bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2021‒05‒02
forty-four papers selected by
Paolo Gallipoli
Barts Cancer Institute, Queen Mary University of London

  1. J Hematol Oncol. 2021 Apr 26. 14(1): 70
      BACKGROUND: BCL-2 inhibition through venetoclax (VEN) targets acute myeloid leukemia (AML) blast cells and leukemic stem cells (LSCs). Although VEN-containing regimens yield 60-70% clinical response rates, the vast majority of patients inevitably suffer disease relapse, likely because of the persistence of drug-resistant LSCs. We previously reported preclinical activity of the ribonucleoside analog 8-chloro-adenosine (8-Cl-Ado) against AML blast cells and LSCs. Moreover, our ongoing phase I clinical trial of 8-Cl-Ado in patients with refractory/relapsed AML demonstrates encouraging clinical benefit. Of note, LSCs uniquely depend on amino acid-driven and/or fatty acid oxidation (FAO)-driven oxidative phosphorylation (OXPHOS) for survival. VEN inhibits OXPHOS in LSCs, which eventually may escape the antileukemic activity of this drug. FAO is activated in LSCs isolated from patients with relapsed AML.METHODS: Using AML cell lines and LSC-enriched blast cells from pre-treatment AML patients, we evaluated the effects of 8-Cl-Ado, VEN and the 8-Cl-Ado/VEN combination on fatty acid metabolism, glycolysis and OXPHOS using liquid scintillation counting, a Seahorse XF Analyzer and gene set enrichment analysis (GSEA). Western blotting was used to validate results from GSEA. HPLC was used to measure intracellular accumulation of 8-Cl-ATP, the cytotoxic metabolite of 8-Cl-Ado. To quantify drug synergy, we created combination index plots using CompuSyn software. The log-rank Kaplan-Meier survival test was used to compare the survival distributions of the different treatment groups in a xenograft mouse model of AML.
    RESULTS: We here report that VEN and 8-Cl-Ado synergistically inhibited in vitro growth of AML cells. Furthermore, immunodeficient mice engrafted with MV4-11-Luc AML cells and treated with the combination of VEN plus 8-Cl-Ado had a significantly longer survival than mice treated with either drugs alone (p ≤ 0.006). We show here that 8-Cl-Ado in the LSC-enriched population suppressed FAO by downregulating gene expression of proteins involved in this pathway and significantly inhibited the oxygen consumption rate (OCR), an indicator of OXPHOS. By combining 8-Cl-Ado with VEN, we observed complete inhibition of OCR, suggesting this drug combination cooperates in targeting OXPHOS and the metabolic homeostasis of AML cells.
    CONCLUSION: Taken together, the results suggest that 8-Cl-Ado enhances the antileukemic activity of VEN and that this combination represents a promising therapeutic regimen for treatment of AML.
    Keywords:  Acute myeloid leukemia; Fatty acid oxidation; Metabolism; Nucleoside analog; Oxidative phosphorylation
  2. Cancers (Basel). 2021 Apr 02. pii: 1693. [Epub ahead of print]13(7):
      Numerous combinations of signaling pathway blockades in association with tyrosine kinase inhibitor (TKI) treatment have been proposed for eradicating leukemic stem cells (LSCs) in chronic myeloid leukemia (CML), but none are currently clinically available. Because targeting protein kinase Cδ (PKCδ) was demonstrated to eliminate cancer stem cells (CSCs) in solid tumors, we evaluated the efficacy of PKCδ inhibition in combination with TKIs for CML cells. We observed that inhibition of PKCδ by a pharmacological inhibitor, by gene silencing, or by using K562 CML cells expressing dominant-negative (DN) or constitutively active (CA) PKCδ isoforms clearly points to PKCδ as a regulator of the expression of the stemness regulator BMI1. As a consequence, inhibition of PKCδ impaired clonogenicity and cell proliferation for leukemic cells. PKCδ targeting in K562 and LAMA-84 CML cell lines clearly enhanced the apoptotic response triggered by any TKI. A strong synergism was observed for apoptosis induction through an increase in caspase-9 and caspase-3 activation and significantly decreased expression of the Bcl-xL Bcl-2 family member. Inhibition of PKCδ did not modify BCR-ABL phosphorylation but acted downstream of the oncogene by downregulating BMI1 expression, decreasing clonogenicity. PKCδ inhibition interfered with the clonogenicity of primary CML CD34+ and BCR-ABL-transduced healthy CD34+ cells as efficiently as any TKI while it did not affect differentiation of healthy CD34+ cells. LTC-IC experiments pinpointed that PKCδ inhibition strongly decreased the progenitors/LSCs frequency. All together, these results demonstrate that targeting of PKCδ in combination with a conventional TKI could be a new therapeutic opportunity to affect for CML cells.
    Keywords:  BMI1; PKCδ; apoptosis; chronic myeloid leukemia; leukemic stem cells; tyrosine kinase inhibitors
  3. Nature. 2021 Apr 26.
      The N6-methyladenosine (m6A) is an abundant internal RNA modification1,2 catalysed predominantly by the METTL3-METTL14 methyltransferase complex3,4. The m6A writer METTL3 has been linked to the initiation and maintenance of acute myeloid leukaemia (AML), but its true therapeutic importance is still unknown5-7. Here we present the identification and characterization of a highly potent and selective first-in-class catalytic inhibitor of METTL3 (STM2457) and its co-crystal structure bound to METTL3/METTL14. Treatment with STM2457 leads to reduced AML growth, and an increase in differentiation and apoptosis. These cellular effects are accompanied by selective reduction of m6A levels on known leukaemogenic mRNAs and a decrease in their expression consistent with a translational defect. We demonstrate that pharmacological inhibition of METTL3 in vivo leads to impaired engraftment and prolonged survival in various AML mouse models, specifically targeting key stem-cell subpopulations of AML. Collectively, these results reveal the inhibition of METTL3 as a potential therapeutic strategy against AML, and provide proof of concept that the targeting of RNA modifying enzymes represents a promising new avenue for anti-cancer therapy.
  4. Cancers (Basel). 2021 Apr 26. pii: 2095. [Epub ahead of print]13(9):
      Acute myeloid leukemia (AML) is characterized by recurrent genetic events. The BCL6 corepressor (BCOR) and its homolog, the BCL6 corepressor-like 1 (BCORL1), have been reported to be rare but recurrent mutations in AML. Previously, smaller studies have reported conflicting results regarding impacts on outcomes. Here, we retrospectively analyzed a large cohort of 1529 patients with newly diagnosed and intensively treated AML. BCOR and BCORL1 mutations were found in 71 (4.6%) and 53 patients (3.5%), respectively. Frequently co-mutated genes were DNTM3A, TET2 and RUNX1. Mutated BCORL1 and loss-of-function mutations of BCOR were significantly more common in the ELN2017 intermediate-risk group. Patients harboring loss-of-function mutations of BCOR had a significantly reduced median event-free survival (HR = 1.464 (95%-Confidence Interval (CI): 1.005-2.134), p = 0.047), relapse-free survival (HR = 1.904 (95%-CI: 1.163-3.117), p = 0.01), and trend for reduced overall survival (HR = 1.495 (95%-CI: 0.990-2.258), p = 0.056) in multivariable analysis. Our study establishes a novel role for loss-of-function mutations of BCOR regarding risk stratification in AML, which may influence treatment allocation.
    Keywords:  BCOR; BCORL1; acute myeloid leukemia; loss-of-function; risk stratification; survival
  5. Am J Hematol. 2021 Apr 26.
      BACKGROUND: The treatment of older patients with newly diagnosed acute myeloid leukemia (AML) using intensive chemotherapy is associated with treatment intolerance and poor survival. We evaluated two new lower-intensity regimens with clofarabine (n=119) or cladribine (n=129) combined with low-dose cytarabine (LDAC) alternating with decitabine.METHODS: We reviewed response rates by subgroup and long term outcomes of 248 patients with newly diagnosed non core-binding-factor AML treated on two clinical trials investigating double nucleoside-analogue therapy (DNT) alternating with HMA from October 2008 to April 2018.
    RESULTS: Of 248 patients with a median age of 69 years (range, 49-85 years), 102 patients (41%) were ≥ 70 years, and 108 (44 %) had adverse karyotype. Overall, 164 patients (66%) responded:147 (59%) complete remission (CR) and 17 (7%) CR with incomplete count recovery (CRi). With a median follow up of 60 months, median relapse-free and overall survival (OS) were 10.8 months and 12.5 months, respectively. The two-year OS was 29%. Among patients with normal karyotype, the CR/CRi rate was 79 % and the median OS 19.9 months. High response rates and OS were observed in patients with mutations in NPM1, FLT3, IDH2, and RUNX1. The 4- and 8-week mortality rates were 2% and 11%, respectively.
    CONCLUSION: The backbone of clofarabine or cladribine and LDAC alternating with decitabine was effective and safe for the treatment of older patients with newly diagnosed AML. Incorporating targeted therapies could extend the efficacy of this approach and provide more curative therapeutic options in this AML population. This article is protected by copyright. All rights reserved.
  6. Front Oncol. 2021 ;11 639387
      Recently, the discovery of biological and clinical properties of mutated isoforms 1 and 2 mutations of isocitrate dehydrogenases (IDH) 1 and 2, affecting approximately 20% of patients with acute myeloid leukemia (AML), lead to the development of an individualized treatment strategy. Promoting differentiation and maturation of the malignant clone targeting IDH is an emerging strategy to promote clinical responses in AML. Phase I/II trials have shown evidence of safety, tolerability, and encouraging evidence of efficacy of two small molecule inhibitors targeting IDH2 and IDH1 gene mutations, respectively enasidenib and ivosidenib. In this review, the contribution of IDH1/IDH2 mutations in leukemogenesis and progress of targeted therapeutics in AML will be highlighted.
    Keywords:  AML; IDH; acute myeloid leukemia; enasidenib; isocitrate dehydrogenase; ivosidenib; target therapy
  7. Expert Opin Ther Targets. 2021 Apr 28. 1-11
      Introduction: RUNX1 is an essential transcription factor for normal and malignant hematopoiesis. RUNX1 forms a heterodimeric complex with CBFB. Germline mutations and somatic alterations (i.e. translocations, mutations and abnormal expression) are frequently associated with acute myeloid leukemia (AML) with RUNX1 mutations conferring unfavorable prognosis. Therefore, RUNX1 constitutes a potential innovative and interesting therapeutic target. In this review, we discuss recent therapeutic advances of RUNX1 targeting in AML.Areas covered: Firstly, we cover the clinical basis for RUNX1 targeting. We have subdivided recent therapeutic approaches either by common biochemical pathways or by similar pharmacological targets. Genome editing of RUNX1 induces anti-leukemic effects; however, off-target events prohibit clinical use. Several molecules inhibit the interaction between RUNX1/CBFB and control AML development and progression. BET protein antagonists target RUNX1 (i.e. specific BET inhibitors, BRD4 shRNRA, proteolysis targeting chimeras (PROTAC) or expression-mimickers). All these molecules improve survival in mutant RUNX1 AML preclinical models.Expert opinion: Some of these novel molecules have shown encouraging anti-leukemic potency at the preclinical stage. A better understanding of RUNX1 function in AML development and progression and its key downstream pathways, may result in more precise and more efficient RUNX1 targeting therapies.
    Keywords:  Acute myeloid leukemia; RUNX1; preclinical drug development; therapeutic targets
  8. Cancers (Basel). 2021 Apr 06. pii: 1746. [Epub ahead of print]13(7):
      Mutations in genes encoding chromatin regulators are early events contributing to developing asymptomatic clonal hematopoiesis of indeterminate potential and its frequent progression to myeloid diseases with increasing severity. We focus on the subset of myeloid diseases encompassing myelodysplastic syndromes and their transformation to secondary acute myeloid leukemia. We introduce the major concepts of chromatin regulation that provide the basis of epigenetic regulation. In greater detail, we discuss those chromatin regulators that are frequently mutated in myelodysplastic syndromes. We discuss their role in the epigenetic regulation of normal hematopoiesis and the consequence of their mutation. Finally, we provide an update on the drugs interfering with chromatin regulation approved or in development for myelodysplastic syndromes and acute myeloid leukemia.
    Keywords:  acute myeloid leukemia (AML); chromatin; clonal hematopoiesis of indeterminate potential (CHIP); epigenetic regulators; epigenetics; myelodysplastic syndromes (MDS); secondary acute myeloid leukemia (sAML)
  9. Front Oncol. 2021 ;11 579881
      The occurrence of gene mutation is a major contributor to the initiation and propagation of acute myeloid leukemia (AML). Accumulating evidence suggests that genes encoding cohesin subunits have a high prevalence of mutations in AML, especially in the t(8;21) subtype. Therefore, it is important to understand how cohesin mutations contribute to leukemogenesis. However, the fundamental understanding of cohesin mutation in clonal expansion and myeloid transformation in hematopoietic cells remains ambiguous. Previous studies briefly introduced the cohesin mutation in AML; however, an in-depth summary of mutations in AML was not provided, and the correlation between cohesin and AML1-ETO in t (8;21) AML was also not analyzed. By summarizing the major findings regarding the cohesin mutation in AML, this review aims to define the characteristics of the cohesin complex mutation, identify its relationships with co-occurring gene mutations, assess its roles in clonal evolution, and discuss its potential for the prognosis of AML. In particular, we focus on the function of cohesin mutations in RUNX1-RUNX1T1 fusion.
    Keywords:  AML1-ETO; acute myeloid leukemia; cohesin mutation; hematopoietic stem and progenitor cells; leukemogenesis
  10. Ann Hematol. 2021 Apr 29.
      Prognosis for relapsed or refractory (R/R) acute myeloid leukemia (AML) despite salvage therapy is dismal. This phase I dose-escalation trial assessed the safety and preliminary clinical activity of selinexor, an oral exportin-1 (XPO1) inhibitor, in combination with FLAG-Ida in younger R/R AML patients. The aim was to find the recommended phase 2 dose (RP2D) and maximum tolerated dose (MTD). Fourteen patients were included, and selinexor dosage was 60 mg (3 patients), 80 mg (3 patients), and 100 mg (7 patients) weekly. No dose-limiting toxicities were reported. Grade ≥3 non-hematologic adverse events (AEs) occurred in 78.6% of patients. Two patients were non MTD evaluable due to early death, and overall, 3 out of 14 patients (21.4%) had fatal AEs. Five out of 12 (42%) response and MTD evaluable patients achieved a complete remission (CR; n=4) or CR with incomplete hematologic recovery (CRi, n=1), and 4 patients (33%) subsequently underwent allogeneic transplantation. The median overall survival (OS) and event-free survival (EFS) were 6.0 (range 0.9-19.3) and 1.1 months (range 0.7-19.3), respectively. Using selinexor 100 mg/weekly, CR/CRi rate of 66.7%, OS 13.6 months (range, 1.6-19.3), and EFS 10.6 months (range, 0.9-19.3). At last follow-up, 3 patients were alive. Selinexor 100 mg/weekly with FLAG-Ida combination in R/R AML showed acceptable tolerability and efficacy, establishing the RP2D of this regimen in future clinical trials. Identifier: NCT03661515.
    Keywords:  AML; FLAG-Ida; KPT-330; Relapsed/refractory; Selinexor; XPO1
  11. Nat Commun. 2021 Apr 30. 12(1): 2482
      While oncogenes promote tumorigenesis, they also induce deleterious cellular stresses, such as apoptosis, that cancer cells must combat by coopting adaptive responses. Whether tumor suppressor gene haploinsufficiency leads to such phenomena and their mechanistic basis is unclear. Here, we demonstrate that elevated levels of the anti-apoptotic factor, CASP8 and FADD-like apoptosis regulator (CFLAR), promotes apoptosis evasion in acute myeloid leukemia (AML) cells haploinsufficient for the cut-like homeobox 1 (CUX1) transcription factor, whose loss is associated with dismal clinical prognosis. Genome-wide CRISPR/Cas9 screening identifies CFLAR as a selective, acquired vulnerability in CUX1-deficient AML, which can be mimicked therapeutically using inhibitor of apoptosis (IAP) antagonists in murine and human AML cells. Mechanistically, CUX1 deficiency directly alleviates CUX1 repression of the CFLAR promoter to drive CFLAR expression and leukemia survival. These data establish how haploinsufficiency of a tumor suppressor is sufficient to induce advantageous anti-apoptosis cell survival pathways and concurrently nominate CFLAR as potential therapeutic target in these poor-prognosis leukemias.
  12. Cancer. 2021 Apr 29.
      BACKGROUND: There are limited data on the clonal mechanisms underlying leukemogenesis, prognostic factors, and optimal therapy for atypical chronic myeloid leukemia (aCML).METHODS: The authors evaluated the clinicopathologic features, outcomes, and responses to therapy of 65 patients with aCML. The median age was 67 years (range, 46-89 years).
    RESULTS: The most frequently mutated genes included ASXL1 (83%), SRSF2 (68%), and SETBP1 (58%). Mutations in SETBP1, SRSF2, TET2, and GATA2 appeared at variant allele frequencies (VAFs) greater than 40%, whereas other RAS pathway mutations were more likely to appear at low VAFs. The acquisition of new, previously undetectable mutations at transformation was observed in 63% of the evaluable patients, with the most common involving signaling pathway mutations. Hypomethylating agents (HMAs) were associated with the highest response rates but with a short duration of response (median, 2.7 months). Therapy with ruxolitinib was not associated with clinically significant responses as a single agent or in combination with an HMA. Allogeneic stem cell transplantation was the only therapy associated with improved outcomes (hazard ratio, 0.144; 95% CI, 0.035-0.593; P = .007). Age, platelet counts, bone marrow blast percentages, and serum lactate dehydrogenase (LDH) levels were independent predictors of survival and were integrated in a multivariable model that allowed the prediction of 1- and 3-year survival.
    CONCLUSIONS: aCML is characterized by high frequencies of ASXL1, SRSF2, and SETBP1 mutations and is associated with a high risk of acute myeloid leukemia transformation. Response and survival outcomes with current therapies remain poor. The incorporation of age, platelet counts, bone marrow blast percentages, and LDH levels can allow survival prediction, and allogeneic stem cell transplantation should be considered for all eligible patients.
    Keywords:  chronic myeloid leukemia; clinical outcomes; mutational codominance
  13. Leukemia. 2021 Apr 28.
      Deregulation of the EVI1 proto-oncogene by the GATA2 distal hematopoietic enhancer (G2DHE) is a key event in high-risk acute myeloid leukemia carrying 3q21q26 aberrations (3q-AML). Upon chromosomal rearrangement, G2DHE acquires characteristics of a super-enhancer and causes overexpression of EVI1 at 3q26.2. However, the transcription factor (TF) complex of G2DHE remains poorly characterized. The aim of this study was to unravel key components of G2DHE-bound TFs involved in the deregulation of EVI1. We have identified several CEBPA and RUNX1 binding sites to be enriched and critical for G2DHE function in 3q-AML cells. Using ChIP-SICAP (ChIP followed by selective isolation of chromatin-associated proteins), a panel of chromatin interactors of RUNX1 and CEBPA were detected in 3q-AML, including PARP1 and IKZF1. PARP1 inhibition (PARPi) caused a reduction of EVI1 expression and a decrease in EVI1-G2DHE interaction frequency, highlighting the involvement of PARP1 in oncogenic super-enhancer formation. Furthermore, 3q-AML cells were highly sensitive to PARPi and displayed morphological changes with higher rates of differentiation and apoptosis as well as depletion of CD34 + cells. In summary, integrative analysis of the 3q-AML super-enhancer complex identified CEBPA and RUNX1 associated proteins and nominated PARP1 as a potential new therapeutic target in EVI1 + 3q-AML.
  14. Blood Adv. 2021 May 11. 5(9): 2294-2304
      Next-generation sequencing (NGS)-based measurable residual disease (MRD) monitoring in patients with acute myeloid leukemia (AML) is widely applicable and prognostic prior to allogeneic hematopoietic cell transplantation (alloHCT). We evaluated the prognostic role of clonal hematopoiesis-associated DNMT3A, TET2, and ASXL1 (DTA) and non-DTA mutations for MRD monitoring post-alloHCT to refine MRD marker selection. Of 154 patients with AML, 138 (90%) had at least one mutation at diagnosis, which were retrospectively monitored by amplicon-based error-corrected NGS on day 90 and/or day 180 post-alloHCT. MRD was detected in 34 patients on day 90 and/or day 180 (25%). The rate of MRD positivity was similar when DTA and non-DTA mutations were considered separately (17.6% vs 19.8%). DTA mutations had no prognostic impact on cumulative incidence of relapse, relapse-free survival, or overall survival in our study and were removed from further analysis. In the remaining 131 patients with at least 1 non-DTA mutation, clinical and transplantation-associated characteristics were similarly distributed between MRD-positive and MRD-negative patients. In multivariate analysis, MRD positivity was an independent adverse predictor of cumulative incidence of relapse, relapse-free survival, and overall survival but not of nonrelapse mortality. The prognostic effect was independent of different cutoffs (above limit of detection, 0.1% and 1% variant allele frequency). MRD log-reduction between diagnosis and post-alloHCT assessment had no prognostic value. MRD status post-alloHCT had the strongest impact in patients who were MRD positive prior to alloHCT. In conclusion, non-DTA mutations are prognostic NGS-MRD markers post-alloHCT, whereas the prognostic role of DTA mutations in the posttransplant setting remains open.
  15. Clin Lymphoma Myeloma Leuk. 2021 Mar 20. pii: S2152-2650(21)00107-5. [Epub ahead of print]
      BACKGROUND: Acute myeloid leukemia (AML) is a common, challenging hematologic malignancy worldwide. Thai data on its characteristics and outcomes have never been systematically reported, to our knowledge. The objective of this study was to determine the clinical features and outcomes of Thai patients with AML.PATIENTS AND METHODS: This was a prospective observational study of nine academic hospitals. Patients with newly diagnosed AML were invited to register online.
    RESULTS: A total of 679 patients with AML were included. The presence of circulating peripheral blood blasts was correlated with a high white blood cell count. Acute promyelocytic leukemia (APL) had predominantly lower white blood cell counts and higher proportions without peripheral blood blasts compared with non-APL AML. Disseminated intravascular coagulation was commonly presented in APL (37.7%). Splenomegaly and normal platelet count were more frequently seen in patients with Philadelphia chromosome-positive AML. The median follow-up time for those who survived more than 1 year was 28.0 months. One-year overall survival rates for non-APL AML and APL were 31.9% and 88.2%, respectively; 2-year overall survival rates were 29.6% and 88.2%, respectively. Hematopoietic stem cell transplantation could improve survival in non-APL AML.
    CONCLUSION: APL should be considered despite absence of peripheral blood blast. This study demonstrates poor outcome of Thai AML and more research to improve outcomes are underway. Expanding access to hematopoietic stem cell transplantation should be considered in Thailand.
    Keywords:  Acute myeloblastic leukemia; Acute promyelocytic leukemia; Leukemic complications; Peripheral blood blast; Philadelphia chromosome-positive AML
  16. Cell Stem Cell. 2021 Apr 23. pii: S1934-5909(21)00156-9. [Epub ahead of print]
      Severe congenital neutropenia (CN) is a pre-leukemic bone marrow failure syndrome that can evolve to acute myeloid leukemia (AML). Mutations in CSF3R and RUNX1 are frequently observed in CN patients, although how they drive the transition from CN to AML (CN/AML) is unclear. Here we establish a model of stepwise leukemogenesis in CN/AML using CRISPR-Cas9 gene editing of CN patient-derived iPSCs. We identified BAALC upregulation and resultant phosphorylation of MK2a as a key leukemogenic event. BAALC deletion or treatment with CMPD1, a selective inhibitor of MK2a phosphorylation, blocked proliferation and induced differentiation of primary CN/AML blasts and CN/AML iPSC-derived hematopoietic stem and progenitor cells (HSPCs) without affecting healthy donor or CN iPSC-derived HSPCs. Beyond detailing a useful method for future investigation of stepwise leukemogenesis, this study suggests that targeting BAALC and/or MK2a phosphorylation may prevent leukemogenic transformation or eliminate AML blasts in CN/AML and RUNX1 mutant BAALC(hi) de novo AML.
    Keywords:  BAALC; CMPD1; CRISPR/Cas9 gene-editing; MK2a phosphorylation; Severe congenital neutropenia (CN or SCN); acquired CSF3R and RUNX1 mutations; acute myeloid leukemia (AML); induced pluripotent stem cells (iPSC) based disease modeling; leukemogenesis; pre-leukemia bone marrow failure syndromes
  17. Proteomes. 2021 Apr 27. pii: 19. [Epub ahead of print]9(2):
      FLT3 mutations are the most frequently identified genetic alterations in acute myeloid leukemia (AML) and are associated with poor clinical outcome, relapse and chemotherapeutic resistance. Elucidating the molecular mechanisms underlying FLT3-dependent pathogenesis and drug resistance is a crucial goal of biomedical research. Given the complexity and intricacy of protein signaling networks, deciphering the molecular basis of FLT3-driven drug resistance requires a systems approach. Here we discuss how the recent advances in mass spectrometry (MS)-based (phospho) proteomics and multiparametric analysis accompanied by emerging computational approaches offer a platform to obtain and systematically analyze cell-specific signaling networks and to identify new potential therapeutic targets.
    Keywords:  (phospho)proteomic; AML; FLT3; drug-resistance; logic-model; signaling-network
  18. Blood Adv. 2021 May 11. 5(9): 2305-2318
      Acute myeloid leukemia (AML) is a heterogenous malignancy characterized by distinct lineage subtypes and various genetic/epigenetic alterations. As with other neoplasms, AML cells have well-known aerobic glycolysis, but metabolic variations depending on cellular lineages also exist. Lysine-specific demethylase-1 (LSD1) has been reported to be crucial for human leukemogenesis, which is currently one of the emerging therapeutic targets. However, metabolic roles of LSD1 and lineage-dependent factors remain to be elucidated in AML cells. Here, we show that LSD1 directs a hematopoietic lineage-specific metabolic program in AML subtypes. Erythroid leukemia (EL) cells particularly showed activated glycolysis and high expression of LSD1 in both AML cell lines and clinical samples. Transcriptome, chromatin immunoprecipitation-sequencing, and metabolomic analyses revealed that LSD1 was essential not only for glycolysis but also for heme synthesis, the most characteristic metabolic pathway of erythroid origin. Notably, LSD1 stabilized the erythroid transcription factor GATA1, which directly enhanced the expression of glycolysis and heme synthesis genes. In contrast, LSD1 epigenetically downregulated the granulo-monocytic transcription factor C/EBPα. Thus, the use of LSD1 knockdown or chemical inhibitor dominated C/EBPα instead of GATA1 in EL cells, resulting in metabolic shifts and growth arrest. Furthermore, GATA1 suppressed the gene encoding C/EBPα that then acted as a repressor of GATA1 target genes. Collectively, we conclude that LSD1 shapes metabolic phenotypes in EL cells by balancing these lineage-specific transcription factors and that LSD1 inhibitors pharmacologically cause lineage-dependent metabolic remodeling.
  19. Nat Chem Biol. 2021 Apr 29.
      Multiple Ras proteins, including N-Ras, depend on a palmitoylation/depalmitoylation cycle to regulate their subcellular trafficking and oncogenicity. General lipase inhibitors such as Palmostatin M (Palm M) block N-Ras depalmitoylation, but lack specificity and target several enzymes displaying depalmitoylase activity. Here, we describe ABD957, a potent and selective covalent inhibitor of the ABHD17 family of depalmitoylases, and show that this compound impairs N-Ras depalmitoylation in human acute myeloid leukemia (AML) cells. ABD957 produced partial effects on N-Ras palmitoylation compared with Palm M, but was much more selective across the proteome, reflecting a plasma membrane-delineated action on dynamically palmitoylated proteins. Finally, ABD957 impaired N-Ras signaling and the growth of NRAS-mutant AML cells in a manner that synergizes with MAP kinase kinase (MEK) inhibition. Our findings uncover a surprisingly restricted role for ABHD17 enzymes as regulators of the N-Ras palmitoylation cycle and suggest that ABHD17 inhibitors may have value as targeted therapies for NRAS-mutant cancers.
  20. Nat Commun. 2021 Apr 30. 12(1): 2474
      As more clinically-relevant genomic features of myeloid malignancies are revealed, it has become clear that targeted clinical genetic testing is inadequate for risk stratification. Here, we develop and validate a clinical transcriptome-based assay for stratification of acute myeloid leukemia (AML). Comparison of ribonucleic acid sequencing (RNA-Seq) to whole genome and exome sequencing reveals that a standalone RNA-Seq assay offers the greatest diagnostic return, enabling identification of expressed gene fusions, single nucleotide and short insertion/deletion variants, and whole-transcriptome expression information. Expression data from 154 AML patients are used to develop a novel AML prognostic score, which is strongly associated with patient outcomes across 620 patients from three independent cohorts, and 42 patients from a prospective cohort. When combined with molecular risk guidelines, the risk score allows for the re-stratification of 22.1 to 25.3% of AML patients from three independent cohorts into correct risk groups. Within the adverse-risk subgroup, we identify a subset of patients characterized by dysregulated integrin signaling and RUNX1 or TP53 mutation. We show that these patients may benefit from therapy with inhibitors of focal adhesion kinase, encoded by PTK2, demonstrating additional utility of transcriptome-based testing for therapy selection in myeloid malignancy.
  21. Annu Rev Genomics Hum Genet. 2021 Apr 30.
      Transcriptional deregulation is a key driver of acute myeloid leukemia (AML), a heterogeneous blood cancer with poor survival rates. Polycomb group (PcG) and Trithorax group (TrxG) genes, originally identified in Drosophila melanogaster several decades ago as master regulators of cellular identity and epigenetic memory, not only are important in mammalian development but also play a key role in AML disease biology. In addition to their classical canonical antagonistic transcriptional functions, noncanonical synergistic and nontranscriptional functions of PcG and TrxG are emerging. Here, we review the biochemical properties of major mammalian PcG and TrxG complexes and their roles in AML disease biology, including disease maintenance as well as drug resistance. We summarize current efforts on targeting PcG and TrxG for treatment of AML and propose rational synthetic lethality and drug-induced antagonistic pleiotropy options involving PcG and TrxG as potential new therapeutic avenues for treatment of AML. Expected final online publication date for the Annual Review of Genomics and Human Genetics, Volume 22 is August 2021. Please see for revised estimates.
  22. FEBS Open Bio. 2021 May 01.
      Adipogenesis of bone marrow mesenchymal stem cells (MSCs) promotes chemoresistance of acute myeloid leukemia (AML) cells. MSCs from AML patients (AML-MSCs) display enhanced adipogenesis compared with bone marrow MSCs from healthy donors (HD-MSCs). However, the precise molecular mechanism by which adipogenesis of MSCs from AML marrow differ from normal counterparts remains obscure. We found that METTL3 significantly inhibits MSC adipogenesis. Here, we aimed to identify the molecular mechanism linking METTL3 and MSC adipogenesis. Analysis of m6 A epigenetic changes in MSCs determined via RIP-qPCR and MeRIP-qPCR indicated that METTL3 affects AKT protein expression in MSCs by mediating m6 A modification of AKT1-mRNA. Downregulated METTL3 expression in AML-MSCs induced an increase of AKT protein, resulting in enhanced MSC adipogenesis, thereby contributing to chemoresistance in AML cells. Therefore, targeting AKT regulation by mRNA modification in MSC adipogenesis might provide a novel therapeutic strategy to overcome AML chemoresistance.
    Keywords:  AML; MSCs; adipogenesis; chemoresistance; m6A
  23. Leuk Lymphoma. 2021 Apr 29. 1-12
      We have reported the genetic mutation profile in previously untreated acute myeloid leukemia (AML) patients using a targeted NGS screening method. In this study, we evaluated the characteristics and prognostic significance of gene mutations in refractory/relapsed (R/R) AML patients by comparing their gene mutation spectrum to those newly diagnosed. The frequencies of tumor suppressor mutations were increased, while the mutation frequencies of nucleophosmin and spliceosome complex were decreased in relapsed AML. The frequency of FLT3-ITD mutation was increased, while that of CEBPA biallelic mutation decreased in refractory AML. Activated signaling mutations predicted a lower complete remission rate. FLT3-ITD mutation predicted an inferior overall survival after relapse. DNMT3A mutation predicted an inferior relapse-free survival in R/R AML. These findings may shed light on the molecular mechanism study of leukemia refractory or relapse and provide new guidance for the dynamic risk assessment of AML.
    Keywords:  Acute myeloid leukemia; gene mutations; next-generation sequencing; refractory; relapse
  24. Blood. 2021 Apr 28. pii: blood.2020008812. [Epub ahead of print]
      Less-intensive induction therapies are increasingly used in older patients with acute myeloid leukemia, assuming they are better than intensive induction. Using an AML-composite model (AML-CM) that assigns higher scores to older age, increased comorbidity-burdens and adverse cytogenetic-risks, we defined three distinct prognostic groups, and within each, compared outcomes after less-intensive versus intensive induction therapies in a multicenter retrospective cohort (n=1292) treated at six institutions from 2008-2012 and a prospective cohort (n=695) treated at thirteen institutions from 2013-2017. Prospective study included impacts of Karnofsky performance status (KPS), quality of life (QOL), and physicians' perceptions of cure. In the retrospective cohort, recipients of less-intensive therapies were older, had more comorbidities, more adverse cytogenetics, and worse KPS. Less-intensive therapies were associated with higher risks for mortality in AML-CM scores of 4-6, 7-9, and ≥10. Results were independent from receipt of allogeneic transplants and similar in those aged 70-79 years old. In the Prospective cohort, the two groups were similar in baseline QOL, geriatric assessment, and patients' outcome preferences. Higher mortality risks were seen after less-intensive therapies. However, in models adjusted for age, physician-assigned KPS and chances of cure, mortality risks and QOL were similar. Less-intensive recipients had lessened length of hospitalization (LOH). Our studies question the survival or QOL, except LOH, benefits from less-intensive therapies in patients with AML, including those aged 70-79 years or with high comorbidity-burden. A randomized trial in older/medically infirm patients is needed to better assess the value of less-intensive, intensive, or a combination of both therapies. #NCT01929408.
  25. Oncogene. 2021 Apr 30.
      The application of tyrosine kinase inhibitors (TKIs) in clinic has revolutionized chronic myelogenous leukemia (CML) treatment, but fails to eliminate leukemia stem cells (LSCs), which are considered as roots of drug resistance and disease relapse. Thus, eradication of LSCs may be a promising strategy for curing CML. In this study, we found that protein lysine methyltransferase G9A was overexpressed in CML LSCs. The upregulation of G9A by BCR-ABL was independent on its tyrosine kinase activity. Knockdown of G9A by shRNAs or pharmacological inhibition of G9A by UNC0642 significantly suppressed survival and impaired self-renewal capacity of CML LSCs. Inhibition of G9a eradicated LSCs in CML mice driven by BCR-ABL gene and dramatically prolonged survival of the mice. Ex vivo treatment with G9A inhibitor inhibited long-term engraftment of CML CD34+ cells in immunodeficient mice. Mechanically, tumor suppressor SOX6 was identified as a direct target of G9A in CML LSCs by RNA-seq analysis. Silencing Sox6 at least partially rescued G9a knockdown-mediated LSCs elimination in vivo. Our findings improve the understanding of LSC regulation network and validate G9A as a therapeutic target in CML LSCs. Targeting G9A may be considered as an additional strategy for the treatment of patients with CML.
  26. Semin Cancer Biol. 2021 Apr 22. pii: S1044-579X(21)00084-5. [Epub ahead of print]
      Myeloid malignancies have always been at the forefront of an improved understanding of the molecular pathogenesis of cancer. In accordance, over the last years, basic research focusing on the aberrations underlying malignant transformation of myeloid cells has provided the basis for precision medicine approaches and subsequently has led to the development of powerful therapeutic strategies. In this review article, we will recapitulate what has happened since in the 1980s the use of all-trans retinoic acid (ATRA), as a first targeted cancer therapy, has changed one of the deadliest leukemia subtypes, acute promyelocytic leukemia (APL), into one that can be cured without classical chemotherapy today. Similarly, imatinib, the first molecularly designed cancer therapy, has revolutionized the management of chronic myeloid leukemia (CML). Thus, targeted treatment approaches have become the paradigm for myeloid malignancy, but many questions still remain unanswered, especially how identical mutations can be associated with different phenotypes. This might be linked to the impact of the cell of origin, gene-gene interactions, or the tumor microenvironment including the immune system. Continuous research in the field of myeloid neoplasia has started to unravel the molecular pathways that are not only crucial for initial treatment response, but also resistance of leukemia cells under therapy. Ongoing studies focusing on leukemia cell vulnerabilities do already point to novel (targetable) "Achilles heels" that can further improve myeloid cancer therapy.
    Keywords:  Acute Myeloid Leukemia (AML); Mastocytosis; Myelodysplastic Syndromes (MDS); Myeloid malignancy; Myeloproliferative Neoplasms (MPN); Precision medicine
  27. Blood. 2021 Apr 28. pii: blood.2020007932. [Epub ahead of print]
      Cancer cells are in most instances characterized by rapid proliferation and uncontrolled cell division. Hence, they must adapt to proliferation-induced metabolic stress through intrinsic or acquired anti-metabolic stress responses to maintain homeostasis and survival. One mechanism to achieve this is to reprogram gene expression in a metabolism-dependent manner. MondoA (also known as MLXIP), a member of the MYC interactome, has been described as an example of such a metabolic sensor. However, the role of MondoA in malignancy is not fully understood and the underlying mechanism in metabolic responses remains elusive. By assessing patient data sets we found that MondoA overexpression is associated with a worse survival in pediatric common acute lymphoblastic leukemia (B-ALL). Using CRISPR/Cas9 and RNA interference approaches, we observed that MondoA depletion reduces transformational capacity of B-ALL cells in vitro and dramatically inhibits malignant potential in an in vivo mouse model. Interestingly, reduced expression of MondoA in patient data sets correlated with enrichment in metabolic pathways. The loss of MondoA correlated with increased tricarboxylic acid (TCA) cycle activity. Mechanistically, MondoA senses metabolic stress in B-ALL cells by restricting oxidative phosphorylation through reduced PDH activity. Glutamine starvation conditions greatly enhance this effect and highlight the inability to mitigate metabolic stress upon loss of MondoA in B-ALL. Our findings give a novel insight into the function of MondoA in pediatric B-ALL and support the notion that MondoA inhibition in this entity offers a therapeutic opportunity and should be further explored.
  28. Leuk Lymphoma. 2021 Apr 30. 1-11
      Acute myeloid leukemia (AML) is a very heterogeneous type of blood cancer, which presents with a high rate of mortality especially in elderly patients. Better understanding of critical players, such as molecules with tumor suppressive properties, may help to fine-tune disease classification and thereby treatment modalities for this detrimental disease. Here, we summarize well-known and established tumor suppressors as well as emerging tumor suppressors, including transcription factors (TCFs) and other transcriptional regulators, such as epigenetic modulators. In addition, we look into the versatile field of miRNAs also interfering with tumorigenesis and progression, which offer new possibilities in AML diagnosis, prognosis, and therapy.
    Keywords:  Acute myeloid leukemia; epigenetic regulator; miRNA; transcription factor; tumor suppressor
  29. Blood Adv. 2021 May 11. 5(9): 2285-2293
      The FMS-like tyrosine kinase 3 (FLT-3) is the most frequently mutated gene in acute myeloid leukemia (AML), a high-risk feature, and now the target of tyrosine kinase inhibitors (TKIs), which are approved and in development. The most common mutation is the internal tandem duplication (ITD). We present a novel mutation, FLT-3/Q575Δ, identified in a patient with AML through next-generation sequencing (NGS). This mutation is activating, drives downstream signaling comparable to FLT-3/ITD, and can be targeted using available FLT-3 TKIs. We present the results of a systematic analysis that identified Y572Δ, E573Δ, and S574Δ as similarly activating and targetable deletions located in the FLT-3 juxtamembrane domain (JMD). These mutations target key residues in the JMD involved in the interactions within FLT-3 that regulate its activation. Our results suggest a new class of FLT-3 mutations that may have an impact on patient care and highlight the increasing importance of a systematic understanding of FLT-3 mutations other than ITD. It is likely that, as NGS becomes more commonly used in the diagnosis of patients with AML, these and other activating mutations will be discovered with increasing frequency.
  30. J Clin Invest. 2021 Apr 29. pii: 136713. [Epub ahead of print]
      Myelofibrosis (MF) are a non-BCR-ABL myeloproliferative neoplasms (NMPs) associated with poor outcomes. Current treatment has little effect on the natural history of the disease. MF results from complex interactions between 1) the malignant clone, 2) an inflammatory context, and 3) remodeling of the bone marrow (BM) microenvironment. Each of these points is a potential target of PPAR-y activation. Here, we demonstrated the therapeutic potential of PPAR-y agonists in resolving MF in three mouse models. We showed that PPAR-y agonists reduce myeloproliferation, modulate inflammation, and protect the BM stroma in vitro and ex vivo. Activation of PPAR-y constitutes a relevant therapeutic target in MF and our data support the possibility of using PPAR-y agonists in clinical practice.
    Keywords:  Fibrosis; Hematology; Leukemias; Stem cells
  31. Nat Commun. 2021 04 28. 12(1): 2455
      The mutational mechanisms underlying recurrent deletions in clonal hematopoiesis are not entirely clear. In the current study we inspect the genomic regions around recurrent deletions in myeloid malignancies, and identify microhomology-based signatures in CALR, ASXL1 and SRSF2 loci. We demonstrate that these deletions are the result of double stand break repair by a PARP1 dependent microhomology-mediated end joining (MMEJ) pathway. Importantly, we provide evidence that these recurrent deletions originate in pre-leukemic stem cells. While DNA polymerase theta (POLQ) is considered a key component in MMEJ repair, we provide evidence that pre-leukemic MMEJ (preL-MMEJ) deletions can be generated in POLQ knockout cells. In contrast, aphidicolin (an inhibitor of replicative polymerases and replication) treatment resulted in a significant reduction in preL-MMEJ. Altogether, our data indicate an association between POLQ independent MMEJ and clonal hematopoiesis and elucidate mutational mechanisms involved in the very first steps of leukemia evolution.
  32. Haematologica. 2021 Apr 29.
      Although great advances have been made in understanding the pathobiology of MLL-rearranged (MLL-r) leukemias, therapies for this leukemia have remained limited, and clinical outcomes remain bleak. To identify novel targets for immunotherapy treatments, we compiled a lineage-independent MLL-r leukemia gene signature using publicly available data sets. Data from large leukemia repositories were filtered through the In-silico Human Surfaceome, providing a list of highly predicted cell surface proteins overexpressed in MLL-r leukemias. LAMP5, a lysosomal associated membrane protein, is expressed highly and specifically in MLL-r leukemia. We found that LAMP5 is a direct target of the oncogenic MLL-fusion protein. LAMP5 depletion significantly inhibited leukemia cell growth in vitro and in vivo. Functional studies showed that LAMP-5 is a novel modulator of innateimmune pathways in MLL-r leukemias. Downregulation of LAMP5 led to inhibition of NF-κB signaling and increased activation of type-1 interferon signaling downstream of Toll-like Receptor/Interleukin 1 Receptor activation. These effects were attributable to the critical role of LAMP-5 in transferring the signal flux from Interferon Signaling Endosomes to Pro-Inflammatory Signaling Endosome. Depletion of IRF7 was able to partially rescue the cell growth inhibition upon LAMP5 downregulation. Lastly, LAMP-5 was readily detected on the surface of MLL-r leukemia cells. Targeting surface LAMP-5 using an antibody-drug conjugate leads to significant cell viability decrease specifically on MLL-r leukemias. Overall, based on the limited expression throughout human tissues, we postulate that LAMP-5 could potentially serve as an immunotherapeutic target with a wide therapeutic window to treat MLL-r leukemias.
  33. Leuk Lymphoma. 2021 Apr 27. 1-9
      Double minute chromosomes (DMs) are rare in hematologic malignancies. We presented the cytogenetic characteristics and clinical features of the largest single-center cohort of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) patients with DMs. A total of 2576 AML patients and 1642 MDS patients were investigated, and 30 patients (AML = 19; MDS = 11) who had DMs were followed up. DMs were more common in primary AML (94.7%) and MDS (90.9%). Monosomal karyotypes (MK) were also the main cytogenetic characteristics, like complex karyotypes (CK). AML with myelodysplasia-related changes (AML-MRC) and MDS-refractory anemia with excess blasts (MDS-RAEB) was common in this cohort. We conclude that DMs-positive AML and DMs-positive MDS are associated with older age, complex karyotypes, monosomal karyotypes, TP53 deletion and TP53 mutations. DMs are a type of chromothripsis, which can be observed by the karyotype analysis. MYC and KMT2A were the most commonly amplified genes in DMs. Most patients with DMs presented an extremely poor prognosis.
    Keywords:  Double minute chromosomes (DMs); TP53 mutation; acute myeloid leukemia (AML); complex karyotype (CK); monosomal karyotype (MK); myelodysplastic syndrome (MDS)
  34. J Exp Med. 2021 Jun 07. pii: e20200560. [Epub ahead of print]218(6):
      The early events that drive myeloid oncogenesis are not well understood. Most studies focus on the cell-intrinsic genetic changes and how they impact cell fate decisions. We consider how chronic exposure to the proinflammatory cytokine, interleukin-1β (IL-1β), impacts Cebpa-knockout hematopoietic stem and progenitor cells (HSPCs) in competitive settings. Surprisingly, we found that Cebpa loss did not confer a hematopoietic cell-intrinsic competitive advantage; rather chronic IL-1β exposure engendered potent selection for Cebpa loss. Chronic IL-1β augments myeloid lineage output by activating differentiation and repressing stem cell gene expression programs in a Cebpa-dependent manner. As a result, Cebpa-knockout HSPCs are resistant to the prodifferentiative effects of chronic IL-1β, and competitively expand. We further show that ectopic CEBPA expression reduces the fitness of established human acute myeloid leukemias, coinciding with increased differentiation. These findings have important implications for the earliest events that drive hematologic disorders, suggesting that chronic inflammation could be an important driver of leukemogenesis and a potential target for intervention.
  35. Blood. 2021 Apr 25. pii: blood.2020010144. [Epub ahead of print]
      Genomic classification has improved risk assignment of pediatric but not adult B-lineage acute lymphoblastic leukemia (B-ALL). The international UKALLXII/ECOG-ACRIN E2993 (NCT00002514) trial accrued 1229 BCR-ABL1-negative adolescent/adult B-ALL patients (aged 14-65 years). While 93% of patients achieved remission, 41% relapsed at a median of 13 months (range 28 days to 12 years). Five-year overall survival (5yr-OS) was 42% (95% CI, 39, 44). Transcriptome sequencing (n=238), gene expression profiling (n=210), cytogenetics (n=197) and fusion PCR (n=274) enabled genomic subtyping of 282 patient samples, of which 264 were eligible for trial, accounting for 64.5% of E2993 patients. Among patients in the outcome analysis, 29.5% of cases had favorable outcomes with 5yr-OS of 65-80% and were deemed standard-risk (DUX4-rearranged [9.2%], ETV6-RUNX1/-like [2.3%], TCF3-PBX1 [6.9%], PAX5 P80R [4.1%], high-hyperdiploid [6.9%]); 50.2% had high-risk genotypes with 5yr-OS of 0-27% (Ph-like [21.2%], KMT2A-AFF1 [12%], low-hypodiploid/near-haploid [14.3%], BCL2/MYC-rearranged [2.8%]); and 20.3% had intermediate-risk genotypes with 5yr-OS of 33-45% (PAX5alt [12.4%], ZNF384/-like [5.1%], MEF2D-rearranged [2.8%]). IKZF1 alterations occurred in 86% of Ph-like and TP53 mutations occurred in low-hypodiploid (54%) and BCL2/MYC-rearranged patients (33%), but were not independently associated with outcome. Of patients considered high-risk for relapse based on presenting age and WBC count, 40% harbored subtype-defining genetic alterations associated with standard- or intermediate-risk outcomes. We identified distinct immunophenotypic features for DUX4-rearranged, PAX5 P80R, ZNF384-R/-like and Ph-like genotypes. These data in a large adult B-ALL cohort treated with a non-risk-adapted approach on a single trial show the prognostic importance of genomic analyses which may translate into future therapeutic benefits.
  36. Genes (Basel). 2021 Apr 12. pii: 559. [Epub ahead of print]12(4):
      JAK2 (Janus kinase 2) V617F, CALR (Calreticulin) exon 9, and MPL (receptor for thrombopoietin) exon 10 mutations are associated with the vast majority of Ph-negative chronic myeloproliferative neoplasms (MPNs). These mutations affect sequential stages of proliferative signal transduction and therefore, after the emergence of one type of mutation, other types should not have any selective advantages for clonal expansion. However, simultaneous findings of these mutations have been reported by different investigators in up to 10% of MPN cases. Our study includes DNA samples from 1958 patients with clinical evidence of MPN, admitted to the National Research Center for Hematology for genetic analysis between 2016 and 2019. In 315 of 1402 cases (22.6%), CALR mutations were detected. In 23 of these 315 cases (7.3%), the JAK2 V617F mutation was found in addition to the CALR mutation. In 16 from 24 (69.6%) cases, with combined CALR and JAK2 mutations, V617F allele burden was lower than 1%. A combination of JAK2 V617F with MPL W515L/K was also observed in 1 out of 1348 cases, only. JAK2 allele burden in this case was also lower than 1%. Additional mutations may coexist over the low background of JAK2 V617F allele. Therefore, in cases of detecting MPNs with a low allelic load JAK2 V617F, it may be advisable to search for other molecular markers, primarily mutations in exon 9 of CALR. The load of the combined mutations measured at different time points may indicate that, at least in some cases, these mutations could be represented by different clones of malignant cells.
    Keywords:  CALR; JAK2 V617F; MPL W515L/K; essential thrombocythemia; myeloproliferative neoplasms; polycythemia vera; primary myelofibrosis
  37. Cells. 2021 Apr 27. pii: 1034. [Epub ahead of print]10(5):
      Myelofibrosis is a myeloproliferative neoplasm characterized by splenomegaly, constitutional symptoms, bone marrow fibrosis, and a propensity towards transformation to acute leukemia. JAK inhibitors are the only approved therapy for myelofibrosis and have been successful in reducing spleen and symptom burden. However, they do not significantly impact disease progression and many patients are ineligible due to coexisting cytopenias. Patients who are refractory to JAK inhibition also have a dismal survival. Therefore, non-JAK inhibitor-based therapies are being explored in pre-clinical and clinical settings. In this review, we discuss novel treatments in development for myelofibrosis with targets outside of the JAK-STAT pathway. We focus on the mechanism, preclinical rationale, and available clinical efficacy and safety information of relevant agents including those that target apoptosis (navitoclax, KRT-232, LCL-161, imetelstat), epigenetic modulation (CPI-0610, bomedemstat), the bone marrow microenvironment (PRM-151, AVID-200, alisertib), signal transduction pathways (parsaclisib), and miscellaneous agents (tagraxofusp. luspatercept). We also provide commentary on the future of therapeutic development in myelofibrosis.
    Keywords:  Aurora kinase; BCL-2/xL; BET; CD123; LSD1; MDM2; PI3K; PRM-151; TGFb; myelofibrosis; telomerase
  38. Blood Adv. 2021 Apr 27. 5(8): 2264-2271
      Since the US Food and Drug Administration (FDA) approvals of parenteral decitabine and azacitidine, DNA methyltransferase inhibitors, otherwise referred to as DNA hypomethylating agents (HMAs), have been a mainstay in the treatment of higher-risk myelodysplastic syndromes. The development of oral HMAs has been an area of active interest; however, oral bioavailability has been quite poor due to rapid metabolism by cytidine deaminase (CDA). This led to the development of the novel CDA inhibitor cedazuridine, which was combined with an oral formulation of decitabine. Preclinical work demonstrated a pharmacokinetic and pharmacodynamic profile approximate to parenteral decitabine, leading to early-phase clinical trials of oral cedazuridine-decitabine (C-DEC) in myelodysplastic syndromes and chronic myelomonocytic leukemia (CMML). A combination of oral decitabine 35 mg with oral cedazuridine 100 mg was established as the recommended phase 2 dose. Phase 2 data confirmed bioequivalence of C-DEC when compared with parenteral decitabine, and a larger phase 3 trial has demonstrated similar results, leading to the FDA approval of C-DEC for use in intermediate/high-risk myelodysplastic syndrome (MDS) and CMML. This review will focus upon the current role of HMA therapy in MDS/CMML, preclinical and clinical development of C-DEC, and potential roles of oral HMA therapy in myeloid malignancies moving forward.