Prognostic significance of ASXL1 mutations in patients with myelodysplastic syndromes

Generation and Characterization of Induced Pluripotent Stem Cells Carrying An ASXL1 Mutation

Additional sex combs-like 1 (ASXL1) is an epigenetic modulator frequently mutated in myeloid malignancies, generally associated with poor prognosis. Current models for ASXL1-mutated diseases are mainly based on the complete deletion of Asxl1 or overexpression of C-terminal truncations in mice models. However, these models cannot fully recapitulate the pathogenesis of myeloid malignancies. Patient-derived induced pluripotent stem cells (iPSCs) provide valuable disease models that allow us to understand disease-related molecular pathways and develop novel targeted therapies. Here, we generated iPSCs from a patient with myeloproliferative neoplasm carrying a heterozygous ASXL1 mutation. The iPSCs we generated exhibited the morphology of pluripotent cells, highly expressed pluripotent markers, excellent differentiation potency in vivo, and normal karyotype. Subsequently, iPSCs with or without ASXL1 mutation were induced to differentiate into hematopoietic stem/progenitor cells, and we found that ASXL1 mutation led to myeloid-biased output and impaired erythroid differentiation. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that terms related to embryonic development, myeloid differentiation, and immune- and neural-related processes were most enriched in the differentially expressed genes. Western blot demonstrated that the global level of H2AK119ub was significantly decreased when mutant ASXL1 was present. Chromatin Immunoprecipitation Sequencing showed that most genes associated with stem cell maintenance were upregulated, whereas occupancies of H2AK119ub around these genes were significantly decreased. Thus, the iPSC model carrying ASXL1 mutation could serve as a potential tool to study the pathogenesis of myeloid malignancies and to screen targeted therapy for patients.

Myelodysplastic syndromes del(5q): Pathogenesis and its therapeutic implications

Myelodysplastic syndromes (MDS) encompass a heterogeneous set of acquired bone marrow neoplastic disorders characterized by ineffective hematopoiesis within one or more bone marrow lineages. Nearly half of MDS patients carry cytogenetic alterations, with del(5q) being the most prevalent. Since its first description, del(5q) was consistently correlated with a typical clinical phenotype marked by anemia, thrombocytosis, and a low risk of evolving into acute leukemia. Presently, the World Health Organization (WHO) classification of myeloid neoplasms recognizes a specific subtype of MDS known as "myelodysplastic neoplasm with low blast and isolated del(5q)" identified by the sole presence of 5q deletion or in combination with one other abnormality excluding -7/del(7q). Several studies have sought to unravel the biological processes triggered by del(5q) in the development of MDS, revealing the involvement of various genes localized in specific regions of chromosome 5 referred to as common deleted regions (CDR). This intricate biological landscape makes the MDS cells with del(5q) exceptionally sensitive to lenalidomide. Several studies have confirmed the efficacy of lenalidomide in this context. Regrettably, the response to lenalidomide is not conclusive, prompting ongoing research into biological mechanisms that drive patients toward leukemia and strategies to circumvent lenalidomide resistance and disease progression.

Prognostic significance of persisting DNMT3A, ASXL1, and TET2 mutation burden in acute myeloid leukemia patients with allogeneic hematopoietic stem cell transplantation during complete remission

We retrospectively analyzed 155 AML patients with DAT mutations at diagnosis who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) at complete remission. Of the 155 AML patients with DAT mutations at diagnosis, 59 (38.1%) patients had persisting DAT mutations pretransplantation. Compared to patients with pretransplant DAT transitions, patients with persisting DAT mutation burden were shown to be older (p = 0.004), and fewer patients had TET2 mutations at diagnosis (p = 0.033). Patients with persistent DAT mutation burden had shorter overall survival (OS) (3-year OS: 59.3% vs. 83.0%, p < 0.001) and disease-free survival (DFS) (3-year DFS: 56.1% vs. 83.0%, p < 0.001) with a higher cumulative incidence of relapse (CIR) (24.6% vs. 17.4%, p = 0.002) than those with DAT transitions. Additionally, multivariate analysis confirmed that persisting DAT mutations were an independent adverse factor for relapse, OS, and DFS. Collectively, persisting DAT mutations prior to allo-HSCT at complete remission for AML correlated with negative outcomes.

Targeting lysine demethylase 6B ameliorates ASXL1 truncation-mediated myeloid malignancies in preclinical models

ASXL1 mutation frequently occurs in all forms of myeloid malignancies and is associated with aggressive disease and poor prognosis. ASXL1 recruits Polycomb repressive complex 2 (PRC2) to specific gene loci to repress transcription through trimethylation of histone H3 on lysine 27 (H3K27me3). ASXL1 alterations reduce H3K27me3 levels, which results in leukemogenic gene expression and the development of myeloid malignancies. Standard therapies for myeloid malignancies have limited efficacy when mutated ASXL1 is present. We discovered upregulation of lysine demethylase 6B (KDM6B), a demethylase for H3K27me3, in ASXL1-mutant leukemic cells, which further reduces H3K27me3 levels and facilitates myeloid transformation. Here, we demonstrated that heterozygous deletion of Kdm6b restored H3K27me3 levels and normalized dysregulated gene expression in Asxl1Y588XTg hematopoietic stem/progenitor cells (HSPCs). Furthermore, heterozygous deletion of Kdm6b decreased the HSPC pool, restored their self-renewal capacity, prevented biased myeloid differentiation, and abrogated progression to myeloid malignancies in Asxl1Y588XTg mice. Importantly, administration of GSK-J4, a KDM6B inhibitor, not only restored H3K27me3 levels but also reduced the disease burden in NSG mice xenografted with human ASXL1-mutant leukemic cells in vivo. This preclinical finding provides compelling evidence that targeting KDM6B may be a therapeutic strategy for myeloid malignancies with ASXL1 mutations.

Prognosis and risk factors for ASXL1 mutations in patients with newly diagnosed acute myeloid leukemia and myelodysplastic syndrome

OBJECTIVE

The objective of the study was to determine the prognosis and risk factors for additional sex combs like 1 (ASXL1) mutations in patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS).

POPULATION AND METHODS

This retrospective study enrolled 219 adult patients with newly diagnosed AML and MDS, who were treated in West China Hospital from October 2018 to January 2022. The primary clinical outcome was evaluated by overall survival (OS) followed up to January 2023. Kaplan-Meier analysis and Cox multivariate regression analysis were performed to identify potential prognostic parameters in patients with ASXL1 mutations (mt).

RESULTS

A total of 34 (15.53%) ASXL1mt were detected, which occurred more frequently in the elderly and MDS cohorts (p < 0.001). Significantly lower blasts% (p < 0.001) and higher frequencies of mutant RUNX1, SRSF2, STAG2, EZH2, and SETBP1 (p < 0.02) were observed in the ASXL1mt cohort. Patients with ASXL1mt manifested with a worse complete remission rate (p = 0.011), and an inferior OS was shown in subgroups with MDS, co-mutations of RUNX1, SRSF2, or NRAS, as well as mutations in G646W (p < 0.05). Multivariate analysis considering age, diagnosis, co-mutations, and mutation site confirmed an independently adverse prognosis of mutations in G646W (HR = 4.302, 95% CI: 1.150-16.097) or RUNX1 co-mutations (HR = 4.620, 95% CI: 1.385-15.414) in the ASXL1mt cohort.

CONCLUSION

Our study indicated that mutations in G646W or RUNX1 co-mutations are closely associated with a dismal clinical outcome in patients with AML and MDS harboring ASXL1mt. Considering the poor prognosis and risk factors in patients with ASXL1mt, more available treatments should be pursued.

Prognostic value of ASXL1 mutations in patients with myelodysplastic syndromes and acute myeloid leukemia: A meta-analysis

Additional sex combs-like 1 (ASXL1) mutations, a hotspot in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), have been frequently reported for their potential prognostic value, but the results are controversial. Therefore, a meta-analysis was performed. Databases, including PubMed, Embase, and Cochrane Library, were searched for relevant studies published up to January 13, 2022. STATA v16.0 software was used to calculate the combined hazard ratios (HRs) and their 95% confidence intervals (CIs) for overall survival (OS) and AML transformation. Subgroup analysis was used to explore the effects of the grouping factors on heterogeneity.Ten studies on ASXL1 mutations and the prognosis of MDS were selected. Our results indicate that ASXL1 mutations have an adverse prognostic impact on OS (HR = 1.68,95%CI:1.45-1.94, p < .0001) and AML transformation (HR = 2.20,95% CI:1.68-2.87, p < .0001). The results for different age groups were not significantly different (HR = 1.87,95% CI: 1.31-2.67; HR = 1.62,95% CI:1.35-2.07). Ten studies covering 5816 patients with AML were included. The pooled HR for OS was 1.37 (95% CI:1.20-1.56, p < .0001). ASXL1 mutations were especially associated with a poorer OS in the subgroup aged ≥60 years (HR = 2.86, 95% CI:1.34-6.08, p = .006); when considering cytogenetically normal AML (CN-AML), the HR was 1.78(95% CI:1.27-2.49, p = .001). This meta-analysis indicates an independent, adverse prognostic impact of ASXL1 mutations in patients with MDS and AML, which also applies to patients with CN-AML. Age was a risk factor for patients with AML and ASXL1 mutations but not for patients with MDS.

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.

A phase 1b study of venetoclax and azacitidine combination in patients with relapsed or refractory myelodysplastic syndromes

Patients with relapsed/refractory (R/R) higher-risk myelodysplastic syndromes (MDS) have a dismal median overall survival (OS) after failing hypomethylating agent (HMA) treatment. There is no standard of care for patients after HMA therapy failure; hence, there is a critical need for effective therapeutic strategies. Herein, we present the safety and efficacy of venetoclax + azacitidine in patients with R/R MDS. This phase 1b, open-label, multicenter study enrolled patients ≥18 years. Patients were treated with escalating doses of oral venetoclax: 100, 200, or 400 mg daily for 14 days every 28-day cycle. Azacitidine was administered on Days 1-7 every cycle at 75 mg/m² /day intravenously/subcutaneously. Responses were assessed per modified 2006 International Working Group (IWG) criteria. Forty-four patients (male 86%, median age 74 years) received venetoclax + azacitidine treatment. Median follow-up was 21.2 months. Hematological adverse events of Grade ≥ 3 included febrile neutropenia (34%), thrombocytopenia (32%), neutropenia (27%), and anemia (18%). Pneumonia (23%) was the most common Grade ≥ 3 infection. Marrow responses were seen including complete remission (CR, n = 3, 7%) and marrow CR (mCR, n = 14, 32%); 36% (16/44) achieved transfusion independence (TI) for RBCs and/or platelets, and 43% (6/14) with mCR achieved hematological improvement (HI). The median time to CR/mCR was 1.2 months, and the median duration of response for CR + mCR was 8.6 months. Median OS was 12.6 months. Venetoclax + azacitidine shows activity in patients with R/R MDS following prior HMA therapy failure and provides clinically meaningful benefits, including HI and TI, and encouraging OS.

Clonal hematopoiesis, somatic mosaicism, and age-associated disease

Somatic mosaicism, the occurrence of multiple genetically distinct cell clones within the same tissue, is an evitable consequence of human aging. The hematopoietic system is no exception to this, where studies have revealed the presence of expanded blood cell clones carrying mutations in preleukemic driver genes and/or genetic alterations in chromosomes. This phenomenon is referred to as clonal hematopoiesis and is remarkably prevalent in elderly individuals. While clonal hematopoiesis represents an early step toward a hematological malignancy, most individuals will never develop blood cancer. Somewhat unexpectedly, epidemiological studies have found that clonal hematopoiesis is associated with an increase in the risk of all-cause mortality and age-related disease, particularly in the cardiovascular system. Studies using murine models of clonal hematopoiesis have begun to shed light on this relationship, suggesting that driver mutations in mature blood cells can causally contribute to aging and disease by augmenting inflammatory processes. Here we provide an up-to-date review of clonal hematopoiesis within the context of somatic mosaicism and aging and describe recent epidemiological studies that have reported associations with age-related disease. We will also discuss the experimental studies that have provided important mechanistic insight into how driver mutations promote age-related disease and how this knowledge could be leveraged to treat individuals with clonal hematopoiesis.

Combination of ruxolitinib with ABT-737 exhibits synergistic effects in cells carrying concurrent JAK2V617F and ASXL1 mutations

The V617F mutation in Janus kinase 2 is considered one of the driver mutations leading to Philadelphia-negative myeloproliferative neoplasms (MPNs). Concurrent JAK2V617F and ASXL1 mutations accelerate the progression of myelofibrosis in patients with MPNs. Few therapies are currently available for patients with these two mutations. In our study, the combination of ruxolitinib with ABT-737 was evaluated in cells carrying JAK2V617F and ASXL1 double mutations. RNA sequencing indicated overactivated oxidative phosphorylation in JAK2V617F;Asxl1+/- cKit+ cells. The cell line model with JAK2V617F and ASXL1 double mutations (HEL-AKO cells) also exhibited dysregulated mitochondrial function with an increase in the reactive oxygen species levels and a decrease in the ATP levels. The colony growth inhibition rates of cells with JAK2V617F and ASXL1 double mutations were significantly lower than those of cells with only the JAK2V617F mutation. Combined treatment with ruxolitinib and ABT-737 promoted apoptosis and inhibited the proliferation of HEL-AKO cells. Cotreatment with the two drugs also inhibited the growth of bone marrow mononuclear cells isolated from patients with concurrent JAK2V617F and ASXL1 mutations. In conclusion, we provide preclinical evidence showing that the combination of ruxolitinib and ABT-737 is a promising therapeutic strategy for MPN patients with concurrent JAK2V617F and ASXL1 mutations.

Myelodysplastic Syndromes with Isolated del(5q): Value of Molecular Alterations for Diagnostic and Prognostic Assessment

Myelodysplastic syndromes (MDS) are a group of clonal hematological neoplasms characterized by ineffective hematopoiesis in one or more bone marrow cell lineages. Consequently, patients present with variable degrees of cytopenia and dysplasia. These characteristics constitute the basis for the World Health Organization (WHO) classification criteria of MDS, among other parameters, for the current prognostic scoring system. Although nearly half of newly diagnosed patients present a cytogenetic alteration, and almost 90% of them harbor at least one somatic mutation, MDS with isolated del(5q) constitutes the only subtype clearly defined by a cytogenetic alteration. The results of several clinical studies and the advances of new technologies have allowed a better understanding of the biological basis of this disease. Therefore, since the first report of the "5q- syndrome" in 1974, changes and refinements have been made in the definition and the characteristics of the patients with MDS and del(5q). Moreover, specific genetic alterations have been found to be associated with the prognosis and response to treatments. The aim of this review is to summarize the current knowledge of the molecular background of MDS with isolated del(5q), focusing on the clinical and prognostic relevance of cytogenetic alterations and somatic mutations.

The genetics of myelodysplastic syndromes and the opportunities for tailored treatments

Genomic instability, microenvironmental aberrations, and somatic mutations contribute to the phenotype of myelodysplastic syndrome and the risk for transformation to AML. Genes involved in RNA splicing, DNA methylation, histone modification, the cohesin complex, transcription, DNA damage response pathway, signal transduction and other pathways constitute recurrent mutational targets in MDS. RNA-splicing and DNA methylation mutations seem to occur early and are reported as driver mutations in over 50% of MDS patients. The improved understanding of the molecular landscape of MDS has led to better disease and risk classification, leading to novel therapeutic opportunities. Based on these findings, novel agents are currently under preclinical and clinical development and expected to improve the clinical outcome of patients with MDS in the upcoming years. This review provides a comprehensive update of the normal gene function as well as the impact of mutations in the pathogenesis, deregulation, diagnosis, and prognosis of MDS, focuses on the most recent advances of the genetic basis of myelodysplastic syndromes and their clinical relevance, and the latest targeted therapeutic approaches including investigational and approved agents for MDS.

Development and validation of a novel prognosis prediction model for patients with myelodysplastic syndrome

Background

Somatic mutations are widespread in patients with Myelodysplastic Syndrome (MDS) and are associated with prognosis. However, a practical prognostic model for MDS that incorporates somatic mutations urgently needs to be developed.

Methods

A cohort of 201 MDS patients from the Gene Expression Omnibus (GEO) database was used to develop the model, and a single-center cohort of 115 MDS cohorts from Northwest China was used for external validation. Kaplan-Meier analysis was performed to compare the effects of karyotype classifications and gene mutations on the prognosis of MDS patients. Univariate and multivariate Cox regression analyses and Lasso regression were used to screen for key prognostic factors. The shinyapps website was used to create dynamic nomograms with multiple variables. The time-dependent receiver operating characteristic (ROC) curves, calibration plots, and decision curve analysis (DCA) were used to evaluate the model’s discrimination, accuracy and clinical utility.

Results

Six risk factors (age, bone morrow blast percentage, ETV6, TP53, EZH2, and ASXL1) were considered as predictor variables in the nomogram. The nomogram showed excellent discrimination, with respective the area under the ROC curve (AUC) values of 0.850, 0.839, 0.933 for the training cohort at 1 year, 3 years and 5 years; 0.715, 0.802 and 0.750 for the testing cohort at 1 year, 3 years and 5 years; and 0.668, 0.646 and 0.731 for the external validation cohort at 1 year, 3 years and 5 years. The calibration curves and decision curve showed that the nomogram had good consistency and clinical practical benefit. Finally, a stratified analysis showed that MDS patients with high risk had worse survival outcomes than patients with low risk.

Conclusion

We developed a nomogram containing six risk factors, which provides reliable and objective predictions of prognosis for MDS patients.

ASXL1/2 mutations and myeloid malignancies

Myeloid malignancies develop through the accumulation of genetic and epigenetic alterations that dysregulate hematopoietic stem cell (HSC) self-renewal, stimulate HSC proliferation and result in differentiation defects. The polycomb group (PcG) and trithorax group (TrxG) of epigenetic regulators act antagonistically to regulate the expression of genes key to stem cell functions. The genes encoding these proteins, and the proteins that interact with them or affect their occupancy at chromatin, are frequently mutated in myeloid malignancies. PcG and TrxG proteins are regulated by Enhancers of Trithorax and Polycomb (ETP) proteins. ASXL1 and ASXL2 are ETP proteins that assemble chromatin modification complexes and transcription factors. ASXL1 mutations frequently occur in myeloid malignancies and are associated with a poor prognosis, whereas ASXL2 mutations frequently occur in AML with t(8;21)/RUNX1-RUNX1T1 and less frequently in other subtypes of myeloid malignancies. Herein, we review the role of ASXL1 and ASXL2 in normal and malignant hematopoiesis by summarizing the findings of mouse model systems and discussing their underlying molecular mechanisms.

Case Report: Heterozygous Germline Variant in EIF6 Additional to Biallelic SBDS Pathogenic Variants in a Patient With Ribosomopathy Shwachman–Diamond Syndrome

Background: Shwachman–Diamond syndrome (SDS) is a rare autosomal recessive ribosomopathy mainly characterized by exocrine pancreatic insufficiency, skeletal alterations, neutropenia, and a relevant risk of hematological transformation. At least 90% of SDS patients have pathogenic variants in SBDS, the first gene associated with the disease with very low allelic heterogeneity; three variants, derived from events of genetic conversion between SBDS and its pseudogene, SBDSP1, provided the alleles observed in about 62% of SDS patients.

Methods: We performed a reanalysis of the available WES files of a group of SDS patients with biallelic SBDS pathogenic variants, studying the results by next bioinformatic and protein structural analysis. Parallelly, careful clinical attention was given to the patient focused in this study.

Results: We found and confirmed in one SDS patient a germline heterozygous missense variant (c.100T>C; p.Phe34Leu) in the EIF6 gene. This variant, inherited from his mother, has a very low frequency, and it is predicted as pathogenic, according to several in silico prediction tools. The protein structural analysis also envisages the variant could reduce the binding to the nascent 60S ribosomal.

Conclusion: This study focused on the hypothesis that the EIF6 germline variant mimics the effect of somatic deletions of chromosome 20, always including the locus of this gene, and similarly may rescue the ribosomal stress and ribosomal dysfunction due to SBDS mutations. It is likely that this rescue may contribute to the stable and not severe hematological status of the proband, but a definite answer on the role of this EIF6 variant can be obtained only by adding a functional layer of evidence. In the future, these results are likely to be useful for selected cases in personalized medicine and therapy.

ASXL1 mutations with serum EPO levels predict poor response to darbepoetin alfa in lower-risk MDS: W-JHS MDS01 trial

Darbepoetin alfa (DA) is used to treat anemia in lower-risk (IPSS low or int-1) myelodysplastic syndromes (MDS). However, whether mutations can predict the effectiveness of DA has not been examined. The present study aimed to determine predictive gene mutations. The primary endpoint was a correlation between the presence of highly frequent (≥ 10%) mutations and hematological improvement-erythroid according to IWG criteria 2006 by DA (240 μg/week) until week 16. The study included 79 patients (age 29–90, median 77.0 years; 52 [65.8%] male). Frequently (≥ 10%) mutated genes were SF3B1 (24 cases, 30.4%), TET2 (20, 25.3%), SRSF2 (10, 12.7%), ASXL1 (9, 11.4%), and DNMT3A (8, 10.1%). Overall response rate to DA was 70.9%. Multivariable analysis including baseline erythropoietin levels and red blood cell transfusion volumes as variables revealed that erythropoietin levels and mutations of ASXL1 gene were significantly associated with worse response (odds ratio 0.146, 95% confidence interval 0.042–0.503; p = 0.0023, odds ratio 0.175, 95% confidence interval 0.033–0.928; p = 0.0406, respectively). This study indicated that anemic patients who have higher erythropoietin levels and harbor ASXL1 gene mutations may respond poorly to DA. Alternative strategies are needed for the treatment of anemia in this population. Trial registration number and date of registration: UMIN000022185 and 09/05/2016.

PCR-Fluo-ASXL1-FA: A fast, sensitive and inexpensive complementary method to detect ASXL1 mutations in haematological malignancies

INTRODUCTION

The additional sex combs like 1 (ASXL1) gene is frequently mutated in a number of haematological neoplasms. The c.1934dupG, known to be the most common alteration in ASXL1, is associated with poor clinical outcome. A systematic determination of ASXL1 mutational status in myeloid malignancies is therefore necessary for prognostic stratification.

METHODS

Because direct sequencing is not sensitive and next-generation sequencing (NGS) is time-consuming, expensive and sometimes does not allow the detection of the c.1934dupG, we have developed a fragment analysis assay, complementary to NGS, that allows the detection of c.1934dupG mutation in addition to other nearby insertions/deletions of ASXL1 located close to it. We called this assay the "PCR-Fluo-ASXL1-FA."

RESULTS

First, we evaluated the efficiency of our approach compared to NGS and Sanger. We showed that "PCR-Fluo-ASXL1-FA" could detect all insertional mutations of ASXL1 located on its area, with a high sensitivity (1.5%). Then, we have illustrated the interest of this technique by three concrete cases.

DISCUSSION

In summary, we have established a fragment analysis approach, which can detect most ASXL1 mutations, in particular the c.1934dupG, in a sensitive, fast and inexpensive manner. We therefore recommend the synchronous use of this method with NGS, to ensure complete detection of all clinically relevant ASXL1 mutations in patients suffering with myeloid neoplasms.

Del(5q) and inv(3) in myelodysplastic syndrome: A rare case report

BACKGROUND

Del(5q) is the most common molecular event in myelodysplastic syndrome (MDS), accounting for 10%-15% of cases. Inv(3) is an adverse cytogenetic abnormality observed in less than 1% of MDS patients. Few studies have reported the coexistence of del(5q) and inv(3) in MDS. Therefore, the pathological mechanism, treatment strategy and prognosis of this subtype need to be elucidated.

CASE SUMMARY

A 66-year-old woman was admitted to the hospital due to chest tightness and shortness of breath. Combining clinical assessments with laboratory examinations, the patient was diagnosed with MDS containing both del(5q) and inv(3). Considering the deletion of chromosome 5q, we first treated the patient with lenalidomide. When drug resistance arose, we tried azacitidine, and the patient had a short remission. Finally, the patient refused treatment with haematopoietic stem cell transplantation and died of severe infection four months later.

CONCLUSION

MDS patients with del(5) and inv(3) have a poor prognosis. Azacitidine may achieve short-term remission for such patients.

The spectrum of genetic mutations in myelodysplastic syndrome: Should we update prognostication?

The natural history of patients with myelodysplastic syndrome (MDS) is dependent upon the presence and magnitude of diverse genetic and molecular aberrations. The International Prognostic Scoring System (IPSS) and revised IPSS (IPSS-R) are the most widely used classification and prognostic systems; however, somatic mutations are not currently incorporated into these systems, despite evidence of their independent impact on prognosis. Our manuscript reviews prognostic information for TP53, EZH2, DNMT3A, ASXL1, RUNX1, SRSF2, CBL, IDH 1/2, TET2, BCOR, ETV6, GATA2, U2AF1, ZRSR2, RAS, STAG2, and SF3B1. Mutations in TP53, EZH2, ASXL1, DNMT3A, RUNX1, SRSF2, and CBL have extensive evidence for their negative impact on survival, whereas SF3B1 is the lone mutation carrying a favorable prognosis. We use the existing literature to propose the incorporation of somatic mutations into the IPSS-R. More data are needed to define the broad spectrum of other genetic lesions, as well as the impact of variant allele frequencies, class of mutation, and impact of multiple interactive genomic lesions. We postulate that the incorporation of these data into MDS prognostication systems will not only enhance our therapeutic decision making but lead to targeted treatment in an attempt to improve outcomes in this formidable disease.

Modeling clonal hematopoiesis in umbilical cord blood cells by CRISPR/Cas9

To investigate clonal hematopoiesis associated gene mutations in vitro and to unravel the direct impact on the human stem and progenitor cell (HSPC) compartment, we targeted healthy, young hematopoietic progenitor cells, derived from umbilical cord blood samples, with CRISPR/Cas9 technology. Site-specific mutations were introduced in defined regions of DNMT3A, TET2, and ASXL1 in CD34⁺ progenitor cells that were subsequently analyzed in short-term as well as long-term in vitro culture assays to assess self-renewal and differentiation capacities. Colony-forming unit (CFU) assays revealed enhanced self-renewal of TET2 mutated (TET2^mut) cells, whereas ASXL1^mut as well as DNMT3A^mut cells did not reveal significant changes in short-term culture. Strikingly, enhanced colony formation could be detected in long-term culture experiments in all mutants, indicating increased self-renewal capacities. While we could also demonstrate preferential clonal expansion of distinct cell clones for all mutants, the clonal composition after long-term culture revealed a mutation-specific impact on HSPCs. Thus, by using primary umbilical cord blood cells, we were able to investigate epigenetic driver mutations without confounding factors like age or a complex mutational landscape, and our findings provide evidence for a direct impact of clonal hematopoiesis-associated mutations on self-renewal and clonal composition of human stem and progenitor cells.

Hypoplastic myelodysplastic syndrome and acquired aplastic anemia: Immune‑mediated bone marrow failure syndromes (Review)

Hypoplastic myelodysplastic syndrome (hMDS) and aplastic anemia (AA) are rare hematopoietic disorders characterized by pancytopenia with hypoplastic bone marrow (BM). hMDS and idiopathic AA share overlapping clinicopathological features, making a diagnosis very difficult. The differential diagnosis is mainly based on the presence of dysgranulopoiesis, dysmegakaryocytopoiesis, an increased percentage of blasts, and abnormal karyotype, all favouring the diagnosis of hMDS. An accurate diagnosis has important clinical implications, as the prognosis and treatment can be quite different for these diseases. Patients with hMDS have a greater risk of neoplastic progression, a shorter survival time and a lower response to immunosuppressive therapy compared with patients with AA. There is compelling evidence that these distinct clinical entities share a common pathophysiology based on the damage of hematopoietic stem and progenitor cells (HSPCs) by cytotoxic T cells. Expanded T cells overproduce proinflammatory cytokines (interferon-γ and tumor necrosis factor-α), resulting in decreased proliferation and increased apoptosis of HSPCs. The antigens that trigger this abnormal immune response are not known, but potential candidates have been suggested, including Wilms tumor protein 1 and human leukocyte antigen class I molecules. Our understanding of the molecular pathogenesis of these BM failure syndromes has been improved by next-generation sequencing, which has enabled the identification of a large spectrum of mutations. It has also brought new challenges, such as the interpretation of variants of uncertain significance and clonal hematopoiesis of indeterminate potential. The present review discusses the main clinicopathological differences between hMDS and acquired AA, focuses on the molecular background and highlights the importance of molecular testing.

Mitochondria and Their Relationship with Common Genetic Abnormalities in Hematologic Malignancies

Hematologic malignancies are known to be associated with numerous cytogenetic and molecular genetic changes. In addition to morphology, immunophenotype, cytochemistry and clinical characteristics, these genetic alterations are typically required to diagnose myeloid, lymphoid, and plasma cell neoplasms. According to the current World Health Organization (WHO) Classification of Tumors of Hematopoietic and Lymphoid Tissues, numerous genetic changes are highlighted, often defining a distinct subtype of a disease, or providing prognostic information. This review highlights how these molecular changes can alter mitochondrial bioenergetics, cell death pathways, mitochondrial dynamics and potentially be related to mitochondrial genetic changes. A better understanding of these processes emphasizes potential novel therapies.

Bioinformatics analysis of high frequency mutations in myelodysplastic syndrome-related patients

Background

Myelodysplastic syndrome (MDS) is a group of hematological malignancies that may progress to acute myeloid leukemia (AML). Bioinformatics-based analysis of high-frequency mutation genes in MDS-related patients is still relatively rare, so we conducted our research to explore whether high-frequency mutation genes in MDS-related patients can play a reference role in clinical guidance and prognosis.

Methods

Next generation sequencing (NGS) technology was used to detect 32 mutations in 64 MDS-related patients. We classified the patients' genes and analyzed them by Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, protein-protein interaction (PPI) analysis, and then calculated the gene survival curve of high-frequency mutations.

Results

We discovered 32 mutant genes such as ASXL1, DNMT3A, KRAS, NRAS, TP53, SF3B1, and SRSF2. The overall survival (OS) of these genes decreased significantly after DNMT3A, ASXL1, RUNX1, and U2AF1 occurred mutation. These genes play a significant role in biological processes, not only in MDS but also in the occurrence and development of other diseases. Through retrospective analysis, genes associated with MDS-related diseases were identified, and their effects on the disease were predicted.

Conclusions

Thirty-two mutant genes were determined in MDS and when mutations occur in DNMT3A, ASXL1, RUNX1, and U2AF1, their survival time decreases significantly. This results providing a theoretical basis for clinical and scientific research and broadening the scope of research on MDS.

Myelodysplastic syndromes: Biological and therapeutic consequences of the evolving molecular aberrations landscape

Myelodysplastic syndromes (MDS) are clonal hematopoietic disorders with heterogeneous presentation, ranging from indolent disease courses to aggressive diseases similar to acute myeloid leukemia (AML). Approximately 90% of MDS patients harbor recurrent mutations , which – with the exception of mutated SF3B1 –have not (yet) been included into the diagnostic criteria or risk stratification for MDS. Accumulating evidence suggests their utility for diagnostic workup, treatment indication and prognosis. Subsequently, in patients with unexplained cytopenia or dysplasia identification of these mutations may lead to earlier diagnosis. The acquisition and expansion of additional driver mutations usually antecedes further disease progression to higher risk MDS or secondary AML and thus, can be clinically helpful to detect individuals that may benefit from aggressive treatment approaches. Here, we review our current understanding of somatic gene mutations, gene expression patterns and flow cytometry regarding their relevance for disease evolution from pre-neoplastic states to MDS and potentially AML.

Molecular Targeted Therapy and Immunotherapy for Myelodysplastic Syndrome

Myelodysplastic syndrome (MDS) is a heterogeneous, clonal hematological disorder characterized by ineffective hematopoiesis, cytopenia, morphologic dysplasia, and predisposition to acute myeloid leukemia (AML). Stem cell genomic instability, microenvironmental aberrations, and somatic mutations contribute to leukemic transformation. The hypomethylating agents (HMAs), azacitidine and decitabine are the standard of care for patients with higher-risk MDS. Although these agents induce responses in up to 40-60% of patients, primary or secondary drug resistance is relatively common. To improve the treatment outcome, combinational therapies comprising HMA with targeted therapy or immunotherapy are being evaluated and are under continuous development. This review provides a comprehensive update of the molecular pathogenesis and immune-dysregulations involved in MDS, mechanisms of resistance to HMA, and strategies to overcome HMA resistance.

The Prognostic Value of Early Detection of Minimal Residual Disease as Defined by Flow Cytometry and Gene Mutation Clearance for Myelodysplastic Syndrome Patients After Myeloablative Allogeneic Hematopoietic Stem-Cell Transplantation

High relapse incidence remains a major problem for myelodysplastic syndrome (MDS) patients who have received an allogeneic hematopoietic stem-cell transplantation (allo-HSCT). We retrospectively analyzed the correlations between clinical outcomes and minimal residual disease (MRD) by using mutations (MUT) and flow cytometry (FCM) analysis of 115 MDS patients with allo-HSCT. We divided 115 MDS patients into four groups based on molecular genetics and FCM MRD results at day 30 post-HSCT. There were significant differences in the 2-year progression-free survival (PFS) between the FCM^high MUT^pos and FCM^low MUT^neg groups (20% vs 79%, P < 0.001). In addition, by univariate analysis, we found that an IPSS-R score ≥4 pre-HSCT (HR, 5.061; P=0.007), DNMT3A mutations (HR, 2.291; P=0.052), TP53 mutations (HR, 3.946; P=0.011), and poor and very poor revised International Prognostic Scoring System (IPSS-R) cytogenetic risk (HR, 4.906; P < 0.001) were poor risk factors for PFS. In multivariate analysis, we found that an IPSS-R score ≥ 4 pre-HSCT (HR, 4.488; P=0.015), DNMT3A mutations (HR, 2.385; P=0.049), positive FCM MRD combined with persistence gene mutations at day 30 (HR, 5.198; P=0.013) were independent risk factors for disease progression. In conclusion, our data indicated that monitoring MRD by FCM combined with gene mutation clearance at day 30 could help in the prediction of disease progression for MDS patients after transplantation.

Polycomb-dependent histone H2A ubiquitination links developmental disorders with cancer

Cell identity is tightly controlled by specific transcriptional programs which require post-translational modifications of histones. These histone modifications allow the establishment and maintenance of active and repressed chromatin domains. Histone H2A lysine 119 ubiquitination (H2AK119ub1) has an essential role in building repressive chromatin domains during development. It is regulated by the counteracting activities of the Polycomb repressive complex 1 (PRC1) and the Polycomb repressive-deubiquitinase (PR-DUB) complexes, two multi-subunit ensembles that write and erase this modification, respectively. We have catalogued the recurrent genetic alterations in subunits of the PRC1 and PR-DUB complexes in both neurodevelopmental disorders and cancer. These genetic lesions are often shared across disorders, and we highlight common mechanisms of H2AK119ub1 dysregulation and how they affect development in multiple disease contexts.

Myelodysplastic syndromes with 20q deletion: incidence, prognostic value and impact on response to azacitidine of ASXL1 chromosomal deletion and genetic mutations

In myelodysplastic syndromes (MDS), the 20q deletion [del(20q)] may cause deletion of the ASXL1 gene. We studied 153 patients with MDS and del(20q) to assess the incidence, prognostic value and impact on response to azacitidine (AZA) of ASXL1 chromosomal alterations and genetic mutations. Additionally, in vitro assay of the response to AZA in HAP1 (HAP1^WT ) and HAP1 ASXL1 knockout (HAP1^KN ) cells was performed. ASXL1 chromosomal alterations were detected in 44 patients (28·5%): 34 patients (22%) with a gene deletion (ASXL1^DEL ) and 10 patients (6·5%) with additional gene copies. ASXL1^DEL was associated with a lower platelet count. The most frequently mutated genes were U2AF1 (16%), ASXL1 (14%), SF3B1 (11%), TP53 (7%) and SRSF2 (6%). ASXL1 alteration due to chromosomal deletion or genetic mutation (ASXL1^DEL /ASXL1^MUT ) was linked by multivariable analysis with shorter overall survival [hazard ratio, (HR) 1·84; 95% confidence interval, (CI): 1·11-3·04; P = 0·018] and a higher rate for acute myeloid leukaemia progression (HR 2·47; 95% CI: 1·07-5·70, P = 0·034). ASXL1^DEL /ASXL1^MUT patients were correlated by univariable analysis with a worse response to AZA. HAP1^KN cells showed more resistance to AZA compared to HAP1^WT cells. In conclusion, ASXL1 alteration exerts a negative impact on MDS with del(20q) and could become useful for prognostic risk stratification and treatment decisions.

Supplemental Association of Clonal Hematopoiesis With Incident Heart Failure

BACKGROUND

Age-related clonal hematopoiesis of indeterminate potential (CHIP), defined as clonally expanded leukemogenic sequence variations (particularly in DNMT3A, TET2, ASXL1, and JAK2) in asymptomatic individuals, is associated with cardiovascular events, including recurrent heart failure (HF).

OBJECTIVES

This study sought to evaluate whether CHIP is associated with incident HF.

METHODS

CHIP status was obtained from whole exome or genome sequencing of blood DNA in participants without prevalent HF or hematological malignancy from 5 cohorts. Cox proportional hazards models were performed within each cohort, adjusting for demographic and clinical risk factors, followed by fixed-effect meta-analyses. Large CHIP clones (defined as variant allele frequency >10%), HF with or without baseline coronary heart disease, and left ventricular ejection fraction were evaluated in secondary analyses.

RESULTS

Of 56,597 individuals (59% women, mean age 58 years at baseline), 3,406 (6%) had CHIP, and 4,694 developed HF (8.3%) over up to 20 years of follow-up. CHIP was prospectively associated with a 25% increased risk of HF in meta-analysis (hazard ratio: 1.25; 95% confidence interval: 1.13-1.38) with consistent associations across cohorts. ASXL1, TET2, and JAK2 sequence variations were each associated with an increased risk of HF, whereas DNMT3A sequence variations were not associated with HF. Secondary analyses suggested large CHIP was associated with a greater risk of HF (hazard ratio: 1.29; 95% confidence interval: 1.15-1.44), and the associations for CHIP on HF with and without prior coronary heart disease were homogenous. ASXL1 sequence variations were associated with reduced left ventricular ejection fraction.

CONCLUSIONS

CHIP, particularly sequence variations in ASXL1, TET2, and JAK2, represents a new risk factor for HF.

Allogeneic hematopoietic stem cell transplantation could improve the survival of acute myeloid leukemia patients with ASXL1 mutations

Objective: To discover the function of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in ASXL1-mutated acute myeloid leukemia (AML) patients.Methods: We analyzed the prognostic value of ASXL1 mutations and explored the role of allo-HSCT in 581 AML patients.Results: According to the definition of intermediate- and adverse-risk AML groups in the European Leukemia Net (ELN), ASXL1-mutated patients had shorter OS and DFS than ASXL1-wild-type patients in the intermediate- and adverse-risk AML groups (3-year OS: 47.5% vs. 60.8%, P<0.001; 3-year DFS: 28.5% vs. 48.9%, P<0.001). Among the cytogenetically normal acute myeloid leukemia (CN-AML), differences were found in both OS (47.4% vs.65.2%, P<0.001) and DFS (21.0% vs. 52.1%, P<0.001) between ASXL1-mutated patients and ASXL1 wild-type patients.In the ASXL1-mutated AML cohort, the patients received allo-HSCT had longer 3-year OS (P=0.0005) and 3-year DFS (P<0.0001) than those who did not receive allo-HSCT. Multivariate analysis revealed that ASXL1 mutation was an independent prognostic factor for OS (HR 2.248, 95% CI 1.155-4.375, P=0.017), and allo-HSCT had a positive impact on OS (HR 7.568, 95% CI 3.597-15.92, P<0.001) and DFS (HR 2.611, 95% CI 1.688-4.039, P<0.001) in ASXL1-mutated patients.Conclusion: The results indicate that the presence of ASXL1 mutations is a factor predictive of poor prognosis in AML patients and allo-HSCT could improve the survival of AML patients with ASXL1 mutations.

Prognosis in Myelodysplastic Syndromes: The Clinical Challenge of Genomic Integration

Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic neoplasms characterized by ineffective hematopoiesis and myelodysplasia with a variable spectrum of clinical-biological features that can be used to build a prognostic estimation. This review summarizes the current most widely used prognostic scoring systems and gives a general view of the prognostic impact of somatic mutations in MDS patients.

Myelodysplasia Syndrome, Clonal Hematopoiesis and Cardiovascular Disease

Simple Summary

The development of blood cancers is a complex process that involves the acquisition of specific blood disorders that precede cancer. These blood disorders are often driven by the accumulation of genetic abnormalities, which are discussed in this review. Likewise, predicting the rate of progression of these diseases is difficult, but it appears to be linked to which specific gene mutations are present in blood cells. In this review, we discuss a variety of genetic abnormalities that drive blood cancer, conditions that precede clinical symptoms of blood cancer, and how alterations in these genes change blood cell function. Additionally, we discuss the novel links between blood cancer development and heart disease.

Abstract

The development of myelodysplasia syndromes (MDS) is multiphasic and can be driven by a plethora of genetic mutations and/or abnormalities. MDS is characterized by a hematopoietic differentiation block, evidenced by increased immature hematopoietic cells, termed blast cells and decreased mature circulating leukocytes in at least one lineage (i.e., cytopenia). Clonal hematopoiesis of indeterminate potential (CHIP) is a recently described phenomenon preceding MDS development that is driven by somatic mutations in hemopoietic stem cells (HSCs). These mutant HSCs have a competitive advantage over healthy cells, resulting in an expansion of these clonal mutated leukocytes. In this review, we discuss the multiphasic development of MDS, the common mutations found in both MDS and CHIP, how a loss-of-function in these CHIP-related genes can alter HSC function and leukocyte development and the potential disease outcomes that can occur with dysfunctional HSCs. In particular, we discuss the novel connections between MDS development and cardiovascular disease.

Clonal haematopoiesis of indeterminate potential: intersections between inflammation, vascular disease and heart failure

Ageing is a major risk factor for the development of cardiovascular disease (CVD) and cancer. Whilst the cumulative effect of exposure to conventional cardiovascular risk factors is important, recent evidence highlights clonal haematopoiesis of indeterminant potential (CHIP) as a further key risk factor. CHIP reflects the accumulation of somatic, potentially pro-leukaemic gene mutations within haematopoietic stem cells over time. The most common mutations associated with CHIP and CVD occur in genes that also play central roles in the regulation of inflammation. While CHIP carriers have a low risk of haematological malignant transformation (<1% per year), their relative risk of mortality is increased by 40% and this reflects an excess of cardiovascular events. Evidence linking CHIP, inflammation and atherosclerotic disease has recently become better defined. However, there is a paucity of information about the role of CHIP in the development and progression of heart failure, particularly heart failure with preserved ejection fraction (HFpEF). While systemic inflammation plays a role in the pathophysiology of both heart failure with reduced and preserved ejection fraction (EF), it may be of greater relevance in the pathophysiology of HFpEF, which is also strongly associated with ageing. This review describes CHIP and its pathogenetic links with ageing, inflammation and CVD, while providing insight into its putative role in HFpEF.

Mutant ASXL1 induces age-related expansion of phenotypic hematopoietic stem cells through activation of Akt/mTOR pathway

Somatic mutations of ASXL1 are frequently detected in age-related clonal hematopoiesis (CH). However, how ASXL1 mutations drive CH remains elusive. Using knockin (KI) mice expressing a C-terminally truncated form of ASXL1-mutant (ASXL1-MT), we examined the influence of ASXL1-MT on physiological aging in hematopoietic stem cells (HSCs). HSCs expressing ASXL1-MT display competitive disadvantage after transplantation. Nevertheless, in genetic mosaic mouse model, they acquire clonal advantage during aging, recapitulating CH in humans. Mechanistically, ASXL1-MT cooperates with BAP1 to deubiquitinate and activate AKT. Overactive Akt/mTOR signaling induced by ASXL1-MT results in aberrant proliferation and dysfunction of HSCs associated with age-related accumulation of DNA damage. Treatment with an mTOR inhibitor rapamycin ameliorates aberrant expansion of the HSC compartment as well as dysregulated hematopoiesis in aged ASXL1-MT KI mice. Our findings suggest that ASXL1-MT provokes dysfunction of HSCs, whereas it confers clonal advantage on HSCs over time, leading to the development of CH.

The Functions and Mechanisms of PR-DUB in Malignancy

The interplay between cancer genome and deregulated epigenomic control is critical for cancer initiation and progression. ASXL1 (Additional Sex combs-like 1) is frequently mutated in tumors especially myeloid malignancies. However, there remains a debate whether the mutations are loss or gain-of-function. Mechanistically, ASXL1 forms a complex with BAP1 for the erasure of mono-ubiquitylation at lysine 119 on Histone H2A (H2AK119ub1), a well-known histone mark associated with transcription repression. Unexpectedly, this de-ubiquitylation complex has been genetically defined as a Polycomb Repressive complex though the regulatory mechanisms are elusive. In this review, we will discuss about the functions of ASXL1 in malignancies and reconcile seemingly paradoxical effects of ASXL1 or BAP1 loss on transcription regulation.

Old Dog, New Trick: Type I IFN-Based Treatment for Acute Myeloid Leukemia

Despite strong biological rationale for the use of type-I IFNs for the treatment of acute myeloid leukemia (AML), their usage is limited to few hematologic malignancies. Here, we propose that innate immune sensing machinery, particularly the stimulator of IFN genes pathway, may be exploited to deliver antileukemic effects in AML.

Loss of ASXL1 expression is associated with lymph node metastasis in colorectal cancer

Context

The function of ASXL1 in colorectal cancer (CRC) has not been investigated yet.

Aims

The purpose of this study was to investigate the clinicopathological and prognostic impact of ASXL1 expression on CRC.

Settings and Design

The intensity of expression was scored as 0-3, and the extent of staining was scored as 0-4, based on the percentage of positive cells. The immunoreactivity score (IRS) was calculated by multiplying the two scores.

Materials and Methods

We performed immunohistochemical staining of ASXL1 using tissue microarrays of 408 CRCs, 46 normal colonic mucosae, 48 adenomas, and 92 metastatic lymph nodes.

Statistical Analysis Used

Clinicopathological variables were compared using Fisher's exact test, χ²-test, or unpaired Student's t-test, depending on the nature of the data.

Results

A negative expression of ASXL1 was observed in 10.9% of normal mucosae, 27.1% of adenomas, 55.6% of adenocarcinomas, and 71.7% of metastatic lymph nodes (P < 0.001). With respect to the IRS cut-off score, lymph node metastasis and lymphatic invasion were more frequent in the IRS 0-6 group than in the IRS 8-12 group (56.3% vs. 33.3%, P = 0.034; 56.0% vs. 33.3%, P = 0.035). The 5-year disease-free survival rate was significantly lower in patients with IRS 0-6 group than those with IRS 8-12 group (78.7 ± 2.5 vs. 100%, P = 0.034).

Conclusion

ASXL1 might act as a tumor suppressor in CRC. The loss of ASXL1 expression might be associated with lymph node metastasis and lymphatic invasion in CRC.

Molecular Pathogenesis and Treatment of Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are clonal hematological disorders arising from hematopoietic stem cells that have accumulated various genetic abnormalities. MDS are heterogeneous in nature but uniformly characterized by chronic and progressive cytopenia from ineffective hematopoiesis, dysplasia in single or multiple lineages, and transformation to acute leukemia in a subset of patients. The genomic landscape revealed by next-generation sequencing has provided a comprehensive picture of the molecular pathways involved in MDS pathogenesis. Recurrent mutational targets in MDS are the genes involved in RNA splicing, DNA methylation, histone modification, transcription, signal transduction, cohesin complex and DNA repair. Sequential acquisition of mutations in these sets of genes serves as a driver for the initiation, clonal evolution and progression of MDS. Based on these findings, novel agents targeting driver mutations of MDS are currently under development and expected to improve the clinical outcome of MDS in the coming decades.

The evolution of epigenetic therapy in myelodysplastic syndromes and acute myeloid leukemia

Mutations in the group of epigenetic modifiers are the largest group of mutated genes in Myelodysplastic Syndromes (MDS) and are very frequently found in Acute Myeloid Leukemia (AML). Our advancements in the understanding of epigenetics in these diseases have helped develop groundbreaking therapeutics that have changed the treatment landscape of MDS and AML, significantly improving outcomes. In this review we describe the most common epigenetic aberrations in MDS and AML, and current treatments that target mutations in epigenetic modifiers, as well as novel treatment combinations, from standard therapies to investigational treatments.

Pathogenic Impacts of Dysregulated Polycomb Repressive Complex Function in Hematological Malignancies

Polycomb repressive complexes (PRCs) are epigenetic regulators that mediate repressive histone modifications. PRCs play a pivotal role in the maintenance of hematopoietic stem cells through repression of target genes involved in cell proliferation and differentiation. Next-generation sequencing technologies have revealed that various hematologic malignancies harbor mutations in PRC2 genes, such as EZH2, EED, and SUZ12, and PRC1.1 genes, such as BCOR and BCORL1. Except for the activating EZH2 mutations detected in lymphoma, most of these mutations compromise PRC function and are frequently associated with resistance to chemotherapeutic agents and poor prognosis. Recent studies have shown that mutations in PRC genes are druggable targets. Several PRC2 inhibitors, including EZH2-specific inhibitors and EZH1 and EZH2 dual inhibitors have shown therapeutic efficacy for tumors with and without activating EZH2 mutations. Moreover, EZH2 loss-of-function mutations appear to be attractive therapeutic targets for implementing the concept of synthetic lethality. Further understanding of the epigenetic dysregulation associated with PRCs in hematological malignancies should improve treatment outcomes.

Patient stratification in myelodysplastic syndromes: how a puzzle may become a map

Heterogeneity is the disease-defining epithet of myelodysplastic syndromes (MDS), a clonal disorder of hematopoietic stem and progenitor cells. During the last decade, significant progress has been made to better understand the diversity of clinical, molecular, cellular, and immunological factors that are bound to the prognosis and outcomes of patients with MDS. Despite the rapid generation of all of this biological information, how to implement it has fallen short. Redefining clinical tools to use this new information remains a challenge. The holistic integration of novel, high-impact individual risk parameters such as patient-reported outcomes or mutational and immunological data into conventional risk stratification systems may further refine patient subgroups, improve predictive power for survival, and provide a next-generation classification and prognosis system for patients with MDS. Dichotomic treatment strategies in patients with MDS according to their patient and disease profiles highlight the importance of precise risk stratification, which may be complemented by the definition of granular cohorts of patients with myeloid neoplasms and a druggable target (ie, IDH1/2 mutations) across conventional blast thresholds.

The Genomics of Myelodysplastic Syndromes: Origins of Disease Evolution, Biological Pathways, and Prognostic Implications

The molecular pathogenesis of myelodysplastic syndrome (MDS) is complex due to the high rate of genomic heterogeneity. Significant advances have been made in the last decade which elucidated the landscape of molecular alterations (cytogenetic abnormalities, gene mutations) in MDS. Seminal experimental studies have clarified the role of diverse gene mutations in the context of disease phenotypes, but the lack of faithful murine models and/or cell lines spontaneously carrying certain gene mutations have hampered the knowledge on how and why specific pathways are associated with MDS pathogenesis. Here, we summarize the genomics of MDS and provide an overview on the deregulation of pathways and the latest molecular targeted therapeutics.

Murine Models of Myelofibrosis

Myelofibrosis (MF) is subtype of myeloproliferative neoplasm (MPN) characterized by a relatively poor prognosis in patients. Understanding the factors that drive MF pathogenesis is crucial to identifying novel therapeutic approaches with the potential to improve patient care. Driver mutations in three main genes (janus kinase 2 (JAK2), calreticulin (CALR), and myeloproliferative leukemia virus oncogene (MPL)) are recurrently mutated in MPN and are sufficient to engender MPN using animal models. Interestingly, animal studies have shown that the underlying molecular mutation and the acquisition of additional genetic lesions is associated with MF outcome and transition from early stage MPN such as essential thrombocythemia (ET) and polycythemia vera (PV) to secondary MF. In this issue, we review murine models that have contributed to a better characterization of MF pathobiology and identification of new therapeutic opportunities in MPN.

ASXL3 bridges BRD4 to BAP1 complex and governs enhancer activity in small cell lung cancer

BACKGROUND

Small cell lung cancer (SCLC) is a more aggressive subtype of lung cancer that often results in rapid tumor growth, early metastasis, and acquired therapeutic resistance. Consequently, such phenotypical characteristics of SCLC set limitations on viable procedural options, making it difficult to develop both screenings and effective treatments. In this study, we examine a novel mechanistic insight in SCLC cells that could potentially provide a more sensitive therapeutic alternative for SCLC patients.

METHODS

Biochemistry studies, including size exclusion chromatography, mass spectrometry, and western blot analysis, were conducted to determine the protein-protein interaction between additional sex combs-like protein 3 (ASXL3) and bromodomain-containing protein 4 (BRD4). Genomic studies, including chromatin immunoprecipitation sequencing (ChIP-seq), RNA sequencing, and genome-wide analysis, were performed in both human and mouse SCLC cells to determine the dynamic relationship between BRD4/ASXL3/BAP1 epigenetic axis in chromatin binding and its effects on transcriptional activity.

RESULTS

We report a critical link between BAP1 complex and BRD4, which is bridged by the physical interaction between ASXL3 and BRD4 in an SCLC subtype (SCLC-A), which expresses a high level of ASCL1. We further showed that ASXL3 functions as an adaptor protein, which directly interacts with BRD4's extra-terminal (ET) domain via a novel BRD4 binding motif (BBM), and maintains chromatin occupancy of BRD4 to active enhancers. Genetic depletion of ASXL3 results in a genome-wide reduction of histone H3K27Ac levels and BRD4-dependent gene expression in SCLC. Pharmacologically induced inhibition with BET-specific chemical degrader (dBET6) selectively inhibits cell proliferation of a subtype of SCLC that is characterized with high expression of ASXL3.

CONCLUSIONS

Collectively, this study provides a mechanistic insight into the oncogenic function of BRD4/ASXL3/BAP1 epigenetic axis at active chromatin enhancers in SCLC-A subtype, as well as a potential new therapeutic option that could become more effective in treating SCLC patients with a biomarker of ASXL3-highly expressed SCLC cells.

EZH2 in Myeloid Malignancies

Our understanding of the significance of epigenetic dysregulation in the pathogenesis of myeloid malignancies has greatly advanced in the past decade. Enhancer of Zeste Homolog 2 (EZH2) is the catalytic core component of the Polycomb Repressive Complex 2 (PRC2), which is responsible for gene silencing through trimethylation of H3K27. EZH2 dysregulation is highly tumorigenic and has been observed in various cancers, with EZH2 acting as an oncogene or a tumor-suppressor depending on cellular context. While loss-of-function mutations of EZH2 frequently affect patients with myelodysplastic/myeloproliferative neoplasms, myelodysplastic syndrome and myelofibrosis, cases of chronic myeloid leukemia (CML) seem to be largely characterized by EZH2 overexpression. A variety of other factors frequently aberrant in myeloid leukemia can affect PRC2 function and disease pathogenesis, including Additional Sex Combs Like 1 (ASXL1) and splicing gene mutations. As the genetic background of myeloid malignancies is largely heterogeneous, it is not surprising that EZH2 mutations act in conjunction with other aberrations. Since EZH2 mutations are considered to be early events in disease pathogenesis, they are of therapeutic interest to researchers, though targeting of EZH2 loss-of-function does present unique challenges. Preliminary research indicates that combined tyrosine kinase inhibitor (TKI) and EZH2 inhibitor therapy may provide a strategy to eliminate the residual disease burden in CML to allow patients to remain in treatment-free remission.

Genetic and Genomic Landscape of Secondary and Therapy-Related Acute Myeloid Leukemia

A subset of acute myeloid leukemia (AML) arises either from an antecedent myeloid malignancy (secondary AML, sAML) or as a complication of DNA-damaging therapy for other cancers (therapy-related myeloid neoplasm, t-MN). These secondary leukemias have unique biological and clinical features that distinguish them from de novo AML. Over the last decade, molecular techniques have unraveled the complex subclonal architecture of sAML and t-MN. In this review, we compare and contrast biological and clinical features of de novo AML with sAML and t-MN. We discuss the role of genetic mutations, including those involved in RNA splicing, epigenetic modification, tumor suppression, transcription regulation, and cell signaling, in the pathogenesis of secondary leukemia. We also discuss clonal hematopoiesis in otherwise healthy individuals, as well as in the context of another malignancy, and how it challenges the conventional notion of sAML/t-MN. We conclude by summarizing the current and emerging treatment strategies, including allogenic transplant, in these complex scenarios.

Perithyroidal Salivary Gland Acinic Cell Carcinoma: Morphological and Molecular Attributes of a Unique Lesion

Rarely, salivary gland tumors such as mucoepidermoid carcinoma, mammary analogue secretory carcinoma and mucinous carcinoma arise as primary tumors from ectopic or metaplastic salivary gland tissue adjacent to or within the thyroid gland. We report for the first time a case of primary salivary acinic cell carcinoma (AcCC) adjacent to the thyroid gland in a 71-year-old female patient with Crohns disease and a previous history of malignant melanoma. Following the development of a nodule adjacent to the left thyroid lobe, a fine-needle aspiration biopsy was reported as consistent with a follicular lesion of undetermined significance (Bethesda III). A left-sided hemithyroidectomy was performed. A circumscribed lesion measuring 33 mm was noted adjacent to the thyroid and trapping parathyroid, it was composed of solid nests and glands with microcystic and follicular patterns. The tumor was negative for thyroid, parathyroid and paraganglioma markers, but positive for pan-cytokeratins, CK7, CD10, CD117, androgen receptor and HNF-beta. A metastasis of a thyroid-like renal cell carcinoma was suspected but ruled out, and the patient had no evident lesions on extensive radiology of the urogenital, pulmonary and GI tracts. Based on the morphology, a diagnosis of AcCC was suggested, and confirmed with DOG1 and PAS-diastase staining. Molecular analyses pinpointed a constitutional ASXL1 variant of uncertain significance, but no fusion events. The patient had no radiological or clinical evidence of parotid, submandibular or sublingual tumors postoperatively, and the excised lesion was therefore assumed to be a primary tumor. We here detail the morphological and immunophenotypic profile of this previously undescribed perithyroidal tumor.