE FUTURE TREATMENT OF PATIENTS WITH CMPNS. SINCE THE HIGHEST EXPRESSION LEVELS OF HDAC GENES WERE RECORDED IN ET, IN PMF AND IN THE ENTIRE CMPN GROUP, THEIR DOWN-REGULATION BY HDAC INHIBITORS MIGHT BE ASSOCIATED WITH DECREASED DISEASE ACTIVITY, INCLUDING REDUCTION OF SPLENOMEGALY. 2012 2 2911 38 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 3 6852 44 [MYELOPROLIFERATIVE NEOPLASMS: UPDATES ON MOLECULAR PATHOPHYSIOLOGY, DIAGNOSIS AND TREATMENT STRATEGIES]. MYELOPROLIFERATIVE NEOPLASMS (MPNS) ARE CHRONIC HEMATOPOIETIC STEM CELL DISORDERS, INCLUDING POLYCYTHEMIA VERA, ESSENTIAL THROMBOCYTOSIS, AND PRIMARY MYELOFIBROSIS. THE JAK2V617F MUTATION WAS IDENTIFIED IN 2005, FOLLOWED BY THE DISCOVERY OF THE JAK2 EXON12, MPNW515 MUTATION, AND CALR MUTATION. ABOUT 90% OF PATIENTS WITH BCR/ABL NEGATIVE MPNS HAVE BEEN SHOWN TO HAVE ONE OF THESE DRIVER MUTATIONS. IN ADDITION, MUTATIONS IN EPIGENETIC REGULATORS AND RNA SPLICING GENES WERE FOUND TO CO-EXIST WITH DRIVER MUTATIONS AND TO PLAY CRITICAL ROLES IN THE DISEASE PROGRESSION OF MPNS. CURRENTLY, EVALUATIONS OF THESE GENE MUTATIONS ARE ESSENTIAL FOR THE DIAGNOSIS OF MPNS, AND ARE ALSO NECESSARY FOR ESTIMATING THE CLINICAL COURSE AND THE RISK OF DISEASE PROGRESSION. GUIDELINES FOR THE MANAGEMENT OF MPNS WERE BASED ON THE RESULTS OF LARGE CLINICAL TRIALS. FURTHERMORE, RECENT ADVANCEMENTS IN UNDERSTANDING THE PATHOGENESIS OF MPNS ARE ANTICIPATED TO PROMOTE THE DEVELOPMENT OF MPN-TARGETED THERAPIES SUCH AS JAK2 INHIBITORS. CLINICAL TRIALS FOR PATIENTS WITH PMF AND PV HAVE CONFIRMED THE EFFICACIES OF JAK2 INHIBITORS. 2016 4 2237 39 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 5 1043 41 CLINICAL CHARACTERISTICS AND WHOLE EXOME/TRANSCRIPTOME SEQUENCING OF COEXISTING CHRONIC MYELOID LEUKEMIA AND MYELOFIBROSIS. MYELOPROLIFERATIVE NEOPLASMS (MPNS) ARE CLONAL HEMATOPOIETIC STEM CELL (HSC) DISORDERS THAT CAN BE CLASSIFIED ON THE BASIS OF GENETIC, CLINICAL, PHENOTYPIC FEATURES. GENETIC LESIONS SUCH AS JAK2 MUTATIONS AND BCR-ABL TRANSLOCATION ARE OFTEN MUTUALLY EXCLUSIVE IN MPN PATIENTS AND LEAD TO ESSENTIAL THROMBOCYTHEMIA, POLYCYTHEMIA VERA, OR MYELOFIBROSIS OR CHRONIC MYELOID LEUKEMIA, RESPECTIVELY. NEVERTHELESS, COEXISTENCE OF THESE GENETIC ABERRATIONS IN THE SAME PATIENT HAS BEEN REPORTED. WHETHER THESE ABERRATIONS OCCUR IN THE SAME STEM CELL OR A DIFFERENT CELL IS UNCLEAR, BUT AN UNSTABLE GENOME IN THE HSCS SEEMS TO BE THE COMMON ANTECEDENT. IN AN EFFORT TO CHARACTERIZE THE UNDERLYING GENETIC EVENTS THAT MIGHT CONTRIBUTE TO THE APPEARANCE OF MORE THAN ONE MPN IN A PATIENT, WE STUDIED NEOPLASTIC CELLS FROM PATIENTS WITH DUAL MPNS BY NEXT-GENERATION SEQUENCING. WE OBSERVED THAT MOST PATIENTS WITH TWO MPNS HARBORED MUTATIONS IN GENES KNOWN TO CONTRIBUTE TO CLONAL HEMATOPOIESIS THROUGH ALTERED EPIGENETIC REGULATION SUCH AS TET2, ASXL1/2, SRSF2, AND IDH2 AT VARYING FREQUENCIES (1%-47%). IN ADDITION, WE FOUND THAT SOME PATIENTS ALSO HARBORED ONCOGENIC MUTATIONS IN N/KRAS, TP53, BRAF, EZH2, AND GNAS AT LOW FREQUENCIES, WHICH PROBABLY REPRESENT CLONAL EVOLUTION. THESE FINDINGS SUPPORT THE HYPOTHESIS THAT HEMATOPOIETIC CELLS FROM MPN PATIENTS HARBOR MULTIPLE GENETIC ABERRATIONS, SOME OF WHICH CAN CONTRIBUTE TO CLONAL DOMINANCE. ACQUIRING MUTATIONS IN JAK2/CALR/MPL OR THE BCR-ABL TRANSLOCATION PROBABLY DRIVE THE ONCOGENIC PHENOTYPE TOWARDS A SPECIFIC MPN. FURTHER, WE PROPOSE THAT THE ACQUISITION OF BCR-ABL IN THESE PATIENTS IS FREQUENTLY A SECONDARY EVENT RESULTING FROM AN UNSTABLE GENOME. 2017 6 4680 36 NEW MUTATIONS AND PATHOGENESIS OF MYELOPROLIFERATIVE NEOPLASMS. MYELOPROLIFERATIVE NEOPLASMS (MPNS) ARE CLONAL DISORDERS CHARACTERIZED BY EXCESSIVE PRODUCTION OF MATURE BLOOD CELLS. IN THE MAJORITY OF CLASSIC MPN--POLYCYTHEMIA VERA, ESSENTIAL THROMBOCYTHEMIA, AND PRIMITIVE MYELOFIBROSIS--DRIVER ONCOGENIC MUTATIONS AFFECTING JANUS KINASE 2 (JAK2) OR MPL LEAD TO CONSTITUTIVE ACTIVATION OF CYTOKINE-REGULATED INTRACELLULAR SIGNALING PATHWAYS. LNK, C-CBL, OR SOCSS (ALL NEGATIVE REGULATORS OF SIGNALING PATHWAYS), ALTHOUGH INFREQUENTLY TARGETED, MAY EITHER DRIVE THE DISEASE OR SYNERGIZE WITH JAK2 AND MPL MUTATIONS. IZF1 DELETIONS OR TP53 MUTATIONS ARE MAINLY FOUND AT TRANSFORMATION PHASES AND ARE PRESENT AT GREATER FREQUENCY THAN IN DE NOVO ACUTE MYELOID LEUKEMIAS. LOSS-OF-FUNCTION MUTATIONS IN 3 GENES INVOLVED IN EPIGENETIC REGULATION, TET2, ASXL1, AND EZH2, MAY BE EARLY EVENTS PRECEDING JAK2V617F BUT MAY ALSO OCCUR LATE DURING DISEASE PROGRESSION. THEY ARE MORE FREQUENTLY OBSERVED IN PMF THAN PV AND ET AND ARE ALSO PRESENT IN OTHER TYPES OF MALIGNANT MYELOID DISEASES. A LIKELY HYPOTHESIS IS THAT THEY FACILITATE CLONAL SELECTION, ALLOWING THE DOMINANCE OF THE JAK2V617F SUBCLONE DURING THE CHRONIC PHASE AND, TOGETHER WITH COOPERATING MUTATIONS, PROMOTE BLAST CRISIS. THEIR PRECISE ROLES IN HEMATOPOIESIS AND IN THE PATHOGENESIS OF MPN, AS WELL AS THEIR PROGNOSTIC IMPACT AND POTENTIAL AS A THERAPEUTIC TARGET, ARE CURRENTLY UNDER INVESTIGATION. 2011 7 144 41 ABERRANT DNA METHYLATION PROFILE OF CHRONIC AND TRANSFORMED CLASSIC PHILADELPHIA-NEGATIVE MYELOPROLIFERATIVE NEOPLASMS. MOST DNA METHYLATION STUDIES IN CLASSIC PHILADELPHIA-NEGATIVE MYELOPROLIFERATIVE NEOPLASMS HAVE BEEN PERFORMED ON A GENE-BY-GENE BASIS. THEREFORE, A MORE COMPREHENSIVE METHYLATION PROFILING IS NEEDED TO STUDY THE IMPLICATIONS OF THIS EPIGENETIC MARKER IN MYELOPROLIFERATIVE NEOPLASMS. HERE, WE HAVE ANALYZED 71 CHRONIC (24 POLYCYTHEMIA VERA, 23 ESSENTIAL THROMBOCYTHEMIA AND 24 PRIMARY MYELOFIBROSIS) AND 13 TRANSFORMED MYELOPROLIFERATIVE NEOPLASMS USING GENOME-WIDE DNA METHYLATION ARRAYS. THE THREE TYPES OF CHRONIC PHILADELPHIA-NEGATIVE MYELOPROLIFERATIVE NEOPLASMS SHOWED A SIMILAR ABERRANT DNA METHYLATION PATTERN WHEN COMPARED TO CONTROL SAMPLES. DIFFERENTIALLY METHYLATED REGIONS WERE ENRICHED IN A GENE NETWORK CENTERED ON THE NF-KAPPAB PATHWAY, INDICATING THAT THEY MAY BE INVOLVED IN THE PATHOGENESIS OF THESE DISEASES. IN THE CASE OF TRANSFORMED MYELOPROLIFERATIVE NEOPLASMS, WE DETECTED AN INCREASED NUMBER OF DIFFERENTIALLY METHYLATED REGIONS WITH RESPECT TO CHRONIC MYELOPROLIFERATIVE NEOPLASMS. INTERESTINGLY, THESE GENES WERE ENRICHED IN A LIST OF DIFFERENTIALLY METHYLATED REGIONS IN PRIMARY ACUTE MYELOID LEUKEMIA AND IN A GENE NETWORK CENTERED AROUND THE IFN PATHWAY. OUR RESULTS SUGGEST THAT ALTERATIONS IN THE DNA METHYLATION LANDSCAPE PLAY AN IMPORTANT ROLE IN THE PATHOGENESIS AND LEUKEMIC TRANSFORMATION OF MYELOPROLIFERATIVE NEOPLASMS. THE THERAPEUTIC MODULATION OF EPIGENETICALLY-DEREGULATED PATHWAYS MAY ALLOW US TO DESIGN TARGETED THERAPIES FOR THESE PATIENTS. 2013 8 1947 50 EPIGENETIC ABNORMALITIES IN MYELOPROLIFERATIVE NEOPLASMS: A TARGET FOR NOVEL THERAPEUTIC STRATEGIES. THE MYELOPROLIFERATIVE NEOPLASMS (MPNS) ARE A GROUP OF CLONAL HEMATOLOGICAL MALIGNANCIES CHARACTERIZED BY A HYPERCELLULAR BONE MARROW AND A TENDENCY TO DEVELOP THROMBOTIC COMPLICATIONS AND TO EVOLVE TO MYELOFIBROSIS AND ACUTE LEUKEMIA. UNLIKE CHRONIC MYELOGENOUS LEUKEMIA, WHERE A SINGLE DISEASE-INITIATING GENETIC EVENT HAS BEEN IDENTIFIED, A MORE COMPLICATED SERIES OF GENETIC MUTATIONS APPEAR TO BE RESPONSIBLE FOR THE BCR-ABL1-NEGATIVE MPNS WHICH INCLUDE POLYCYTHEMIA VERA, ESSENTIAL THROMBOCYTHEMIA, AND PRIMARY MYELOFIBROSIS. RECENT STUDIES HAVE REVEALED A NUMBER OF EPIGENETIC ALTERATIONS THAT ALSO LIKELY CONTRIBUTE TO DISEASE PATHOGENESIS AND DETERMINE CLINICAL OUTCOME. INCREASING EVIDENCE INDICATES THAT ALTERATIONS IN DNA METHYLATION, HISTONE MODIFICATION, AND MICRORNA EXPRESSION PATTERNS CAN COLLECTIVELY INFLUENCE GENE EXPRESSION AND POTENTIALLY CONTRIBUTE TO MPN PATHOGENESIS. EXAMPLES INCLUDE MUTATIONS IN GENES ENCODING PROTEINS THAT MODIFY CHROMATIN STRUCTURE (EZH2, ASXL1, IDH1/2, JAK2V617F, AND IKZF1) AS WELL AS EPIGENETIC MODIFICATION OF GENES CRITICAL FOR CELL PROLIFERATION AND SURVIVAL (SUPPRESSORS OF CYTOKINE SIGNALING, POLYCYTHEMIA RUBRA VERA-1, CXC CHEMOKINE RECEPTOR 4, AND HISTONE DEACETYLASE (HDAC)). THESE EPIGENETIC LESIONS SERVE AS NOVEL TARGETS FOR EXPERIMENTAL THERAPEUTIC INTERVENTIONS. CLINICAL TRIALS ARE CURRENTLY UNDERWAY EVALUATING HDAC INHIBITORS AND DNA METHYLTRANSFERASE INHIBITORS FOR THE TREATMENT OF PATIENTS WITH MPNS. 2011 9 171 39 ABROGATION OF HISTONE DEACETYLASES (HDACS) DECREASES SURVIVAL OF CHRONIC MYELOID LEUKEMIA CELLS: NEW INSIGHT INTO ATTENUATING EFFECTS OF THE PI3K/C-MYC AXIS ON PANOBINOSTAT CYTOTOXICITY. ALTHOUGH THE IDENTIFICATION OF TYROSINE KINASE INHIBITORS (TKIS) HAS CHANGED THE TREATMENT PARADIGM OF MANY CANCER TYPES INCLUDING CHRONIC MYELOID LEUKEMIA (CML), STILL ADJUSTMENT OF NEOPLASTIC CELLS TO CYTOTOXIC EFFECTS OF ANTICANCER DRUGS IS A SERIOUS CHALLENGE. IN THE AREA OF DRUG RESISTANCE, EPIGENETIC ALTERATIONS ARE AT THE CENTER OF ATTENTION AND THE PRESENT STUDY AIMED TO EVALUATE WHETHER BLOCKAGE OF EPIGENETICS MECHANISMS USING A PAN-HISTONE DEACETYLASE (HDAC) INHIBITOR INDUCES CELL DEATH IN CML-DERIVED K562 CELLS. WE FOUND THAT THE ABROGATION OF HDACS USING PANOBINOSTAT RESULTED IN A REDUCTION IN SURVIVAL OF THE K562 CELL LINE THROUGH P27-MEDIATED CELL CYCLE ARREST. NOTEWORTHY, THE RESULTS OF THE SYNERGISTIC EXPERIMENTS REVEALED THAT HDAC SUPPRESSION COULD BE RECRUITED AS A WAY TO POTENTIATE CYTOTOXICITY OF IMATINIB AND TO ENHANCE THE THERAPEUTIC EFFICACY OF CML. HERE, WE PROPOSED FOR THE FIRST TIME THAT THE INHIBITORY EFFECT OF PANOBINOSTAT WAS OVERSHADOWED, AT LEAST PARTIALLY, THROUGH THE ABERRANT ACTIVATION OF THE PHOSPHOINOSITIDE 3-KINASE (PI3K)/C-MYC AXIS. MEANWHILE, WE FOUND THAT UPON BLOCKAGE OF AUTOPHAGY AND THE PROTEASOME PATHWAY, AS THE MAIN AXIS INVOLVED IN THE ACTIVATION OF AUTOPHAGY, THE ANTI-LEUKEMIC PROPERTY OF THE HDAC INHIBITOR WAS POTENTIATED. TAKEN TOGETHER, OUR STUDY SUGGESTS THE BENEFICIAL APPLICATION OF HDAC INHIBITION IN THE TREATMENT STRATEGIES OF CML; HOWEVER, FURTHER IN VIVO STUDIES ARE NEEDED TO DETERMINE THE EFFICACY OF THIS INHIBITOR, EITHER AS A SINGLE AGENT OR IN COMBINATION WITH SMALL MOLECULE INHIBITORS OF PI3K AND/OR C-MYC IN THIS MALIGNANCY. 2021 10 2781 36 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 11 5691 35 SILENCING OF HDAC6 AS A THERAPEUTIC TARGET IN CHRONIC LYMPHOCYTIC LEUKEMIA. ALTHOUGH THE TREATMENT PARADIGM FOR CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) IS RAPIDLY CHANGING, THE DISEASE REMAINS INCURABLE, EXCEPT WITH ALLOGENEIC BONE MARROW TRANSPLANTATION, AND RESISTANCE, RELAPSED DISEASE, AND PARTIAL RESPONSES PERSIST AS SIGNIFICANT CHALLENGES. RECENT STUDIES HAVE UNCOVERED ROLES FOR EPIGENETIC MODIFICATION IN THE REGULATION OF MECHANISMS CONTRIBUTING TO MALIGNANT PROGRESSION OF CLL B CELLS. HOWEVER, THE EXTENT TO WHICH EPIGENETIC MODIFIERS CAN BE TARGETED FOR THERAPEUTIC BENEFIT IN CLL PATIENTS REMAINS POORLY EXPLORED. WE REPORT FOR THE FIRST TIME THAT EXPRESSION OF EPIGENETIC MODIFIER HISTONE DEACETYLASE 6 (HDAC6) IS UPREGULATED IN CLL PATIENT SAMPLES, CELL LINES, AND EUTCL1 TRANSGENIC MOUSE MODELS COMPARED WITH HDAC6 IN NORMAL CONTROLS. GENETIC SILENCING OF HDAC6 CONFERRED SURVIVAL BENEFIT IN EUTCL1 MICE. ADMINISTRATION OF ISOFORM-SPECIFIC HDAC6 INHIBITOR ACY738 IN THE EUTCL1 AGING AND ADOPTIVE TRANSFER MODELS DETERRED PROLIFERATION OF CLL B CELLS, DELAYED DISEASE ONSET VIA DISRUPTION OF B-CELL RECEPTOR SIGNALING, AND SENSITIZED CLL B CELLS TO APOPTOSIS. FURTHERMORE, COADMINISTRATION OF ACY738 AND IBRUTINIB DISPLAYED SYNERGISTIC CELL KILL AGAINST CLL CELL LINES AND IMPROVED OVERALL SURVIVAL COMPARED WITH EITHER SINGLE AGENT IN VIVO. THESE RESULTS DEMONSTRATE FOR THE FIRST TIME THE THERAPEUTIC EFFICACY OF SELECTIVE HDAC6 INHIBITION IN PRECLINICAL CLL MODELS AND SUGGEST A RATIONALE FOR THE CLINICAL DEVELOPMENT OF HDAC6 INHIBITORS FOR CLL TREATMENT, EITHER ALONE OR IN COMBINATION WITH BRUTON TYROSINE KINASE INHIBITION. 2018 12 3532 36 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 13 535 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 14 358 41 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 15 1542 40 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 16 2462 38 EPIGENETIC THERAPY OF MYELODYSPLASTIC SYNDROMES CONNECTS TO CELLULAR DIFFERENTIATION INDEPENDENTLY OF ENDOGENOUS RETROELEMENT DEREPRESSION. BACKGROUND: MYELODYSPLASTIC SYNDROMES (MDS) AND ACUTE MYELOID LEUKAEMIA (AML) ARE CHARACTERISED BY ABNORMAL EPIGENETIC REPRESSION AND DIFFERENTIATION OF BONE MARROW HAEMATOPOIETIC STEM CELLS (HSCS). DRUGS THAT REVERSE EPIGENETIC REPRESSION, SUCH AS 5-AZACYTIDINE (5-AZA), INDUCE HAEMATOLOGICAL IMPROVEMENT IN HALF OF TREATED PATIENTS. ALTHOUGH THE MECHANISMS UNDERLYING THERAPY SUCCESS ARE NOT YET CLEAR, INDUCTION OF ENDOGENOUS RETROELEMENTS (ERES) HAS BEEN HYPOTHESISED. METHODS: USING RNA SEQUENCING (RNA-SEQ), WE COMPARED THE TRANSCRIPTION OF ERES IN BONE MARROW HSCS FROM A NEW COHORT OF MDS AND CHRONIC MYELOMONOCYTIC LEUKAEMIA (CMML) PATIENTS BEFORE AND AFTER 5-AZA TREATMENT WITH HSCS FROM HEALTHY DONORS AND AML PATIENTS. WE FURTHER EXAMINED ERE TRANSCRIPTION USING THE MOST COMPREHENSIVE ANNOTATION OF ERE-OVERLAPPING TRANSCRIPTS EXPRESSED IN HSCS, GENERATED HERE BY DE NOVO TRANSCRIPT ASSEMBLY AND SUPPORTED BY FULL-LENGTH RNA-SEQ. RESULTS: CONSISTENT WITH PRIOR REPORTS, WE FOUND THAT TREATMENT WITH 5-AZA INCREASED THE REPRESENTATION OF ERE-DERIVED RNA-SEQ READS IN THE TRANSCRIPTOME. HOWEVER, SUCH INCREASES WERE COMPARABLE BETWEEN TREATMENT RESPONSES AND FAILURES. THE EXTENDED VIEW OF HSC TRANSCRIPTIONAL DIVERSITY OFFERED BY DE NOVO TRANSCRIPT ASSEMBLY ARGUED AGAINST 5-AZA-RESPONSIVE ERES AS DETERMINANTS OF THE OUTCOME OF THERAPY. INSTEAD, IT UNCOVERED PRE-TREATMENT EXPRESSION AND ALTERNATIVE SPLICING OF DEVELOPMENTALLY REGULATED GENE TRANSCRIPTS AS PREDICTORS OF THE RESPONSE OF MDS AND CMML PATIENTS TO 5-AZA TREATMENT. CONCLUSIONS: OUR STUDY IDENTIFIES THE DEVELOPMENTALLY REGULATED TRANSCRIPTIONAL SIGNATURES OF PROTEIN-CODING AND NON-CODING GENES, RATHER THAN ERES, AS CORRELATES OF A FAVOURABLE RESPONSE OF MDS AND CMML PATIENTS TO 5-AZA TREATMENT AND OFFERS NOVEL CANDIDATES FOR FURTHER EVALUATION. 2019 17 5982 40 TET2 REGULATES IMMUNE TOLERANCE IN CHRONICALLY ACTIVATED MAST CELLS. MUTATION OF THE TET2 DNA-HYDROXYMETHYLASE HAS BEEN ASSOCIATED WITH A NUMBER OF IMMUNE PATHOLOGIES. THE DISPARITY IN PHENOTYPE AND CLINICAL PRESENTATION AMONG THESE PATHOLOGIES LEADS TO QUESTIONS REGARDING THE ROLE OF TET2 MUTATION IN PROMOTING DISEASE EVOLUTION IN DIFFERENT IMMUNE CELL TYPES. HERE WE SHOW THAT, IN PRIMARY MAST CELLS, TET2 EXPRESSION IS INDUCED IN RESPONSE TO CHRONIC AND ACUTE ACTIVATION SIGNALS. IN TET2-DEFICIENT MAST CELLS, CHRONIC ACTIVATION VIA THE ONCOGENIC KITD816V ALLELE ASSOCIATED WITH MASTOCYTOSIS, SELECTS FOR A SPECIFIC EPIGENETIC SIGNATURE CHARACTERIZED BY HYPERMETHYLATED DNA REGIONS (HMR) AT IMMUNE RESPONSE GENES. H3K27AC AND TRANSCRIPTION FACTOR BINDING IS CONSISTENT WITH PRIMING OR MORE OPEN CHROMATIN AT BOTH HMR AND NON-HMR IN PROXIMITY TO IMMUNE GENES IN THESE CELLS, AND THIS SIGNATURE COINCIDES WITH INCREASED PATHOLOGICAL INFLAMMATION SIGNALS. HMR ARE ALSO ASSOCIATED WITH A SUBSET OF IMMUNE GENES THAT ARE DIRECT TARGETS OF TET2 AND REPRESSED IN TET2-DEFICIENT CELLS. REPRESSION OF THESE GENES RESULTS IN IMMUNE TOLERANCE TO ACUTE STIMULATION THAT CAN BE RESCUED WITH VITAMIN C TREATMENT OR REITERATED WITH A TET INHIBITOR. OVERALL, OUR DATA SUPPORT A MODEL WHERE TET2 PLAYS A DIRECT ROLE IN PREVENTING IMMUNE TOLERANCE IN CHRONICALLY ACTIVATED MAST CELLS, SUPPORTING TET2 AS A VIABLE TARGET TO REPROGRAM THE INNATE IMMUNE RESPONSE FOR INNOVATIVE THERAPIES. 2022 18 5455 34 RESCUE OF A PRIMARY MYELOFIBROSIS MODEL BY RETINOID-ANTAGONIST THERAPY. MOLECULAR TARGETING OF THE TWO RECEPTOR INTERACTION DOMAINS OF THE EPIGENETIC REPRESSOR SILENCING MEDIATOR OF RETINOID AND THYROID HORMONE RECEPTORS (SMRT(MRID)) PRODUCED A TRANSPLANTABLE SKELETAL SYNDROME THAT REDUCED RADIAL BONE GROWTH, INCREASED NUMBERS OF BONE-RESORBING PERIOSTEAL OSTEOCLASTS, AND INCREASED BONE FRACTURE RISK. FURTHERMORE, SMRT(MRID) MICE DEVELOP SPONTANEOUS PRIMARY MYELOFIBROSIS, A CHRONIC, USUALLY IDIOPATHIC DISORDER CHARACTERIZED BY PROGRESSIVE BONE MARROW FIBROSIS. FREQUENTLY LINKED TO POLYCYTHEMIA VERA AND CHRONIC MYELOID LEUKEMIA, MYELOFIBROSIS DISPLAYS HIGH PATIENT MORBIDITY AND MORTALITY, AND CURRENT TREATMENT IS MOSTLY PALLIATIVE. TO DECIPHER THE ETIOLOGY OF THIS DISEASE, WE IDENTIFIED THE THROMBOPOIETIN (TPO) GENE AS A TARGET OF THE SMRT-RETINOIC ACID RECEPTOR SIGNALING PATHWAY IN BONE MARROW STROMAL CELLS. CHRONIC INDUCTION OF TPO IN SMRT(MRID) MICE RESULTS IN UP-REGULATION OF TGF-BETA AND PDGF IN MEGAKARYOCYTES, UNCONTROLLED PROLIFERATION OF BONE MARROW RETICULAR CELLS, AND FIBROSIS OF THE MARROW COMPARTMENT. OF THERAPEUTIC RELEVANCE, WE SHOW THAT THIS SYNDROME CAN BE RESCUED BY RETINOID ANTAGONISTS, DEMONSTRATING THAT THE PHYSICAL INTERFACE BETWEEN SMRT AND RETINOIC ACID RECEPTOR CAN BE A POTENTIAL THERAPEUTIC TARGET TO BLOCK PRIMARY MYELOFIBROSIS DISEASE PROGRESSION. 2013 19 1076 30 CLONAL HEMATOPOIESIS IN MYELOPROLIFERATIVE NEOPLASMS CONFERS A PREDISPOSITION TO BOTH THROMBOSIS AND CANCER. PURPOSE OF REVIEW: THIS REVIEW FOCUSES ON VASCULAR COMPLICATIONS ASSOCIATED WITH CHRONIC MYELOPROLIFERATIVE NEOPLASMS (MPN) AND MORE SPECIFICALLY AIMS TO DISCUSS THE CLINICAL AND BIOLOGICAL EVIDENCE SUPPORTING THE EXISTENCE OF A LINK BETWEEN CLONAL HEMATOPOIESIS, CARDIOVASCULAR EVENTS (CVE), AND SOLID CANCER (SC). RECENT FINDINGS: THE MPN NATURAL HISTORY IS DRIVEN BY UNCONTROLLED CLONAL MYELOPROLIFERATION SUSTAINED BY ACQUIRED SOMATIC MUTATIONS IN DRIVER (JAK2, CALR, AND MPL) AND NON-DRIVER GENES, INVOLVING EPIGENETIC (E.G., TET2, DNMT3A) REGULATORS, CHROMATIN REGULATOR GENES (E.G., ASXL1, EZH2), AND SPLICING MACHINERY GENES (E.G., SF3B1). THE GENOMIC ALTERATIONS AND ADDITIONAL THROMBOSIS ACQUIRED RISK FACTORS ARE DETERMINANTS FOR CVE. THERE IS EVIDENCE THAT CLONAL HEMATOPOIESIS CAN ELICIT A CHRONIC AND SYSTEMIC INFLAMMATION STATUS THAT ACTS AS DRIVING FORCE FOR THE DEVELOPMENT OF THROMBOSIS, MPN EVOLUTION, AND SECOND CANCER (SC). THIS NOTION MAY EXPLAIN THE MECHANISM THAT LINKS ARTERIAL THROMBOSIS IN MPN PATIENTS AND SUBSEQUENT SOLID TUMORS. IN THE LAST DECADE, CLONAL HEMATOPOIESIS OF INDETERMINATE POTENTIAL (CHIP) HAS BEEN DETECTED IN THE GENERAL POPULATION PARTICULARLY IN THE ELDERLY AND INITIALLY FOUND IN MYOCARDIAL INFARCTION AND STROKE, RISING THE HYPOTHESIS THAT THE INFLAMMATORY STATUS CHIP-ASSOCIATED COULD CONFER PREDISPOSITION TO BOTH CARDIOVASCULAR DISEASES AND CANCER. IN SUMMARY, CLONAL HEMATOPOIESIS IN MPN AND CHIP CONFER A PREDISPOSITION TO CARDIOVASCULAR EVENTS AND CANCER THROUGH CHRONIC AND SYSTEMIC INFLAMMATION. THIS ACQUISITION COULD OPEN NEW AVENUES FOR ANTITHROMBOTIC THERAPY BOTH IN MPNS AND IN GENERAL POPULATION BY TARGETING BOTH CLONAL HEMATOPOIESIS AND INFLAMMATION. 2023 20 4728 31 NOTCH SIGNALING PROMOTES DISEASE INITIATION AND PROGRESSION IN MURINE CHRONIC LYMPHOCYTIC LEUKEMIA. NOTCH1 GAIN-OF-FUNCTION MUTATIONS ARE RECURRENT IN B-CELL CHRONIC LYMPHOCYTIC LEUKEMIA (B-CLL), WHERE THEY ARE ASSOCIATED WITH ACCELERATED DISEASE PROGRESSION AND REFRACTORINESS TO CHEMOTHERAPY. THE SPECIFIC ROLE OF NOTCH1 IN THE DEVELOPMENT AND PROGRESSION OF THIS MALIGNANCY IS UNCLEAR. HERE, WE ASSESS THE IMPACT OF LOSS OF NOTCH SIGNALING AND PATHWAY HYPERACTIVATION IN AN IN VIVO MOUSE MODEL OF CLL (IGH.TEMU) THAT FAITHFULLY REPLICATES MANY FEATURES OF THE HUMAN PATHOLOGY. ABLATION OF CANONICAL NOTCH SIGNALING USING CONDITIONAL GENE INACTIVATION OF RBP-J IN IMMATURE HEMATOPOIETIC OR B-CELL PROGENITORS DELAYED CLL INDUCTION AND REDUCED INCIDENCE OF MICE DEVELOPING DISEASE. IN CONTRAST, FORCED EXPRESSION OF A DOMINANT ACTIVE FORM OF NOTCH RESULTED IN MORE ANIMALS DEVELOPING CLL WITH EARLY DISEASE ONSET. COMPARATIVE ANALYSIS OF GENE EXPRESSION AND EPIGENETIC FEATURES OF NOTCH GAIN-OF-FUNCTION AND CONTROL CLL CELLS REVEALED DIRECT AND INDIRECT REGULATION OF CELL CYCLE-ASSOCIATED GENES, WHICH LED TO INCREASED PROLIFERATION OF NOTCH GAIN-OF-FUNCTION CLL CELLS IN VIVO. THESE RESULTS DEMONSTRATE THAT NOTCH SIGNALING FACILITATES DISEASE INITIATION AND PROMOTES CLL CELL PROLIFERATION AND DISEASE PROGRESSION. 2021