1 4571 116 MYELOMONOCYTIC SKEWING IN CHRONIC MYELOMONOCYTIC LEUKEMIA: PHENOTYPIC, MOLECULAR AND BIOLOGIC FEATURES AND IMPACT ON SURVIVAL. BACKGROUND: MYELOMONOCYTIC SKEWING IS CONSIDERED AS A KEY PATHOPHYSIOLOGIC PHENOMENON IN CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML), BUT ITS PREVALENCE AND POTENTIAL CORRELATION WITH PHENOTYPIC, GENOTYPIC, AND CLINICAL FEATURES ARE POORLY DEFINED. METHODS: SKEWED DIFFERENTIATION TOWARD THE MYELOMONOCYTIC OVER ERYTHROID COMMITMENT AS INDICATED BY AN INVERSE RATIO OF MYELOMONOCYTIC/ERYTHROID COLONIES WAS INVESTIGATED IN 146 PATIENTS WITH CMML BY SEMISOLID IN VITRO CULTURES. RESULTS: THERE WAS A HIGH PREVALENCE OF MYELOMONOCYTIC SKEWING IN PATIENTS WITH CMML (120/146, 82%); WHEREAS, THIS PHENOMENON WAS RARE IN NORMAL INDIVIDUALS (1/98, 1%). PATIENTS WITH CMML WITH MYELOMONOCYTIC SKEWING HAD HIGHER WHITE BLOOD CELL AND PERIPHERAL BLAST CELL COUNTS, AND LOWER PLATELET VALUES. THE NUMBER OF MUTATIONS IN GENES OF THE EPIGENETIC AND/OR SPLICING CATEGORY WAS HIGHER IN CMML PATIENTS WITH AS COMPARED WITH PATIENTS WITHOUT SKEWING. PATIENTS WITH MYELOMONOCYTIC SKEWING HAD MORE FREQUENTLY MUTATIONS IN RASOPATHY GENES AND HIGHER GROWTH FACTOR INDEPENDENT MYELOID COLONY FORMATION. INTERESTINGLY, THE LACK OF MYELOMONOCYTIC SKEWING DISCRIMINATED PATIENTS WITH CMML WITH A PARTICULARLY FAVORABLE PROGNOSIS (60 VS 19 MONTHS, P = .003) AND A MINIMAL RISK OF TRANSFORMATION. CONCLUSION: MYELOMONOCYTIC SKEWING AS DETERMINED BY SEMISOLID CULTURES CAN DISCRIMINATE SUBGROUPS OF PATIENTS WITH CMML WITH A DIFFERENT PHENOTYPE, A DIFFERENT GENOTYPE, AND A DIFFERENT PROGNOSIS. 2021 2 3760 15 INTEGRATED SINGLE CELL ANALYSIS SHOWS CHRONIC ALCOHOL DRINKING DISRUPTS MONOCYTE DIFFERENTIATION IN THE BONE MARROW. CHRONIC HEAVY ALCOHOL DRINKING (CHD) REWIRES MONOCYTES AND MACROPHAGES TOWARD HEIGHTENED INFLAMMATORY STATES WITH COMPROMISED ANTIMICROBIAL DEFENSES THAT PERSIST AFTER 1-MONTH ABSTINENCE. TO DETERMINE WHETHER THESE CHANGES ARE MEDIATED THROUGH ALTERATIONS IN THE BONE MARROW NICHE, WE PROFILED MONOCYTES AND HEMATOPOIETIC STEM CELL PROGENITORS (HSCPS) FROM CHD RHESUS MACAQUES USING A COMBINATION OF FUNCTIONAL ASSAYS AND SINGLE CELL GENOMICS. CHD RESULTED IN TRANSCRIPTIONAL PROFILES CONSISTENT WITH INCREASED ACTIVATION AND INFLAMMATION WITHIN BONE MARROW RESIDENT MONOCYTES AND MACROPHAGES. FURTHERMORE, CHD RESULTED IN TRANSCRIPTIONAL SIGNATURES ASSOCIATED WITH INCREASED OXIDATIVE AND CELLULAR STRESS IN HSCP. DIFFERENTIATION OF HSCP IN VITRO REVEALED SKEWING TOWARD MONOCYTES EXPRESSING "NEUTROPHIL-LIKE" MARKERS WITH GREATER INFLAMMATORY RESPONSES TO BACTERIAL AGONISTS. FURTHER ANALYSES OF HSCPS SHOWED BROAD EPIGENETIC CHANGES THAT WERE IN LINE WITH EXACERBATED INFLAMMATORY RESPONSES WITHIN MONOCYTES AND THEIR PROGENITORS. IN SUMMARY, CHD ALTERS HSCPS IN THE BONE MARROW LEADING TO THE PRODUCTION OF MONOCYTES POISED TO GENERATE DYSREGULATED HYPER-INFLAMMATORY RESPONSES. 2023 3 1070 25 CLONAL ARCHITECTURE OF CHRONIC MYELOMONOCYTIC LEUKEMIAS. GENOMIC STUDIES IN CHRONIC MYELOID MALIGNANCIES, INCLUDING MYELOPROLIFERATIVE NEOPLASMS (MPN), MYELODYSPLASTIC SYNDROMES (MDS), AND MPN/MDS, HAVE IDENTIFIED COMMON MUTATIONS IN GENES ENCODING SIGNALING, EPIGENETIC, TRANSCRIPTION, AND SPLICING FACTORS. IN THE PRESENT STUDY, WE INTERROGATED THE CLONAL ARCHITECTURE BY MUTATION-SPECIFIC DISCRIMINATION ANALYSIS OF SINGLE-CELL-DERIVED COLONIES IN 28 PATIENTS WITH CHRONIC MYELOMONOCYTIC LEUKEMIAS (CMML), THE MOST FREQUENT MPN/MDS. THIS ANALYSIS REVEALS A LINEAR ACQUISITION OF THE STUDIED MUTATIONS WITH LIMITED BRANCHING THROUGH LOSS OF HETEROZYGOSITY. SERIAL ANALYSIS OF UNTREATED AND TREATED SAMPLES DEMONSTRATES A DYNAMIC ARCHITECTURE ON WHICH MOST CURRENT THERAPEUTIC APPROACHES HAVE LIMITED EFFECTS. THE MAIN DISEASE CHARACTERISTICS ARE EARLY CLONAL DOMINANCE, ARISING AT THE CD34(+)/CD38(-) STAGE OF HEMATOPOIESIS, AND GRANULOMONOCYTIC DIFFERENTIATION SKEWING OF MULTIPOTENT AND COMMON MYELOID PROGENITORS. COMPARISON OF CLONAL EXPANSIONS OF TET2 MUTATIONS IN MDS, MPN, AND CMML, TOGETHER WITH FUNCTIONAL INVALIDATION OF TET2 IN SORTED PROGENITORS, SUGGESTS A CAUSATIVE LINK BETWEEN EARLY CLONAL DOMINANCE AND SKEWED GRANULOMONOCYTIC DIFFERENTIATION. ALTOGETHER, EARLY CLONAL DOMINANCE MAY DISTINGUISH CMML FROM OTHER CHRONIC MYELOID NEOPLASMS WITH SIMILAR GENE MUTATIONS. 2013 4 5983 30 TET2 RESTRAINS INFLAMMATORY GENE EXPRESSION IN MACROPHAGES. TET METHYLCYTOSINE DIOXYGENASE 2 (TET2) IS ONE OF THE EARLIEST AND MOST FREQUENTLY MUTATED GENES IN CLONAL HEMATOPOIESIS OF INDETERMINATE POTENTIAL (CHIP) AND MYELOID CANCERS, INCLUDING MYELODYSPLASTIC SYNDROMES (MDS) AND CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML). TET2 CATALYZES THE OXIDATION OF 5-METHYLCYTOSINE TO 5-HYDROXYMETHYLCYTOSINE, LEADING TO DNA DEMETHYLATION, AND ALSO AFFECTS TRANSCRIPTION BY RECRUITING HISTONE MODIFIERS. INACTIVATING TET2 MUTATIONS CAUSE EPIGENETIC DYSREGULATION, CLONAL HEMATOPOIETIC STEM CELL (HSC) DOMINANCE, AND MONOCYTIC LINEAGE SKEWING. HERE, WE FOUND THAT TET2 WAS THE MOST HIGHLY EXPRESSED TET ENZYME IN MURINE MACROPHAGE (MPHI) DIFFERENTIATION. TET2 TRANSCRIPTION WAS FURTHER INDUCED BY LIPOPOLYSACCHARIDE (LPS), BUT NOT INTERLEUKIN (IL)-4, STIMULATION, POTENTIALLY IN A NUCLEAR FACTOR KAPPABETA-DEPENDENT MANNER. TET2 LOSS DID NOT AFFECT EARLY LPS GENE RESPONSES IN VITRO, BUT INCREASED IL-1B, IL-6, AND ARGINASE 1 (ARG1) MRNA EXPRESSION AT LATER STAGES OF STIMULATION IN BONE-MARROW-DERIVED MPHIS (BMMPHIS). TET2-DEFICIENT PERITONEAL MPHIS, HOWEVER, DEMONSTRATED PROFOUND, CONSTITUTIVE EXPRESSION OF LPS-INDUCED GENES ASSOCIATED WITH AN INFLAMMATORY STATE IN VIVO. IN CONTRAST, TET2 DEFICIENCY DID NOT AFFECT ALTERNATIVE MPHI GENE EXPRESSION SIGNIFICANTLY IN RESPONSE TO IL-4. THESE RESULTS SUGGESTED IMPAIRED RESOLUTION OF INFLAMMATION IN THE ABSENCE OF TET2 BOTH IN VITRO AND IN VIVO. FOR THE FIRST TIME, WE ALSO DETECTED TET2 MUTATIONS IN BMMPHIS FROM MDS AND CMML PATIENTS AND ASSAYED THEIR EFFECTS ON LPS RESPONSES, INCLUDING THEIR POTENTIAL INFLUENCE ON HUMAN IL-6 EXPRESSION. OUR RESULTS SHOW THAT TET2 RESTRAINS INFLAMMATION IN MURINE MPHIS AND MICE, RAISING THE POSSIBILITY THAT LOSS OF TET2 FUNCTION IN MPHIS MAY ALTER THE IMMUNE ENVIRONMENT IN THE LARGE ELDERLY POPULATION WITH TET2-MUTANT CHIP AND IN TET2-MUTANT MYELOID CANCER PATIENTS. 2017 5 3759 22 INTEGRATED SINGLE CELL ANALYSIS SHOWS CHRONIC ALCOHOL DRINKING DISRUPTS MONOCYTE DIFFERENTIATION IN THE BONE MARROW NICHE. CHRONIC ALCOHOL DRINKING REWIRES CIRCULATING MONOCYTES AND TISSUE-RESIDENT MACROPHAGES TOWARDS HEIGHTENED INFLAMMATORY STATES WITH COMPROMISED ANTI-MICROBIAL DEFENSES. AS THESE EFFECTS REMAIN CONSISTENT IN SHORT-LIVED MONOCYTES AFTER A 1-MONTH ABSTINENCE PERIOD IT IS UNCLEAR WHETHER THESE CHANGES ARE RESTRICTED TO THE PERIPHERY OR MEDIATED THROUGH ALTERATIONS IN THE PROGENITOR NICHE. TO TEST THIS HYPOTHESIS, WE PROFILED MONOCYTES/MACROPHAGES AND HEMATOPOIETIC STEM CELL PROGENITORS (HSCP) OF THE BONE MARROW COMPARTMENT FROM RHESUS MACAQUES AFTER 12 MONTHS OF ETHANOL CONSUMPTION USING A COMBINATION OF FUNCTIONAL ASSAYS AND SINGLE CELL GENOMICS. BONE MARROW-RESIDENT MONOCYTES/MACROPHAGES FROM ETHANOL-CONSUMING ANIMALS EXHIBITED HEIGHTENED INFLAMMATION. DIFFERENTIATION OF HSCP IN VITRO REVEALED SKEWING TOWARDS MONOCYTES EXPRESSING NEUTROPHIL-LIKE MARKERS WITH HEIGHTENED INFLAMMATORY RESPONSES TO BACTERIAL AGONISTS. SINGLE CELL TRANSCRIPTIONAL ANALYSIS OF HSCPS SHOWED REDUCED PROLIFERATION BUT INCREASED INFLAMMATORY MARKERS IN MATURE MYELOID PROGENITORS. WE OBSERVED TRANSCRIPTIONAL SIGNATURES ASSOCIATED WITH INCREASED OXIDATIVE AND CELLULAR STRESS AS WELL AS OXIDATIVE PHOSPHORYLATION IN IMMATURE AND MATURE MYELOID PROGENITORS. SINGLE CELL ANALYSIS OF THE CHROMATIN LANDSCAPE SHOWED ALTERED DRIVERS OF DIFFERENTIATION IN MONOCYTES AND PROGENITORS. COLLECTIVELY, THESE DATA INDICATE THAT CHRONIC ETHANOL DRINKING RESULTS IN REMODELING OF THE TRANSCRIPTIONAL AND EPIGENETIC LANDSCAPES OF THE BONE MARROW COMPARTMENT LEADING TO ALTERED FUNCTIONS IN THE PERIPHERY. 2023 6 4876 23 OVEREXPRESSION OF ARGINASE 1 IS LINKED TO DNMT3A AND TET2 MUTATIONS IN LOWER-GRADE MYELODYSPLASTIC SYNDROMES AND CHRONIC MYELOMONOCYTIC LEUKEMIA. IMMUNE DYSREGULATION IS A COMMON FEATURE OF MYELODYSPLASTIC SYNDROMES (MDS) AND CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML), PARTICULARLY IN EARLY STAGES. HOWEVER, THE GENETIC BASIS REMAINS POORLY UNDERSTOOD. WE RECENTLY REPORTED THAT MACROPHAGES FROM MICE DEFICIENT IN TET METHYLCYTOSINE DIOXYGENASE 2 (TET2), A MODEL OF MDS/CMML, ARE HYPERINFLAMMATORY AND HAVE INCREASED EXPRESSION OF ARGINASE 1 (ARG1). IN MACROPHAGES AND MYELOID DERIVED SUPPRESSOR CELLS (MDSCS) EXPRESSION OF ARG1 CONTRIBUTES TO T-CELL SUPPRESSION AND IMMUNE EVASION BY L-ARGININE DEPLETION, IN THE SETTING OF CHRONIC INFLAMMATION AND CANCER. SINCE HUMAN MDS AND CMML ARE DRIVEN BY TET2 MUTATIONS AND ASSOCIATED WITH CHRONIC INFLAMMATION, WE HYPOTHESIZED THAT ARGINASE ENZYMATIC ACTIVITY AND ARG1 EXPRESSION WOULD BE INCREASED IN HUMAN MDS/CMML BONE MARROW. ELEVATED ARGINASE ACTIVITY WAS OBSERVED IN BONE MARROW MONONUCLEAR CELLS OF MDS AND CMML PATIENTS WITH LOWER-GRADE FEATURES. IMMUNOHISTOCHEMICAL STUDIES CONFIRMED THAT MYELOMONOCYTIC CELLS OVEREXPRESS ARG1. ADDITIONALLY, MUTATIONS IN THE EPIGENETIC REGULATORS TET2 AND DNMT3A CORRESPONDED TO HIGH ARG1 EXPRESSION AND ACTIVITY. THESE FINDINGS SUGGEST ARG1 IS A BIOMARKER OF IMMUNE DYSREGULATION IN EARLY MDS AND CMML. RECENT MURINE FINDINGS HAVE IMPLICATED TET2 AND DNMT3A IN REGULATION OF INNATE IMMUNITY. OUR STUDY SUGGESTS SIMILAR CHANGES MAY BE DRIVEN BY HUMAN TET2 AND DNMT3A MUTATIONS. 2018 7 5911 25 TARGETED NEXT-GENERATION SEQUENCING IN MYELODYSPLASTIC SYNDROME AND CHRONIC MYELOMONOCYTIC LEUKEMIA AIDS DIAGNOSIS IN CHALLENGING CASES AND IDENTIFIES FREQUENT SPLICEOSOME MUTATIONS IN TRANSFORMED ACUTE MYELOID LEUKEMIA. OBJECTIVES: OPTIMAL INTEGRATION OF NEXT-GENERATION SEQUENCING (NGS) INTO CLINICAL PRACTICE IN HEMATOLOGIC MALIGNANCIES REMAINS UNCLEAR. WE EVALUATE THE UTILITY OF NGS IN MYELOID MALIGNANCIES. METHODS: A 42-GENE PANEL WAS USED TO SEQUENCE 109 CASES OF MYELODYSPLASTIC SYNDROME (MDS, N = 38), CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML, N = 14), MYELOPROLIFERATIVE NEOPLASM (MPN, N = 24), AND MDS AND/OR MPN TRANSFORMED TO ACUTE MYELOID LEUKEMIA (AML, N = 33). RESULTS: AT LEAST ONE PATHOGENIC MUTATION WAS IDENTIFIED IN 74% OF CASES OF MDS, 100% OF CMMLS, AND 96% OF MPNS. IN CONTRAST, ONLY 47% OF CASES OF MDS (18/38) AND 7% (1/14) OF CMMLS EXHIBITED ABNORMAL CYTOGENETICS. IN DIAGNOSTICALLY DIFFICULT CASES OF MDS OR CMML WITH NORMAL CYTOGENETICS, NGS IDENTIFIED A PATHOGENIC MUTATION AND WAS CRITICAL IN ESTABLISHING THE CORRECT DIAGNOSIS. SPLICEOSOMAL GENES AND EPIGENETIC MODIFIERS WERE FREQUENTLY MUTATED. SPLICEOSOME MUTATIONS WERE ALSO FREQUENTLY DETECTED IN AML ARISING FROM MDS, CMML, OR MPN (39%) COMPARED WITH THE REPORTED RATE IN DE NOVO AML (7%-14%). CONCLUSIONS: IN DIFFICULT CASES OF MDS OR MPN, NGS FACILITATES DIAGNOSIS BY DETECTION OF GENE MUTATIONS TO CONFIRM CLONALITY, AND AMLS EVOLVING FROM MDS OR MPN CARRY FREQUENT MUTATIONS IN SPLICEOSOMAL GENES. 2016 8 5965 24 TEN-ELEVEN-TRANSLOCATION 2 (TET2) NEGATIVELY REGULATES HOMEOSTASIS AND DIFFERENTIATION OF HEMATOPOIETIC STEM CELLS IN MICE. THE TEN-ELEVEN-TRANSLOCATION 2 (TET2) GENE ENCODES A MEMBER OF TET FAMILY ENZYMES THAT ALTERS THE EPIGENETIC STATUS OF DNA BY OXIDIZING 5-METHYLCYTOSINE TO 5-HYDROXYMETHYLCYTOSINE (5HMC). SOMATIC LOSS-OF-FUNCTION MUTATIONS OF TET2 ARE FREQUENTLY OBSERVED IN PATIENTS WITH DIVERSE MYELOID MALIGNANCIES, INCLUDING MYELODYSPLASTIC SYNDROMES, MYELOPROLIFERATIVE NEOPLASMS, AND CHRONIC MYELOMONOCYTIC LEUKEMIA. BY ANALYZING MICE WITH TARGETED DISRUPTION OF THE TET2 CATALYTIC DOMAIN, WE SHOW HERE THAT TET2 IS A CRITICAL REGULATOR OF SELF-RENEWAL AND DIFFERENTIATION OF HEMATOPOIETIC STEM CELLS (HSCS). TET2 DEFICIENCY LED TO DECREASED GENOMIC LEVELS OF 5HMC AND AUGMENTED THE SIZE OF THE HEMATOPOIETIC STEM/PROGENITOR CELL POOL IN A CELL-AUTONOMOUS MANNER. IN COMPETITIVE TRANSPLANTATION ASSAYS, TET2-DEFICIENT HSCS WERE CAPABLE OF MULTILINEAGE RECONSTITUTION AND POSSESSED A COMPETITIVE ADVANTAGE OVER WILD-TYPE HSCS, RESULTING IN ENHANCED HEMATOPOIESIS INTO BOTH LYMPHOID AND MYELOID LINEAGES. IN VITRO, TET2 DEFICIENCY DELAYED HSC DIFFERENTIATION AND SKEWED DEVELOPMENT TOWARD THE MONOCYTE/MACROPHAGE LINEAGE. OUR DATA INDICATE THAT TET2 HAS A CRITICAL ROLE IN REGULATING THE EXPANSION AND FUNCTION OF HSCS, PRESUMABLY BY CONTROLLING 5HMC LEVELS AT GENES IMPORTANT FOR THE SELF-RENEWAL, PROLIFERATION, AND DIFFERENTIATION OF HSCS. 2011 9 5789 27 SRSF2(P95H/+) CO-OPERATES WITH LOSS OF TET2 TO PROMOTE MYELOID BIAS AND INITIATE A CHRONIC MYELOMONOCYTIC LEUKEMIA-LIKE DISEASE IN MICE. RECURRENT MUTATIONS IN RNA SPLICING PROTEINS AND EPIGENETIC REGULATORS CONTRIBUTE TO THE DEVELOPMENT OF MYELODYSPLASTIC SYNDROME (MDS) AND RELATED MYELOID NEOPLASMS. IN CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML), SRSF2 MUTATIONS OCCUR IN ~50% OF PATIENTS AND TET2 MUTATIONS IN ~60%. CLONAL ANALYSIS INDICATES THAT EITHER MUTATION CAN ARISE AS THE FOUNDER LESION. BASED ON HUMAN CANCER GENETICS WE CROSSED AN INDUCIBLE SRSF2(P95H/+) MUTANT MODEL WITH TET2(FL/FL) MICE TO MUTATE BOTH CONCOMITANTLY IN HEMATOPOIETIC STEM CELLS. AT 20-24 WEEKS POST MUTATION INDUCTION, WE OBSERVED SUBTLE DIFFERENCES IN THE SRSF2/TET2 MUTANTS COMPARED TO EITHER SINGLE MUTANT. UNDER CONDITIONS OF NATIVE HEMATOPOIESIS WITH AGING, WE SEE A DISTINCT MYELOID BIAS AND MONOCYTOSIS IN THE SRSF2/TET2 MUTANTS. A SUBSET OF THE COMPOUND SRSF2/TET2 MUTANTS DISPLAY AN INCREASED GRANULOCYTIC AND DISTINCTIVE MONOCYTIC PROLIFERATION (MYELOMONOCYTIC HYPERPLASIA), WITH INCREASED IMMATURE PROMONOCYTES AND MONOBLASTS AND BINUCLEATE PROMONOCYTES. EXOME ANALYSIS OF PROGRESSED DISEASE DEMONSTRATED MUTATIONS IN GENES AND PATHWAYS SIMILAR TO THOSE REPORTED IN HUMAN CMML. UPON TRANSPLANTATION, RECIPIENTS DEVELOPED LEUKOCYTOSIS, MONOCYTOSIS, AND SPLENOMEGALY. WE REPRODUCE SRSF2/TET2 CO-OPERATIVITY IN VIVO, YIELDING A DISEASE WITH CORE CHARACTERISTICS OF CMML, UNLIKE SINGLE SRSF2 OR TET2 MUTATION. THIS MODEL REPRESENTS A SIGNIFICANT STEP TOWARD BUILDING HIGH FIDELITY AND GENETICALLY TRACTABLE MODELS OF CMML. 2022 10 4540 50 MULTISTEP PATHOGENESIS OF CHRONIC MYELOMONOCYTIC LEUKEMIA IN PATIENTS. BACKGROUND: A MULTISTEP PATHOGENESIS OF MYELOID LEUKEMIA INCLUDING MUTATIONS IN EPIGENETIC, SPLICEOSOME, AND SIGNALING GENES HAS BEEN RECENTLY DEMONSTRATED IN A PRECLINICAL MODEL BUT IS POORLY VALIDATED IN PATIENTS. METHODS: CLINICAL, PHENOTYPIC, AND BIOLOGIC FEATURES WERE COMPARED BETWEEN THREE DISTINCT MOLECULARLY DEFINED CMML COHORTS INCLUDING TET2 MONOMUTATED PATIENTS (T, N = 10), TET2/SRSF2 BIMUTATED PATIENTS (TS, N = 19), AND PATIENTS WHO HAD NRAS MUTATIONS IN ADDITION TO TET2/SRSF2 COMUTATIONS (TSN, N = 14). RESULTS: MEDIAN SURVIVAL WAS 90, 45, AND 9 MONTHS, RESPECTIVELY (P = .001). WHEREAS NO PATIENT IN THE T AND TS GROUP TRANSFORMED INTO ACUTE MYELOID LEUKEMIA (AML), 6/14 PATIENTS IN THE TSN GROUP HAD AML AT STUDY ENTRY OR TRANSFORMED DURING FOLLOW-UP. LEUKOCYTE COUNTS, BLAST CELL COUNTS, AND LDH LEVELS WERE SIGNIFICANTLY HIGHER IN TSN VS. TS AND T, RESPECTIVELY, WHEREAS HEMOGLOBIN AND PLATELET VALUES WERE NOT SIGNIFICANTLY DIFFERENT. INCREASED GROWTH FACTOR-INDEPENDENT MYELOID COLONY FORMATION WAS RESTRICTED TO TSN BUT NOT FOUND IN T AND TS, RESPECTIVELY. THE PROPORTION OF PATIENTS SHOWING IN VITRO MYELOMONOCYTIC SKEWING IN T, TS, AND TSN WAS 0%, 56%, AND 100%, RESPECTIVELY (P = .010). CONCLUSION: OUR RESULTS DEMONSTRATE THAT THE MODEL OF MULTISTEP PATHOGENESIS IN CMML CAN BE RECAPITULATED IN PATIENTS REGARDING CLINICAL, PHENOTYPIC, AND BIOLOGIC FEATURES. 2022 11 2277 29 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 12 1184 16 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 5980 26 TET2 MUTATIONS WERE PREDICTIVE OF INFERIOR PROGNOSIS IN THE PRESENCE OF ASXL1 MUTATIONS IN PATIENTS WITH CHRONIC MYELOMONOCYTIC LEUKEMIA. BACKGROUND: SOMATIC MUTATIONS INVOLVING EPIGENETIC REGULATORS, HISTONE MODIFICATION AND CHROMATIN REGULATION, SPLICING COMPONENTS, TRANSCRIPTION FACTORS AND SIGNALING REGULATOR GENES ARE COMMON IN CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML) PATIENTS. IT HAS BEEN CONSENSUS THAT ASXL1 MUTATIONS HAVE ADVERSELY IMPACT ON OVERALL SURVIVAL (OS), WHILE THE EFFECT OF TET2 MUTATIONS REMAINS CONTROVERSIAL AND UNDEFINED. METHODS: ASXL1 AND TET2 MUTATIONS WERE ANALYZED IN 141 PATIENTS WITH CMML USING SANGER SEQUENCING, WITH THE AIM TO IDENTIFY THE INTERPLAY OF ASXL1 AND TET2 MUTATIONS IN THE PROGNOSIS OF CMML. RESULTS: SIXTY-FIVE (46.1%) OF THE CMML PATIENTS HARBORED ASXL1 MUTATIONS (FRAMESHIFT AND NONSENSE), AND 46 (32.6%) HAD TET2 MUTATIONS (FRAME SHIFT, NONSENSE AND MISSENSE). IN A SEPARATE MULTIVARIABLE ANALYSIS THAT INCLUDED THE MAYO PROGNOSTIC MODEL AS A SINGLE VARIABLE ALONG WITH ASXL1WT/TET2WT, THE RESPECTIVE HAZARD RATIOS OF ASXL1MUT/TET2MUT, ASXL1MUT/TET2WT AND ASXL1WT/TET2MUT WERE 4.7 (95% CI, 2.2-10.3; P<0.001), 2.2 (95% CI, 1.1-4.2; P=0.025) AND 1.3 (95% CI, 0.6-2.5; P=0.521). CONCLUSIONS: OUR STUDY SHOWED THAT ASXL1 MUTATIONS PREDICT INFERIOR OS, AND ADDITIONAL TET2 MUTATIONS WERE ASSOCIATED WITH POOR SURVIVAL IN THE PRESENCE OF ASXL1 MUTATIONS OF CMML PATIENTS. 2016 14 4553 35 MUTATIONAL LANDSCAPE OF CHRONIC MYELOMONOCYTIC LEUKEMIA IN CHINESE PATIENTS. BACKGROUND: CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML) IS A RARE AND HETEROGENEOUS HEMATOLOGICAL MALIGNANCY. IT HAS BEEN SHOWN THAT THE MOLECULAR ABNORMALITIES SUCH AS ASXL1, TET2, SETBP1, AND SRSF2 MUTATIONS ARE COMMON IN CAUCASIAN POPULATION. METHODS: WE RETROSPECTIVELY ANALYZED 178 CHINESE CMML PATIENTS. THE TARGETED NEXT GENERATION SEQUENCING (NGS) WAS USED TO EVALUATE 114 GENE VARIATIONS, AND THE PROGNOSTIC FACTORS FOR OS WERE DETERMINED BY COX REGRESSION ANALYSIS. RESULTS: THE CMML PATIENTS SHOWED A UNIQUE MUTATIONAL SPECTRUM, INCLUDING TET2 (36.5%), NRAS (31.5%), ASXL1 (28.7%), SRSF2 (24.7%), AND RUNX1 (21.9%). OF THE 102 PATIENTS WITH CLONAL ANALYSIS, THE ANCESTRAL EVENTS PREFERENTIALLY OCCURRED IN TET2 (18.5%), SPLICING FACTORS (16.5%), RAS (14.0%), AND ASXL1 (7.8%), AND THE SUBCLONAL GENES WERE MAINLY ASXL1, TET2, AND RAS. IN ADDITION, THE SECONDARY ACUTE MYELOID LEUKEMIA (SAML) TRANSFORMED FROM CMML OFTEN HAD MUTATIONS IN DNMT3A, ETV6, FLT3, AND NPM1, WHILE THE PRIMARY AML (PAML) DEMONSTRATED MORE MUTATIONS IN CEBPA, DNMT3A, FLT3, IDH1/2, NPM1, AND WT1. IT WAS OF NOTE THAT A SERIES OF CLONES WERE EMERGED DURING THE PROGRESSION FROM CMML TO AML, INCLUDING DNMT3A, FLT3, AND NPM1. BY UNIVARIATE ANALYSIS, ASXL1 MUTATION, INTERMEDIATE- AND HIGH-RISK CYTOGENETIC ABNORMALITY, CMML-SPECIFIC PROGNOSTIC SCORING SYSTEM (CPSS) STRATIFICATIONS (INTERMEDIATE-2 AND HIGH GROUP), AND TREATMENT OPTIONS (BEST SUPPORTIVE CARE) PREDICTED FOR WORSE OS. MULTIVARIATE ANALYSIS REVEALED A SIMILAR OUTCOME. CONCLUSIONS: THE COMMON MUTATIONS IN CHINESE CMML PATIENTS INCLUDED EPIGENETIC MODIFIERS (TET2 AND ASXL1), SIGNALING TRANSDUCTION PATHWAY COMPONENTS (NRAS), AND SPLICING FACTOR (SRSF2). THE CMML PATIENTS WITH DNMT3A, ETV6, FLT3, AND NPM1 MUTATIONS TENDED TO PROGRESS TO SAML. ASXL1 MUTATION AND THERAPEUTIC MODALITIES WERE INDEPENDENT PROGNOSTIC FACTORS FOR CMML. 2022 15 4555 27 MUTATIONAL SPECTRUM ANALYSIS OF CHRONIC MYELOMONOCYTIC LEUKEMIA INCLUDES GENES ASSOCIATED WITH EPIGENETIC REGULATION: UTX, EZH2, AND DNMT3A. CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML), A MYELODYSPLASTIC/MYELOPROLIFERATIVE NEOPLASM, IS CHARACTERIZED BY MONOCYTIC PROLIFERATION, DYSPLASIA, AND PROGRESSION TO ACUTE MYELOID LEUKEMIA. CMML HAS BEEN ASSOCIATED WITH SOMATIC MUTATIONS IN DIVERSE RECENTLY IDENTIFIED GENES. WE ANALYZED 72 WELL-CHARACTERIZED PATIENTS WITH CMML (N = 52) AND CMML-DERIVED ACUTE MYELOID LEUKEMIA (N = 20) FOR RECURRENT CHROMOSOMAL ABNORMALITIES WITH THE USE OF ROUTINE CYTOGENETICS AND SINGLE NUCLEOTIDE POLYMORPHISM ARRAYS ALONG WITH COMPREHENSIVE MUTATIONAL SCREENING. CYTOGENETIC ABERRATIONS WERE PRESENT IN 46% OF CASES, WHEREAS SINGLE NUCLEOTIDE POLYMORPHISM ARRAY INCREASED THE DIAGNOSTIC YIELD TO 60%. AT LEAST 1 MUTATION WAS FOUND IN 86% OF ALL CASES; NOVEL UTX, DNMT3A, AND EZH2 MUTATIONS WERE FOUND IN 8%, 10%, AND 5.5% OF PATIENTS, RESPECTIVELY. TET2 MUTATIONS WERE PRESENT IN 49%, ASXL1 IN 43%, CBL IN 14%, IDH1/2 IN 4%, KRAS IN 7%, NRAS IN 4%, AND JAK2 V617F IN 1% OF PATIENTS. VARIOUS MUTANT GENOTYPE COMBINATIONS WERE OBSERVED, INDICATING MOLECULAR HETEROGENEITY IN CMML. OUR RESULTS SUGGEST THAT MOLECULAR DEFECTS AFFECTING DISTINCT PATHWAYS CAN LEAD TO SIMILAR CLINICAL PHENOTYPES. 2011 16 1075 25 CLONAL HEMATOPOIESIS DRIVEN BY DNMT3A AND TET2 MUTATIONS: ROLE IN MONOCYTE AND MACROPHAGE BIOLOGY AND ATHEROSCLEROTIC CARDIOVASCULAR DISEASE. PURPOSE OF REVIEW: CLONAL HEMATOPOIESIS OF INDETERMINATE POTENTIAL (CHIP), DEFINED BY THE PRESENCE OF SOMATIC MUTATIONS IN HEMATOPOIETIC CELLS, IS ASSOCIATED WITH ADVANCED AGE AND INCREASED MORTALITY DUE TO CARDIOVASCULAR DISEASE. GENE MUTATIONS IN DNMT3A AND TET2 ARE THE MOST FREQUENTLY IDENTIFIED VARIANTS AMONG PATIENTS WITH CHIP AND PROVIDE SELECTIVE ADVANTAGE THAT SPURS CLONAL EXPANSION AND MYELOID SKEWING. ALTHOUGH DNMT3A AND TET2 APPEAR TO HAVE OPPOSING ENZYMATIC INFLUENCE ON DNA METHYLATION, MOUNTING DATA HAS CHARACTERIZED CONVERGENT INFLAMMATORY PATHWAYS, PROVIDING INSIGHTS TO HOW CHIP MAY MEDIATE ATHEROSCLEROTIC CARDIOVASCULAR DISEASE (ASCVD). RECENT FINDINGS: WE REVIEW A MULTITUDE OF STUDIES THAT CHARACTERIZE ABERRANT INFLAMMATORY SIGNALING AS RESULT OF DNMT3A AND TET2 DEFICIENCY IN MONOCYTES AND MACROPHAGES, IMMUNE CELLS WITH PROMINENT ROLES IN ATHEROSCLEROSIS. ALTHOUGH SPECIFIC DNA METHYLATION SIGNATURES ASSOCIATED WITH THESE KNOWN EPIGENETIC REGULATORS HAVE BEEN IDENTIFIED, MANY STUDIES HAVE ALSO CHARACTERIZED DIVERSE MODULATORY FUNCTIONS OF DNTM3A AND TET2 THAT URGE CELL AND CONTEXT-SPECIFIC EXPERIMENTAL STUDIES TO FURTHER DEFINE HOW DNMT3A AND TET2 MAY NONENZYMATICALLY ACTIVATE INFLAMMATORY PATHWAYS WITH CLINICALLY MEANINGFUL CONSEQUENCES. SUMMARY: CHIP, COMMON IN ELDERLY INDIVIDUALS, PROVIDES AN OPPORTUNITY UNDERSTAND AND POTENTIALLY MODIFY AGE-RELATED CHRONIC INFLAMMATORY ASCVD RISK. 2022 17 3871 22 JUVENILE MYELOMONOCYTIC LEUKEMIA - A BONA FIDE RASOPATHY SYNDROME. JUVENILE MYELOMONOCYTIC LEUKEMIA (JMML) IS A PEDIATRIC MYELODYSPLASTIC/MYELOPROLIFERATIVE NEOPLASM OVERLAP SYNDROME WITH SUSTAINED PERIPHERAL BLOOD MONOCYTOSIS, AGGRESSIVE FEATURES, AND POOR OUTCOMES. IN >90% OF CASES JMML IS DRIVEN BY GERMLINE OR SOMATIC MUTATIONS INVOLVING THE CANONICAL RAS PATHWAY (PTPN11, NRAS, CBL, KRAS AND NF1), WITH SOMATIC MUTATIONS/ALTERATIONS IN RAS PATHWAY GENES (SECOND HIT), SETBP1, ASXL1 AND JAK3 RESULTING IN DISEASE PROGRESSION. WHILE SPONTANEOUS REGRESSION HAS BEEN SEEN IN GERMLINE PTPN11 AND CBL MUTANT JMML, IN MOST PATIENTS, ALLOGENEIC STEM CELL TRANSPLANT IS THE ONLY CURATIVE MODALITY. JMML SHARES SEVERAL PHENOTYPIC FEATURES WITH ITS ADULT COUNTERPART PROLIFERATIVE, CHRONIC MYELOMONOCYTIC LEUKEMIA (PCMML). PCMML LARGELY OCCURS DUE TO RAS PATHWAY MUTATIONS THAT OCCUR IN THE CONTEXT OF AGE RELATED CLONAL HEMATOPOIESIS (TET2, SRSF2, ASXL1), WHILE JMML IS A BONA FIDE RASOPATHY, WITH ADDITIONAL SOMATIC MUTATIONS, INCLUDING IN EPIGENETIC REGULATORS GENES RESULTING IN DISEASE PROGRESSION. 2020 18 6040 26 THE CHRONIC MYELOPROLIFERATIVE DISORDERS: CLONALITY AND CLINICAL HETEROGENEITY. THE CHRONIC MYELOPROLIFERATIVE DISORDERS (MPD), POLYCYTHEMIA VERA (PV), CHRONIC IDIOPATHIC MYELOFIBROSIS (IMF), ESSENTIAL THROMBOCYTOSIS (ET), AND CHRONIC MYELOGENOUS LEUKEMIA (CML), ARE THOUGHT TO BE CLONAL DISORDERS ARISING IN A MULTIPOTENT HEMATOPOIETIC PROGENITOR CELL. HOWEVER, ESTABLISHING THE DIAGNOSIS OF AN MPD OTHER THAN CML IS PROBLEMATIC DUE TO A LACK OF CLINICALLY APPLICABLE CLONAL MARKERS. FURTHERMORE, IN SOME PATIENTS, IN WHOM A CLASSICAL MPD PHENOTYPE IS PRESENT, THE HEMATOPOIETIC STEM CELLS APPEAR TO BE POLYCLONAL, SUGGESTING THAT THE CHRONIC MPD OTHER THAN CML MAY ACTUALLY BE A GENETICALLY HETEROGENEOUS GROUP OF DISORDERS. FURTHERMORE, SINCE THE ABERRANT CLONE IS BELIEVED TO ARISE FROM A MULTIPOTENT HEMATOPOIETIC STEM CELL, THE NON-CML CHRONIC MPD-ET, PV, AND IMF-COULD BE RELATED. ADDITIONAL UNRESOLVED ISSUES REGARDING THE MPD INCLUDE: IDENTIFICATION OF THE MULTIPOTENT HEMATOPOIETIC PROGENITOR CELL INVOLVED, THE MOLECULAR BASIS FOR THE CLINICAL HETEROGENEITY AMONGST THE INDIVIDUAL MPD, THE CLINICAL SIGNIFICANCE OF CLONALITY IN NON-CML MPD, AND RECONCILIATION OF THERAPY WITH THE CLONAL AND CLINICAL HETEROGENEITY OF THESE DISORDERS. DETERMINATION OF CLONALITY HAS LARGELY BEEN CARRIED OUT USING X CHROMOSOME-LINKED POLYMORPHISMS, BUT SUCH STUDIES ARE LIMITED TO WOMEN AND WITH INCREASING PATIENT AGE ARE COMPROMISED BY SKEWING OF ALLELIC EXPRESSION IN BOTH NEUTROPHILS AND T LYMPHOCYTES, MAKING THE RESULTS DIFFICULT TO INTERPRET. X CHROMOSOME-LINKED POLYMORPHISM STUDIES HAVE INDICATED THAT IN PV THE TARGET STEM CELL IS ONE THAT GIVES RISE TO BOTH LYMPHOID AND MYELOID PROGENITORS. RECENTLY, TWO EPIGENETIC MARKERS HAVE BEEN IDENTIFIED IN THE MPD: IMPAIRED EXPRESSION OF THE THROMBOPOIETIN RECEPTOR, MPL, IN PLATELETS AND MEGAKARYOCYTES, AND OVEREXPRESSION IN NEUTROPHILS OF THE MRNA OF A GENE DESIGNATED POLYCYTHEMIA RUBRA VERA-1 (PRV-1). THE ROLE OF THESE EPIGENETIC ABNORMALITIES IN THE DIAGNOSIS OF THE MPD REMAINS TO BE ESTABLISHED. CURRENTLY, GIVEN THE UNRESOLVED ISSUES WITH RESPECT TO THE CLINICAL AND CLONAL HETEROGENEITY OF THE MPD, TREATMENT NEEDS TO BE TAILORED INDIVIDUALLY IN PATIENTS WITH AN MPD. 2004 19 4748 23 NOVEL MUTATIONS AND THEIR FUNCTIONAL AND CLINICAL RELEVANCE IN MYELOPROLIFERATIVE NEOPLASMS: JAK2, MPL, TET2, ASXL1, CBL, IDH AND IKZF1. MYELOPROLIFERATIVE NEOPLASMS (MPNS) ORIGINATE FROM GENETICALLY TRANSFORMED HEMATOPOIETIC STEM CELLS THAT RETAIN THE CAPACITY FOR MULTILINEAGE DIFFERENTIATION AND EFFECTIVE MYELOPOIESIS. BEGINNING IN EARLY 2005, A NUMBER OF NOVEL MUTATIONS INVOLVING JANUS KINASE 2 (JAK2), MYELOPROLIFERATIVE LEUKEMIA VIRUS (MPL), TET ONCOGENE FAMILY MEMBER 2 (TET2), ADDITIONAL SEX COMBS-LIKE 1 (ASXL1), CASITAS B-LINEAGE LYMPHOMA PROTO-ONCOGENE (CBL), ISOCITRATE DEHYDROGENASE (IDH) AND IKAROS FAMILY ZINC FINGER 1 (IKZF1) HAVE BEEN DESCRIBED IN BCR-ABL1-NEGATIVE MPNS. HOWEVER, NONE OF THESE MUTATIONS WERE MPN SPECIFIC, DISPLAYED MUTUAL EXCLUSIVITY OR COULD BE TRACED BACK TO A COMMON ANCESTRAL CLONE. JAK2 AND MPL MUTATIONS APPEAR TO EXERT A PHENOTYPE-MODIFYING EFFECT AND ARE DISTINCTLY ASSOCIATED WITH POLYCYTHEMIA VERA, ESSENTIAL THROMBOCYTHEMIA AND PRIMARY MYELOFIBROSIS; THE CORRESPONDING MUTATIONAL FREQUENCIES ARE APPROXIMATELY 99, 55 AND 65% FOR JAK2 AND 0, 3 AND 10% FOR MPL MUTATIONS. THE INCIDENCE OF TET2, ASXL1, CBL, IDH OR IKZF1 MUTATIONS IN THESE DISORDERS RANGES FROM 0 TO 17%; THESE LATTER MUTATIONS ARE MORE COMMON IN CHRONIC (TET2, ASXL1, CBL) OR JUVENILE (CBL) MYELOMONOCYTIC LEUKEMIAS, MASTOCYTOSIS (TET2), MYELODYSPLASTIC SYNDROMES (TET2, ASXL1) AND SECONDARY ACUTE MYELOID LEUKEMIA, INCLUDING BLAST-PHASE MPN (IDH, ASXL1, IKZF1). THE FUNCTIONAL CONSEQUENCES OF MPN-ASSOCIATED MUTATIONS INCLUDE UNREGULATED JAK-STAT (JANUS KINASE/SIGNAL TRANSDUCER AND ACTIVATOR OF TRANSCRIPTION) SIGNALING, EPIGENETIC MODULATION OF TRANSCRIPTION AND ABNORMAL ACCUMULATION OF ONCOPROTEINS. HOWEVER, IT IS NOT CLEAR AS TO WHETHER AND HOW THESE ABNORMALITIES CONTRIBUTE TO DISEASE INITIATION, CLONAL EVOLUTION OR BLASTIC TRANSFORMATION. 2010 20 4838 23 ONCOGENIC N-RAS AND TET2 HAPLOINSUFFICIENCY COLLABORATE TO DYSREGULATE HEMATOPOIETIC STEM AND PROGENITOR CELLS. CONCURRENT GENETIC LESIONS EXIST IN A MAJORITY OF PATIENTS WITH HEMATOLOGIC MALIGNANCIES. AMONG THESE, SOMATIC MUTATIONS THAT ACTIVATE RAS ONCOGENES AND INACTIVATE THE EPIGENETIC MODIFIER TEN-ELEVEN TRANSLOCATION 2 (TET2) FREQUENTLY CO-OCCUR IN HUMAN CHRONIC MYELOMONOCYTIC LEUKEMIAS (CMMLS) AND ACUTE MYELOID LEUKEMIAS, SUGGESTING A COOPERATIVITY IN MALIGNANT TRANSFORMATION. TO TEST THIS, WE APPLIED A CONDITIONAL MURINE MODEL THAT ENDOGENOUSLY EXPRESSED ONCOGENIC NRAS(G12D) AND MONOALLELIC LOSS OF TET2 AND EXPLORED THE COLLABORATIVE ROLE SPECIFICALLY WITHIN HEMATOPOIETIC STEM AND PROGENITOR CELLS (HSPCS) AT DISEASE INITIATION. WE DEMONSTRATE THAT THE 2 MUTATIONS COLLABORATED TO ACCELERATE A TRANSPLANTABLE CMML-LIKE DISEASE IN VIVO, WITH AN OVERALL SHORTENED SURVIVAL AND INCREASED DISEASE PENETRANCE COMPARED WITH SINGLE MUTANTS. AT PRELEUKEMIC STAGE, N-RAS(G12D) AND TET2 HAPLOINSUFFICIENCY TOGETHER INDUCED BALANCED HEMATOPOIETIC STEM CELL (HSC) PROLIFERATION AND ENHANCED COMPETITIVENESS. NRAS(G12D/+)/TET2(+/-) HSCS DISPLAYED INCREASED SELF-RENEWAL IN PRIMARY AND SECONDARY TRANSPLANTATIONS, WITH SIGNIFICANTLY HIGHER RECONSTITUTION THAN SINGLE MUTANTS. STRIKINGLY, THE 2 MUTATIONS TOGETHER CONFERRED LONG-TERM RECONSTITUTION AND SELF-RENEWAL POTENTIAL TO MULTIPOTENT PROGENITORS, A POOL OF CELLS THAT USUALLY HAVE LIMITED SELF-RENEWAL COMPARED WITH HSCS. MOREOVER, HSPCS FROM NRAS(G12D/+)/TET2(+/-) MICE DISPLAYED INCREASED CYTOKINE SENSITIVITY IN RESPONSE TO THROMBOPOIETIN. THEREFORE, OUR STUDIES ESTABLISH A NOVEL TRACTABLE CMML MODEL AND PROVIDE INSIGHTS INTO HOW DYSREGULATED SIGNALING PATHWAYS AND EPIGENETIC MODIFIERS COLLABORATE TO MODULATE HSPC FUNCTION AND PROMOTE LEUKEMOGENESIS. 2018