1 5666 108 SF3B1-MUTATED CHRONIC LYMPHOCYTIC LEUKEMIA SHOWS EVIDENCE OF NOTCH1 PATHWAY ACTIVATION INCLUDING CD20 DOWNREGULATION. CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) IS CHARACTERIZED BY A LOW CD20 EXPRESSION, IN PART EXPLAINED BY AN EPIGENETIC-DRIVEN DOWNREGULATION TRIGGERED BY MUTATIONS OF THE NOTCH1 GENE. IN THE PRESENT STUDY, BY TAKING ADVANTAGE OF A WIDE AND WELL-CHARACTERIZED CLL COHORT (N=537), WE DEMONSTRATE THAT CD20 EXPRESSION IS DOWNREGULATED IN SF3B1-MUTATED CLL IN AN EXTENT SIMILAR TO NOTCH1-MUTATED CLL. IN FACT, SF3B1-MUTATED CLL CELLS SHOW COMMON FEATURES WITH NOTCH1-MUTATED CLL CELLS, INCLUDING A GENE EXPRESSION PROFILE ENRICHED OF NOTCH1-RELATED GENE SETS AND ELEVATED EXPRESSION OF THE ACTIVE INTRACYTOPLASMIC NOTCH1. ACTIVATION OF THE NOTCH1 SIGNALING AND DOWN-REGULATION OF SURFACE CD20 IN SF3B1-MUTATED CLL CELLS CORRELATE WITH OVER-EXPRESSION OF AN ALTERNATIVELY SPLICED FORM OF DVL2, A COMPONENT OF THE WNT PATHWAY AND NEGATIVE REGULATOR OF THE NOTCH1 PATHWAY. THESE FINDINGS ARE CONFIRMED BY SEPARATELY ANALYZING THE CD20-DIM AND CD20-BRIGHT CELL FRACTIONS FROM SF3B1-MUTATED CASES AS WELL AS BY DVL2 KNOCK-OUT EXPERIMENTS IN CLL-LIKE CELL MODELS. ALTOGETHER, THE CLINICAL AND BIOLOGICAL FEATURES THAT CHARACTERIZE NOTCH1-MUTATED CLL MAY ALSO BE RECAPITULATED IN SF3B1-MUTATED CLL, CONTRIBUTING TO EXPLAIN THE POOR PROGNOSIS OF THIS CLL SUBSET AND PROVIDING THE RATIONALE FOR EXPANDING NOVEL AGENTS-BASED THERAPIES TO SF3B1-MUTATED CLL. 2021 2 40 33 A COMPARISON OF HERPES SIMPLEX VIRUS TYPE 1 AND VARICELLA-ZOSTER VIRUS LATENCY AND REACTIVATION. HERPES SIMPLEX VIRUS TYPE 1 (HSV-1; HUMAN HERPESVIRUS 1) AND VARICELLA-ZOSTER VIRUS (VZV; HUMAN HERPESVIRUS 3) ARE HUMAN NEUROTROPIC ALPHAHERPESVIRUSES THAT CAUSE LIFELONG INFECTIONS IN GANGLIA. FOLLOWING PRIMARY INFECTION AND ESTABLISHMENT OF LATENCY, HSV-1 REACTIVATION TYPICALLY RESULTS IN HERPES LABIALIS (COLD SORES), BUT CAN OCCUR FREQUENTLY ELSEWHERE ON THE BODY AT THE SITE OF PRIMARY INFECTION (E.G. WHITLOW), PARTICULARLY AT THE GENITALS. RARELY, HSV-1 REACTIVATION CAN CAUSE ENCEPHALITIS; HOWEVER, A THIRD OF THE CASES OF HSV-1 ENCEPHALITIS ARE ASSOCIATED WITH HSV-1 PRIMARY INFECTION. PRIMARY VZV INFECTION CAUSES VARICELLA (CHICKENPOX) FOLLOWING WHICH LATENT VIRUS MAY REACTIVATE DECADES LATER TO PRODUCE HERPES ZOSTER (SHINGLES), AS WELL AS AN INCREASINGLY RECOGNIZED NUMBER OF SUBACUTE, ACUTE AND CHRONIC NEUROLOGICAL CONDITIONS. FOLLOWING PRIMARY INFECTION, BOTH VIRUSES ESTABLISH A LATENT INFECTION IN NEURONAL CELLS IN HUMAN PERIPHERAL GANGLIA. HOWEVER, THE DETAILED MECHANISMS OF VIRAL LATENCY AND REACTIVATION HAVE YET TO BE UNRAVELLED. IN BOTH CASES LATENT VIRAL DNA EXISTS IN AN 'END-LESS' STATE WHERE THE ENDS OF THE VIRUS GENOME ARE JOINED TO FORM STRUCTURES CONSISTENT WITH UNIT LENGTH EPISOMES AND CONCATEMERS, FROM WHICH VIRAL GENE TRANSCRIPTION IS RESTRICTED. IN LATENTLY INFECTED GANGLIA, THE MOST ABUNDANTLY DETECTED HSV-1 RNAS ARE THE SPLICED PRODUCTS ORIGINATING FROM THE PRIMARY LATENCY ASSOCIATED TRANSCRIPT (LAT). THIS PRIMARY LAT IS AN 8.3 KB UNSTABLE TRANSCRIPT FROM WHICH TWO STABLE (1.5 AND 2.0 KB) INTRONS ARE SPLICED. TRANSCRIPTS MAPPING TO 12 VZV GENES HAVE BEEN DETECTED IN HUMAN GANGLIA REMOVED AT AUTOPSY; HOWEVER, IT IS DIFFICULT TO ASCRIBE THESE AS TRANSCRIPTS PRESENT DURING LATENT INFECTION AS EARLY-STAGE VIRUS REACTIVATION MAY HAVE TRANSPIRED IN THE POST-MORTEM TIME PERIOD IN THE GANGLIA. NONETHELESS, LOW-LEVEL TRANSCRIPTION OF VZV ORF63 HAS BEEN REPEATEDLY DETECTED IN MULTIPLE GANGLIA REMOVED AS CLOSE TO DEATH AS POSSIBLE. THERE IS INCREASING EVIDENCE THAT HSV-1 AND VZV LATENCY IS EPIGENETICALLY REGULATED. IN VITRO MODELS THAT PERMIT PATHWAY ANALYSIS AND IDENTIFICATION OF BOTH EPIGENETIC MODULATIONS AND GLOBAL TRANSCRIPTIONAL MECHANISMS OF HSV-1 AND VZV LATENCY HOLD MUCH PROMISE FOR OUR FUTURE UNDERSTANDING IN THIS COMPLEX AREA. THIS REVIEW SUMMARIZES THE MOLECULAR BIOLOGY OF HSV-1 AND VZV LATENCY AND REACTIVATION, AND ALSO PRESENTS FUTURE DIRECTIONS FOR STUDY. 2015 3 6885 32 [RNA SPLICING DYSREGULATION IN HEMATOLOGICAL MALIGNANCIES]. RECURRENT MUTATIONS IN GENES ENCODING KEY SPLICING FACTORS, SF3B1, SRSF2, U2AF1, AND ZRSR2 HAVE BEEN FOUND IN A VARIETY OF CANCERS, PARTICULARLY IN HEMATOLOGIC MALIGNANCIES, INCLUDING MYELODYSPLASTIC SYNDROMES, CHRONIC MYELOMONOCYTIC LEUKEMIA, ACUTE MYELOID LEUKEMIA, AND CHRONIC LYMPHOCYTIC LEUKEMIA. GLOBAL MIS-SPLICING OF MRNAS TARGETED BY ABERRANT SPLICING FACTORS PARTLY CONTRIBUTES TO LEUKEMOGENESIS THROUGH DECREASE PROTEIN EXPRESSION OF TUMOR SUPPRESSORS AND EPIGENETIC MODIFIERS, CAUSED BY MRNAS DEGRADATION OF ABERRANTLY SPLICED. SOME OF THE MIS-SPLICED MRNAS INFLUENCE INTRACELLULAR ONCOGENIC PATHWAYS AND CELLULAR PROCESSES THROUGH A DYSREGULATED EXPRESSION OF ASSOCIATED PROTEINS, WHEREAS OTHERS INFLUENCE THE FUNCTION OF CO-MUTATED GENES SUCH AS ABERRANT TRANSCRIPTIONAL REGULATORS. SPLICEOSOMAL DISRUPTION IS COMMON IN MANY CANCERS, MAKING SPLICEOSOME AN APPEALING THERAPEUTIC TARGET. THE FINDINGS THAT SPLICEOSOMAL MUTANT CELLS RELY ON WILD-TYPE SPLICING MACHINERY FOR SURVIVAL AND THAT SPLICING FACTOR MUTATIONS OCCUR IN A MUTUALLY EXCLUSIVE MANNER STRONGLY SUGGEST THAT INHIBITING WILD-TYPE SPLICING MACHINERY CAUSES SYNTHETIC LETHALITY IN CANCER CELLS WITH THESE MUTATIONS. WE DISCUSS THE CHARACTERISTICS AND ONCOGENIC MECHANISMS OF SPLICING FACTOR MUTATIONS, AS WELL AS THE DEVELOPMENT OF NOVEL TREATMENT STRATEGIES TARGETING ABERRANT SPLICING FACTORS IN HEMATOLOGIC MALIGNANCIES. 2023 4 1733 38 E-CADHERIN GENE RE-EXPRESSION IN CHRONIC LYMPHOCYTIC LEUKEMIA CELLS BY HDAC INHIBITORS. BACKGROUND: THE TUMOR SUPPRESSOR GENE E-CADHERIN GENE IS FREQUENTLY SILENCED IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) CELLS AND RESULTS IN WNT-PATHWAY ACTIVATION. WE ANALYZED THE ROLE OF HISTONE EPIGENETIC MODIFICATIONS IN E-CADHERIN GENE SILENCING. METHODS: CLL SPECIMENS WERE TREATED WITH HISTONE DEACETYLASE INHIBITOR (HDACI) MS-275 AND ANALYZED FOR E-CADHERIN EXPRESSION WITH WESTERN BLOT AND RT-PCR ANALYSIS. THE DOWNSTREAM EFFECTS OF HDACI TREATED LEUKEMIC CELLS WERE STUDIED BY ANALYZING THE EFFECT ON WNT-PATHWAY SIGNALING. HDACI INDUCED ALTERATIONS IN E-CADHERIN SPLICING WERE INVESTIGATED BY TRANSCRIPT SPECIFIC REAL TIME PCR ANALYSIS. RESULTS: TREATMENT OF CLL SPECIMENS WITH HISTONE DEACETYLASE INHIBITORS (HDACI) TREATMENT RESULTED IN AN INCREASE OF THE E-CADHERIN RNA TRANSCRIPT (5 TO 119 FOLD INCREASE, N=10) IN EIGHT OUT OF TEN CLL SPECIMENS INDICATING THAT THIS GENE IS DOWN REGULATED BY HISTONE HYPOACETYLATION IN A MAJORITY OF CLL SPECIMENS. THE E-CADHERIN RE-EXPRESSION IN CLL SPECIMENS WAS NOTED BY WESTERN BLOT ANALYSIS AS WELL. BESIDES EPIGENETIC SILENCING ANOTHER MECHANISM OF E-CADHERIN INACTIVATION IS ABERRANT EXON 11 SPLICING RESULTING IN AN ALTERNATIVELY SPLICED TRANSCRIPT THAT LACKS EXON 11 AND IS DEGRADED BY THE NON-SENSE MEDIATED DECAY (NMD) PATHWAY. OUR CHROMATIN IMMUNOPRECIPITATION EXPERIMENTS SHOW THAT HDACI INCREASED THE ACETYLATION OF HISTONES H3 AND H4 IN THE E-CADHERIN PROMOTER REGION. THIS ALSO AFFECTED THE E-CADHERIN EXON 11 SPLICING PATTERN AS HDACI TREATED CLL SPECIMENS PREFERENTIALLY EXPRESSED THE CORRECTLY SPLICED TRANSCRIPT AND NOT THE EXON 11 SKIPPED ABERRANT TRANSCRIPT. THE RE-EXPRESSED E- CADHERIN BINDS TO BETA-CATENIN WITH INHIBITION OF THE ACTIVE WNT-BETA-CATENIN PATHWAY IN THESE CELLS. THIS RESULTED IN A DOWN REGULATION OF TWO WNT TARGET GENES, LEF AND CYCLIND1 AND THE WNT PATHWAY REPORTER. CONCLUSION: THE E-CADHERIN GENE IS EPIGENETICALLY MODIFIED AND HYPOACETYLATED IN CLL LEUKEMIC CELLS. TREATMENT OF CLL SPECIMENS WITH HDACI MS-275 ACTIVATES TRANSCRIPTION FROM THIS SILENT GENE WITH EXPRESSION OF MORE CORRECTLY SPLICED E-CADHERIN TRANSCRIPTS AS COMPARED TO THE ABERRANT EXON11 SKIPPED TRANSCRIPTS THAT IN TURN INHIBITS THE WNT SIGNALING PATHWAY. THE DATA HIGHLIGHTS THE ROLE OF EPIGENETIC MODIFICATIONS IN ALTERING GENE SPLICING PATTERNS. 2013 5 5861 33 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 6 4729 40 NOTCH1 MUTATIONS ASSOCIATE WITH LOW CD20 LEVEL IN CHRONIC LYMPHOCYTIC LEUKEMIA: EVIDENCE FOR A NOTCH1 MUTATION-DRIVEN EPIGENETIC DYSREGULATION. IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL), NOTCH1 MUTATIONS HAVE BEEN ASSOCIATED WITH CLINICAL RESISTANCE TO THE ANTI-CD20 RITUXIMAB, ALTHOUGH THE MECHANISMS BEHIND THIS PECULIAR BEHAVIOR REMAIN TO BE CLARIFIED. IN A WIDE CLL SERIES (N=692), WE DEMONSTRATED THAT CLL CELLS FROM NOTCH1-MUTATED CASES (87/692) WERE CHARACTERIZED BY LOWER CD20 EXPRESSION AND LOWER RELATIVE LYSIS INDUCED BY ANTI-CD20 EXPOSURE IN VITRO. CONSISTENTLY, CD20 EXPRESSION BY CLL CELLS WAS UPREGULATED IN VITRO BY GAMMA-SECRETASE INHIBITORS OR NOTCH1-SPECIFIC SMALL INTERFERING RNA AND THE STABLE TRANSFECTION OF A MUTATED (C.7541-7542DELCT) NOTCH1 INTRACELLULAR DOMAIN (NICD-MUT) INTO CLL-LIKE CELLS RESULTED IN A STRONG DOWNREGULATION OF BOTH CD20 PROTEIN AND TRANSCRIPT. BY USING THESE NICD-MUT TRANSFECTANTS, WE INVESTIGATED PROTEIN INTERACTIONS OF RBPJ, A TRANSCRIPTION FACTOR ACTING EITHER AS ACTIVATOR OR REPRESSOR OF NOTCH1 PATHWAY WHEN RESPECTIVELY BOUND TO NICD OR HISTONE DEACETYLASES (HDACS). COMPARED WITH CONTROLS, NICD-MUT TRANSFECTANTS HAD RBPJ PREFERENTIALLY COMPLEXED TO NICD AND SHOWED HIGHER LEVELS OF HDACS INTERACTING WITH THE PROMOTER OF THE CD20 GENE. FINALLY, TREATMENT WITH THE HDAC INHIBITOR VALPROIC ACID UPREGULATED CD20 IN BOTH NICD-MUT TRANSFECTANTS AND PRIMARY CLL CELLS. IN CONCLUSION, NOTCH1 MUTATIONS ARE ASSOCIATED WITH LOW CD20 LEVELS IN CLL AND ARE RESPONSIBLE FOR A DYSREGULATION OF HDAC-MEDIATED EPIGENETIC REPRESSION OF CD20 EXPRESSION. 2016 7 6697 27 VARICELLA-ZOSTER VIRUS HUMAN GANGLIONIC LATENCY: A CURRENT SUMMARY. VARICELLA-ZOSTER VIRUS (VZV) IS A UBIQUITOUS HUMAN HERPES VIRUS TYPICALLY ACQUIRED IN CHILDHOOD WHEN IT CAUSES VARICELLA (CHICKENPOX), FOLLOWING WHICH THE VIRUS ESTABLISHES A LATENT INFECTION IN TRIGEMINAL AND DORSAL ROOT GANGLIA THAT LASTS FOR THE LIFE OF THE INDIVIDUAL. VZV SUBSEQUENTLY REACTIVATES, SPONTANEOUSLY OR AFTER SPECIFIC TRIGGERING FACTORS, TO CAUSE HERPES ZOSTER (SHINGLES), WHICH MAY BE COMPLICATED BY POSTHERPETIC NEURALGIA AND SEVERAL OTHER NEUROLOGICAL COMPLICATIONS INCLUDING VASCULOPATHY. OUR UNDERSTANDING OF VZV LATENCY LAGS BEHIND OUR KNOWLEDGE OF HERPES SIMPLEX VIRUS TYPE 1 (HSV-1) LATENCY PRIMARILY DUE TO THE DIFFICULTY IN PROPAGATING THE VIRUS TO HIGH TITERS IN A CELL-FREE STATE, AND THE LACK OF A SUITABLE SMALL-ANIMAL MODEL FOR STUDYING VIRUS LATENCY AND REACTIVATION. IT IS NOW ESTABLISHED BEYOND DOUBT THAT LATENT VZV IS PREDOMINANTLY LOCATED IN HUMAN GANGLIONIC NEURONS. VIRUS GENE TRANSCRIPTION DURING LATENCY IS EPIGENETICALLY REGULATED, AND APPEARS TO BE RESTRICTED TO EXPRESSION OF AT LEAST SIX GENES, WITH EXPRESSION OF GENE 63 BEING THE HALLMARK OF LATENCY. HOWEVER, VIRAL GENE TRANSCRIPTION MAY BE MORE EXTENSIVE THAN PREVIOUSLY THOUGHT. THERE IS ALSO EVIDENCE FOR SEVERAL VZV GENES BEING EXPRESSED AT THE PROTEIN LEVEL, INCLUDING VZV GENE 63-ENCODED PROTEIN, BUT RECENT EVIDENCE SUGGESTS THAT THIS MAY NOT BE A COMMON EVENT. THE NATURE AND EXTENT OF THE CHRONIC INFLAMMATORY RESPONSE IN LATENTLY INFECTED GANGLIA IS ALSO OF CURRENT INTEREST. THERE REMAIN SEVERAL QUESTIONS CONCERNING THE VZV LATENCY PROCESS THAT STILL NEED TO BE RESOLVED UNAMBIGUOUSLY AND IT IS LIKELY THAT THIS WILL REQUIRE THE USE OF NEWLY DEVELOPED MOLECULAR TECHNOLOGIES, SUCH AS GEXPS MULTIPLEX POLYMERASE CHAIN REACTION (PCR) FOR VIRUS TRANSCRIPTIONAL ANALYSIS AND CHIP-SEQ TO STUDY THE EPIGENETIC OF LATENT VIRUS GENOME ( LIU ET AL, 2010 , BMC BIOL 8: 56). 2010 8 5940 27 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 9 5664 22 SF3B1 MUTATIONS IN CHRONIC LYMPHOCYTIC LEUKEMIA. SF3B1 IS A CRITICAL COMPONENT OF THE SPLICING MACHINERY, WHICH CATALYZES THE REMOVAL OF INTRONS FROM PRECURSOR MESSENGER RNA (MRNA). NEXT-GENERATION SEQUENCING STUDIES HAVE IDENTIFIED MUTATIONS IN SF3B1 IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) AT HIGH FREQUENCY. IN CLL, SF3B1 MUTATION IS ASSOCIATED WITH MORE AGGRESSIVE DISEASE AND SHORTER SURVIVAL, AND RECENT STUDIES SUGGEST THAT IT CAN BE INCORPORATED INTO PROGNOSTIC SCHEMA TO IMPROVE THE PREDICTION OF DISEASE PROGRESSION. MUTATIONS IN SF3B1 ARE PREDOMINANTLY SUBCLONAL GENETIC EVENTS IN CLL, AND HENCE ARE LIKELY LATER EVENTS IN THE PROGRESSION OF CLL. EVIDENCE OF ALTERED PRE-MRNA SPLICING HAS BEEN DETECTED IN CLL CASES WITH SF3B1 MUTATIONS. ALTHOUGH THE CAUSATIVE LINK BETWEEN SF3B1 MUTATION AND CLL PATHOGENESIS REMAINS UNCLEAR, SEVERAL LINES OF EVIDENCE SUGGEST SF3B1 MUTATION MIGHT BE LINKED TO GENOMIC STABILITY AND EPIGENETIC MODIFICATION. 2013 10 6171 31 THE HDAC INHIBITOR VALPROATE INDUCES A BIVALENT STATUS OF THE CD20 PROMOTER IN CLL PATIENTS SUGGESTING DISTINCT EPIGENETIC REGULATION OF CD20 EXPRESSION IN CLL IN VIVO. TREATMENT WITH ANTI-CD20 ANTIBODIES IS ONLY MODERATELY EFFICIENT IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL), A FEATURE WHICH HAS BEEN EXPLAINED BY THE INHERENTLY LOW CD20 EXPRESSION IN CLL. IT HAS BEEN SHOWN THAT CD20 IS EPIGENETICALLY REGULATED AND THAT HISTONE DEACETYLASE INHIBITORS (HDACIS) CAN INCREASE CD20 EXPRESSION IN VITRO IN CLL. TO ASSESS WHETHER HDACIS CAN UPREGULATE CD20 ALSO IN VIVO IN CLL, THE HDACI VALPROATE WAS GIVEN TO THREE DEL13Q/NOTCH1WT CLL PATIENTS AND CD20 LEVELS WERE ANALYSED (THE PREVAIL STUDY). VALPROATE TREATMENT RESULTED IN EXPECTED GLOBAL ACTIVATING HISTONE MODIFICATIONS SUGGESTING HDAC INHIBITORY EFFECTS. HOWEVER, ALTHOUGH VALPROATE INDUCED EXPRESSION OF CD20 MRNA AND PROTEIN IN THE DEL13Q/NOTCH1WT I83-E95 CLL CELL LINE, NO SUCH EFFECTS WERE OBSERVED IN THE PATIENTS STUDIED. IN CONTRAST TO THE CELL LINE, IN PATIENTS VALPROATE TREATMENT RESULTED IN TRANSIENT RECRUITMENT OF THE TRANSCRIPTIONAL REPRESSOR EZH2 TO THE CD20 PROMOTER, CORRELATING TO AN INCREASE OF THE REPRESSIVE HISTONE MARK H3K27ME3. THIS SUGGESTS THAT VALPROATE-MEDIATED INDUCTION OF CD20 MAY BE HAMPERED BY EZH2 MEDIATED H3K27ME3 IN VIVO IN CLL. MOREOVER, VALPROATE TREATMENT RESULTED IN INDUCTION OF EZH2 AND GLOBAL H3K27ME3 IN PATIENT CELLS, SUGGESTING TRANSCRIPTIONALLY REPRESSIVE EFFECTS OF VALPROATE IN CLL. OUR RESULTS SUGGEST NEW IN VIVO MECHANISMS OF HDACIS WHICH MAY HAVE IMPLICATIONS ON THE DESIGN OF FUTURE CLINICAL TRIALS IN B-CELL MALIGNANCIES. 2017 11 2971 23 GENETIC AND EPIGENETIC SILENCING OF MICRORNA-203 ENHANCES ABL1 AND BCR-ABL1 ONCOGENE EXPRESSION. THE MAMMALIAN GENOME CONTAINS SEVERAL HUNDRED MICRORNAS THAT REGULATE GENE EXPRESSION THROUGH MODULATION OF TARGET MRNAS. HERE, WE REPORT A FRAGILE CHROMOSOMAL REGION LOST IN SPECIFIC HEMATOPOIETIC MALIGNANCIES. THIS 7 MB REGION ENCODES ABOUT 12% OF ALL GENOMIC MICRORNAS, INCLUDING MIR-203. THIS MICRORNA IS ADDITIONALLY HYPERMETHYLATED IN SEVERAL HEMATOPOIETIC TUMORS, INCLUDING CHRONIC MYELOGENOUS LEUKEMIAS AND SOME ACUTE LYMPHOBLASTIC LEUKEMIAS. A PUTATIVE MIR-203 TARGET, ABL1, IS SPECIFICALLY ACTIVATED IN THESE HEMATOPOIETIC MALIGNANCIES IN SOME CASES AS A BCR-ABL1 FUSION PROTEIN (PHILADELPHIA CHROMOSOME). RE-EXPRESSION OF MIR-203 REDUCES ABL1 AND BCR-ABL1 FUSION PROTEIN LEVELS AND INHIBITS TUMOR CELL PROLIFERATION IN AN ABL1-DEPENDENT MANNER. THUS, MIR-203 FUNCTIONS AS A TUMOR SUPPRESSOR, AND RE-EXPRESSION OF THIS MICRORNA MIGHT HAVE THERAPEUTIC BENEFITS IN SPECIFIC HEMATOPOIETIC MALIGNANCIES. 2008 12 1184 21 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 13 4361 35 MIR-96 ACTS AS A TUMOR SUPPRESSOR VIA TARGETING THE BCR-ABL1 ONCOGENE IN CHRONIC MYELOID LEUKEMIA BLASTIC TRANSFORMATION. MICRORNA-MEDIATED POSTTRANSCRIPTIONAL REGULATION IS AN IMPORTANT EPIGENETIC REGULATORY MECHANISM OF GENE EXPRESSION, AND ITS DYSREGULATION IS INVOLVED IN THE DEVELOPMENT AND PROGRESSION OF A VARIETY OF MALIGNANCIES, INCLUDING CHRONIC MYELOID LEUKEMIA (CML). THE BCR-ABL1 FUSION GENE IS NOT ONLY THE INITIATING FACTOR OF CML, BUT IT IS ALSO AN IMPORTANT DRIVING FACTOR FOR BLASTIC TRANSFORMATION. TYROSINE KINASE INHIBITORS (TKIS) TARGETING BCR-ABL1 TYROSINE KINASE ACTIVITY, REPRESENTED BY IMATINIB, ARE CURRENTLY THE FIRST-LINE TREATMENT FOR CML. HOWEVER, DUE TO PRIMARY RESISTANCE OR SECONDARY RESISTANCE CAUSED BY MUTATIONS IN THE BCR-ABL1 KINASE DOMAIN, TKIS CANNOT COMPLETELY PREVENT THE PROGRESSION OF CML; THUS, THE STUDY OF BCR-ABL1 GENE EXPRESSION REGULATION IS OF GREAT SIGNIFICANCE. IN THIS STUDY, BIOINFORMATICS ANALYSIS AND OUR RESULTS SHOWED THAT MIR-96 COULD DIRECTLY BIND TO THE 3'UTR REGION OF BCR-ABL1 TO REGULATE FUSION PROTEIN EXPRESSION, THEREBY REGULATING ITS DOWNSTREAM SIGNALING PATHWAY ACTIVITY. WE ALSO FOUND THAT MIR-96 WAS DOWNREGULATED DURING THE PROGRESSION FROM THE CHRONIC PHASE (CML-CP) TO THE BLAST CRISIS (CML-BC). DOWNREGULATION OF MIR-96 COULD PROMOTE THE PROLIFERATION AND PARTICIPATE IN THE CELL DIFFERENTIATION OF CML-BC CELLS. ADDITIONALLY, WE FOUND THAT THE NOVEL HISTONE DEACETYLASE DRUG CHIDAMIDE AND THE DNA METHYLTRANSFERASE INHIBITOR DECITABINE COULD RESTORE THE LOW EXPRESSION OF MIR-96 IN CML CELLS, AND THERE WERE TWO ABNORMAL HYPERMETHYLATED SITES IN THE PROMOTER REGION OF MIR-96 IN CML, SUGGESTING THAT ITS LOW EXPRESSION MIGHT BE AT LEAST PARTIALLY REGULATED BY EPIGENETIC MECHANISMS. IN ADDITION, RE-EXPRESSION OF MIR-96 COULD INCREASE THE SENSITIVITY OF CML-BC CELLS TO IMATINIB. THUS, MIR-96 FUNCTIONS AS A TUMOR SUPPRESSOR, AND RE-EXPRESSION OF THIS MICRORNA MIGHT HAVE THERAPEUTIC BENEFITS IN CML BLASTIC TRANSFORMATION. 2019 14 784 19 CELL-SPECIFIC EXON METHYLATION AND CTCF BINDING IN NEURONS REGULATE CALCIUM ION CHANNEL SPLICING AND FUNCTION. CELL-SPECIFIC ALTERNATIVE SPLICING MODULATES MYRIAD CELL FUNCTIONS AND IS DISRUPTED IN DISEASE. THE MECHANISMS GOVERNING ALTERNATIVE SPLICING ARE KNOWN FOR RELATIVELY FEW GENES AND TYPICALLY FOCUS ON RNA SPLICING FACTORS. IN SENSORY NEURONS, CELL-SPECIFIC ALTERNATIVE SPLICING OF THE PRESYNAPTIC CA(V) CHANNEL CACNA1B GENE MODULATES OPIOID SENSITIVITY. HOW THIS SPLICING IS REGULATED IS UNKNOWN. WE FIND THAT CELL AND EXON-SPECIFIC DNA HYPOMETHYLATION PERMITS CTCF BINDING, THE MASTER REGULATOR OF MAMMALIAN CHROMATIN STRUCTURE, WHICH, IN TURN, CONTROLS SPLICING IN A DRG-DERIVED CELL LINE. IN VIVO, HYPOMETHYLATION OF AN ALTERNATIVE EXON SPECIFICALLY IN NOCICEPTORS, LIKELY PERMITS CTCF BINDING AND EXPRESSION OF CA(V)2.2 CHANNEL ISOFORMS WITH INCREASED OPIOID SENSITIVITY IN MICE. FOLLOWING NERVE INJURY, EXON METHYLATION IS INCREASED, AND SPLICING IS DISRUPTED. OUR STUDIES DEFINE THE MOLECULAR MECHANISMS OF CELL-SPECIFIC ALTERNATIVE SPLICING OF A FUNCTIONALLY VALIDATED EXON IN NORMAL AND DISEASE STATES - AND REVEAL A POTENTIAL TARGET FOR THE TREATMENT OF CHRONIC PAIN. 2020 15 4565 23 MYELOID MALIGNANCIES: MUTATIONS, MODELS AND MANAGEMENT. MYELOID MALIGNANT DISEASES COMPRISE CHRONIC (INCLUDING MYELODYSPLASTIC SYNDROMES, MYELOPROLIFERATIVE NEOPLASMS AND CHRONIC MYELOMONOCYTIC LEUKEMIA) AND ACUTE (ACUTE MYELOID LEUKEMIA) STAGES. THEY ARE CLONAL DISEASES ARISING IN HEMATOPOIETIC STEM OR PROGENITOR CELLS. MUTATIONS RESPONSIBLE FOR THESE DISEASES OCCUR IN SEVERAL GENES WHOSE ENCODED PROTEINS BELONG PRINCIPALLY TO FIVE CLASSES: SIGNALING PATHWAYS PROTEINS (E.G. CBL, FLT3, JAK2, RAS), TRANSCRIPTION FACTORS (E.G. CEBPA, ETV6, RUNX1), EPIGENETIC REGULATORS (E.G. ASXL1, DNMT3A, EZH2, IDH1, IDH2, SUZ12, TET2, UTX), TUMOR SUPPRESSORS (E.G. TP53), AND COMPONENTS OF THE SPLICEOSOME (E.G. SF3B1, SRSF2). LARGE-SCALE SEQUENCING EFFORTS WILL SOON LEAD TO THE ESTABLISHMENT OF A COMPREHENSIVE REPERTOIRE OF THESE MUTATIONS, ALLOWING FOR A BETTER DEFINITION AND CLASSIFICATION OF MYELOID MALIGNANCIES, THE IDENTIFICATION OF NEW PROGNOSTIC MARKERS AND THERAPEUTIC TARGETS, AND THE DEVELOPMENT OF NOVEL THERAPIES. GIVEN THE IMPORTANCE OF EPIGENETIC DEREGULATION IN MYELOID DISEASES, THE USE OF DRUGS TARGETING EPIGENETIC REGULATORS APPEARS AS A MOST PROMISING THERAPEUTIC APPROACH. 2012 16 2277 26 EPIGENETIC REGULATION BY ASXL1 IN MYELOID MALIGNANCIES. MYELOID MALIGNANCIES ARE CLONAL HEMATOPOIETIC DISORDERS THAT ARE COMPRISED OF A SPECTRUM OF GENETICALLY HETEROGENEOUS DISORDERS, INCLUDING MYELODYSPLASTIC SYNDROMES (MDS), MYELOPROLIFERATIVE NEOPLASMS (MPN), CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML), AND ACUTE MYELOID LEUKEMIA (AML). MYELOID MALIGNANCIES ARE CHARACTERIZED BY EXCESSIVE PROLIFERATION, ABNORMAL SELF-RENEWAL, AND/OR DIFFERENTIATION DEFECTS OF HEMATOPOIETIC STEM CELLS (HSCS) AND MYELOID PROGENITOR CELLS HEMATOPOIETIC STEM/PROGENITOR CELLS (HSPCS). MYELOID MALIGNANCIES CAN BE CAUSED BY GENETIC AND EPIGENETIC ALTERATIONS THAT PROVOKE KEY CELLULAR FUNCTIONS, SUCH AS SELF-RENEWAL, PROLIFERATION, BIASED LINEAGE COMMITMENT, AND DIFFERENTIATION. ADVANCES IN NEXT-GENERATION SEQUENCING LED TO THE IDENTIFICATION OF MULTIPLE MUTATIONS IN MYELOID NEOPLASMS, AND MANY NEW GENE MUTATIONS WERE IDENTIFIED AS KEY FACTORS IN DRIVING THE PATHOGENESIS OF MYELOID MALIGNANCIES. THE POLYCOMB PROTEIN ASXL1 WAS IDENTIFIED TO BE FREQUENTLY MUTATED IN ALL FORMS OF MYELOID MALIGNANCIES, WITH MUTATIONAL FREQUENCIES OF 20%, 43%, 10%, AND 20% IN MDS, CMML, MPN, AND AML, RESPECTIVELY. SIGNIFICANTLY, ASXL1 MUTATIONS ARE ASSOCIATED WITH A POOR PROGNOSIS IN ALL FORMS OF MYELOID MALIGNANCIES. THE FACT THAT ASXL1 MUTATIONS ARE ASSOCIATED WITH POOR PROGNOSIS IN PATIENTS WITH CMML, MDS, AND AML, POINTS TO THE POSSIBILITY THAT ASXL1 MUTATION IS A KEY FACTOR IN THE DEVELOPMENT OF MYELOID MALIGNANCIES. THIS REVIEW SUMMARIZES THE RECENT ADVANCES IN UNDERSTANDING MYELOID MALIGNANCIES WITH A SPECIFIC FOCUS ON ASXL1 MUTATIONS. 2023 17 5782 26 SPLICING ANOMALIES IN MYELOPROLIFERATIVE NEOPLASMS: PAVING THE WAY FOR NEW THERAPEUTIC VENUES. SINCE THE DISCOVERY OF SPLICEOSOME MUTATIONS IN MYELOID MALIGNANCIES, ABNORMAL PRE-MRNA SPLICING, WHICH HAS BEEN WELL STUDIED IN VARIOUS CANCERS, HAS ATTRACTED NOVEL INTEREST IN HEMATOLOGY. HOWEVER, DESPITE THE COMMON OCCURRENCE OF SPLICEOSOME MUTATIONS IN MYELO-PROLIFERATIVE NEOPLASMS (MPN), NOT MUCH IS KNOWN REGARDING THE CHARACTERIZATION AND MECHANISMS OF SPLICING ANOMALIES IN MPN. IN THIS ARTICLE, WE REVIEW THE CURRENT SCIENTIFIC LITERATURE REGARDING "SPLICING AND MYELOPROLIFERATIVE NEOPLASMS". WE FIRST ANALYSE THE CLINICAL SERIES REPORTING SPLICEOSOME MUTATIONS IN MPN AND THEIR CLINICAL CORRELATES. WE THEN PRESENT THE CURRENT KNOWLEDGE ABOUT MOLECULAR MECHANISMS BY WHICH THESE MUTATIONS PARTICIPATE IN THE PATHOGENESIS OF MPN OR OTHER MYELOID MALIGNANCIES. BESIDE SPLICEOSOME MUTATIONS, SPLICING ANOMALIES HAVE BEEN DESCRIBED IN MYELOPROLIFERATIVE NEOPLASMS, AS WELL AS IN ACUTE MYELOID LEUKEMIAS, A DREADFUL COMPLICATION OF THESE CHRONIC DISEASES. BASED ON SPLICING ANOMALIES REPORTED IN CHRONIC MYELOGENOUS LEUKEMIA AS WELL AS IN ACUTE LEUKEMIA, AND THE MECHANISMS PRESIDING SPLICING DEREGULATION, WE PROPOSE THAT ABNORMAL SPLICING PLAYS A MAJOR ROLE IN THE EVOLUTION OF MYELOPROLIFERATIVE NEOPLASMS AND MAY BE THE TARGET OF SPECIFIC THERAPEUTIC STRATEGIES. 2020 18 5319 29 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 19 1304 29 DEFECTS IN SPLICEOSOMAL MACHINERY: A NEW PATHWAY OF LEUKAEMOGENESIS. PROPER SPLICING OF PRE-MRNA IS REQUIRED FOR PROTEIN SYNTHESIS AND THEREFORE IS A FUNDAMENTAL CELLULAR FUNCTION. THE DISCOVERY OF A VARIETY OF SOMATIC SPLICEOSOMAL MUTATIONS IN HAEMATOLOGICAL MALIGNANCIES, INCLUDING MYELOID NEOPLASMS AND CHRONIC LYMPHOCYTIC LEUKAEMIA HAS POINTED TO A NEW LEUKAEMOGENIC PATHWAY INVOLVING SPLICEOSOMAL DYSFUNCTION. THEORETICALLY, SPLICEOSOMAL MUTATIONS CAN LEAD TO ACTIVATION OF INCORRECT SPLICE SITES, INTRON RETENTION OR ABERRANT ALTERNATIVE SPLICING OCCURRING IN PATTERNS GENERATED BY MUTATIONS OF INDIVIDUAL SPLICEOSOMAL PROTEINS. SUCH EVENTS CAN PRODUCE A DEFECTIVE BALANCE BETWEEN PROTEIN ISOFORMS LEADING TO FUNCTIONAL CONSEQUENCES INCLUDING DEFECTIVE REGULATION OF PROLIFERATION AND DIFFERENTIATION. THE OBSERVED PATTERN OF OCCURRENCE OF HIGHLY SPECIFIC MISSENSE MUTATIONS, COUPLED WITH THE LACK OF NONSENSE MUTATIONS AND DELETIONS, IMPLIES A GAIN-OF-FUNCTION OR BETTER GAIN-OF-DYSFUNCTION MECHANISM. INCORRECT SPLICING OF DOWNSTREAM GENES, SUCH AS TUMOUR SUPPRESSOR GENES, MAY RESULT IN HAPLOINSUFFICIENT EXPRESSION THROUGH NONSENSE-MEDIATED MRNA DECAY. THUS, SPLICEOSOMAL MUTATIONS MAY, DEPENDING ON THE PATTERN OF AFFECTED PROTEINS, LEAD TO SIMILAR FUNCTIONAL EFFECTS ON TUMOUR SUPPRESSOR GENES AS CHROMOSOMAL DELETIONS, EPIGENETIC SILENCING OR INACTIVATING/HYPOMORPHIC MUTATIONS. THE PROGNOSTIC VALUE OF THE MOST COMMON MUTATIONS AND THEIR PHENOTYPIC ASSOCIATION IN THE CLINICAL SETTING IS CURRENTLY UNDER INVESTIGATION. IT IS LIKELY THAT SPLICEOSOMAL MUTATIONS MAY INDICATE SENSITIVITY TO SPLICEOSOME INHIBITORS APPLIED IN THE FORM OF A SYNTHETIC LETHAL APPROACH. THIS REVIEW DISCUSSES THE MOST CURRENT ASPECTS OF SPLICEOSOMAL RESEARCH IN THE CONTEXT OF HAEMATOLOGICAL MALIGNANCIES. 2012 20 690 23 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