1 4741 177 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 2 3615 27 IN VITRO FOLATE DEFICIENCY INDUCES DEOXYNUCLEOTIDE POOL IMBALANCE, APOPTOSIS, AND MUTAGENESIS IN CHINESE HAMSTER OVARY CELLS. THE GENETIC AND EPIGENETIC EFFECTS OF NUTRITIONAL FOLATE DEFICIENCY WERE STUDIED IN TWO CHINESE HAMSTER OVARY (CHO) CELL LINES. THE CHO-AA8 CELL LINE (HEMIZYGOUS AT THE APRT LOCUS) AND CHO-UV5 (DNA REPAIR-DEFICIENT MUTANT OF AA8) WERE CULTURED IN HAM'S F-12 MEDIUM OR IN CUSTOM-PREPARED HAM'S F-12 MEDIUM LACKING FOLIC ACID, THYMIDINE, AND HYPOXANTHINE. CELLS CULTURED ACUTELY IN THE FOLATE DEFICIENT MEDIUM EXHIBITED INITIAL GROWTH ARREST, FOLLOWED BY MASSIVE CELL DEATH AND DNA FRAGMENTATION INTO NUCLEOSOMAL MULTIMERS CHARACTERISTIC OF APOPTOSIS. ALTHOUGH PROLONGED CULTURE IN THE FOLATE DEFICIENT MEDIUM WAS CYTOSTATIC AND LETHAL TO THE MAJORITY CELLS, MINOR SUBPOPULATIONS IN BOTH CELL LINES FAILED TO INITIATE CELL DEATH, EXHIBITED PHENOTYPIC ABNORMALITIES, AND ADAPTED A SELECTIVE GROWTH ADVANTAGE UNDER MARGINAL FOLATE CONDITIONS. THESE "RESISTANT" CLONES EXHIBITED MAJOR ALTERATIONS IN DEOXYNUCLEOTIDE POOLS ASSOCIATED WITH AN INCREASE IN MUTANT FREQUENCY AT THE APRT LOCUS AS DETECTED BY RESISTANCE TO CYTOTOXICITY IN 8-AZAADENOSINE. THE MUTATION FREQUENCY IN THE DNA REPAIR-DEFICIENT CHO-UV5 CELLS WAS APPROXIMATELY 100-FOLD GREATER THAN THAT IN THE PARENTAL AA8 CLONES, UNDERSCORING THE IMPORTANCE OF DNA REPAIR UNDER CONDITIONS OF FOLATE DEFICIENCY AND NUCLEOTIDE POOL IMBALANCE. THE ENHANCED MUTATION FREQUENCY IN THE DNA REPAIR-COMPETENT FOLATE-DEFICIENT CHO-AA8 CELLS SUGGESTS THAT DNA REPAIR ACTIVITY IS LESS EFFECTIVE UNDER FOLATE-DEFICIENT CONDITIONS. THESE RESULTS ADD TO THE ACCUMULATING CLINICAL AND EXPERIMENTAL EVIDENCE RELATING CHRONIC FOLATE DEFICIENCY TO GENOMIC INSTABILITY AND CARCINOGENESIS. 1994 3 5319 46 PTEN IS FUNDAMENTAL FOR ELIMINATION OF LEUKEMIA STEM CELLS MEDIATED BY GSK126 TARGETING EZH2 IN CHRONIC MYELOGENOUS LEUKEMIA. PURPOSE: LEUKEMIA STEM CELLS (LSCS) ARE AN IMPORTANT SOURCE OF TYROSINE KINASE INHIBITOR RESISTANCE AND DISEASE RELAPSE IN PATIENTS WITH CHRONIC MYELOGENOUS LEUKEMIA (CML). TARGETING LSCS MAY BE AN ATTRACTIVE STRATEGY TO OVERRIDE THIS THORNY PROBLEM. GIVEN THAT EZH2 WAS OVEREXPRESSED IN PRIMARY CML CD34(+) CELLS, OUR PURPOSE IN THIS STUDY WAS TO EVALUATE THE EFFECTS OF TARGETING EZH2 ON CML LSCS AND CLARIFY ITS UNDERLYING MECHANISM.EXPERIMENTAL DESIGN: HUMAN PRIMARY CML CD34(+) CELLS AND RETROVIRALLY BCR-ABL-DRIVEN CML MOUSE MODELS WERE EMPLOYED TO EVALUATE THE EFFECTS OF SUPPRESSION OF EZH2 BY GSK126- OR EZH2-SPECIFIC SHRNA IN VITRO AND IN VIVO RECRUITMENT OF EZH2 AND H3K27ME3 ON THE PROMOTER OF TUMOR-SUPPRESSOR GENE PTEN IN CML CELLS WAS MEASURED BY CHROMATIN IMMUNOPRECIPITATION ASSAY.RESULTS: OUR RESULTS SHOWED THAT PHARMACOLOGIC INHIBITION OF EZH2 BY GSK126 NOT ONLY ELICITED APOPTOSIS AND RESTRICTED CELL GROWTH IN CML BULK LEUKEMIA CELLS, BUT ALSO DECREASED LSCS IN CML CD34(+) CELLS WHILE SPARING THOSE FROM NORMAL BONE MARROW CD34(+) CELLS. SUPPRESSION OF EZH2 BY GSK126 OR SPECIFIC SHRNA PROLONGED SURVIVAL OF CML MICE AND REDUCED THE NUMBER OF LSCS IN MICE. EZH2 KNOCKDOWN RESULTED IN ELEVATION OF PTEN AND LED TO IMPAIRED RECRUITMENT OF EZH2 AND H3K27ME3 ON THE PROMOTER OF PTEN GENE. THE EFFECT OF EZH2 KNOCKDOWN IN THE CML MICE WAS AT LEAST PARTIALLY REVERSED BY PTEN KNOCKDOWN.CONCLUSIONS: THESE FINDINGS IMPROVE THE UNDERSTANDING OF THE EPIGENETIC REGULATION OF STEMNESS IN CML LSCS AND WARRANT CLINICAL TRIAL OF GSK126 IN REFRACTORY PATIENTS WITH CML. CLIN CANCER RES; 24(1); 145-57. (C)2017 AACR. 2018 4 2402 58 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 5 5934 39 TARGETING FEATURES OF CURAXIN CBL0137 ON HEMATOLOGICAL MALIGNANCIES IN VITRO AND IN VIVO. THE ANTICANCER ACTIVITY OF CURAXIN CBL0137, A DNA-BINDING SMALL MOLECULE WITH CHROMATIN REMODULATING EFFECT, HAS BEEN DEMONSTRATED IN DIFFERENT CANCERS. HEREIN, A COMPARATIVE EVALUATION OF CBL0137 ACTIVITY WAS PERFORMED IN RESPECT TO ACUTE MYELOID LEUKEMIA (AML), ACUTE LYMPHOBLASTIC LEUKEMIA (ALL), CHRONIC MYELOID LEUKEMIA AND MULTIPLE MYELOMA (MM) CULTURED IN VITRO. MTT ASSAY SHOWED AML AND MM HIGHER SENSITIVITY TO CBL0137'S CYTOSTATIC EFFECT COMPARATIVELY TO OTHER HEMATOLOGICAL MALIGNANCY CELLS. FLOW CYTOMETRY CELL CYCLE ANALYSIS REVEALED AN INCREASE IN SUBG1 AND G2/M POPULATIONS AFTER CBL0137 CELL TREATMENT, BUT THE PREVALENT TYPE OF ARREST VARIED. APOPTOSIS ACTIVATION BY CBL0137 MEASURED BY ANNEXIN-V/PI DUAL STAINING WAS MORE ACTIVE IN AML AND MM CELLS. RT2 PCR ARRAY SHOWED THAT CHANGES CAUSED BY CBL0137 IN SIGNALING PATHWAYS INVOLVED IN CANCER PATHOGENESIS WERE MORE INTENSIVE IN AML AND MM CELLS. ON THE MURINE MODEL OF AML WEHI-3, CBL0137 SHOWED SIGNIFICANT ANTICANCER EFFECTS IN VIVO, WHICH WERE EVALUATED BY CORRESPONDING CHANGES IN SPLEEN AND LIVER. THUS, MORE PRONOUNCED ANTICANCER EFFECTS OF CBL0137 IN VITRO WERE OBSERVED IN RESPECT TO AML AND MM. EXPERIMENTS IN VIVO ALSO INDICATED THE PERSPECTIVE OF CBL0137 USE FOR AML TREATMENT. THIS IN ACCORDANCE WITH THE FRONTLINE TREATMENT APPROACH IN AML USING EPIGENETIC DRUGS. 2023 6 3877 44 KDM6A PROMOTES IMATINIB RESISTANCE THROUGH YY1-MEDIATED TRANSCRIPTIONAL UPREGULATION OF TRKA INDEPENDENTLY OF ITS DEMETHYLASE ACTIVITY IN CHRONIC MYELOGENOUS LEUKEMIA. RATIONALE: DESPITE LANDMARK THERAPY OF CHRONIC MYELOGENOUS LEUKEMIA (CML) WITH TYROSINE KINASE INHIBITORS (TKIS), DRUG RESISTANCE REMAINS PROBLEMATIC. CANCER PATHOGENESIS INVOLVES EPIGENETIC DYSREGULATION AND IN PARTICULAR, HISTONE LYSINE DEMETHYLASES (KDMS) HAVE BEEN IMPLICATED IN TKI RESISTANCE. WE SOUGHT TO IDENTIFY KDMS WITH ALTERED EXPRESSION IN CML AND DEFINE THEIR CONTRIBUTION TO IMATINIB RESISTANCE. METHODS: BIOINFORMATICS SCREENING COMPARED KDM EXPRESSION IN CML VERSUS NORMAL BONE MARROW WITH SHRNA KNOCKDOWN AND FLOW CYTOMETRY USED TO MEASURE EFFECTS ON IMATINIB-INDUCED APOPTOSIS IN K562 CELLS. TRANSCRIPTOMIC ANALYSES WERE PERFORMED AGAINST KDM6A CRISPR KNOCKOUT/SHRNA KNOCKDOWN K562 CELLS ALONG WITH GENE RESCUE EXPERIMENTS USING WILDTYPE AND MUTANT DEMETHYLASE-DEAD KDM6A CONSTRUCTS. CO-IMMUNOPRECIPITATION, LUCIFERASE REPORTER AND CHIP WERE EMPLOYED TO ELUCIDATE MECHANISMS OF KDM6A-DEPENDENT RESISTANCE. RESULTS: AMONGST FIVE KDMS UPREGULATED IN CML, ONLY KDM6A DEPLETION SENSITIZED CML CELLS TO IMATINIB-INDUCED APOPTOSIS. RE-INTRODUCTION OF DEMETHYLASE-DEAD KDM6A AS WELL AS WILD-TYPE KDM6A RESTORED IMATINIB RESISTANCE. RNA-SEQ IDENTIFIED NTRK1 GENE DOWNREGULATION AFTER DEPLETION OF KDM6A. MOREOVER, NTRK1 EXPRESSION POSITIVELY CORRELATED WITH KDM6A IN A SUBSET OF CLINICAL CML SAMPLES AND KDM6A KNOCKDOWN IN FRESH CML ISOLATES DECREASED NTRK1 ENCODED PROTEIN (TRKA) EXPRESSION. MECHANISTICALLY, KDM6A WAS RECRUITED TO THE NTRK1 PROMOTER BY THE TRANSCRIPTION FACTOR YY1 WITH SUBSEQUENT TRKA UPREGULATION ACTIVATING DOWN-STREAM SURVIVAL PATHWAYS TO INVOKE IMATINIB RESISTANCE. CONCLUSION: CONTRARY TO ITS REPORTED ROLE AS A TUMOR SUPPRESSOR AND INDEPENDENT OF ITS DEMETHYLASE FUNCTION, KDM6A PROMOTES IMATINIB-RESISTANCE IN CML CELLS. THE IDENTIFICATION OF THE KDM6A/YY1/TRKA AXIS AS A NOVEL IMATINIB-RESISTANCE MECHANISM REPRESENTS AN UNEXPLORED AVENUE TO OVERCOME TKI RESISTANCE IN CML. 2021 7 5940 51 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 8 690 39 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 9 3982 39 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 10 2189 48 EPIGENETIC MECHANISMS UNDERLYING THE THERAPEUTIC EFFECTS OF HDAC INHIBITORS IN CHRONIC MYELOID LEUKEMIA. CHRONIC MYELOID LEUKEMIA (CML) IS A HEMATOLOGICAL DISORDER CAUSED BY THE ONCOGENIC BCR-ABL FUSION PROTEIN IN MORE THAN 90% OF PATIENTS. DESPITE THE STRIKING IMPROVEMENTS IN THE MANAGEMENT OF CML PATIENTS SINCE THE INTRODUCTION OF TYROSINE KINASE INHIBITORS (TKIS), THE APPEARANCE OF TKI RESISTANCE AND SIDE EFFECTS LEAD TO TREATMENT FAILURE, JUSTIFYING THE NEED OF NOVEL THERAPEUTIC APPROACHES. HISTONE DEACETYLASE INHIBITORS (HDACIS), ABLE TO MODULATE GENE EXPRESSION PATTERNS AND IMPORTANT CELLULAR SIGNALING PATHWAYS THROUGH THE REGULATION OF THE ACETYLATION STATUS OF BOTH HISTONE AND NON-HISTONE PROTEIN TARGETS, HAVE BEEN REPORTED TO DISPLAY PROMISING ANTI-LEUKEMIC PROPERTIES ALONE OR IN COMBINATION WITH TKIS. THIS REVIEW SUMMARIZES PRE-CLINICAL AND CLINICAL STUDIES THAT INVESTIGATED THE MECHANISMS UNDERLYING THE ANTICANCER POTENTIAL OF HDACIS AND DISCUSSES THE RATIONALE FOR A COMBINATION OF HDACIS WITH TKIS AS A THERAPEUTIC OPTION IN CML. 2020 11 2848 32 FREQUENT SOMATIC MUTATIONS IN EPIGENETIC REGULATORS IN NEWLY DIAGNOSED CHRONIC MYELOID LEUKEMIA. ALTHOUGH TYROSINE KINASE INHIBITORS (TKIS) HAVE SIGNIFICANTLY IMPROVED THE PROGNOSIS OF CHRONIC MYELOID LEUKEMIA (CML), THE ABILITY OF TKIS TO ERADICATE CML REMAINS UNCERTAIN AND PATIENTS MUST CONTINUE TKI THERAPY FOR INDEFINITE PERIODS. IN THIS STUDY, WE PERFORMED WHOLE-EXOME SEQUENCING TO IDENTIFY SOMATIC MUTATIONS IN 24 PATIENTS WITH NEWLY DIAGNOSED CHRONIC PHASE CML WHO WERE REGISTERED IN THE JALSG CML212 STUDY. WE IDENTIFIED 191 SOMATIC MUTATIONS OTHER THAN THE BCR-ABL1 FUSION GENE (MEDIAN 8, RANGE 1-17). AGE, HEMOGLOBIN CONCENTRATION AND WHITE BLOOD CELL COUNTS WERE CORRELATED WITH THE NUMBER OF MUTATIONS. PATIENTS WITH MUTATIONS ?6 SHOWED HIGHER RATE OF ACHIEVING MAJOR MOLECULAR RESPONSE THAN THOSE<6 (P=0.0381). MUTATIONS IN EPIGENETIC REGULATOR, ASXL1, TET2, TET3, KDM1A AND MSH6 WERE FOUND IN 25% OF PATIENTS. TET2 OR TET3, AKT1 AND RUNX1 WERE MUTATED IN ONE PATIENT EACH. ASXL1 WAS MUTATED WITHIN EXON 12 IN THREE CASES. MUTATED GENES WERE SIGNIFICANTLY ENRICHED WITH CELL SIGNALING AND CELL DIVISION PATHWAYS. FURTHERMORE, DNA COPY NUMBER ANALYSIS SHOWED THAT 2 OF 24 PATIENTS HAD UNIPARENTAL DISOMY OF CHROMOSOME 1P OR 3Q, WHICH DISAPPEARED MAJOR MOLECULAR RESPONSE WAS ACHIEVED. THESE MUTATIONS MAY PLAY SIGNIFICANT ROLES IN CML PATHOGENESIS IN ADDITION TO THE STRONG DRIVER MUTATION BCR-ABL1. 2017 12 32 40 A CASE OF TYROSINE KINASE INHIBITOR-RESISTANT CHRONIC MYELOID LEUKEMIA, CHRONIC PHASE WITH ASXL1 MUTATION. HEMATOLOGICAL MALIGNANCIES, INCLUDING CHRONIC MYELOID LEUKEMIA (CML), EXHIBIT ASXL1 MUTATIONS; HOWEVER, THE FUNCTION AND MOLECULAR MECHANISM OF THESE MUTATIONS REMAIN UNCLEAR. ASXL1 WAS ORIGINALLY IDENTIFIED AS TUMOR SUPPRESSOR GENE, IN WHICH LOSS OF FUNCTION CAUSES MYELODYSPLASTIC SYNDROME (MDS). ASXL1 MUTATIONS ARE COMMON AND ASSOCIATED WITH DISEASE PROGRESSION IN MYELOID MALIGNANCIES INCLUDING MDS, ACUTE MYELOID LEUKEMIA, AND SIMILARLY IN CML. IN MDS, ASXL1 MUTATIONS HAVE BEEN ASSOCIATED WITH POOR PROGNOSIS; HOWEVER, THE IMPACT OF ASXL1 MUTATIONS IN CML HAS NOT BEEN WELL DESCRIBED. A 31-YEAR-OLD MALE WAS DIAGNOSED AS CML-CHRONIC PHASE (CP). LABORATORY FINDINGS SHOWED A WHITE BLOOD CELL COUNT OF 187,200/MICROL, WITH ASYMPTOMATIC SPLENOMEGALY. BLAST COUNT WAS 5.0% IN PERIPHERAL BLOOD AND 7.3% IN BONE MARROW. THERE WAS NO ADDITIONAL CHROMOSOMAL ABNORMALITY EXCEPT FOR T(9;22)(Q34;Q11.2) BY CHROMOSOMAL ANALYSIS. AT ONSET, THE SOKAL SCORE WAS 1.4, INDICATING HIGH RISK. THE PATIENT RECEIVED TYROSINE KINASE INHIBITOR (TKI) THERAPY, COMPRISING NILOTINIB APPROXIMATELY 600 MG/DAY, BOSUTINIB APPROXIMATELY 600 MG/DAY, PONATINIB APPROXIMATELY 45 MG/DAY, AND DASATINIB APPROXIMATELY 100 MG/DAY. NEVERTHELESS, AFTER 1.5 YEARS OF CONTINUOUS TKI THERAPY, THE BEST OUTCOME WAS A HEMATOLOGICAL RESPONSE. ALTHOUGH ADDITIONAL CHROMOSOMAL ABERRATIONS AND ABL1 KINASE MUTATIONS WERE ANALYZED REPEATEDLY BEFORE AND DURING TKI THERAPY, KNOWN GENETIC ABNORMALITIES WERE NOT DETECTED. THEREAFTER, THE PATIENT UNDERWENT BONE MARROW TRANSPLANTATION FROM AN HLA 7/8 MATCHED UNRELATED DONOR (HLA-CW 1 LOCUS MISMATCH, GRAFT-VERSUS-HOST DIRECTION). THE PATIENT ACHIEVED NEUTROPHIL ENGRAFTMENT, 18 DAYS AFTER TRANSPLANTATION, LEADING TO COMPLETE REMISSION WITH AN UNDETECTABLE LEVEL OF BCR-ABL1 MRNA. THE PATIENT, HOWEVER, DIED FROM GRAFT-VERSUS-HOST DISEASE AND THROMBOTIC MICROANGIOPATHY AFTER 121 DAYS. GENE SEQUENCE ANALYSIS OF HIS CML CELL BEFORE STEM CELL TRANSPLANTATION REVEALED ASXL1 MUTATIONS. PHYSIOLOGICALLY, ASXL1 CONTRIBUTES TO EPIGENETIC REGULATION. IN THE CML-CP PATIENT IN THIS CASE REPORT, ASXL1 MUTATION CONFERRED RESISTANCE TO TKI THROUGH OBSCURE RESISTANCE MECHANISMS. EVEN THOUGH A MOLECULAR MECHANISM FOR TKI RESISTANCE IN ASXL1 MUTATION IN CML HAS REMAINED OBSCURE, EPIGENETIC MODULATION IS A PLAUSIBLE MODE OF CML DISEASE PROGRESSION. THE CLINICAL IMPACT INCLUDING PROGNOSIS OF ASXL1 FOR CML IS UNDERSCORED. AND THE TREATMENT STRATEGY OF CML WITH ASXL1 MUTATION HAS NOT BEEN ESTABLISHED. A DISCUSSION OF THIS CASE WAS EXPECTED TO FACILITATE TREATMENT OPTIONS. 2020 13 1272 41 CYTOTOXIC ACTIVITY OF VALPROIC ACID ON PRIMARY CHRONIC LYMPHOCYTIC LEUKEMIA CELLS. BACKGROUND: CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) IS THE MOST COMMON ADULT LEUKEMIA IN WESTERN CIVILIZATION. THE ACCUMULATION OF CD5+CD19+ B LYMPHOCYTES IN PERIPHERAL BLOOD IS DUE TO A DEFECT IN THE APOPTOTIC PATHWAY RATHER THAN EXCESSIVE PROLIFERATION IN THE BONE MARROW AND LYMPH NODES. DESPITE A NUMBER OF TREATMENTS, CLL REMAINS AN INCURABLE DISEASE. VALPROIC ACID (VPA) ACTIVITY, AS A HISTONE DEACETYLASE INHIBITOR, COULD RESTORE THE EPIGENETIC CHANGES UNDERLYING THE PATHOGENESIS OF CLL AND THUS INDUCE CELL DEATH. OBJECTIVES: IN THE PRESENT STUDY WE HYPOTHESIZED THAT VPA COULD INDUCE CLL PRIMARY CELLS DEATH THROUGH ACTIVATION OF APOPTOSIS. MATERIAL AND METHODS: PERIPHERAL BLOOD SAMPLES WERE OBTAINED FROM 53 CLL PATIENTS. PERIPHERAL BLOOD MONONUCLEAR CELLS WERE ISOLATED THROUGH DENSITY GRADIENT CENTRIFUGATION AND WERE THE SUBJECT OF A 24-HOUR CELL CULTURE WITH 10 MM OF VPA. THE CYTOTOXIC EFFECT OF VPA WAS EVALUATED WITH AN XTT TEST AND THEREAFTER CONFIRMED USING ANNEXIN V-FITC/PI STAINING AND FLOW CYTOMETRY TECHNIQUES. RESULTS: IN THIS STUDY, A MEDIAN VPA CYTOTOXICITY OF 13.88% WITH A RANGE OF 0-54.65% WAS OBSERVED. ANNEXIN V/PI STAINING CONFIRMED THAT THE DEMONSTRATED CYTOTOXICITY WAS CAUSED BY INCREASED APOPTOSIS IN THE VPA TREATED CELLS AS COMPARED TO CONTROL CELLS. STATISTICAL ANALYSIS SHOWED THAT VPA'S EFFECT ON CLL CELLS DEPENDS ON LACTATE DEHYDROGENASE SERUM LEVELS, BUT IS INDEPENDENT OF ALL OTHER PROGNOSTIC MARKERS. CONCLUSIONS: THE RESULTS OF THE PRESENT EXPERIMENTS FOUND THAT VPA AT A CLINICALLY APPLICABLE CONCENTRATION SIGNIFICANTLY INDUCES APOPTOSIS INDEPENDENTLY OF THE DISEASE STAGE AND MIGHT BE A VALUABLE THERAPEUTIC AGENT FOR ALL CLL PATIENTS. 2015 14 6688 41 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 15 1069 47 CLOFARABINE?PHYTOCHEMICAL COMBINATION EXPOSURES IN CML CELLS INHIBIT DNA METHYLATION MACHINERY, UPREGULATE TUMOR SUPPRESSOR GENES AND PROMOTE CASPASE?DEPENDENT APOPTOSIS. CLOFARABINE (2?CHLORO?2'?FLUORO?2'?DEOXYARABINOSYLADENINE, CIF), A SECOND?GENERATION 2'?DEOXYADENOSINE ANALOG, POSSESSES A VARIETY OF ANTI?CANCER ACTIVITIES, INCLUDING THE CAPACITY TO MODULATE DNA METHYLATION MARKS. BIOACTIVE NUTRIENTS, INCLUDING RESVERATROL (RSV) AND ALL?TRANS RETINOIC ACID (ATRA) HAVE BEEN INDICATED TO REGULATE EPIGENETIC MACHINERY IN MALIGNANT CELLS. THE PURPOSE OF THE CURRENT STUDY WAS TO EVALUATE WHETHER THE TESTED PHYTOCHEMICALS, RSV OR ATRA, CAN IMPROVE THE THERAPEUTIC EPIGENETIC EFFECTS OF CIF IN CHRONIC MYELOID LEUKEMIA (CML) CELLS. THE PRESENT STUDY INVESTIGATES, TO THE BEST OF OUR KNOWLEDGE, FOR THE FIRST TIME, THE INFLUENCE OF CIF IN COMBINATION WITH RSV OR ATRA ON THE EXPRESSION OF RELEVANT MODIFIERS OF DNA METHYLATION MACHINERY, INCLUDING DNA METHYLTRANSFERASE 1 (DNMT1) AND CYCLIN DEPENDENT KINASE INHIBITOR 1A (CDKN1A) IN CML CELLS. SUBSEQUENTLY, THE COMBINATORIAL EFFECTS ON PROMOTER METHYLATION AND TRANSCRIPT LEVELS OF METHYLATION?SILENCED TUMOR SUPPRESSOR GENES (TSGS), INCLUDING PHOSPHATASE AND TENSIN HOMOLOGUE (PTEN) AND RETINOIC ACID RECEPTOR BETA (RARB), WERE ESTIMATED USING MSRA AND QPCR, RESPECTIVELY. THE TESTED TSGS WERE CHOSEN ACCORDING TO BIOINFORMATICAL ANALYSIS OF PUBLICLY AVAILABLE CLINICAL DATA OF HUMAN DNA METHYLATION AND GENE EXPRESSION ARRAYS IN LEUKEMIA PATIENTS. THE K562 CELL LINE WAS USED AS AN EXPERIMENTAL CML IN VITRO MODEL. FOLLOWING A PERIOD OF 72 H EXPOSURE OF K562 CELLS, THE TESTED COMBINATIONS LED TO SIGNIFICANT CELL GROWTH INHIBITION AND INDUCTION OF CASPASE?3?DEPENDENT APOPTOSIS. THESE OBSERVATIONS WERE ACCOMPANIED BY DNMT1 DOWNREGULATION AND CDKN1A UPREGULATION, WITH A CONCOMITANT ENHANCED DECREASE IN DNMT1 PROTEIN LEVEL, ESPECIALLY AFTER ATRA TREATMENT WITH CIF. CONCURRENT METHYLATION?MEDIATED RARB AND PTEN REACTIVATION WAS DETECTED. THE RESULTS OF THE CURRENT STUDY DEMONSTRATED THAT CIF THAT WAS USED IN COMBINATION WITH THE TESTED PHYTOCHEMICALS, RSV OR ATRA, EXHIBITED A GREATER ABILITY TO REMODEL DNA METHYLATION MARKS AND PROMOTE CELL DEATH IN CML CELLS. THESE RESULTS MAY SUPPORT THE APPLICATION OF CIF COMBINATIONS WITH NATURAL BIOACTIVE AGENTS IN ANTI?LEUKEMIC EPIGENETIC THERAPY. 2019 16 5850 35 SUBEROYLANILIDE HYDROXAMIC ACID (SAHA) REDUCES FIBROSIS MARKERS AND DEACTIVATES HUMAN STELLATE CELLS VIA THE EPITHELIAL-MESENCHYMAL TRANSITION (EMT). HEPATIC FIBROSIS IS KNOWN AS THE ACCUMULATION OF CONNECTIVE TISSUE SECONDARY TO CHRONIC DAMAGE TO THE LIVER. EPITHELIAL-MESENCHYMAL TRANSITION (EMT) CORRESPONDING INCREASE IN LIVER FIBROGENESIS WAS SHOWN WITH IMMUNOHISTOCHEMISTRY AND PCR-BASED STUDIES. SUBEROYLANILIDE HYDROXAMIC ACID (SAHA), A SYNTHETIC COMPOUND APPROVED AS A HISTONE DEACETYLASE INHIBITOR (HDAC) BY THE FDA TO TREAT CUTANEOUS T-CELL LYMPHOMA IS UNDER INVESTIGATION FOR THE TREATMENT OF LUNG AND RENAL FIBROSIS. EXPERIMENTAL MODELING FOR HEPATIC FIBROSIS CAN BE CONSTRUCTED WITH AN LX2 CELL LINE ISOLATED FROM HUMAN HEPATIC STELLATE CELLS (HSCS). IN THIS STUDY, WE AIMED TO INVESTIGATE THE MODULATION OF SAHA IN THE PATHOGENESIS OF LIVER FIBROSIS BY DETECTING THE LEVELS OF PROTEINS; (E-CADHERIN (E-CAD), N-CADHERIN (N-CAD), VIMENTIN (VIM), AND GENES; E-CAD, N-CAD, VIM, TRANSFORMING GROWTH FACTOR-BETA (TGF-BETA), ALPHA-SMOOTH MUSCLE ACTIN (ALPHA-SMA), TYPE 1 COLLAGEN (COL1A1), TYPE 3 COLLAGEN (COL3A1)) THAT PLAY A SIGNIFICANT ROLE IN EMT WITH THE LX2 CELL LINE. WE ALSO EVALUATED THE ACTION OF SAHA WITH CELL PROLIFERATION, CLONOGENIC, AND MIGRATION ASSAY. CELL PROLIFERATION WAS PERFORMED BY FLOW CYTOMETRY. ALL THE PROTEIN LEVELS WERE DETERMINED BY WESTERN BLOT ANALYSIS, AND GENE EXPRESSION LEVELS WERE MEASURED BY REAL-TIME PCR. OUR STUDY OBSERVED THAT SAHA TREATMENT DECREASED CELL VIABILITY, COLONY FORMATION AND MIGRATION IN LX2 CELLS. WE FOUND THAT SAHA INCREASED E-CAD EXPRESSION LEVEL, WHILE IT DECREASED N-CAD, VIM, COL1A1, COL3A1, ALPHA-SMA TGF-BETA GENES EXPRESSION LEVELS. SAHA DECREASED THE LEVEL OF E-CAD, N-CAD, AND VIM PROTEIN LEVELS. WE THOUGHT THAT SAHA POSSESSES POTENT ANTIFIBROTIC AND ANTI-EMT PROPERTIES IN LX2. 2021 17 439 40 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 18 5212 37 PRESERVATION OF QUIESCENT CHRONIC MYELOGENOUS LEUKEMIA STEM CELLS BY THE BONE MARROW MICROENVIRONMENT. THE MAJORITY OF LEUKEMIA PATIENTS ACHIEVING REMISSION ULTIMATELY RELAPSE. PERSISTENCE OF LEUKEMIA STEM CELLS (LSC) CAPABLE OF REGENERATING LEUKEMIA IS A MAJOR CAUSE OF RELAPSE. THERE IS A PRESSING NEED TO BETTER UNDERSTAND MECHANISMS OF LSC REGULATION AND THEIR RESISTANCE TO THERAPY IN ORDER TO IMPROVE OUTCOMES FOR LEUKEMIA. CHRONIC MYELOGENOUS LEUKEMIA (CML) IS A LETHAL MYELOPROLIFERATIVE DISORDER THAT THAT IS CAUSED BY HEMATOPOIETIC STEM CELL (HSC) TRANSFORMATION BY THE BCR-ABL TYROSINE KINASE. TREATMENT WITH TYROSINE KINASE INHIBITORS (TKI) HAS REVOLUTIONIZED CML TREATMENT, BUT FAILS TO ELIMINATE LSC RESPONSIBLE FOR PROPAGATING AND REGENERATING LEUKEMIA. THEREFORE, PATIENTS REQUIRE CONTINUED TREATMENT TO PREVENT RELAPSE. LEUKEMIC AND NORMAL STEM CELLS SHARE PROPERTIES OF QUIESCENCE AND SELF-RENEWAL, THAT ARE SUPPORTED BY BONE MARROW NICHES. PERSISTENCE OF LSC AFTER TKI TREATMENT IS RELATED TO TYROSINE KINASE INDEPENDENT MECHANISMS WHICH INCLUDE INTRINSIC PROPERTIES OF LSCS DETERMINED BY EPIGENETIC ALTERATIONS, ALTERED TRANSCRIPTIONAL REGULATORY NETWORKS OR MITOCHONDRIAL/METABOLIC CHANGES. IN ADDITION TO CELL INTRINSIC CHANGES, SIGNALS FROM THE BONE MARROW MICROENVIRONMENT (BMM) PLAY A CRITICAL ROLE IN PROTECTING LSC FROM TKI TREATMENT. EACH TYPE OF ALTERATION MAY OFFER POTENTIAL POINTS OF INTERVENTION FOR THERAPEUTIC TARGETING OF LSC. 2018 19 4533 49 MULTIPLE GENE KNOCKDOWN STRATEGIES FOR INVESTIGATING THE PROPERTIES OF HUMAN LEUKEMIA STEM CELLS AND EXPLORING NEW THERAPIES. THE PAST TWO DECADES HAVE WITNESSED SIGNIFICANT STRIDES IN LEUKEMIA THERAPIES THROUGH APPROVAL OF THERAPEUTIC INHIBITORS TARGETING ONCOGENE-DRIVING DYSREGULATED TYROSINE KINASE ACTIVITIES AND KEY EPIGENETIC AND APOPTOSIS REGULATORS. ALTHOUGH THESE DRUGS HAVE BROUGHT ABOUT COMPLETE REMISSION IN THE MAJORITY OF PATIENTS, MANY PATIENTS FACE RELAPSE OR HAVE REFRACTORY DISEASE. THE MAIN FACTOR CONTRIBUTING TO RELAPSE IS THE PRESENCE OF A SMALL SUBPOPULATION OF DORMANT DRUG-RESISTANT LEUKEMIA CELLS THAT POSSESS STEM CELL FEATURES (TERMED AS LEUKEMIA STEM CELLS OR LSCS). THUS, OVERCOMING DRUG RESISTANCE AND TARGETING LSCS REMAIN MAJOR CHALLENGES FOR CURATIVE TREATMENT OF HUMAN LEUKEMIA. CHRONIC MYELOID LEUKEMIA (CML) IS A GOOD EXAMPLE, WITH RARE, PROPAGATING LSCS AND DRUG-RESISTANT CELLS THAT CANNOT BE ERADICATED BY BCR-ABL-DIRECTED TYROSINE KINASE INHIBITOR (TKI) MONOTHERAPY AND THAT ARE RESPONSIBLE FOR DISEASE RELAPSE/PROGRESSION. THEREFORE, IT IS IMPERATIVE TO IDENTIFY KEY PLAYERS IN REGULATING BCR-ABL1-DEPENDENT AND INDEPENDENT DRUG-RESISTANCE MECHANISMS, AND THEIR KEY PATHWAYS, SO THAT CML LSCS CAN BE SELECTIVELY TARGETED OR SENSITIZED TO TKIS. HERE, WE DESCRIBE SEVERAL EASILY ADAPTABLE GENE KNOCKDOWN APPROACHES IN CD34(+) CML STEM/PROGENITOR CELLS THAT CAN BE USED TO INVESTIGATE THE BIOLOGICAL PROPERTIES OF LSCS AND MOLECULAR EFFECTS OF GENES OF INTEREST (GOI), WHICH CAN BE FURTHER EXPLORED AS THERAPEUTIC MODALITIES AGAINST LSCS IN THE CONTEXT OF HUMAN LEUKEMIA. 2022 20 3158 45 GLYCOGEN SYNTHASE KINASE 3BETA MISSPLICING CONTRIBUTES TO LEUKEMIA STEM CELL GENERATION. RECENT EVIDENCE SUGGESTS THAT A RARE POPULATION OF SELF-RENEWING CANCER STEM CELLS (CSC) IS RESPONSIBLE FOR CANCER PROGRESSION AND THERAPEUTIC RESISTANCE. CHRONIC MYELOID LEUKEMIA (CML) REPRESENTS AN IMPORTANT PARADIGM FOR UNDERSTANDING THE GENETIC AND EPIGENETIC EVENTS INVOLVED IN CSC PRODUCTION. CML PROGRESSES FROM A CHRONIC PHASE (CP) IN HEMATOPOIETIC STEM CELLS (HSC) THAT HARBOR THE BCR-ABL TRANSLOCATION, TO BLAST CRISIS (BC), CHARACTERIZED BY ABERRANT ACTIVATION OF BETA-CATENIN WITHIN GRANULOCYTE-MACROPHAGE PROGENITORS (GMP). A MAJOR BARRIER TO PREDICTING AND INHIBITING BLAST CRISIS TRANSFORMATION HAS BEEN THE IDENTIFICATION OF MECHANISMS DRIVING BETA-CATENIN ACTIVATION. HERE WE SHOW THAT BC CML MYELOID PROGENITORS, IN PARTICULAR GMP, SERIALLY TRANSPLANT LEUKEMIA IN IMMUNOCOMPROMISED MICE AND THUS ARE ENRICHED FOR LEUKEMIA STEM CELLS (LSC). NOTABLY, CDNA SEQUENCING OF WNT/BETA-CATENIN PATHWAY REGULATORY GENES, INCLUDING ADENOMATOUS POLYPOSIS COLI, GSK3BETA, AXIN 1, BETA-CATENIN, LYMPHOID ENHANCER FACTOR-1, CYCLIN D1, AND C-MYC, REVEALED A NOVEL IN-FRAME SPLICE DELETION OF THE GSK3BETA KINASE DOMAIN IN THE GMP OF BC SAMPLES THAT WAS NOT DETECTABLE BY SEQUENCING IN BLASTS OR NORMAL PROGENITORS. MOREOVER, BC CML PROGENITORS WITH MISSPLICED GSK3BETA HAVE ENHANCED BETA-CATENIN EXPRESSION AS WELL AS SERIAL ENGRAFTMENT POTENTIAL WHILE REINTRODUCTION OF FULL-LENGTH GSK3BETA REDUCES BOTH IN VITRO REPLATING AND LEUKEMIC ENGRAFTMENT. WE PROPOSE THAT CP CML IS INITIATED BY BCR-ABL EXPRESSION IN AN HSC CLONE BUT THAT PROGRESSION TO BC MAY INCLUDE MISSPLICING OF GSK3BETA IN GMP LSC, ENABLING UNPHOSPHORYLATED BETA-CATENIN TO PARTICIPATE IN LSC SELF-RENEWAL. MISSPLICING OF GSK3BETA REPRESENTS A UNIQUE MECHANISM FOR THE EMERGENCE OF BC CML LSC AND MIGHT PROVIDE A NOVEL DIAGNOSTIC AND THERAPEUTIC TARGET. 2009