1 10 120 14-3-3 LIGAND PREVENTS NUCLEAR IMPORT OF C-ABL PROTEIN IN CHRONIC MYELOID LEUKEMIA. HERE WE DEMONSTRATED THAT THE 'LOSS OF FUNCTION' OF NOT-REARRANGED C-ABL IN CHRONIC MYELOID LEUKEMIA (CML) IS PROMOTED BY ITS CYTOPLASMIC COMPARTMENTALIZATION BOUND TO 14-3-3 SIGMA SCAFFOLDING PROTEIN. IN PARTICULAR, CONSTITUTIVE TYROSINE KINASE (TK) ACTIVITY OF P210 BCR-ABL BLOCKS C-JUN N-TERMINAL KINASE (JNK) PHOSPHORYLATION LEADING TO 14-3-3 SIGMA PHOSPHORYLATION AT A CRITICAL RESIDUE (SER(186)) FOR C-ABL BINDING IN RESPONSE TO DNA DAMAGE. MOREOVER, IT IS ASSOCIATED WITH 14-3-3 SIGMA OVER-EXPRESSION ARISING FROM EPIGENETIC MECHANISMS (PROMOTER HYPER-ACETYLATION). ACCORDINGLY, P210 BCR-ABL TK INHIBITION BY THE TK INHIBITOR IMATINIB MESYLATE (IM) EVOKES MULTIPLE EVENTS, INCLUDING JNK PHOSPHORYLATION AT THR(183), P38 MITOGEN-ACTIVATED PROTEIN KINASE (MAPK) PHOSPHORYLATION AT THR(180), C-ABL DE-PHOSPHORYLATION AT SER RESIDUES INVOLVED IN 14-3-3 BINDING AND REDUCTION OF 14-3-3 SIGMA EXPRESSION, THAT LET C-ABL RELEASE FROM 14-3-3 SIGMA AND NUCLEAR IMPORT, AND ADDRESS BCR-ABL-EXPRESSING CELLS TOWARDS APOPTOTIC DEATH. INFORMATIONAL SPECTRUM METHOD (ISM), A VIRTUAL SPECTROSCOPY METHOD FOR ANALYSIS OF PROTEIN INTERACTIONS BASED ON THEIR STRUCTURE, AND MATHEMATICAL FILTERING IN CROSS SPECTRUM (CS) ANALYSIS IDENTIFIED 14-3-3 SIGMA/C-ABL BINDING SITES. FURTHER INVESTIGATION ON CS PROFILES OF C-ABL- AND P210 BCR-ABL-CONTAINING COMPLEXES REVEALED THE MECHANISM LIKELY INVOLVED 14-3-3 PRECLUDED PHOSPHORYLATION IN CML CELLS. 2009 2 573 34 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 3 1268 47 CYTOPLASMATIC COMPARTMENTALIZATION BY BCR-ABL PROMOTES TET2 LOSS-OF-FUNCTION IN CHRONIC MYELOID LEUKEMIA. THE LOSS-OF-FUNCTION OF TEN-ELEVEN-TRANSLOCATION (TET) 2, A FE(2+) -OXOGLUTARATE-DEPENDENT DIOXYGENASE CATALYZING 5 METHYL CYTOSINE (5MC) CONVERSION INTO 5-HYDROXYMETHYLCYTOSINE (5HMC), CONTRIBUTES TO THE HEMATOPOIETIC TRANSFORMATION IN VIVO. THE AIM OF OUR STUDY WAS TO ELUCIDATE ITS ROLE IN THE PHENOTYPE OF CHRONIC MYELOID LEUKEMIA (CML), A MYELOPROLIFERATIVE DISEASE CAUSED BY THE BCR-ABL REARRANGED GENE. WE FIRST CONFIRMED TET2 INTERACTION WITH THE BCR-ABL PROTEIN PREDICTED BY A FOURIER-BASED BIOINFORMATIC METHOD. SUCH INTERACTION LED TO TET2 CYTOPLASMATIC COMPARTMENTALIZATION IN A COMPLEX TETHERED BY THE FUSION PROTEIN TYROSINE KINASE (TK) AND ENCOMPASSING THE FORKHEAD BOX O3A (FOXO3A) TRANSCRIPTION FACTOR. WE THEN FOCUSED THE IMPACT OF TET2 LOSS-OF-FUNCTION ON EPIGENETIC TRANSCRIPTIONAL REGULATION OF BCL2-INTERACTING MEDIATOR (BIM), A PRO-APOPTOTIC PROTEIN TRANSCRIPTIONALLY REGULATED BY FOXO3A. BIM DOWNREGULATION IS A CRITICAL COMPONENT OF CML PROGENITOR EXTENDED SURVIVAL AND IS ALSO INVOLVED IN THE DISEASE RESISTANCE TO IMATINIB (IM). HERE WE REPORTED THAT TET2 RELEASE FROM BCR-ABL PROTEIN FOLLOWING TK INHIBITION IN RESPONSE TO IM TRIGGERS A CHAIN OF EVENTS INCLUDING TET2 NUCLEAR TRANSLOCATION, RE-ACTIVATION OF ITS ENZYMATIC FUNCTION AT 5MC AND RECRUITMENT AT THE BIM PROMOTER FOLLOWED BY BIM TRANSCRIPTIONAL INDUCTION. 5HMC INCREMENT FOLLOWING TET2 RE-ACTIVATION WAS ASSOCIATED WITH THE REDUCTION OF HISTONE H3 TRI-METHYLATION AT LYSINE 9 (H3K9ME3), WHICH MAY CONTRIBUTE WITH DNA DE-METHYLATION REPORTED ELSEWHERE TO RECAST A PERMISSIVE EPIGENETIC "LANDSCAPE" FOR FOXO3A TRANSCRIPTIONAL ACTIVITY. 2012 4 4741 37 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 5 4388 35 MLL2/KMT2D AND MLL3/KMT2C EXPRESSION CORRELATES WITH DISEASE PROGRESSION AND RESPONSE TO IMATINIB MESYLATE IN CHRONIC MYELOID LEUKEMIA. BACKGROUND: CHRONIC MYELOID LEUKEMIA (CML) IS A CLONAL MYELOPROLIFERATIVE NEOPLASM WHOSE PATHOGENESIS IS LINKED TO THE PHILADELPHIA CHROMOSOME PRESENCE THAT GENERATES THE BCR-ABL1 FUSION ONCOGENE. TYROSINE KINASE INHIBITORS (TKI) SUCH AS IMATINIB MESYLATE (IM) DRAMATICALLY IMPROVED THE TREATMENT EFFICIENCY AND SURVIVAL OF CML PATIENTS BY TARGETING BCR-ABL TYROSINE KINASE. THE DISEASE SHOWS THREE DISTINCT CLINICAL-LABORATORY STAGES: CHRONIC PHASE, ACCELERATED PHASE AND BLAST CRISIS. ALTHOUGH PATIENTS IN THE CHRONIC PHASE RESPOND WELL TO TREATMENT, PATIENTS IN THE ACCELERATED PHASE OR BLAST CRISIS USUALLY SHOW THERAPY RESISTANCE AND CML RELAPSE. IT IS CRUCIAL, THEREFORE, TO IDENTIFY BIOMARKERS TO PREDICT CML GENETIC EVOLUTION AND RESISTANCE TO TKI THERAPY, CONSIDERING NOT ONLY THE EFFECTS OF GENETIC ABERRATIONS BUT ALSO THE ROLE OF EPIGENETIC ALTERATIONS DURING THE DISEASE. ALTHOUGH DYSREGULATIONS IN EPIGENETIC MODULATORS SUCH AS HISTONE METHYLTRASNFERASES HAVE ALREADY BEEN DESCRIBED FOR SOME HEMATOLOGIC MALIGNANCIES, TO DATE VERY LIMITED DATA IS AVAILABLE FOR CML, ESPECIALLY WHEN CONSIDERING THE LYSINE METHYLTRANSFERASE MLL2/KMT2D AND MLL3/KMT2C. METHODS: HERE WE INVESTIGATED THE EXPRESSION PROFILE OF BOTH GENES IN CML PATIENTS IN DIFFERENT STAGES OF THE DISEASE, IN PATIENTS SHOWING DIFFERENT RESPONSES TO THERAPY WITH IM AND IN NON-NEOPLASTIC CONTROL SAMPLES. IMATINIB SENSITIVE AND RESISTANT CML CELL LINES WERE ALSO USED TO INVESTIGATE WHETHER TREATMENT WITH OTHER TYROSINE KINASE INHIBITORS INTERFERED IN THEIR EXPRESSION. RESULTS: IN PATIENTS, BOTH METHYLTRANSFERASES WERE EITHER UPREGULATED OR WITH BASAL EXPRESSION LEVEL DURING THE CHRONIC PHASE COMPARED TO CONTROLS. INTERESTINGLY, MLL3/KMT2C AND SPECIALLY MLL2/KMT2D LEVELS DECREASED DURING DISEASE PROGRESSION CORRELATING WITH DISTINCT CLINICAL STAGES. FURTHERMORE, MLL2/KMT2D WAS DECREASED IN PATIENTS RESISTANT TO IM TREATMENT. A RESCUE IN THE EXPRESSION OF BOTH MLL GENES WAS OBSERVED IN KCL22S, A CML CELL LINE SENSITIVE TO IM, AFTER TREATMENT WITH DASATINIB OR NILOTINIB WHICH WAS ASSOCIATED WITH A HIGHER RATE OF APOPTOSIS, AN ENHANCED EXPRESSION OF P21 (CDKN1A) AND A CONCOMITANT DECREASE IN THE EXPRESSION OF CDK2, CDK4 AND CYCLIN B1 (CCNB1) IN COMPARISON TO UNTREATED KCL22S CONTROL OR IM RESISTANT KCL22R CELL LINE, WHICH SUGGESTS INVOLVEMENT OF P53 REGULATED PATHWAY. CONCLUSION: OUR RESULTS ESTABLISHED A NEW ASSOCIATION BETWEEN MLL2/KMT2D AND MLL3/KMT2C GENES WITH CML AND SUGGEST THAT MLL2/KMT2D IS ASSOCIATED WITH DISEASE EVOLUTION AND MAY BE A POTENTIAL MARKER TO PREDICT THE DEVELOPMENT OF THERAPY RESISTANCE. 2018 6 3352 24 HISTONE DEMETHYLASE RBP2 MEDIATES THE BLAST CRISIS OF CHRONIC MYELOID LEUKEMIA THROUGH AN RBP2/PTEN/BCR-ABL CASCADE. EPIGENETIC DISORDERS PLAY A KEY ROLE IN TUMORIGENESIS AND DEVELOPMENT, AMONG WHICH HISTONE METHYLATION ABNORMALITIES ARE COMMON. WHILE PATIENTS LIVING WITH CHRONIC MYELOID LEUKEMIA IN THE CHRONIC PHASE (CML-CP) HAVE A GOOD RESPONSE TO TKI, BLASTIC PHASE (CML-BP) PATIENTS DEMONSTRATE POOR EFFICACY AND HIGH FATALITY RATES. HOWEVER, WHILE THE MECHANISM OF BLAST CRISIS OF CHRONIC MYELOID LEUKEMIA REMAINS UNCLEAR, HIGH EXPRESSION AND ACTIVATION OF BCR-ABL ARE USUALLY RELATED TO CML BLAST CRISIS TRANSITION. WE FOUND THAT HISTONE H3 LYSINE 4 (H3K4) DEMETHYLASE RBP2 EXPRESSION IS NEGATIVELY CORRELATED WITH BCR-ABL EXPRESSION, WHICH SUGGESTS A REGULATORY LINK BETWEEN THESE TWO GENES. WE ALSO DISCOVERED THAT RBP2 MEDIATES THE DEPHOSPHORYLATION OF BCR-ABL BY DIRECTLY DOWNREGULATING PTEN EXPRESSION, DEPENDING ON HISTONE DEMETHYLASE ACTIVITY, WHILE PTEN TARGETS PROTEIN PHOSPHATASE ACTIVITY OF BCR-ABL, A PHOSPHATASE WHICH DIRECTLY DEPHOSPHORYLATES BCR-ABL. IN CLINICAL SPECIMENS, THE MRNA EXPRESSION OF RBP2 WAS FOUND TO BE POSITIVELY CORRELATED WITH THAT OF PTEN. THESE DATA SUGGEST THAT THE UNDER-EXPRESSION OF RBP2 PROMOTES BLAST CRISIS TRANSITION BY ACTIVATING AN RBP2/PTEN/BCR-ABL CASCADE. 2019 7 3982 30 LONG-TERM EXPOSURE OF LEUKEMIA CELLS TO MULTI-TARGETED TYROSINE KINASE INHIBITOR INDUCES ACTIVATIONS OF AKT, ERK AND STAT5 SIGNALING VIA EPIGENETIC SILENCING OF THE PTEN GENE. IMATINIB INDUCES COMPLETE MOLECULAR RESPONSE IN PATIENTS WITH CHRONIC MYELOID LEUKEMIA (CML) AND CHRONIC EOSINOPHILIC LEUKEMIA (CEL). HOWEVER, DEVELOPMENT OF RESISTANCE TO IMATINIB HAS EMERGED AS AN IMPORTANT CLINICAL PROBLEM FOR MOLECULAR-TARGETED THERAPY IN CML AND CEL. IN THIS STUDY, WE HAVE ESTABLISHED THE IMATINIB-RESISTANT CEL EOL-1 SUB-LINES (DESIGNATED AS EOL-1R) BY CULTURING CELLS WITH INCREASING CONCENTRATIONS OF IMATINIB FOR 6 MONTHS. INTERESTINGLY, EOL-1R CELLS SHOWED EPIGENETIC SILENCING OF THE PHOSPHATASE AND TENSIN HOMOLOG DELETED ON CHROMOSOME TEN (PTEN) GENE. EXPOSURE OF EOL-1R CELLS TO IMATINIB FAILED TO DEPHOSPHORYLATE AKT, ERK AND STAT5, ALTHOUGH PDGFRALPHA WAS EFFECTIVELY INACTIVATED. THE FORCED EXPRESSION OF PTEN NEGATIVELY REGULATED THESE SIGNAL PATHWAYS AND SENSITIZED EOL-1R CELLS TO IMATINIB. NOTABLY, HYPERMETHYLATION OF THE PROMOTER REGION OF THE PTEN GENE IN ASSOCIATION WITH THE DOWNREGULATION OF THIS GENE'S TRANSCRIPTS WAS IDENTIFIED IN IMATINIB-RESISTANT LEUKEMIA CELLS ISOLATED FROM INDIVIDUALS WITH CEL, CML AND PHILADELPHIA-POSITIVE ACUTE LYMPHOBLASTIC LEUKEMIA. IN ADDITION, ANTI-EPIGENETIC AGENTS RESTORED PTEN EXPRESSION, RESULTING IN THE SENSITIZATION OF EOL-1R CELLS TO IMATINIB. TAKEN TOGETHER, EPIGENETIC SILENCE OF PTEN IS ONE OF THE MECHANISMS THAT CAUSE DRUG RESISTANCE IN INDIVIDUALS WITH LEUKEMIA AFTER EXPOSURE TO IMATINIB. ANTI-EPIGENETIC AGENTS MAY BE USEFUL FOR OVERCOMING DRUG RESISTANCE IN SUCH A CASE. 2010 8 4877 26 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 9 139 26 ABERRANT DNA METHYLATION IS ASSOCIATED WITH DISEASE PROGRESSION, RESISTANCE TO IMATINIB AND SHORTENED SURVIVAL IN CHRONIC MYELOGENOUS LEUKEMIA. THE EPIGENETIC IMPACT OF DNA METHYLATION IN CHRONIC MYELOGENOUS LEUKEMIA (CML) IS NOT COMPLETELY UNDERSTOOD. TO ELUCIDATE ITS ROLE WE ANALYZED 120 PATIENTS WITH CML FOR METHYLATION OF PROMOTER-ASSOCIATED CPG ISLANDS OF 10 GENES. FIVE GENES WERE IDENTIFIED BY DNA METHYLATION SCREENING IN THE K562 CELL LINE AND 3 GENES IN PATIENTS WITH MYELOPROLIFERATIVE NEOPLASMS. THE CDKN2B GENE WAS SELECTED FOR ITS FREQUENT METHYLATION IN MYELOID MALIGNANCIES AND ABL1 AS THE TARGET OF BCR-ABL TRANSLOCATION. THIRTY PATIENTS WERE IMATINIB-NAIVE (MOSTLY TREATED BY INTERFERON-ALPHA BEFORE THE IMATINIB ERA), 30 WERE IMATINIB-RESPONSIVE, 50 WERE IMATINIB-RESISTANT, AND 10 WERE IMATINIB-INTOLERANT. WE QUANTIFIED DNA METHYLATION BY BISULFITE PYROSEQUENCING. THE AVERAGE NUMBER OF METHYLATED GENES WAS 4.5 PER PATIENT IN THE CHRONIC PHASE, INCREASING SIGNIFICANTLY TO 6.2 IN THE ACCELERATED AND 6.4 IN THE BLASTIC PHASE. HIGHER NUMBERS OF METHYLATED GENES WERE ALSO OBSERVED IN PATIENTS RESISTANT OR INTOLERANT TO IMATINIB. THESE PATIENTS ALSO SHOWED ALMOST EXCLUSIVE METHYLATION OF A PUTATIVE TRANSPORTER OSCP1. ABNORMAL METHYLATION OF A SRC SUPPRESSOR GENE PDLIM4 WAS ASSOCIATED WITH SHORTENED SURVIVAL INDEPENDENTLY OF CML STAGE AND IMATINIB RESPONSIVENESS. WE CONCLUDE THAT ABERRANT DNA METHYLATION IS ASSOCIATED WITH CML PROGRESSION AND THAT DNA METHYLATION COULD BE A MARKER ASSOCIATED WITH IMATINIB RESISTANCE. FINALLY, DNA METHYLATION OF PDLIM4 MAY HELP IDENTIFY A SUBSET OF CML PATIENTS THAT WOULD BENEFIT FROM TREATMENT WITH SRC/ABL INHIBITORS. 2011 10 5924 29 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 2128 28 EPIGENETIC INACTIVATION OF PLCD1 IN CHRONIC MYELOID LEUKEMIA. PHOSPHOLIPASE C DELTA1 (PLCD1), IS LOCATED AT THE IMPORTANT TUMOR SUPPRESSOR LOCUS 3P22. IT ENCODES AN ENZYME THAT MEDIATES REGULATORY SIGNALING OF ENERGY METABOLISM, CALCIUM HOMEOSTASIS AND INTRACELLULAR MOVEMENTS. PLCD1 HAS BEEN STUDIED IN SOME HUMAN SOLID TUMORS RELATING TO THE CPG ISLAND METHYLATION OF THE GENE PROMOTER AS A FUNCTIONAL TUMOR SUPPRESSOR. HOWEVER, NO SUCH INFORMATION IS AVAILABLE IN CHRONIC MYELOID LEUKEMIA (CML). IN THIS STUDY, WE INVESTIGATED PLCD1 EXPRESSION IN THE CML K562 CELL LINE (0/1) AND 15% (2/13) OF BONE MARROW MONONUCLEAR CELLS WITH CML BY USING SEMI-QUANTITATIVE PCR. THE CPG ISLAND (CGI) METHYLATION STATUS OF THE PLCD1 PROMOTER WAS DETECTED IN K562 (0/1) AND 56% (23/41) OF CML PATIENTS BY METHYLATION-SPECIFIC PCR (MSP), BUT NOT IN THE NORMAL ADULT BONE MARROW MONONUCLEAR CELLS. FURTHERMORE, THE DNA DEMETHYLATION AGENT 5'-AZA-2'DEOXYCYTIDINE RESTORED THE EXPRESSION OF PLCD1 IN K562 CELLS. FUNCTIONAL STUDIES SHOWED THAT ECTOPIC EXPRESSION OF PLCD1 IN K562 CELLS WAS ABLE TO DRAMATICALLY INHIBIT THEIR COLONY FORMATION AND INDUCE CELL CYCLE G1 ARREST, SUGGESTING THAT PLCD1 ACTS AS A FUNCTIONAL TUMOR SUPPRESSOR AND MAY SERVE AS A BIOMARKER FOR POSSIBLE EARLY DETECTION AND PROGNOSIS OF CML. 2012 12 5669 24 SFRP1 PROMOTER METHYLATION IS ASSOCIATED WITH PERSISTENT PHILADELPHIA CHROMOSOME IN CHRONIC MYELOID LEUKEMIA. EPIGENETIC SILENCING OF SFRP GENES HAS BEEN SHOWN TO LEAD TO CONSTITUTIVE ACTIVATION OF THE CANONICAL WNT-SIGNALING PATHWAY. THE FIRST DESCRIPTION OF DEREGULATED WNT-SIGNALING ACTIVATION IN A HEMATOLOGICAL MALIGNANCY WAS REPORTED IN CHRONIC MYELOID LEUKEMIA (CML). TO INVESTIGATE WHETHER EPIGENETIC SILENCING OF SFRP IS RESPONSIBLE FOR THE OBSERVED WNT ACTIVATION IN CML, WE STUDIED THE METHYLATION AND MUTATIONAL STATUS OF THE SFRP1 PROMOTER IN 48 CHRONIC PHASE CML PATIENTS. OF THE 48 CML PATIENTS 41 WERE SHOWN TO BE UNMETHYLATED, 6 PATIENTS HEMI-METHYLATED AND 1 PATIENT FULLY METHYLATED AT THE SFRP1 PROMOTER. ALBEIT OBSERVED INFREQUENTLY IN CHRONIC PHASE CML, SFRP1 PROMOTER METHYLATION CORRELATED WITH PRIMARY CYTOGENETIC RESISTANCE TO IMATINIB MESYLATE. SFRP1 PROMOTER METHYLATION MAY INDICATE A GENETICALLY MORE UNSTABLE FORM OF DISEASE RESISTANT TO THERAPY AND PROVIDE A KEY BIOLOGICAL DIFFERENCE IN THERAPY RESISTANT PATIENTS, IN ADDITION TO A POSSIBLE MECHANISM FOR THE OBSERVED ACTIVATION OF CANONICAL WNT SIGNALING IN CML. 2009 13 3530 30 IMATINIB (ST1571) PROVIDES ONLY LIMITED SELECTIVITY FOR CML CELLS AND TREATMENT MIGHT BE COMPLICATED BY SILENT BCR-ABL GENES. VERY PROMISING RESULTS HAVE BEEN OBTAINED IN CLINICAL TRIALS ON CHRONIC-PHASE CHRONIC MYELOID LEUKEMIA (CP-CML) PATIENTS TREATED WITH IMATINIB MESYLATE (IM; GLEEVECR, STI571), A BCR-ABL TYROSINE KINASE INHIBITOR. HOWEVER, WE FOUND THAT IM CAUSED CONSIDERABLE INHIBITION OF NORMAL HEMATOPOIETIC PROGENITOR CELLS UPON TREATING CONTROL BONE MARROW (BM) CULTURES. IN VITRO IM TREATMENT GAVE A DECREASE IN THE YIELD AND SIZE OF COLONIES FROM BM OF UNTREATED CP-CML PATIENTS THAT WAS ONLY TWO TO THREE TIMES THAT FROM THE NORMAL SAMPLES. MOREOVER, ABOUT 30% OF MYELOID PROGENITORS (CFU-GM) FROM CML BM STILL FORMED COLONIES IN THE PRESENCE OF IM, MOST OF WHICH HAD BCR-ABL RNA. ABOUT HALF OF THESE TREATED COLONIES ALSO DISPLAYED METHYLATION OF THE INTERNAL ABL PA PROMOTER, A CML-SPECIFIC EPIGENETIC ALTERATION, WHICH WAS USED IN THIS STUDY AS A MARKER FOR BCR-ABL TRANSLOCATION-CONTAINING CELLS. HOWEVER, ~5-8% OF THE TREATED OR THE UNTREATED CML BM-DERIVED COLONIES HAD NO DETECTABLE BCR-ABL RNA BY TWO OR THREE ROUNDS OF RT-PCR DESPITE BEING POSITIVE FOR THE INTERNAL STANDARD RNA AND DISPLAYING HALLMARKS OF CML, EITHER T(9;22)(Q34;QL 1) OR ABL PA METHYLATION. OUR RESULTS INDICATE THAT IM IS ONLY PARTIALLY SPECIFIC FOR CML PROGENITOR CELLS COMPARED TO NORMAL HEMATOPOIETIC PROGENITOR CELLS AND SUGGEST THAT SOME CML CELLS MAY HAVE A SILENT BCR-ABL ONCOGENE THAT COULD INTERFERE WITH THERAPY. 2003 14 6402 22 THE ROLES OF EPIGENETIC MODIFICATIONS OF PROAPOPTOTIC BID AND BIM GENES IN IMATINIB-RESISTANT CHRONIC MYELOID LEUKEMIA CELLS. IN CHRONIC MYELOID LEUKEMIA (CML), EPIGENETIC MODIFICATIONS SUCH AS PROMOTER HYPERMETHYLATION AND INACTIVE HISTONE MODIFICATION ARE KNOWN MECHANISMS OF DRUG RESISTANCE. IN OUR STUDY, WE INVESTIGATED THE ROLES OF PROMOTER HYPERMETHYLATION OF BIM AND BID GENES AND H3K27ME3 HISTONE MODIFICATION ON IMATINIB RESISTANCE. WE DETECTED HIGHER EXPRESSION LEVELS OF BIM AND BID GENES AND LOWER EXPRESSION LEVELS OF EZH2, EED2, SIRT1, AND SUZ12 GENES IN IMATINIB-RESISTANT K562/IMA-3 CELLS COMPARED TO IMATINIB-NON-RESISTANT K562 CELLS. WHILE WE DETERMINED THE EZH2 AND DNMT ENZYMES AS BOUNDED TO THE PROMOTER OF THE BIM GENE, WE DID NOT DETECT HYPERMETHYLATION OF THIS PROMOTER. WE ALSO FOUND THE H3K27ME3 HISTONE MODIFICATION PROMOTER OF BIM AND BID GENES IN BOTH CELL LINES. IN CONCLUSION, OUR RESULTS SUPPORT THE NOTION THAT DNA PROMOTER METHYLATION MAY BE FORMED INDEPENDENTLY FROM EZH2-H3K27ME3 AND PRO-APOPTOTIC BIM AND BID GENES ARE NOT METHYLLATED IN THE IMATINIB RESISTANCE OF CML CELLS. 2013 15 1234 29 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 16 162 23 ABL1 METHYLATION IN PH-POSITIVE ALL IS EXCLUSIVELY ASSOCIATED WITH THE P210 FORM OF BCR-ABL. IN HUMAN PH-POSITIVE LEUKEMIA THERE IS A CLEAR ASSOCIATION OF DIFFERENT FORMS OF THE BCR-ABL ONCOGENE WITH DISTINCT TYPES OF LEUKEMIA. THE P190 FORM OF BCR-ABL IS RARELY OBSERVED IN CHRONIC MYELOID LEUKEMIA (CML) BUT IS PRESENT IN 50% OF PH-POSITIVE ACUTE LYMPHOBLASTIC LEUKEMIA (ALL). IN CONTRAST, THE P210 FORM IS OBSERVED BOTH IN CML AND 50% OF PH-POSITIVE ALL. METHYLATION OF THE PROXIMAL PROMOTER OF THE ABL1 GENE HAS BEEN SHOWN TO BE A NEARLY UNIVERSAL EVENT ASSOCIATED WITH CLINICAL PROGRESSION OF CML. THIS RAISES THE QUESTION OF WHETHER METHYLATION OF THE ABL1 PROMOTER IS AN EPIGENETIC MODIFICATION ALSO ASSOCIATED WITH PH-POSITIVE ALL. TO STUDY THIS ISSUE, WE USED METHYLATION-SPECIFIC PCR AND BISULFITE SEQUENCING TO DETERMINE THE METHYLATION STATUS OF THE ABL1 PROMOTER IN 18 PH-POSITIVE ALL SAMPLES. WE REPORT HERE THAT GENE-SPECIFIC ABL1 PROMOTER METHYLATION IS ASSOCIATED MAINLY WITH THE P210 FORM OF BCR-ABL AND NOT THE P190 FORM. WHILE SIX OUT OF THE SEVEN P210-POSITIVE ALL SAMPLES HAD ABL1 PROMOTER METHYLATION, NONE OF THE 11 P190-POSITIVE ALL SAMPLES DEMONSTRATED ABL1 PROMOTER METHYLATION. IN ADDITION, WE ESTIMATED THE EXTENT AND RELATIVE ABUNDANCE OF ABL1 PROMOTER METHYLATION IN SEVERAL PH-POSITIVE ALL SAMPLES AND COMPARED IT TO THE METHYLATION PATTERN IN CHRONIC, ACCELERATED AND BLASTIC CRISIS PHASES OF CML. WE PUT FORTH A MODEL THAT CORRELATES THE DIFFERENT TYPES OF LEUKEMIAS WITH THE DIFFERENT LEVELS OF ABL1 PROMOTER METHYLATION. 2001 17 5861 30 SUPER-ENHANCER LANDSCAPE REVEALS LEUKEMIA STEM CELL RELIANCE ON X-BOX BINDING PROTEIN 1 AS A THERAPEUTIC VULNERABILITY. RELAPSE OF PATIENTS WITH CHRONIC MYELOGENOUS LEUKEMIA (CML) MAY OCCUR AT LEAST PARTIALLY BECAUSE LEUKEMIA STEM CELLS (LSCS) LACK SENSITIVITY TO TYROSINE KINASE INHIBITORS (TKIS) SUCH AS IMATINIB. THE PRECISE REGULATION OF LSC STEMNESS IS INCOMPLETELY UNDERSTOOD. GIVEN THAT TRAITS OF LSCS ARE SUBJECT TO EPIGENETIC REGULATION, WE HYPOTHESIZED THAT LSCS MIGHT BE DEPENDENT ON CONTINUOUS ACTIVE TRANSCRIPTION OF GENES ASSOCIATED WITH SUPER-ENHANCERS (SES), WHICH MIGHT, IN TURN, SUGGEST AN OPPORTUNITY FOR INTERVENTION. IN THIS STUDY, WE TESTED THIS HYPOTHESIS AND DELINEATED THE SE LANDSCAPE IN LSCS FROM PATIENTS WITH CML. DISRUPTION OF THE SE-ASSOCIATED GENE TRANSCRIPTION BY THZ1, A COVALENT CYCLIN-DEPENDENT KINASE 7 (CDK7) INHIBITOR, EFFICIENTLY ERADICATED LSCS IN RETROVIRAL BCR-ABL-DRIVEN CML MICE WHILE SPARING NORMAL HEMATOPOIETIC STEM CELLS. FURTHERMORE, WE FOUND THAT X-BOX BINDING PROTEIN 1 (XBP1), A SUBSTRATE OF MRNA-SPLICING ENDONUCLEASE IRE1ALPHA IN THE UNFOLDED PROTEIN RESPONSE PATHWAY, WAS AN SE-ASSOCIATED ONCOGENE IN LSCS. KNOCKDOWN OF XBP1 REDUCED SURVIVAL AND SELF-RENEWAL CAPACITY IN PRIMARY CML CD34(+) CELLS AND ERADICATED LSCS IN CML MICE. SELECTIVELY BLOCKING GENERATION OF THE SPLICED FORM OF XBP1 BY HEMATOPOIETIC CELL-SPECIFIC IRE1 CONDITIONAL KNOCKOUT SUPPRESSED THE PROGRESSION OF CML AND IMPAIRED THE LEUKEMOGENESIS OF LSCS IN CML MICE. OVERALL, WE IDENTIFIED AN EPIGENETIC TRANSCRIPTIONAL PROGRAM IN LSCS, ADDING TO EVIDENCE FOR THE THEORY OF "ONCOGENE ADDICTION" AND SUGGESTING A POTENTIAL TARGETING STRATEGY FOR CML. 2021 18 1669 25 DOWNREGULATION OF THE HISTONE METHYLTRANSFERASE SETD2 PROMOTES IMATINIB RESISTANCE IN CHRONIC MYELOID LEUKAEMIA CELLS. OBJECTIVES: EPIGENETIC MODIFIERS WERE IMPORTANT PLAYERS IN THE DEVELOPMENT OF HAEMATOLOGICAL MALIGNANCIES AND SENSITIVITY TO THERAPY. MUTATIONS OF SET DOMAIN-CONTAINING 2 (SETD2), A METHYLTRANSFERASE THAT CATALYSES THE TRIMETHYLATION OF HISTONE 3 ON LYSINE 36 (H3K36ME3), WERE FOUND IN VARIOUS MYELOID MALIGNANCIES. HOWEVER, THE DETAILED MECHANISMS THROUGH WHICH SETD2 CONFERS CHRONIC MYELOID LEUKAEMIA PROGRESSION AND RESISTANCE TO THERAPY TARGETING ON BCR-ABL REMAIN UNCLEAR. MATERIALS AND METHODS: THE LEVEL OF SETD2 IN IMATINIB-SENSITIVE AND IMATINIB-RESISTANT CHRONIC MYELOID LEUKAEMIA (CML) CELLS WAS EXAMINED BY IMMUNOBLOTTING AND QUANTITATIVE REAL-TIME PCR. WE ANALYSED CD34(+) CD38(-) LEUKAEMIC STEM CELLS BY FLOW CYTOMETRY AND COLONY FORMATION ASSAYS UPON SETD2 KNOCKDOWN OR OVEREXPRESSION. THE IMPACT OF SETD2 EXPRESSION ALTERATIONS OR SMALL-MOLECULE INHIBITOR JIB-04 TARGETING H3K36ME3 LOSS ON IMATINIB SENSITIVITY WAS ASSESSED BY IC50, CELL APOPTOSIS AND PROLIFERATION ASSAYS. FINALLY, RNA SEQUENCING AND CHIP-QUANTITATIVE PCR WERE PERFORMED TO VERIFY PUTATIVE DOWNSTREAM TARGETS. RESULTS: SETD2 WAS FOUND TO ACT AS A TUMOUR SUPPRESSOR IN CML. THE NOVEL ONCOGENIC TARGETS MYCN AND ERG WERE SHOWN TO BE THE DIRECT DOWNSTREAM TARGETS OF SETD2, WHERE THEIR OVEREXPRESSION INDUCED BY SETD2 KNOCKDOWN CAUSED IMATINIB INSENSITIVITY AND LEUKAEMIC STEM CELL ENRICHMENT IN CML CELL LINES. TREATMENT WITH JIB-04, AN INHIBITOR THAT RESTORES H3K36ME3 LEVELS THROUGH BLOCKADE OF ITS DEMETHYLATION, SUCCESSFULLY IMPROVED THE CELL IMATINIB SENSITIVITY AND ENHANCED THE CHEMOTHERAPEUTIC EFFECT. CONCLUSIONS: OUR STUDY NOT ONLY EMPHASIZES THE REGULATORY MECHANISM OF SETD2 IN CML, BUT ALSO PROVIDES PROMISING THERAPEUTIC STRATEGIES FOR OVERCOMING THE IMATINIB RESISTANCE IN PATIENTS WITH CML. 2019 19 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 20 690 27 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