1 2956 122 GENETIC AND EPIGENETIC FACTORS INTERACTING WITH CLONAL HEMATOPOIESIS RESULTING IN CHRONIC MYELOMONOCYTIC LEUKEMIA. PURPOSE OF REVIEW: SINCE 2016, THE WHO HAS RECOGNIZED THE SIGNIFICANT PHENOTYPIC HETEROGENEITY OF CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML) AS A MYELODYSPLASTIC SYNDROME/MYELOPROLIFERATIVE NEOPLASM (MDS/MPN) OVERLAP DISEASE. ALTHOUGH SHARING MANY SOMATIC MUTATIONS WITH MDS AND MPN, THE PURPOSE OF THIS REVIEW IS TO PUT RECENT BIOLOGICAL FINDINGS OF CMML IN THE CONTEXT OF EVOLUTIONARY THEORY, HIGHLIGHTING IT AS A DISTINCT EVOLUTIONARY TRAJECTORY OCCURRING IN THE CONTEXT OF CLONAL HEMATOPOIESIS. RECENT FINDINGS: CLONAL HEMATOPOIESIS OF INDETERMINATE POTENTIAL (CHIP), WITH A MUTATIONAL SPECTRUM AND PREVALENCE CORRELATED WITH AGE, HAS BEEN DEFINED. ENRICHED IN DNMT3A, TET2, AND ASXL1 MUTATIONS, CLONAL EVOLUTION CAN PROGRESS INTO VARIOUS EVOLUTIONARY TRAJECTORIES INCLUDING CMML. IMPACT OF FOUNDER MUTATIONS (PRIMARILY TET2) ON INCREASED HEMATOPOIETIC STEM CELL FITNESS HAS BEEN WELL CHARACTERIZED. EPISTATIC INTERACTIONS BETWEEN MUTATIONS AND EPIGENETIC EVENTS HAVE BEEN EXPLORED, BOTH IN CMML AND ITS PEDIATRIC COUNTERPART JUVENILE MYELOMONOCYTIC LEUKEMIA, INCLUDING CMML TRANSFORMATION TO ACUTE MYELOID LEUKEMIA. TOGETHER, THESE FINDINGS HAVE CONTRIBUTED SIGNIFICANTLY TOWARD CMML EVOLUTIONARY DYNAMICS. SUMMARY: DESPITE RELATIVELY FEW 'DRIVER' MUTATIONS IN CMML, EVOLUTIONARY DEVELOPMENT OF CHRONIC LEUKEMIA REMAINS INCOMPLETELY UNDERSTOOD. RECENT STUDIES HAVE SHED LIGHT ON THE IMPORTANCE OF STUDYING EPIGENETIC CONSEQUENCES OF MUTATIONS AND EPISTASIS BETWEEN KEY MUTATIONS TO BETTER UNDERSTAND CLONAL ARCHITECTURE AND EVOLUTIONARY DYNAMICS. 2020 2 2981 35 GENETIC COMPLEXITY OF CHRONIC MYELOMONOCYTIC LEUKEMIA. IN RECENT YEARS CMML HAS RECEIVED INCREASED ATTENTION AS THE MOST COMMONLY OBSERVED MDS/MPN OVERLAP SYNDROME. RENEWED INTEREST HAS OCCURRED IN PART DUE TO WIDESPREAD ADOPTION OF NEXT-GENERATION SEQUENCING PANELS THAT HELP RENDER THE DIAGNOSIS IN THE ABSENCE OF MORPHOLOGIC DYSPLASIA. ALTHOUGH MOST CMML PATIENTS EXHIBIT SOMATIC MUTATIONS IN EPIGENETIC MODIFIERS, SPLICEOSOME COMPONENTS, TRANSCRIPTION FACTORS AND SIGNAL TRANSDUCTION GENES, IT IS INCREASINGLY CLEAR THAT A SMALL SUBSET HARBORS AN INHERITED PREDISPOSITION TO CMML AND OTHER MYELOID NEOPLASMS. MORE INTRIGUING IS THE FACT THAT THE MUTATIONAL SPECTRUM OBSERVED IN CMML IS FOUND IN OTHER TYPES OF MYELOID LEUKEMIAS, BEGGING THE QUESTION OF HOW SIMILAR GENETIC BACKGROUNDS CAN LEAD TO SUCH DIVERGENT CLINICAL PHENOTYPES. IN THIS REVIEW WE PRESENT A CONTEMPORARY SNAPSHOT OF THE GENETIC COMPLEXITY INHERENT TO CMML, EXPLORE THE RELATIONSHIP BETWEEN GENOTYPE-PHENOTYPE AND PRESENT A STEPWISE MODEL OF CMML PATHOGENESIS AND PROGRESSION. 2021 3 957 30 CHRONIC MYELOMONOCYTIC LEUKAEMIA: A CONCISE CLINICAL AND PATHOPHYSIOLOGICAL REVIEW. CHRONIC MYELOMONOCYTIC LEUKAEMIA (CMML) IS A CLONAL HAEMATOPOIETIC STEM CELL DISORDER WITH MYELODYSPLASTIC AND MYELOPROLIFERATIVE OVERLAP FEATURES, AND AN INHERENT TENDENCY TO TRANSFORM TO ACUTE MYELOID LEUKAEMIA. APPROXIMATELY 30% OF PATIENTS PRESENT WITH CLONAL CYTOGENETIC ABNORMALITIES, WHILE ALMOST 90% HAVE MOLECULAR ABERRATIONS INVOLVING EPIGENETIC REGULATION, THE SPLICEOSOME COMPONENT MACHINERY, TUMOUR SUPPRESSOR GENES AND TRANSCRIPTION FACTORS/REGULATORS. NUMEROUS PROGNOSTIC MODELS EXIST FOR CMML, WITH MORE RECENT MODELS INCORPORATING PROGNOSTIC MUTATIONS, SUCH AS THOSE INVOLVING ASXL1. OTHER VARIABLES THAT SEEM TO CONSISTENTLY AFFECT OUTCOMES INCLUDE THE DEGREE OF LEUCOCYTOSIS/MONOCYTOSIS, ANAEMIA AND THROMBOCYTOPENIA. ALLOGENEIC STEM CELL TRANSPLANT REMAINS THE ONLY CURATIVE OPTION FOR CMML, WHILE HYPOMETHYLATING AGENTS CAN BE USED FOR TRANSPLANT-INELIGIBLE PATIENTS OR THOSE WITHOUT SUITABLE STEM CELL SOURCES. TARGETING BIOLOGICAL PATHWAYS ACTIVATED IN CMML OFFERS POTENTIAL HOPE FOR MORE EFFECTIVE AND LESS TOXIC THERAPIES. 2014 4 963 37 CHRONIC MYELOMONOCYTIC LEUKEMIA: INSIGHTS INTO BIOLOGY, PROGNOSTIC FACTORS, AND TREATMENT. PURPOSE OF REVIEW: CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML) IS A CLONAL HEMATOLOGICAL MALIGNANCY CHARACTERIZED BY BOTH DYSPLASTIC AND PROLIFERATIVE FEATURES, WITH AN INHERENT RISK FOR LEUKEMIC TRANSFORMATION. WITH THE HELP OF THIS REVIEW, WE AIM TO SUMMARIZE KEY CONCEPTS WITH REGARDS TO CMML BIOLOGY, DIAGNOSIS, RISK STRATIFICATION, AND THERAPEUTICS. RECENT FINDINGS: BASED ON RECENT STUDIES, CMML IS HALLMARKED BY A RELATIVELY LOW GENETIC COMPLEXITY, WHICH CONTRASTS WITH A COMPELLING PHENOTYPICAL HETEROGENEITY, LARGELY DRIVEN BY EPIGENETIC MECHANISMS. RECENT ADVANCES IN THE CHARACTERIZATION OF CMML BIOLOGY HAS LED TO AN IMPROVEMENT IN RISK-STRATIFICATION, BY MEANS OF INCORPORATING PROGNOSTICALLY RELEVANT GENE MUTATIONS. THIS, HOWEVER, HAS NOT SIGNIFICANTLY IMPACTED AVAILABLE THERAPIES AND OUTCOMES CONTINUE TO REMAIN POOR. ADVANCES IN CMML BIOLOGY HAVE BETTER EXPLAINED THE PHENOTYPIC HETEROGENEITY, WHILE CONTINUING TO DEFINE THE GENETIC AND EPIGENETIC LANDSCAPE. IN SPITE OF RECENT ADVANCES, LIMITED EFFECTIVE THERAPIES EXIST AND DEVELOPING RATIONALLY DERIVED THERAPEUTIC APPROACHES IS MUCH NEEDED. 2019 5 384 43 AN EVOLUTIONARY PERSPECTIVE ON CHRONIC MYELOMONOCYTIC LEUKEMIA. CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML) SHARES WITH OTHER MYELOID DISEASES A NUMBER OF SOMATIC GENE MUTATIONS. THESE MUTATIONS CAN NOW BE INTEGRATED WITHIN THE FRAMEWORK OF EVOLUTION THEORY TO ADDRESS THE MECHANISMS OF THE DISEASE. SEVERAL EVIDENCES INDICATE THAT THE DISEASE EMERGES IN ADULT HEMATOPOIETIC STEM CELLS (HSC) THROUGH THE AGE-DEPENDENT ACCUMULATION OF DNA DAMAGE, LEADING STOCHASTICALLY TO A DRIVER MUTATION THAT CONFERS A COMPETITIVE ADVANTAGE TO THE CELL. A MUTATION IN TET2 GENE COULD BE ONE OF THESE DRIVER MUTATIONS PROVOKING THE EMERGENCE OF CLONALITY. AFTER A LONG LATENCY, SECONDARY LESIONS, SUCH AS MUTATIONS IN THE SRSF2 GENE, CONTRIBUTE TO PROGRESSION TO FULL-BLOWN MALIGNANCY, WITH ABNORMAL DIFFERENTIATION. ADDITIONAL MUTATIONS ACCUMULATE AND BRANCHING ARISING MOSTLY THROUGH MITOTIC RECOMBINATION GENERATES CLONAL HETEROGENEITY. MODIFICATIONS IN THE MICROENVIRONMENT PROBABLY AFFECT THIS CLONAL DYNAMICS, WHEREAS EPIGENETIC ALTERATIONS, SUCH AS HYPERMETHYLATION OF THE TIF1GAMMA GENE PROMOTER, MAY GENERATE PHENOTYPIC DIVERSIFICATION OF OTHERWISE CLONAL POPULATIONS. THE PRESERVED ALTHOUGH DEREGULATED MYELOID DIFFERENTIATION THAT CHARACTERIZES CMML, WITH GRANULOMONOCYTE EXPANSION AND VARIOUS CYTOPENIAS, MAY DEPEND ON EARLY CLONAL DOMINANCE IN THE HEMATOPIETIC CELL HIERARCHY. PROGRESSION TO ACUTE MYELOID LEUKEMIA OBSERVED IN 25-30% OF THE PATIENTS MAY ARISE FROM THE MASSIVE EXPANSION OF A CLONE WITH NOVEL GENETIC LESIONS, PROVIDING A HIGH FITNESS TO PREVIOUSLY MINOR SUBCLONES WHEN IN CHRONIC PHASE OF THE DISEASE. THIS REVIEW DISCUSSES THE VARIOUS MODELS OF DISEASE EMERGENCE AND PROGRESSION AND HOW THIS RECENT KNOWLEDGE COULD DRIVE RATIONAL THERAPEUTIC STRATEGIES. 2013 6 1039 43 CLINICAL AND BIOLOGICAL IMPLICATIONS OF DRIVER MUTATIONS IN MYELODYSPLASTIC SYNDROMES. MYELODYSPLASTIC SYNDROMES (MDS) ARE A HETEROGENEOUS GROUP OF CHRONIC HEMATOLOGICAL MALIGNANCIES CHARACTERIZED BY DYSPLASIA, INEFFECTIVE HEMATOPOIESIS AND A VARIABLE RISK OF PROGRESSION TO ACUTE MYELOID LEUKEMIA. SEQUENCING OF MDS GENOMES HAS IDENTIFIED MUTATIONS IN GENES IMPLICATED IN RNA SPLICING, DNA MODIFICATION, CHROMATIN REGULATION, AND CELL SIGNALING. WE SEQUENCED 111 GENES ACROSS 738 PATIENTS WITH MDS OR CLOSELY RELATED NEOPLASMS (INCLUDING CHRONIC MYELOMONOCYTIC LEUKEMIA AND MDS-MYELOPROLIFERATIVE NEOPLASMS) TO EXPLORE THE ROLE OF ACQUIRED MUTATIONS IN MDS BIOLOGY AND CLINICAL PHENOTYPE. SEVENTY-EIGHT PERCENT OF PATIENTS HAD 1 OR MORE ONCOGENIC MUTATIONS. WE IDENTIFY COMPLEX PATTERNS OF PAIRWISE ASSOCIATION BETWEEN GENES, INDICATIVE OF EPISTATIC INTERACTIONS INVOLVING COMPONENTS OF THE SPLICEOSOME MACHINERY AND EPIGENETIC MODIFIERS. COUPLED WITH INFERENCES ON SUBCLONAL MUTATIONS, THESE DATA SUGGEST A HYPOTHESIS OF GENETIC "PREDESTINATION," IN WHICH EARLY DRIVER MUTATIONS, TYPICALLY AFFECTING GENES INVOLVED IN RNA SPLICING, DICTATE FUTURE TRAJECTORIES OF DISEASE EVOLUTION WITH DISTINCT CLINICAL PHENOTYPES. DRIVER MUTATIONS HAD EQUIVALENT PROGNOSTIC SIGNIFICANCE, WHETHER CLONAL OR SUBCLONAL, AND LEUKEMIA-FREE SURVIVAL DETERIORATED STEADILY AS NUMBERS OF DRIVER MUTATIONS INCREASED. THUS, ANALYSIS OF ONCOGENIC MUTATIONS IN LARGE, WELL-CHARACTERIZED COHORTS OF PATIENTS ILLUSTRATES THE INTERCONNECTIONS BETWEEN THE CANCER GENOME AND DISEASE BIOLOGY, WITH CONSIDERABLE POTENTIAL FOR CLINICAL APPLICATION. 2013 7 1076 41 CLONAL HEMATOPOIESIS IN MYELOPROLIFERATIVE NEOPLASMS CONFERS A PREDISPOSITION TO BOTH THROMBOSIS AND CANCER. PURPOSE OF REVIEW: THIS REVIEW FOCUSES ON VASCULAR COMPLICATIONS ASSOCIATED WITH CHRONIC MYELOPROLIFERATIVE NEOPLASMS (MPN) AND MORE SPECIFICALLY AIMS TO DISCUSS THE CLINICAL AND BIOLOGICAL EVIDENCE SUPPORTING THE EXISTENCE OF A LINK BETWEEN CLONAL HEMATOPOIESIS, CARDIOVASCULAR EVENTS (CVE), AND SOLID CANCER (SC). RECENT FINDINGS: THE MPN NATURAL HISTORY IS DRIVEN BY UNCONTROLLED CLONAL MYELOPROLIFERATION SUSTAINED BY ACQUIRED SOMATIC MUTATIONS IN DRIVER (JAK2, CALR, AND MPL) AND NON-DRIVER GENES, INVOLVING EPIGENETIC (E.G., TET2, DNMT3A) REGULATORS, CHROMATIN REGULATOR GENES (E.G., ASXL1, EZH2), AND SPLICING MACHINERY GENES (E.G., SF3B1). THE GENOMIC ALTERATIONS AND ADDITIONAL THROMBOSIS ACQUIRED RISK FACTORS ARE DETERMINANTS FOR CVE. THERE IS EVIDENCE THAT CLONAL HEMATOPOIESIS CAN ELICIT A CHRONIC AND SYSTEMIC INFLAMMATION STATUS THAT ACTS AS DRIVING FORCE FOR THE DEVELOPMENT OF THROMBOSIS, MPN EVOLUTION, AND SECOND CANCER (SC). THIS NOTION MAY EXPLAIN THE MECHANISM THAT LINKS ARTERIAL THROMBOSIS IN MPN PATIENTS AND SUBSEQUENT SOLID TUMORS. IN THE LAST DECADE, CLONAL HEMATOPOIESIS OF INDETERMINATE POTENTIAL (CHIP) HAS BEEN DETECTED IN THE GENERAL POPULATION PARTICULARLY IN THE ELDERLY AND INITIALLY FOUND IN MYOCARDIAL INFARCTION AND STROKE, RISING THE HYPOTHESIS THAT THE INFLAMMATORY STATUS CHIP-ASSOCIATED COULD CONFER PREDISPOSITION TO BOTH CARDIOVASCULAR DISEASES AND CANCER. IN SUMMARY, CLONAL HEMATOPOIESIS IN MPN AND CHIP CONFER A PREDISPOSITION TO CARDIOVASCULAR EVENTS AND CANCER THROUGH CHRONIC AND SYSTEMIC INFLAMMATION. THIS ACQUISITION COULD OPEN NEW AVENUES FOR ANTITHROMBOTIC THERAPY BOTH IN MPNS AND IN GENERAL POPULATION BY TARGETING BOTH CLONAL HEMATOPOIESIS AND INFLAMMATION. 2023 8 2277 42 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 9 5284 36 PROPOSALS FOR CLINICAL TRIALS IN CHRONIC MYELOMONOCYTIC LEUKEMIA. CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML) IS A CLONAL HEMATOLOGIC MALIGNANCY OF MOSTLY OLDER INDIVIDUALS THAT EXHIBITS BOTH MYELODYSPLASTIC AND MYELOPROLIFERATIVE FEATURES. CMML PRESENTATION AND OUTCOME ARE VARIABLE, REFLECTING GENETIC AND CLINICAL HETEROGENEITY. HYPOMETHYLATING AGENTS ARE THE MAINSTAY OF THERAPY BUT INDUCE COMPLETE REMISSIONS IN LESS THAN 20% OF PATIENTS AND DO NOT PROLONG SURVIVAL COMPARED TO HYDROXYUREA. ALLOGENEIC STEM CELL TRANSPLANT (ASCT) IS POTENTIALLY CURATIVE, BUT FEW PATIENTS QUALIFY DUE TO ADVANCED AGE AND/OR COMORBIDITIES. WORK OF THE PAST SEVERAL YEARS HAS IDENTIFIED KEY MOLECULAR PATHWAYS THAT DRIVE DISEASE PROLIFERATION AND TRANSFORMATION TO ACUTE LEUKEMIA, INCLUDING JAK/STAT AND MAPK SIGNALING AND EPIGENETIC DYSREGULATION. THERE IS INCREASINGLY COMPELLING EVIDENCE THAT INFLAMMATION IS A MAJOR DRIVER OF CMML PROGRESSION. THUS FAR HOWEVER, THIS MECHANISTIC KNOWLEDGE HAS NOT YET BEEN TRANSLATED INTO IMPROVED OUTCOMES, SUGGESTING THAT FUNDAMENTALLY NEW APPROACHES ARE REQUIRED. IN THIS REVIEW, WE DISCUSS THE DISEASE COURSE, NEW CLASSIFICATIONS, AND CURRENT TREATMENT LANDSCAPE OF CMML. WE REVIEW ONGOING CLINICAL STUDIES AND DISCUSS OPTIONS FOR RATIONALLY BASED FUTURE CLINICAL TRIALS. 2023 10 5782 29 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 11 4442 33 MOLECULAR GENETICS OF MDS/MPN OVERLAP SYNDROMES. THE MYELODYSPLASTIC/MYELOPROLIFERATIVE NEOPLASMS (MDS/MPN) ARE A HETEROGENOUS GROUP OF MYELOID MALIGNANCIES HALLMARKED BY CLINICOPATHOLOGIC FEATURES THAT OVERLAP WITH MYELODYSPLASTIC SYNDROMES AND MYELOPROLIFERATIVE NEOPLASMS. FORMALLY RECOGNIZED BY THE WORLD HEALTH ORGANIZATION, THIS GROUP INCLUDES THE ENTITIES CHRONIC MYELOMONOCYTIC LEUKEMIA, JUVENILE MYELOMONOCYTIC LEUKEMIA, ATYPICAL CHRONIC MYELOID LEUKEMIA, MDS/MPN WITH RING SIDEROBLASTS AND THROMBOCYTOSIS AND MDS/MPN, UNCLASSIFIABLE. ADVANCEMENTS IN NEXT GENERATION SEQUENCING HAVE BEGUN TO UNRAVEL THE MOLECULAR UNDERPINNINGS OF THESE DISEASES, IDENTIFYING AN ARRAY OF RECURRENTLY MUTATED GENES INVOLVED IN EPIGENETIC REGULATION, RNA SPLICING, TRANSCRIPTION, AND CELL SIGNALING. DESPITE MOLECULAR OVERLAP WITH OTHER MYELOID MALIGNANCIES, EACH ENTITY DISPLAYS A UNIQUE SPECTRUM OF SOMATIC MUTATIONS SUPPORTING THEIR UNIQUE PATHOBIOLOGY AND CLINICAL FEATURES. IMPORTANTLY, MOLECULAR PROFILING IS BECOMING AN INTEGRAL TOOL UTILIZED IN ROUTINE CLINICAL PRACTICE. THIS REVIEW SUMMARIZES OUR CURRENT UNDERSTANDING OF THE MOLECULAR PATHOGENESIS OF OVERLAP SYNDROMES AND DETAILS THE IMPACT OF SOMATIC MUTATIONS IN DIAGNOSTIC, PROGNOSTIC, AND THERAPEUTIC DECISION-MAKING. 2020 12 2582 34 EPIGENETICS OF MYELODYSPLASTIC SYNDROMES. MYELODYSPLASTIC SYNDROMES (MDS) ARE CLONAL DISEASES OF THE ELDERLY CHARACTERIZED BY CHRONIC CYTOPENIAS, DYSPLASIA AND A VARIABLE RISK OF PROGRESSION TO ACUTE MYELOID LEUKEMIA (AML). ABERRANT METHYLATION OF TUMOR-SUPPRESSOR GENE PROMOTERS HAS BEEN ESTABLISHED FOR MANY YEARS AND RECENTLY TRACKED TO THE MOST IMMATURE CELLS OF MDS, SUGGESTING THAT THESE ALTERATIONS ARE DRIVERS OF MDS PATHOGENESIS. IN RECENT YEARS, RECURRENT SOMATIC MUTATIONS IN GENES ENCODING PROTEINS INVOLVED IN DNA METHYLATION AND DEMETHYLATION AND IN COVALENT HISTONE MODIFICATIONS HAVE BEEN REPORTED IN MYELOID MALIGNANCIES, INCLUDING MDS. WHOLE-GENOME EPIGENETIC PROFILES OF MDS ARE ALSO EMERGING. IN PARALLEL WITH THESE ADVANCES IN THE MOLECULAR PATHOGENESIS OF MDS, CLINICAL TRIALS HAVE ESTABLISHED HYPOMETHYLATING AGENTS (HMAS) AS THE MAINSTAY OF THERAPY IN THE ADVANCED FORMS OF THE DISEASE. IN THIS REVIEW, WE SUMMARIZE THE CURRENT UNDERSTANDING OF THE MOLECULAR MACHINERY INVOLVED IN EPIGENETIC REGULATION, DISCUSS HOW EPIGENETIC ALTERATIONS ARISE IN MDS AND CONTRIBUTE TO ITS PATHOGENESIS AND THEN DISCUSS THE MODE OF ACTION OF HMAS IN MDS. 2014 13 4681 30 NEW OPTIONS IN THE TREATMENT OF MYELODYSPLASTIC SYNDROME. MYELODYSPLASTIC SYNDROME (MDS) IS A HETEROGENEOUS GROUP OF PROGRESSIVE CHRONIC HEMATOPOIETIC DISORDERS, USUALLY PRESENTING AS REFRACTORY ANEMIA OR CYTOPENIA, WITH AN APPROXIMATELY 25% RISK OF PROGRESSION TOWARD ACUTE MYELOID LEUKAEIMA (AML), AND NO PROVEN CURATIVE TREATMENT. NOVEL BIOLOGICAL TREATMENT STRATEGIES TARGETING BOTH THE MALIGNANT BLOOD CELL AND ITS MICROENVIRONMENT CAN OVERCOME RESISTANCE TO CURRENT THERAPIES, AND REPRESENT A PROMISING TREATMENT PARADIGM FOR IMPROVING PATIENT OUTCOME. MANY OF THESE AGENTS HAVE MULTIPLE BIOLOGIC ACTIVITIES. THE OBJECTIVE OF THIS ARTICLE IS TO PRESENT A COMPARATIVE REVIEW OF CLASSIFICATION SYSTEMS IN MDS AND TO DISCUSS THE EVOLVING TRENDS IN THE TREATMENT OF MDS (IMMUNOSUPPRESIVE THERAPY, IMMUNOMODULATORY DRUGS, ARSENIC TRIOXIDE, PROTEASOME INHIBITORS, EPIGENETIC THERAPY). 2005 14 2237 38 EPIGENETIC MODIFIERS IN MYELOID MALIGNANCIES: THE ROLE OF HISTONE DEACETYLASE INHIBITORS. MYELOID HEMATOLOGICAL MALIGNANCIES ARE CLONAL BONE MARROW NEOPLASMS, COMPRISING OF ACUTE MYELOID LEUKEMIA (AML), THE MYELODYSPLASTIC SYNDROMES (MDS), CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML), THE MYELOPROLIFERATIVE NEOPLASMS (MPN) AND SYSTEMIC MASTOCYTOSIS (SM). THE FIELD OF EPIGENETIC REGULATION OF NORMAL AND MALIGNANT HEMATOPOIESIS IS RAPIDLY GROWING. IN RECENT YEARS, HETEROZYGOUS SOMATIC MUTATIONS IN GENES ENCODING EPIGENETIC REGULATORS HAVE BEEN FOUND IN ALL SUBTYPES OF MYELOID MALIGNANCIES, SUPPORTING THE RATIONALE FOR TREATMENT WITH EPIGENETIC MODIFIERS. HISTONE DEACETYLASE INHIBITORS (HDACI) ARE EPIGENETIC MODIFIERS THAT, IN VITRO, HAVE BEEN SHOWN TO INDUCE GROWTH ARREST, APOPTOTIC OR AUTOPHAGIC CELL DEATH, AND TERMINAL DIFFERENTIATION OF MYELOID TUMOR CELLS. THESE EFFECTS WERE OBSERVED BOTH AT THE BULK TUMOR LEVEL AND IN THE MOST IMMATURE CD34(+)38(-) CELL COMPARTMENTS CONTAINING THE LEUKEMIC STEM CELLS. THUS, THERE IS A STRONG RATIONALE SUPPORTING HDACI THERAPY IN MYELOID MALIGNANCIES. HOWEVER, DESPITE INITIAL PROMISING RESULTS IN PHASE I TRIALS, HDACI IN MONOTHERAPY AS WELL AS IN COMBINATION WITH OTHER DRUGS, HAVE FAILED TO IMPROVE RESPONSES OR SURVIVAL. THIS REVIEW PROVIDES AN OVERVIEW OF THE RATIONALE FOR HDACI IN MYELOID MALIGNANCIES, CLINICAL RESULTS AND SPECULATIONS ON WHY CLINICAL TRIALS HAVE THUS FAR NOT MET THE EXPECTATIONS, AND HOW THIS MAY BE IMPROVED IN THE FUTURE. 2018 15 1070 33 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 16 2547 26 EPIGENETICS IN MYELOID MALIGNANCIES. MYELOID HEMATOLOGICAL MALIGNANCIES ARE AMONG THE EPIGENETICALLY BEST CHARACTERIZED NEOPLASMS. THE COMPARATIVELY LOW NUMBER OF RECURRING BALANCED AND UNBALANCED CHROMOSOMAL ABNORMALITIES AS WELL AS COMMON GENETIC MUTATIONS HAS ENABLED SCIENTISTS TO RELATE EPIGENETIC STATES TO THESE. THE EASE OF ACCESSING MALIGNANT CELLS THROUGH BONE MARROW ASPIRATION HAS CERTAINLY CONTRIBUTED TO THE FAST EXPANSION OF KNOWLEDGE. EVEN SO, THE CLINICAL AND PATHOGENETIC RELEVANCE OF EPIGENETIC CHANGES IS STILL NOT KNOWN, AND THE FIELD WILL CERTAINLY EVOLVE VERY FAST WITH THE DEVELOPMENT OF NEW ANALYTIC TECHNIQUES. THE FIRST EXAMPLE OF SUCCESSFUL EPIGENETIC THERAPY IS SEEN IN MYELOID MALIGNANCIES, IN THE HIGH-RISK MYELODYSPLASTIC SYNDROMES (MDS) WHICH ARE ROUTINELY TREATED WITH THE DEMETHYLATING AGENT AZACYTIDINE.THIS CHAPTER WILL CONCENTRATE ON DESCRIBING THE EPIGENETIC CHANGES IN ACUTE MYELOID LEUKEMIA (AML), CHRONIC MYELOID LEUKEMIA (CML) AND MDS. AN OVERVIEW OF CLINICAL RELEVANCE AND EPIGENETIC THERAPEUTIC APPROACHES IS ALSO MADE. 2012 17 4557 24 MUTATIONS IN ASXL1 ARE ASSOCIATED WITH POOR PROGNOSIS ACROSS THE SPECTRUM OF MALIGNANT MYELOID DISEASES. THE ASXL1 GENE IS ONE OF THE MOST FREQUENTLY MUTATED GENES IN MALIGNANT MYELOID DISEASES. THE ASXL1 PROTEIN BELONGS TO PROTEIN COMPLEXES INVOLVED IN THE EPIGENETIC REGULATION OF GENE EXPRESSION. ASXL1 MUTATIONS ARE FOUND IN MYELOPROLIFERATIVE NEOPLASMS (MPN), MYELODYSPLASTIC SYNDROMES (MDS), CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML) AND ACUTE MYELOID LEUKEMIA (AML). THEY ARE GENERALLY ASSOCIATED WITH SIGNS OF AGGRESSIVENESS AND POOR CLINICAL OUTCOME. BECAUSE OF THIS, A SYSTEMATIC DETERMINATION OF ASXL1 MUTATIONAL STATUS IN MYELOID MALIGNANCIES SHOULD HELP IN PROGNOSIS ASSESSMENT. 2012 18 1043 34 CLINICAL CHARACTERISTICS AND WHOLE EXOME/TRANSCRIPTOME SEQUENCING OF COEXISTING CHRONIC MYELOID LEUKEMIA AND MYELOFIBROSIS. MYELOPROLIFERATIVE NEOPLASMS (MPNS) ARE CLONAL HEMATOPOIETIC STEM CELL (HSC) DISORDERS THAT CAN BE CLASSIFIED ON THE BASIS OF GENETIC, CLINICAL, PHENOTYPIC FEATURES. GENETIC LESIONS SUCH AS JAK2 MUTATIONS AND BCR-ABL TRANSLOCATION ARE OFTEN MUTUALLY EXCLUSIVE IN MPN PATIENTS AND LEAD TO ESSENTIAL THROMBOCYTHEMIA, POLYCYTHEMIA VERA, OR MYELOFIBROSIS OR CHRONIC MYELOID LEUKEMIA, RESPECTIVELY. NEVERTHELESS, COEXISTENCE OF THESE GENETIC ABERRATIONS IN THE SAME PATIENT HAS BEEN REPORTED. WHETHER THESE ABERRATIONS OCCUR IN THE SAME STEM CELL OR A DIFFERENT CELL IS UNCLEAR, BUT AN UNSTABLE GENOME IN THE HSCS SEEMS TO BE THE COMMON ANTECEDENT. IN AN EFFORT TO CHARACTERIZE THE UNDERLYING GENETIC EVENTS THAT MIGHT CONTRIBUTE TO THE APPEARANCE OF MORE THAN ONE MPN IN A PATIENT, WE STUDIED NEOPLASTIC CELLS FROM PATIENTS WITH DUAL MPNS BY NEXT-GENERATION SEQUENCING. WE OBSERVED THAT MOST PATIENTS WITH TWO MPNS HARBORED MUTATIONS IN GENES KNOWN TO CONTRIBUTE TO CLONAL HEMATOPOIESIS THROUGH ALTERED EPIGENETIC REGULATION SUCH AS TET2, ASXL1/2, SRSF2, AND IDH2 AT VARYING FREQUENCIES (1%-47%). IN ADDITION, WE FOUND THAT SOME PATIENTS ALSO HARBORED ONCOGENIC MUTATIONS IN N/KRAS, TP53, BRAF, EZH2, AND GNAS AT LOW FREQUENCIES, WHICH PROBABLY REPRESENT CLONAL EVOLUTION. THESE FINDINGS SUPPORT THE HYPOTHESIS THAT HEMATOPOIETIC CELLS FROM MPN PATIENTS HARBOR MULTIPLE GENETIC ABERRATIONS, SOME OF WHICH CAN CONTRIBUTE TO CLONAL DOMINANCE. ACQUIRING MUTATIONS IN JAK2/CALR/MPL OR THE BCR-ABL TRANSLOCATION PROBABLY DRIVE THE ONCOGENIC PHENOTYPE TOWARDS A SPECIFIC MPN. FURTHER, WE PROPOSE THAT THE ACQUISITION OF BCR-ABL IN THESE PATIENTS IS FREQUENTLY A SECONDARY EVENT RESULTING FROM AN UNSTABLE GENOME. 2017 19 959 34 CHRONIC MYELOMONOCYTIC LEUKEMIA AND ATYPICAL CHRONIC MYELOID LEUKEMIA: NOVEL PATHOGENETIC LESIONS. CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML) AND ATYPICAL CHRONIC MYELOID LEUKEMIA (ACML) ARE DISTINCT, YET RELATED, ENTITIES OF MYELODYSPLASTIC/MYELOPROLIFERATIVE NEOPLASMS (MDS/MPN) CHARACTERIZED BY MORPHOLOGIC DYSPLASIA WITH ACCUMULATION OF MONOCYTES OR NEUTROPHILS, RESPECTIVELY. OUR UNDERSTANDING OF THE MOLECULAR PATHOGENESIS OF CMML AND ACML HAS ADVANCED, MAINLY DUE TO THE APPLICATION OF NOVEL TECHNOLOGIES SUCH AS ARRAY-BASED KARYOTYPING AND NEXT-GENERATION SEQUENCING. IN ADDITION TO PREVIOUSLY KNOWN RECURRENT ABERRATIONS, SOMATIC UNIPARENTAL DISOMY AFFECTING CHROMOSOMES 3, 4, 7, AND 11 FREQUENTLY OCCURS IN CMML. NOVEL SOMATIC MUTATIONS OF GENES, INCLUDING THOSE ASSOCIATED WITH PROLIFERATION SIGNALING (CBL, RAS, RUNX1, JAK2 (V617F)) AND WITH MODIFICATION OF EPIGENETIC STATUS (TET2, ASXL1, UTX, EZH2) HAVE BEEN FOUND. VARIOUS COMBINATIONS OF MUTATIONS SUGGEST A MULTISTEP PATHOGENESIS AND MAY ACCOUNT FOR CLINICAL HETEROGENEITY. MOST RECENTLY, SEVERAL SPLICEOSOME-ASSOCIATED-GENE MUTATIONS WERE REPORTED AND SRSF2 MUTATIONS ARE FREQUENTLY DETECTED IN CMML. THE PROGNOSTIC AND DIAGNOSTIC SIGNIFICANCE OF THESE MOLECULAR LESIONS, IN PARTICULAR THEIR VALUE AS BIOMARKERS OF RESPONSE OR RESISTANCE TO SPECIFIC THERAPIES, WHILE UNCERTAIN NOW IS LIKELY TO BE CLARIFIED AS LARGE SYSTEMATIC STUDIES COME TO COMPLETION. 2012 20 4565 29 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