1 6688 119 VALPROATE SYNERGIZES WITH PURINE NUCLEOSIDE ANALOGUES TO INDUCE APOPTOSIS OF B-CHRONIC LYMPHOCYTIC LEUKAEMIA CELLS. RESISTANCE TO CHEMOTHERAPY AND DRUG TOXICITY ARE TWO MAJOR CONCERNS OF CHRONIC LYMPHOCYTIC LEUKAEMIA (B-CLL) TREATMENT BY PURINE NUCLEOSIDE ANALOGUES (PNA, I.E. FLUDARABINE AND CLADRIBINE). WE HYPOTHESIZED THAT TARGETING EPIGENETIC CHANGES MIGHT ADDRESS THESE ISSUES AND EVALUATED THE EFFECT OF THE HISTONE DEACETYLASE INHIBITOR VALPROATE (VPA) AT A CLINICALLY RELEVANT CONCENTRATION. VPA ACTED IN A HIGHLY SYNERGISTIC/ADDITIVE MANNER WITH FLUDARABINE AND CLADRIBINE TO INDUCE APOPTOSIS OF B-CLL CELLS. IMPORTANTLY, VPA ALSO RESTORED SENSITIVITY TO FLUDARABINE IN B CELLS FROM POOR PROGNOSIS CLL PATIENTS WHO BECAME RESISTANT TO CHEMOTHERAPY. MECHANISM OF APOPTOSIS INDUCED BY VPA ALONE OR COMBINED WITH FLUDARABINE OR TO CLADRIBINE WAS CASPASE-DEPENDENT AND INVOLVED THE EXTRINSIC PATHWAY. VPA, BUT NEITHER FLUDARABINE NOR CLADRIBINE, ENHANCED THE PRODUCTION OF REACTIVE OXYGEN SPECIES (ROS) AND INHIBITION OF ROS WITH N-ACETYLCYSTEINE DECREASES APOPTOSIS OF CLL CELLS. VPA STIMULATES HYPERPHOSPHORYLATION OF P42/P44 ERK, CYTOCHROME C RELEASE AND OVEREXPRESSION OF BAX AND FAS. TOGETHER, OUR DATA INDICATE THAT VPA MAY AMELIORATE THE OUTCOME OF PNA-BASED THERAPEUTIC PROTOCOLS AND PROVIDE A POTENTIAL ALTERNATIVE TREATMENT IN BOTH THE RELAPSED AND FRONT-LINE RESISTANT PATIENTS AND IN PATIENTS WITH HIGH RISK FEATURES. 2009 2 5849 36 SUBEROYLANILIDE HYDROXAMIC ACID (SAHA) AND CLADRIBINE SYNERGISTICALLY INDUCE APOPTOSIS IN NK-LGL LEUKAEMIA. NATURAL KILLER (NK) LARGE GRANULAR LYMPHOCYTE (LGL) LEUKAEMIA FEATURES A CLONAL PROLIFERATION OF CD3(-) NK CELLS THAT CAN BE CLASSIFIED INTO EITHER AGGRESSIVE OR CHRONIC CATEGORIES. THE NKL CELL LINE, DERIVED FROM AN AGGRESSIVE ASIAN NK CELL LEUKAEMIA, AND PATIENT SAMPLES FROM CHRONIC NK-LGL LEUKAEMIA WERE USED IN OUR STUDY TO PROBE FOR SYNERGISTIC EFFICACY OF THE EPIGENETIC DRUGS VORINOSTAT (SAHA) AND CLADRIBINE IN THIS DISEASE. WE DEMONSTRATE THAT HISTONE DEACETYLASES (HDACS) ARE OVER-EXPRESSED IN BOTH AGGRESSIVE AND CHRONIC NK LEUKAEMIA. ADMINISTRATION OF THE HDAC INHIBITOR SAHA REDUCES CLASS I AND II HDAC EXPRESSION AND ENHANCES HISTONE ACETYLATION IN LEUKAEMIC NK CELLS. IN VITRO COMBINATION TREATMENT WITH SAHA AND CLADRIBINE DOSE-DEPENDENTLY EXERTS SYNERGISTIC CYTOTOXIC AND APOPTOTIC EFFECTS ON LEUKAEMIC NK CELLS. EXPRESSION PROFILING OF APOPTOTIC REGULATORY GENES SUGGESTS THAT BOTH COMPOUNDS LED TO CASPASE-DEPENDENT APOPTOSIS THROUGH ACTIVATION OF INTRINSIC MITOCHONDRIAL AND EXTRINSIC DEATH RECEPTOR PATHWAYS. COLLECTIVELY, THESE DATA SHOW THAT COMBINED EPIGENETIC THERAPY, USING HDAC AND DNA METHYLTRANSFERASE INHIBITORS, MAY BE A PROMISING THERAPEUTIC APPROACH FOR NK-LGL LEUKAEMIA. 2015 3 4560 21 MUTATIONS WITH EPIGENETIC EFFECTS IN MYELOPROLIFERATIVE NEOPLASMS AND RECENT PROGRESS IN TREATMENT: PROCEEDINGS FROM THE 5TH INTERNATIONAL POST-ASH SYMPOSIUM. IMMEDIATELY FOLLOWING THE 2010 ANNUAL AMERICAN SOCIETY OF HEMATOLOGY (ASH) MEETING, THE 5TH INTERNATIONAL POST-ASH SYMPOSIUM ON CHRONIC MYELOGENOUS LEUKEMIA AND BCR-ABL1-NEGATIVE MYELOPROLIFERATIVE NEOPLASMS (MPNS) TOOK PLACE ON 7-8 DECEMBER 2010 IN ORLANDO, FLORIDA, USA. DURING THIS MEETING, THE MOST RECENT ADVANCES IN LABORATORY RESEARCH AND CLINICAL PRACTICE, INCLUDING THOSE THAT WERE PRESENTED AT THE 2010 ASH MEETING, WERE DISCUSSED AMONG RECOGNIZED AUTHORITIES IN THE FIELD. THE CURRENT PAPER SUMMARIZES THE PROCEEDINGS OF THIS MEETING IN BCR-ABL1-NEGATIVE MPN. WE PROVIDE A DETAILED OVERVIEW OF NEW MUTATIONS WITH PUTATIVE EPIGENETIC EFFECTS (TET ONCOGENE FAMILY MEMBER 2 (TET2), ADDITIONAL SEX COMB-LIKE 1 (ASXL1), ISOCITRATE DEHYDROGENASE (IDH) AND ENHANCER OF ZESTE HOMOLOG 2 (EZH2)) AND AN UPDATE ON TREATMENT WITH JANUS KINASE (JAK) INHIBITORS, POMALIDOMIDE, EVEROLIMUS, INTERFERON-ALPHA, MIDOSTAURIN AND CLADRIBINE. IN ADDITION, THE NEW 'DYNAMIC INTERNATIONAL PROGNOSTIC SCORING SYSTEM (DIPSS)-PLUS' PROGNOSTIC MODEL FOR PRIMARY MYELOFIBROSIS (PMF) AND THE CLINICAL RELEVANCE OF DISTINGUISHING ESSENTIAL THROMBOCYTHEMIA FROM PREFIBROTIC PMF ARE DISCUSSED. 2011 4 4864 19 ORLANDO MAGIC: REPORT FROM THE 57TH MEETING OF THE AMERICAN SOCIETY OF HAEMATOLOGY, 5-7 DECEMBER 2015, ORLANDO, USA. THE 57TH AMERICAN SOCIETY OF HAEMATOLOGY (ASH) MEETING HELD IN ORLANDO, FL WAS CERTAINLY THE YEAR WHEN MYELOMA MANAGEMENT CHANGED FOR GOOD, WITH A PLETHORA OF NEWLY FOOD AND DRUG ADMINISTRATION (FDA)-APPROVED DRUGS SHOWING IMPRESSIVE OUTCOME IMPROVEMENTS AND THE INTRODUCTION OF NEW TECHNIQUES FOR DISEASE MONITORING. ALSO, CHIMERIC ANTIGEN RECEPTOR (CAR) T CELLS CONTINUED THEIR TRIUMPHAL MARCH, CONSOLIDATING THEIR SUCCESS IN LYMPHOMA AND CHRONIC LYMHOCYTIC LEUKAEMIA (CLL) AND VENTURING INTO NEW FIELDS SUCH AS AGAIN MULTIPLE MYELOMA. SOME EXPERIMENTAL DRUGS SHOWED LONG-AWAITED RESULTS (MIDOSTAURIN IN FLT3-MUTATED ACUTE MYELOID LEUKAEMIA (AML)) AND SOME BRAND NEW DRUGS SHOWED PROMISING RESULTS IN THE CLINIC AFTER EXTENSIVE PRECLINICAL STUDIES, SUCH AS THOSE TARGETING NEW EPIGENETIC FACTORS (HISTONE METHYLTRANSFERASES) AND APOPTOSIS. 2016 5 4748 18 NOVEL MUTATIONS AND THEIR FUNCTIONAL AND CLINICAL RELEVANCE IN MYELOPROLIFERATIVE NEOPLASMS: JAK2, MPL, TET2, ASXL1, CBL, IDH AND IKZF1. MYELOPROLIFERATIVE NEOPLASMS (MPNS) ORIGINATE FROM GENETICALLY TRANSFORMED HEMATOPOIETIC STEM CELLS THAT RETAIN THE CAPACITY FOR MULTILINEAGE DIFFERENTIATION AND EFFECTIVE MYELOPOIESIS. BEGINNING IN EARLY 2005, A NUMBER OF NOVEL MUTATIONS INVOLVING JANUS KINASE 2 (JAK2), MYELOPROLIFERATIVE LEUKEMIA VIRUS (MPL), TET ONCOGENE FAMILY MEMBER 2 (TET2), ADDITIONAL SEX COMBS-LIKE 1 (ASXL1), CASITAS B-LINEAGE LYMPHOMA PROTO-ONCOGENE (CBL), ISOCITRATE DEHYDROGENASE (IDH) AND IKAROS FAMILY ZINC FINGER 1 (IKZF1) HAVE BEEN DESCRIBED IN BCR-ABL1-NEGATIVE MPNS. HOWEVER, NONE OF THESE MUTATIONS WERE MPN SPECIFIC, DISPLAYED MUTUAL EXCLUSIVITY OR COULD BE TRACED BACK TO A COMMON ANCESTRAL CLONE. JAK2 AND MPL MUTATIONS APPEAR TO EXERT A PHENOTYPE-MODIFYING EFFECT AND ARE DISTINCTLY ASSOCIATED WITH POLYCYTHEMIA VERA, ESSENTIAL THROMBOCYTHEMIA AND PRIMARY MYELOFIBROSIS; THE CORRESPONDING MUTATIONAL FREQUENCIES ARE APPROXIMATELY 99, 55 AND 65% FOR JAK2 AND 0, 3 AND 10% FOR MPL MUTATIONS. THE INCIDENCE OF TET2, ASXL1, CBL, IDH OR IKZF1 MUTATIONS IN THESE DISORDERS RANGES FROM 0 TO 17%; THESE LATTER MUTATIONS ARE MORE COMMON IN CHRONIC (TET2, ASXL1, CBL) OR JUVENILE (CBL) MYELOMONOCYTIC LEUKEMIAS, MASTOCYTOSIS (TET2), MYELODYSPLASTIC SYNDROMES (TET2, ASXL1) AND SECONDARY ACUTE MYELOID LEUKEMIA, INCLUDING BLAST-PHASE MPN (IDH, ASXL1, IKZF1). THE FUNCTIONAL CONSEQUENCES OF MPN-ASSOCIATED MUTATIONS INCLUDE UNREGULATED JAK-STAT (JANUS KINASE/SIGNAL TRANSDUCER AND ACTIVATOR OF TRANSCRIPTION) SIGNALING, EPIGENETIC MODULATION OF TRANSCRIPTION AND ABNORMAL ACCUMULATION OF ONCOPROTEINS. HOWEVER, IT IS NOT CLEAR AS TO WHETHER AND HOW THESE ABNORMALITIES CONTRIBUTE TO DISEASE INITIATION, CLONAL EVOLUTION OR BLASTIC TRANSFORMATION. 2010 6 3336 27 HISTONE DEACETYLASE INHIBITORS INDUCE PROTEOLYSIS OF ACTIVATED CDC42-ASSOCIATED KINASE-1 IN LEUKEMIC CELLS. PURPOSE: ACTIVATED CDC42-ASSOCIATED KINASE-1 (ACK1/TNK2) AND EPIGENETIC REGULATORS OF THE HISTONE DEACETYLASE (HDAC) FAMILY REGULATE THE PROLIFERATION AND SURVIVAL OF LEUKEMIC CELLS. 18 HDACS FALL INTO FOUR CLASSES (I-IV). WE TESTED THE IMPACT OF CLINICALLY RELEVANT HISTONE DEACETYLASE INHIBITORS (HDACI) ON ACK1 AND IF SUCH DRUGS COMBINE FAVORABLY WITH THE THERAPEUTICALLY USED ACK1 INHIBITOR DASATINIB. METHODS: WE APPLIED THE BROAD-RANGE HDACI PANOBINOSTAT/LBH589 AND THE CLASS I HDAC-SPECIFIC INHIBITOR ENTINOSTAT/MS-275 TO VARIOUS ACUTE AND CHRONIC MYELOID LEUKEMIA CELLS (AML/CML). WE ALSO USED THE REPLICATIVE STRESS INDUCER HYDROXYUREA (HU), A STANDARD DRUG FOR LEUKEMIC PATIENTS, AND THE APOPTOSIS INDUCER STAUROSPORINE (STS). TO ASSESS CYTOTOXIC EFFECTS OF HDACI, WE MEASURED CELL CYCLE PROFILES AND DNA FRAGMENTATION BY FLOW CYTOMETRY. WESTERN BLOT WAS EMPLOYED TO ANALYZE PROTEIN EXPRESSION AND PHOSPHORYLATION. RESULTS: LBH589 AND MS-275 INDUCE PROTEOLYSIS OF ACK1 IN CML AND AML CELLS. PANOBINOSTAT MORE STRONGLY INDUCES APOPTOSIS THAN ENTINOSTAT, AND THIS CORRELATES WITH A SIGNIFICANTLY PRONOUNCED LOSS OF ACK1. STS AND HU ALSO PROPEL THE DEGRADATION OF ACK1 IN LEUKEMIC CELLS. MOREOVER, THE CASPASE INHIBITOR Z-VAD-FMK REDUCES ACK1 DEGRADATION IN THE PRESENCE OF HDACI. CONCOMITANT WITH THE ATTENUATION OF ACK1, WE NOTICED DECREASED PHOSPHORYLATION OF STAT3. DIRECT INHIBITION OF ACK1 WITH DASATINIB ALSO SUPPRESSES STAT3 PHOSPHORYLATION. FURTHERMORE, DASATINIB AND HDACI COMBINATIONS ARE EFFECTIVE AGAINST CML CELLS. CONCLUSION: HDACS SUSTAIN THE ACK1-STAT3 SIGNALING NODE AND LEUKEMIC CELL GROWTH. CONSISTENT WITH THEIR DIFFERENT EFFECTS ON ACK1 STABILITY OR AUTO-PHOSPHORYLATION, DASATINIB AND HDACI COMBINATIONS PRODUCE BENEFICIAL ANTILEUKEMIC EFFECTS. 2016 7 4741 41 NOVEL HDAC INHIBITOR MAKV-8 AND IMATINIB SYNERGISTICALLY KILL CHRONIC MYELOID LEUKEMIA CELLS VIA INHIBITION OF BCR-ABL/MYC-SIGNALING: EFFECT ON IMATINIB RESISTANCE AND STEM CELLS. BACKGROUND: CHRONIC MYELOID LEUKEMIA (CML) PATHOGENESIS IS MAINLY DRIVEN BY THE ONCOGENIC BREAKPOINT CLUSTER REGION-ABELSON MURINE LEUKEMIA VIRAL ONCOGENE HOMOLOG 1 (BCR-ABL) FUSION PROTEIN. SINCE BCR-ABL DISPLAYS ABNORMAL CONSTITUTIVE TYROSINE KINASE ACTIVITY, THERAPIES USING TYROSINE KINASE INHIBITORS (TKIS) SUCH AS IMATINIB REPRESENT A MAJOR BREAKTHROUGH FOR THE OUTCOME OF CML PATIENTS. NEVERTHELESS, THE DEVELOPMENT OF TKI RESISTANCE AND THE PERSISTENCE OF LEUKEMIA STEM CELLS (LSCS) REMAIN BARRIERS TO CURE THE DISEASE, JUSTIFYING THE DEVELOPMENT OF NOVEL THERAPEUTIC APPROACHES. SINCE THE ACTIVITY OF HISTONE DEACETYLASE (HDAC) IS DEREGULATED IN NUMEROUS CANCERS INCLUDING CML, PAN-HDAC INHIBITORS MAY REPRESENT PROMISING THERAPEUTIC REGIMENS FOR THE TREATMENT OF CML CELLS IN COMBINATION WITH TKI. RESULTS: WE ASSESSED THE ANTI-LEUKEMIC ACTIVITY OF A NOVEL HYDROXAMATE-BASED PAN-HDAC INHIBITOR MAKV-8, WHICH COMPLIED WITH THE LIPINSKI'S "RULE OF FIVE," IN VARIOUS CML CELLS ALONE OR IN COMBINATION WITH IMATINIB. WE VALIDATED THE IN VITRO HDAC-INHIBITORY POTENTIAL OF MAKV-8 AND DEMONSTRATED EFFICIENT BINDING TO THE LIGAND-BINDING POCKET OF HDAC ISOENZYMES. IN CELLULO, MAKV-8 SIGNIFICANTLY INDUCED TARGET PROTEIN ACETYLATION, DISPLAYED CYTOSTATIC AND CYTOTOXIC PROPERTIES, AND TRIGGERED CONCOMITANT ER STRESS/PROTECTIVE AUTOPHAGY LEADING TO CANONICAL CASPASE-DEPENDENT APOPTOSIS. CONSIDERING THE SPECIFIC UPREGULATION OF SELECTED HDACS IN LSCS FROM CML PATIENTS, WE INVESTIGATED THE DIFFERENTIAL TOXICITY OF A CO-TREATMENT WITH MAKV-8 AND IMATINIB IN CML VERSUS HEALTHY CELLS. WE ALSO SHOWED THAT BECLIN-1 KNOCKDOWN PREVENTED MAKV-8-IMATINIB COMBINATION-INDUCED APOPTOSIS. MOREOVER, MAKV-8 AND IMATINIB CO-TREATMENT SYNERGISTICALLY REDUCED BCR-ABL-RELATED SIGNALING PATHWAYS INVOLVED IN CML CELL GROWTH AND SURVIVAL. SINCE OUR RESULTS SHOWED THAT LSCS FROM CML PATIENTS OVEREXPRESSED C-MYC, IMPORTANTLY MAKV-8-IMATINIB CO-TREATMENT REDUCED C-MYC LEVELS AND THE LSC POPULATION. IN VIVO, TUMOR GROWTH OF XENOGRAFTED K-562 CELLS IN ZEBRAFISH WAS COMPLETELY ABROGATED UPON COMBINED TREATMENT WITH MAKV-8 AND IMATINIB. CONCLUSIONS: COLLECTIVELY, THE PRESENT FINDINGS SHOW THAT COMBINATIONS HDAC INHIBITOR-IMATINIB ARE LIKELY TO OVERCOME DRUG RESISTANCE IN CML PATHOLOGY. 2020 8 1287 26 DECITABINE-INDUCED APOPTOSIS IS DERIVED BY PUMA AND NOXA INDUCTION IN CHRONIC MYELOID LEUKEMIA CELL LINE AS WELL AS IN PBL AND IS POTENTIATED BY SAHA. RESTORATION OF CELLULAR APOPTOTIC PATHWAYS PLAYS A CRUCIAL ROLE IN CANCER THERAPY STRATEGIES. IN A BROAD SPECTRUM OF ANTICANCER DRUGS, EPIGENETIC EFFECTORS ARE IN THE CENTER OF INTEREST MOSTLY BECAUSE OF POTENTIAL REVERSIBILITY OF THEIR ACTION. METHYLATION STATUS OF THE CELLS IS INFLUENCED BY METHYLTRANSFERASE INHIBITOR 2-DEOXY-5'-AZACYTIDINE (DECITABINE, DAC), BUT HIGHER CONCENTRATIONS OF THIS AGENT CAUSE A DNA-DAMAGE. IN OUR STUDY, TUMOR SUPRESSOR P53-APOPTOTIC PATHWAY WAS ACTIVATED IN DECITABINE-INDUCED CELL DEATH. EXPRESSION OF P53-INDUCIBLE BH3-ONLY APOPTOTIC PROTEINS PUMA AND NOXA WAS ELEVATED AND LARGE ACTIVATION OF EXECUTIVE CASPASES WAS OBSERVED. THE EXTENT OF ACETYLATION IN THE CELL IS AFFECTED BY HISTONEDEACETYLASE INHIBITOR SUBEROYLANILIDE HYDROXAMIC ACID (SAHA). COMBINATION OF SAHA WITH DECITABINE BROUGHT SYNERGISTIC EFFECT ON APOPTOSIS TRIGGERING IN CML-T1 CELL LINE, BUT APOPTOSIS AS WELL AS NECROSIS OCCURRED ALSO IN NORMAL PERIPHERAL BLOOD LYMPHOCYTES. THEREFORE, PROMISING POTENTIAL OF SUCH COMBINED THERAPY CALLS FOR MORE DETAILED INVESTIGATION OF UNWANTED EFFECTS IN NORMAL CELLS. 2011 9 5940 30 TARGETING METHYLTRANSFERASE PRMT5 ELIMINATES LEUKEMIA STEM CELLS IN CHRONIC MYELOGENOUS LEUKEMIA. IMATINIB-INSENSITIVE LEUKEMIA STEM CELLS (LSCS) ARE BELIEVED TO BE RESPONSIBLE FOR RESISTANCE TO BCR-ABL TYROSINE KINASE INHIBITORS AND RELAPSE OF CHRONIC MYELOGENOUS LEUKEMIA (CML). IDENTIFYING THERAPEUTIC TARGETS TO ERADICATE CML LSCS MAY BE A STRATEGY TO CURE CML. IN THE PRESENT STUDY, WE DISCOVERED A POSITIVE FEEDBACK LOOP BETWEEN BCR-ABL AND PROTEIN ARGININE METHYLTRANSFERASE 5 (PRMT5) IN CML CELLS. OVEREXPRESSION OF PRMT5 WAS OBSERVED IN HUMAN CML LSCS. SILENCING PRMT5 WITH SHRNA OR BLOCKING PRMT5 METHYLTRANSFERASE ACTIVITY WITH THE SMALL-MOLECULE INHIBITOR PJ-68 REDUCED SURVIVAL, SERIAL REPLATING CAPACITY, AND LONG-TERM CULTURE-INITIATING CELLS (LTC-ICS) IN LSCS FROM CML PATIENTS. FURTHER, PRMT5 KNOCKDOWN OR PJ-68 TREATMENT DRAMATICALLY PROLONGED SURVIVAL IN A MURINE MODEL OF RETROVIRAL BCR-ABL-DRIVEN CML AND IMPAIRED THE IN VIVO SELF-RENEWAL CAPACITY OF TRANSPLANTED CML LSCS. PJ-68 ALSO INHIBITED LONG-TERM ENGRAFTMENT OF HUMAN CML CD34+ CELLS IN IMMUNODEFICIENT MICE. MOREOVER, INHIBITION OF PRMT5 ABROGATED THE WNT/BETA-CATENIN PATHWAY IN CML CD34+ CELLS BY DEPLETING DISHEVELLED HOMOLOG 3 (DVL3). THIS STUDY SUGGESTS THAT EPIGENETIC METHYLATION MODIFICATION ON HISTONE PROTEIN ARGININE RESIDUES IS A REGULATORY MECHANISM TO CONTROL SELF-RENEWAL OF LSCS AND INDICATES THAT PRMT5 MAY REPRESENT A POTENTIAL THERAPEUTIC TARGET AGAINST LSCS. 2016 10 5924 26 TARGETING DNMT1 BY DEMETHYLATING AGENT OR-2100 INCREASES TYROSINE KINASE INHIBITORS-SENSITIVITY AND DEPLETES LEUKEMIC STEM CELLS IN CHRONIC MYELOID LEUKEMIA. ABL1 TYROSINE KINASE INHIBITORS (TKIS) DRAMATICALLY IMPROVE THE PROGNOSIS OF CHRONIC MYELOID LEUKEMIA (CML), BUT 10-20% OF PATIENTS ACHIEVE SUBOPTIMAL RESPONSES WITH LOW TKIS SENSITIVITY. FURTHERMORE, RESIDUAL LEUKEMIC STEM CELLS (LSCS) ARE INVOLVED IN THE MOLECULAR RELAPSE AFTER TKIS DISCONTINUATION. ABERRANT DNA HYPERMETHYLATION CONTRIBUTES TO LOW TKIS SENSITIVITY AND THE PERSISTENCE OF LSCS IN CML. DNMT1 IS A KEY REGULATOR OF HEMATOPOIETIC STEM CELLS, SUGGESTING THAT ABERRANT DNA HYPERMETHYLATION TARGETING DNMT1 REPRESENTS A POTENTIAL THERAPEUTIC TARGET FOR CML. WE INVESTIGATED THE EFFICACY OF OR-2100 (OR21), THE FIRST ORALLY AVAILABLE SINGLE-COMPOUND PRODRUG OF DECITABINE. OR21 EXHIBITED ANTI-TUMOR EFFECTS AS A MONOTHERAPY, AND IN COMBINATION THERAPY IT INCREASED TKI-INDUCED APOPTOSIS AND INDUCTION OF TUMOR SUPPRESSOR GENES INCLUDING PTPN6 ENCODING SHP-1 IN CML CELLS. OR21 IN COMBINATION WITH IMATINIB SIGNIFICANTLY SUPPRESSED TUMOR GROWTH IN A XENOTRANSPLANT MODEL. OR21 AND COMBINATION THERAPY DECREASED THE ABUNDANCE OF LSCS AND INHIBITED ENGRAFTMENT IN A BCR-ABL1-TRANSDUCED MOUSE MODEL. THESE RESULTS DEMONSTRATE THAT TARGETING DNMT1 USING OR21 EXERTS ANTI-TUMOR EFFECTS AND IMPAIRS LSCS IN CML. THEREFORE, COMBINATION TREATMENT OF TKIS AND OR21 REPRESENTS A PROMISING TREATMENT STRATEGY IN CML. 2022 11 690 25 BRD4 DEGRADATION BLOCKS EXPRESSION OF MYC AND MULTIPLE FORMS OF STEM CELL RESISTANCE IN PH(+) CHRONIC MYELOID LEUKEMIA. IN MOST PATIENTS WITH CHRONIC MYELOID LEUKEMIA (CML) CLONAL CELLS CAN BE KEPT UNDER CONTROL BY BCR::ABL1 TYROSINE KINASE INHIBITORS (TKI). HOWEVER, OVERT RESISTANCE OR INTOLERANCE AGAINST THESE TKI MAY OCCUR. WE IDENTIFIED THE EPIGENETIC READER BRD4 AND ITS DOWNSTREAM-EFFECTOR MYC AS GROWTH REGULATORS AND THERAPEUTIC TARGETS IN CML CELLS. BRD4 AND MYC WERE FOUND TO BE EXPRESSED IN PRIMARY CML CELLS, CD34(+) /CD38(-) LEUKEMIC STEM CELLS (LSC), AND IN THE CML CELL LINES KU812, K562, KCL22, AND KCL22(T315I) . THE BRD4-TARGETING DRUG JQ1 WAS FOUND TO SUPPRESS PROLIFERATION IN KU812 CELLS AND PRIMARY LEUKEMIC CELLS IN THE MAJORITY OF PATIENTS WITH CHRONIC PHASE CML. IN THE BLAST PHASE OF CML, JQ1 WAS LESS EFFECTIVE. HOWEVER, THE BRD4 DEGRADER DBET6 WAS FOUND TO BLOCK PROLIFERATION AND/OR SURVIVAL OF PRIMARY CML CELLS IN ALL PATIENTS TESTED, INCLUDING BLAST PHASE CML AND CML CELLS EXHIBITING THE T315I VARIANT OF BCR::ABL1. MOREOVER, DBET6 WAS FOUND TO BLOCK MYC EXPRESSION AND TO SYNERGIZE WITH BCR::ABL1 TKI IN INHIBITING THE PROLIFERATION IN THE JQ1-RESISTANT CELL LINE K562. FURTHERMORE, BRD4 DEGRADATION WAS FOUND TO OVERCOME OSTEOBLAST-INDUCED TKI RESISTANCE OF CML LSC IN A CO-CULTURE SYSTEM AND TO BLOCK INTERFERON-GAMMA-INDUCED UPREGULATION OF THE CHECKPOINT ANTIGEN PD-L1 IN LSC. FINALLY, DBET6 WAS FOUND TO SUPPRESS THE IN VITRO SURVIVAL OF CML LSC AND THEIR ENGRAFTMENT IN NSG MICE. TOGETHER, TARGETING OF BRD4 AND MYC THROUGH BET DEGRADATION SENSITIZES CML CELLS AGAINST BCR::ABL1 TKI AND IS A POTENT APPROACH TO OVERCOME MULTIPLE FORMS OF DRUG RESISTANCE IN CML LSC. 2022 12 671 32 BOTHROPS MOOJENI L-AMINO ACID OXIDASE INDUCES APOPTOSIS AND EPIGENETIC MODULATION ON BCR-ABL(+) CELLS. BACKGROUND: RESISTANCE TO APOPTOSIS IN CHRONIC MYELOID LEUKEMIA (CML) IS ASSOCIATED WITH CONSTITUTIVE TYROSINE KINASE ACTIVITY OF THE BCR-ABL ONCOPROTEIN. THE DEREGULATED EXPRESSION OF APOPTOSIS-RELATED GENES AND ALTERATION IN EPIGENETIC MACHINERY MAY ALSO CONTRIBUTE TO APOPTOSIS RESISTANCE IN CML. TYROSINE KINASE INHIBITORS TARGET THE BCR-ABL ONCOPROTEIN AND ARE USED IN CML TREATMENT. THE RESISTANCE OF CML PATIENTS TO TYROSINE KINASE INHIBITORS HAS GUIDED THE SEARCH FOR NEW COMPOUNDS THAT MAY INDUCE APOPTOSIS IN BCR-ABL(+) LEUKEMIC CELLS AND IMPROVE THE DISEASE TREATMENT. METHODS: IN THE PRESENT STUDY, WE INVESTIGATED WHETHER THE L-AMINO ACID OXIDASE ISOLATED FROM BOTHROPS MOOJENI SNAKE VENOM (BMOOLAAO-I) (I) WAS CYTOTOXIC TO BCR-ABL(+) CELL LINES (HL-60.BCR-ABL, K562-S, AND K562-R), HL-60 (ACUTE PROMYELOCYTIC LEUKEMIA) CELLS, THE NON-TUMOR CELL LINE HEK-293, AND PERIPHERAL BLOOD MONONUCLEAR CELLS (PBMC); AND (II) AFFECTED EPIGENETIC MECHANISMS, INCLUDING DNA METHYLATION AND MICRORNAS EXPRESSION IN VITRO. RESULTS: BMOOLAAO-I INDUCED ROS PRODUCTION, APOPTOSIS, AND DIFFERENTIAL DNA METHYLATION PATTERN OF REGULATORY APOPTOSIS GENES. THE TOXIN UPREGULATED EXPRESSION OF THE PRO-APOPTOTIC GENES BID AND FADD AND DOWNREGULATED DFFA EXPRESSION IN LEUKEMIC CELL LINES, AS WELL AS INCREASED MIR-16 EXPRESSION - WHOSE MAJOR PREDICTED TARGET IS THE ANTI-APOPTOTIC GENE BCL2 - IN BCR-ABL(+) CELLS. CONCLUSION: BMOOLAAO-I EXERTS SELECTIVE ANTITUMOR ACTION MEDIATED BY H(2)O(2) RELEASE AND INDUCES APOPTOSIS, AND ALTERATIONS IN EPIGENETIC MECHANISMS. THESE RESULTS SUPPORT FUTURE INVESTIGATIONS ON THE EFFECT OF BMOOLAAO-I ON IN VIVO MODELS TO DETERMINE ITS POTENTIAL IN CML THERAPY. 2020 13 1234 24 CRYPTOTANSHINONE SUPPRESSES KEY ONCO-PROLIFERATIVE AND DRUG-RESISTANT PATHWAYS OF CHRONIC MYELOID LEUKEMIA BY TARGETING STAT5 AND STAT3 PHOSPHORYLATION. C-MYC AND SIGNAL TRANSDUCER AND ACTIVATOR OF TRANSCRIPTION (STAT) FAMILY PROTEINS HAVE BEEN PROPOSED TO BE IMPORTANT DOWNSTREAM GENES OF BCR-ABL, WHICH CHARACTERIZES MOST CASES OF CHRONIC MYELOID LEUKEMIA (CML). HERE, WE REPORT A C-MYC PATHWAY-TARGETED SCREENING OF SEVEN NATURAL ANTICANCER COMPOUNDS, IN WHICH WE IDENTIFIED CRYPTOTANSHINONE AS A HIGHLY PROMISING AGENT FOR CML THERAPY. CRYPTOTANSHINONE DEPLETES C-MYC IN CML BY REPRESSING THE PHOSPHORYLATION OF STAT5. DECREASED VIABILITY OF K562 CELLS CORRELATED WITH P-STAT5 SUPPRESSION. UNEXPECTEDLY, IMATINIB ACTIVATES RATHER THAN INHIBITS THE PHOSPHORYLATION OF STAT3 IN K562 CELLS. WE DEMONSTRATED THAT CRYPTOTANSHINONE, AS A DUAL INHIBITOR OF P-STAT5 AND P-STAT3, CAN EFFECTIVELY BLOCK IL-6-MEDIATED STAT3 ACTIVATION AND REVERSE BCR-ABL KINASE-INDEPENDENT DRUG RESISTANCE. MOREOVER, WE SHOWED THAT THE EPIGENETIC REBALANCE BETWEEN DECREASED BCR-ABL/STAT5/C-MYC AND ENHANCED STAT3/MULTI-DRUG RESISTANCE (MDR) PATHWAYS IS CHARACTERISTIC OF THE CANCER STEM CELL-LIKE PROPERTY OF K562/ADR. SIMULTANEOUSLY SUPPRESSING THESE TWO PATHWAYS USING CRYPTOTANSHINONE PROVES TO BE CRITICAL FOR THE MALIGNANT NETWORK REDRESS AND MDR REVERSAL OF K562/ADR. THESE STUDIES REVEAL THE DUAL FUNCTIONS OF CRYPTOTANSHINONE THAT SUPPRESS KEY ONCOGENIC PROLIFERATION AND DRUG-RESISTANT PATHWAYS IN CML CELLS BY TARGETING P-STAT5 AND P-STAT3, PROVIDING A NEW STRATEGY FOR CML THERAPY THAT TAKES ADVANTAGE OF NATURAL PRODUCTS. 2018 14 571 25 BCR-ABL INDUCES AUTOCRINE IGF-1 SIGNALING. BCR-ABL ONCOGENE IS RESPONSIBLE FOR THE INITIAL PHASE OF CHRONIC MYELOGENOUS LEUKEMIA (CML), WHICH IS EFFECTIVELY TREATED BY THE BCR-ABL INHIBITOR IMATINIB. OVER TIME PATIENTS BECOME RESISTANT TO TREATMENT AND PROGRESS TO BLAST CRISIS, AN EVENT THAT IS DRIVEN BY ADDITIONAL GENETIC AND EPIGENETIC ABERRATIONS. RECENTLY, WE SHOWED THAT RIZ1 EXPRESSION DECREASES IN BLAST CRISIS AND THAT RE-EXPRESSION OF RIZ1 INHIBITS IGF-1 EXPRESSION. IGF-1 SIGNALING IS REQUIRED IN MANY STAGES OF HEMATOPOIESIS AND INAPPROPRIATE ACTIVATION OF AUTOCRINE IGF-1 SIGNALING MAY FACILITATE TRANSFORMATION TO BLAST CRISIS. WE OBSERVED THAT IN 8 OUT OF 11 MATCHED CML PATIENT BIOPSIES THE IGF-1 EXPRESSION IS ELEVATED IN BLAST CRISIS. WE EXAMINED MECHANISMS USED BY CML BLAST CRISIS CELL LINES TO ACTIVATE IGF-1 EXPRESSION. WE FOUND THAT BCR-ABL ACTIVATES AUTOCRINE IGF-1 SIGNALING USING HCK AND STAT5B. INHIBITION OF THESE SIGNALING COMPONENTS USING SMALL MOLECULE DRUGS OR SHRNA DECREASES PROLIFERATION AND ENHANCES APOPTOSIS. TOGETHER, OUR STUDY SUGGESTS THAT ABERRANT IGF-1 SIGNALING IS AN IMPORTANT EVENT IN BLAST CRISIS TRANSFORMATION AND IT PROVIDES A MECHANISM TO EXPLAIN THE ACTIVITY OF IGF-1R AND HCK INHIBITORS IN BLOCKING CML BLAST CRISIS PHENOTYPES. 2008 15 4877 29 OVEREXPRESSION OF MIR-4433 BY SUBEROYLANILIDE HYDROXAMIC ACID SUPPRESSES GROWTH OF CML CELLS AND INDUCES APOPTOSIS THROUGH TARGETING BCR-ABL. BACKGROUND: TARGETING BCR-ABL IS THE KEY FOR THE TREATMENT OF CML. ALTHOUGH GREAT PROGRESS HAS BEEN ACHIEVED FOR THE TREATMENT OF CML PATIENTS IN CHRONIC STAGE, EFFECTIVE DRUGS WITH GOOD SAFETY ARE NOT AVAILABLE FOR THOSE IN ADVANCED STAGES OF CML PATIENTS. IN PRESENT STUDY, A HISTONE DEACETYLASE INHIBITOR, SUBEROYLANILIDE HYDROXAMIC ACID (SAHA), WAS USED TO SCREEN FOR MICRORNA THAT CAN TARGET BCR-ABL. METHODS: RT-QPCR WAS USED TO DETERMINE BCR-ABL AND MIR-4433 TRANSCRIPTION LEVEL IN CML CELLS. IN CML CELLS, PROTEINS INCLUDING PARP, CASPASE-3, ACETYL-HISTONE 3, HISTONE 3 AND BCR-ABL, AS WELL AS BCR-ABL DOWNSTREAM PROTEINS WERE DETECTED USING WESTERN BLOT. CELL VIABILITY AND APOPTOSIS WERE MONITORED RESPECTIVELY BY MTS ASSAY AND FLOW CYTOMETRY. THE CORRELATION BETWEEN MIR-4433 AND BCR-ABL WAS DETERMINED BY LUCIFERASE REPORTER ASSAY. THE ANTI-TUMOR EFFECT OF MIR-4433 TO K562 CELLS WAS EVALUATED BY NUDE MOUSE XENOGRAFT MODEL IN VIVO. RESULTS: SAHA UP-REGULATED THE ACETYLATION LEVEL OF HISTONE 3, AND EFFECTIVELY INHIBITED BCR-ABL MRNA LEVEL AND ITS DOWNSTREAM SIGNAL TRANSDUCTION PATHWAY, WHILE INHIBITING THE GROWTH OF CML CELLS AND INDUCING APOPTOSIS. FURTHERMORE, BIOINFORMATICS TOOLS PREDICTED THAT MIR-4433 IS A PUTATIVE MICRORNA TARGETING BCR-ABL AND THAT THE EXPRESSION LEVEL OF MIR-4433 WAS SIGNIFICANTLY INCREASED AFTER SAHA TREATMENT IN K562 CELLS. LUCIFERASE ACTIVITY ANALYSIS REVEALED THAT MIR-4433 DIRECTLY TARGETS BCR-ABL. ADDITIONALLY, TRANSIENT EXPRESSION OF MIR-4433 ABROGATED BCR-ABL ACTIVITY AND ITS DOWNSTREAM SIGNALING PATHWAYS WHILE INDUCING APOPTOSIS IN K562 CELLS. MOREOVER, STABLE EXPRESSION OF MIR-4433 SUPPRESSED BCR-ABL AND ITS DOWNSTREAM SIGNALING PATHWAY, AND INHIBITED THE GROWTH OF K562 CELLS IN VITRO AND THE GROWTH OF K562-XENOGRAFTS IN NUDE MICE. CONCLUSION: MIR-4433 WAS IDENTIFIED AS A MICRORNA TARGETING BCR-ABL, WHICH MAY BE SUBJECT TO EPIGENETIC REGULATION OF SAHA, A HISTONE DEACETYLASE INHIBITOR THAT HAS BEEN APPROVED BY THE US FDA FOR THE TREATMENT OF CUTANEOUS T-CELL LYMPHOMA. THE FINDINGS OF THIS STUDY PROVIDE A MOLECULAR BASIS FROM ANOTHER ANGLE FOR THE USE OF SAHA IN THE TREATMENT OF CML. 2019 16 439 35 ANTILEUKEMIC ACTIVITY OF VALPROIC ACID IN CHRONIC LYMPHOCYTIC LEUKEMIA B CELLS DEFINED BY MICROARRAY ANALYSIS. EPIGENETIC CODE MODIFICATIONS BY HISTONE DEACETYLASE INHIBITORS HAVE RECENTLY BEEN PROPOSED AS POTENTIAL NEW THERAPIES FOR HEMATOLOGICAL MALIGNANCIES. CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) REMAINS INCURABLE DESPITE THE INTRODUCTION OF NEW TREATMENTS. CLL B CELLS ARE CHARACTERIZED BY AN APOPTOSIS DEFECT RATHER THAN EXCESSIVE PROLIFERATION, BUT PROLIFERATION CENTERS HAVE BEEN FOUND IN ORGANS SUCH AS THE BONE MARROW AND LYMPH NODES. IN THIS STUDY, WE ANALYZED GENE EXPRESSION MODIFICATIONS IN CLL B CELLS AFTER TREATMENT WITH VALPROIC ACID (VPA), A WELL-TOLERATED ANTI-EPILEPTIC DRUG WITH HDAC INHIBITORY ACTIVITY. CLL B CELLS OBTAINED FROM 14 PATIENTS WERE TREATED IN VITRO WITH A CONCENTRATION OF 1 MM VPA FOR 4 H. VPA EFFECTS ON GENE EXPRESSION WERE THEREAFTER STUDIED USING AFFYMETRIX TECHNOLOGY, AND SOME IDENTIFIED GENES WERE VALIDATED BY REAL-TIME PCR AND WESTERN BLOT. WE OBSERVED THAT VPA INDUCED APOPTOSIS BY DOWNREGULATING SEVERAL ANTI-APOPTOTIC GENES AND BY UPREGULATING PRO-APOPTOTIC GENES. FURTHERMORE, VPA SIGNIFICANTLY INCREASED CHEMOSENSITIVITY TO FLUDARABINE, FLAVOPIRIDOL, BORTEZOMIB, THALIDOMIDE AND LENALIDOMIDE. VPA INHIBITED THE PROLIFERATION OF CPG/IL2-STIMULATED CLL B CELLS AND MODULATED MANY CELL CYCLE MESSENGER RNAS. IN CONCLUSION, EXPOSURE OF CLL B CELLS TO VPA INDUCED APOPTOSIS, POTENTIATED CHEMOTHERAPEUTIC AGENT EFFECTS AND INHIBITED PROLIFERATION. THESE DATA STRONGLY SUGGEST THE USE OF VPA IN CLL TREATMENT, PARTICULARLY IN COMBINATION WITH ANTILEUKEMIA AGENTS. 2009 17 573 30 BCR-ABL1-INDUCED DOWNREGULATION OF WASP IN CHRONIC MYELOID LEUKEMIA INVOLVES EPIGENETIC MODIFICATION AND CONTRIBUTES TO MALIGNANCY. CHRONIC MYELOID LEUKEMIA (CML) IS A MYELOPROLIFERATIVE DISEASE CAUSED BY THE BCR-ABL1 TYROSINE KINASE (TK). THE DEVELOPMENT OF TK INHIBITORS (TKIS) REVOLUTIONIZED THE TREATMENT OF CML PATIENTS. HOWEVER, TKIS ARE NOT EFFECTIVE TO THOSE AT ADVANCED PHASES WHEN AMPLIFIED BCR-ABL1 LEVELS AND INCREASED GENOMIC INSTABILITY LEAD TO SECONDARY ONCOGENIC MODIFICATIONS. WISKOTT-ALDRICH SYNDROME PROTEIN (WASP) IS AN IMPORTANT REGULATOR OF SIGNALING TRANSDUCTION IN HEMATOPOIETIC CELLS AND WAS SHOWN TO BE AN ENDOGENOUS INHIBITOR OF THE C-ABL TK. HERE, WE SHOW THAT THE EXPRESSION OF WASP DECREASES WITH THE PROGRESSION OF CML, INVERSELY CORRELATES WITH THE EXPRESSION OF BCR-ABL1 AND IS PARTICULARLY LOW IN BLAST CRISIS. ENFORCED EXPRESSION OF BCR-ABL1 NEGATIVELY REGULATES THE EXPRESSION OF WASP. DECREASED EXPRESSION OF WASP IS PARTIALLY DUE TO DNA METHYLATION OF THE PROXIMAL WASP PROMOTER. IMPORTANTLY, LOWER LEVELS OF WASP IN CML ADVANCED PHASE PATIENTS CORRELATE WITH POORER OVERALL SURVIVAL (OS) AND IS ASSOCIATED WITH TKI RESPONSE. INTERESTINGLY, ENFORCED EXPRESSION OF WASP IN BCR-ABL1-POSITIVE K562 CELLS INCREASES THE SUSCEPTIBILITY TO APOPTOSIS INDUCED BY TRAIL OR CHEMOTHERAPEUTIC DRUGS AND NEGATIVELY MODULATES BCR-ABL1-INDUCED TUMORIGENESIS IN VITRO AND IN VIVO. TAKEN TOGETHER, OUR DATA REVEAL A NOVEL MOLECULAR MECHANISM THAT OPERATES IN BCR-ABL1-INDUCED TUMORIGENESIS THAT CAN BE USED TO DEVELOP NEW STRATEGIES TO HELP TKI-RESISTANT, CML PATIENTS IN BLAST CRISIS (BC). 2017 18 5867 29 SUPPRESSIVE EFFECT OF THE HISTONE DEACETYLASE INHIBITOR SUBEROYLANILIDE HYDROXAMIC ACID (SAHA) ON HEPATITIS C VIRUS REPLICATION. THE HISTONE DEACETYLASE (HDAC) INHIBITOR SUBEROYLANILIDE HYDROXAMIC ACID (SAHA) HAS A CLINICAL PROMISE FOR TREATMENT OF CANCER INCLUDING HEPATOCELLULAR CARCINOMA (HCC). TO INVESTIGATE EFFECT OF SAHA ON HEPATITIS C VIRUS (HCV) REPLICATION, WE TREATED THE HCV REPLICON CELL OR6 WITH SAHA. HCV REPLICATION WAS SIGNIFICANTLY INHIBITED BY SAHA AT CONCENTRATIONS BELOW 1 MUM WITH NO CELLULAR TOXICITY. ANOTHER HDAC INHIBITOR, TRICOSTATIN A, ALSO SHOWED REDUCTION OF HCV REPLICATION. THE MICROARRAY ANALYSIS AND QUANTITATIVE RT-PCR DEMONSTRATED UP-REGULATION OF OSTEOPONTIN (OPN) AND DOWN-REGULATION OF APOLIPOPROTEIN-A1 (APO-A1) AFTER SAHA TREATMENT. DIRECT GENE INDUCTION OF OPN AND KNOCKDOWN OF APO-A1 ALSO SHOWED REDUCTION OF HCV REPLICATION. THE LIVER SPECIFIC MICRORNA-122, WHICH IS INVOLVED IN HCV REPLICATION, WAS NOT AFFECTED BY SAHA TREATMENT. THESE RESULTS SUGGEST THAT SAHA HAS SUPPRESSIVE EFFECT ON HCV REPLICATION THROUGH ALTERATIONS OF GENE EXPRESSION SUCH AS OPN AND APO-A1 IN HOST CELLS. EPIGENETIC TREATMENT WITH HDAC INHIBITORS MAY BE A NOVEL THERAPEUTIC APPROACH FOR DISEASES ASSOCIATED WITH HCV INFECTION SUCH AS CHRONIC HEPATITIS, LIVER CIRRHOSIS, AND HCC. 2013 19 1184 22 COOPERATIVE EPIGENETIC REMODELING BY TET2 LOSS AND NRAS MUTATION DRIVES MYELOID TRANSFORMATION AND MEK INHIBITOR SENSITIVITY. MUTATIONS IN EPIGENETIC MODIFIERS AND SIGNALING FACTORS OFTEN CO-OCCUR IN MYELOID MALIGNANCIES, INCLUDING TET2 AND NRAS MUTATIONS. CONCURRENT TET2 LOSS AND NRAS(G12D) EXPRESSION IN HEMATOPOIETIC CELLS INDUCED MYELOID TRANSFORMATION, WITH A FULLY PENETRANT, LETHAL CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML), WHICH WAS SERIALLY TRANSPLANTABLE. TET2 LOSS AND NRAS MUTATION COOPERATIVELY LED TO DECREASE IN NEGATIVE REGULATORS OF MITOGEN-ACTIVATED PROTEIN KINASE (MAPK) ACTIVATION, INCLUDING SPRY2, THEREBY CAUSING SYNERGISTIC ACTIVATION OF MAPK SIGNALING BY EPIGENETIC SILENCING. TET2/NRAS DOUBLE-MUTANT LEUKEMIA SHOWED PREFERENTIAL SENSITIVITY TO MAPK KINASE (MEK) INHIBITION IN BOTH MOUSE MODEL AND PATIENT SAMPLES. THESE DATA PROVIDE INSIGHTS INTO HOW EPIGENETIC AND SIGNALING MUTATIONS COOPERATE IN MYELOID TRANSFORMATION AND PROVIDE A RATIONALE FOR MECHANISM-BASED THERAPY IN CMML PATIENTS WITH THESE HIGH-RISK GENETIC LESIONS. 2018 20 2402 31 EPIGENETIC REPROGRAMMING SENSITIZES CML STEM CELLS TO COMBINED EZH2 AND TYROSINE KINASE INHIBITION. A MAJOR OBSTACLE TO CURING CHRONIC MYELOID LEUKEMIA (CML) IS RESIDUAL DISEASE MAINTAINED BY TYROSINE KINASE INHIBITOR (TKI)-PERSISTENT LEUKEMIC STEM CELLS (LSC). THESE ARE BCR-ABL1 KINASE INDEPENDENT, REFRACTORY TO APOPTOSIS, AND SERVE AS A RESERVOIR TO DRIVE RELAPSE OR TKI RESISTANCE. WE DEMONSTRATE THAT POLYCOMB REPRESSIVE COMPLEX 2 IS MISREGULATED IN CHRONIC PHASE CML LSCS. THIS IS ASSOCIATED WITH EXTENSIVE REPROGRAMMING OF H3K27ME3 TARGETS IN LSCS, THUS SENSITIZING THEM TO APOPTOSIS UPON TREATMENT WITH AN EZH2-SPECIFIC INHIBITOR (EZH2I). EZH2I DOES NOT IMPAIR NORMAL HEMATOPOIETIC STEM CELL SURVIVAL. STRIKINGLY, TREATMENT OF PRIMARY CML CELLS WITH EITHER EZH2I OR TKI ALONE CAUSED SIGNIFICANT UPREGULATION OF H3K27ME3 TARGETS, AND COMBINED TREATMENT FURTHER POTENTIATED THESE EFFECTS AND RESULTED IN SIGNIFICANT LOSS OF LSCS COMPARED TO TKI ALONE, IN VITRO, AND IN LONG-TERM BONE MARROW MURINE XENOGRAFTS. OUR FINDINGS POINT TO A PROMISING EPIGENETIC-BASED THERAPEUTIC STRATEGY TO MORE EFFECTIVELY TARGET LSCS IN PATIENTS WITH CML RECEIVING TKIS. SIGNIFICANCE: IN CML, TKI-PERSISTENT LSCS REMAIN AN OBSTACLE TO CURE, AND APPROACHES TO ERADICATE THEM REMAIN A SIGNIFICANT UNMET CLINICAL NEED. WE DEMONSTRATE THAT EZH2 AND H3K27ME3 REPROGRAMMING IS IMPORTANT FOR LSC SURVIVAL, BUT RENDERS LSCS SENSITIVE TO THE COMBINED EFFECTS OF EZH2I AND TKI. THIS REPRESENTS A NOVEL APPROACH TO MORE EFFECTIVELY TARGET LSCS IN PATIENTS RECEIVING TKI TREATMENT. CANCER DISCOV; 6(11); 1248-57. (C)2016 AACR.SEE RELATED ARTICLE BY XIE ET AL., P. 1237THIS ARTICLE IS HIGHLIGHTED IN THE IN THIS ISSUE FEATURE, P. 1197. 2016