bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2021‒02‒28
thirty papers selected by
Paolo Gallipoli
Barts Cancer Institute, Queen Mary University of London

  1. Front Oncol. 2020 ;10 621458
      Metabolism in acute myeloid leukemia (AML) cells is dependent primarily on oxidative phosphorylation. However, in order to sustain their high proliferation rate and metabolic demand, leukemic blasts use a number of metabolic strategies, including glycolytic metabolism. Understanding whether monocarboxylate transporters MCT1 and MCT4, which remove the excess of lactate produced by cancer cells, represent new hematological targets, and whether their respective inhibitors, AR-C155858 and syrosingopine, can be useful in leukemia therapy, may reveal a novel treatment strategy for patients with AML. We analyzed MCT1 and MCT4 expression and function in hematopoietic progenitor cells from healthy cord blood, in several leukemic cell lines and in primary leukemic blasts from patients with AML, and investigated the effects of AR-C155858 and syrosingopine, used alone or in combination with arabinosylcytosine, on leukemic cell proliferation. We found an inverse correlation between MCT1 and MCT4 expression levels in leukemic cells, and showed that MCT4 overexpression is associated with poor prognosis in AML patients. We also found that AR-C155858 and syrosingopine inhibit leukemic cell proliferation by activating two different cell-death related pathways, i.e., necrosis for AR-C155858 treatment and autophagy for syrosingopine, and showed that AR-C155858 and syrosingopine exert an anti-proliferative effect, additive to chemotherapy, by enhancing leukemic cells sensitivity to chemotherapeutic agents. Altogether, our study shows that inhibition of MCT1 or MCT4 impairs leukemic cell proliferation, suggesting that targeting lactate metabolism may be a new therapeutic strategy for AML, and points to MCT4 as a potential therapeutic target in AML patients and to syrosingopine as a new anti-proliferative drug and inducer of autophagy to be used in combination with conventional chemotherapeutic agents in AML treatment.
    Keywords:  AR-C155858; MCT1; MCT4; acute myeloid leukemia; autophagy; lactate metabolism; syrosingopine
  2. Cancer. 2021 Feb 24.
      BACKGROUND: Options to treat elderly patients (≥65 years old) newly diagnosed with acute myeloid leukemia (AML) include intensive and attenuated chemotherapy, hypomethylating agents with or without venetoclax, and supportive care. This multicenter, randomized, open-label, phase 3 trial was designed to assess the efficacy and safety of a fludarabine, cytarabine, and filgrastim (FLUGA) regimen in comparison with azacitidine (AZA).METHODS: Patients (n = 283) were randomized 1:1 to FLUGA (n = 141) or AZA (n = 142). Response was evaluated after cycles 1, 3, 6, and 9. Measurable residual disease (MRD) was assessed after cycle 9. When MRD was ≥0.01%, patients continued with the treatment until relapse or progressive disease. Patients with MRD < 0.01% suspended treatment to enter the follow-up phase.
    RESULTS: The complete remission (CR) rate after 3 cycles was significantly better in the FLUGA arm (18% vs 9%; P = .04), but the CR/CR with incomplete recovery rate at 9 months was similar (33% vs 29%; P = .41). There were no significant differences between arms in early mortality at 30 or 60 days. Hematologic toxicities were more frequent with FLUGA, especially during induction. The 1-year overall survival (OS) rate and the median OS were superior with AZA versus FLUGA: 47% versus 27% and 9.8 months (95% confidence interval [CI], 5.6-14 months) versus 4.1 months (95% CI, 2.7-5.5 months; P = .005), respectively. The median event-free survival was 4.9 months (95% CI, 2.8-7 months) with AZA and 3 months (95% CI, 2.5-3.5 months) with FLUGA (P = .001).
    CONCLUSIONS: FLUGA achieved more remissions after 3 cycles, but the 1-year OS rate was superior with AZA. However, long-term outcomes were disappointing in both arms (3-year OS rate, 10% vs 5%). This study supports the use of an AZA backbone for future combinations in elderly patients with AML.
    Keywords:  acute myeloid leukemia; azacitidine; cytarabine; elderly patients; fludarabine
  3. Sci Transl Med. 2021 Feb 24. pii: eabc4822. [Epub ahead of print]13(582):
      Chemoresistance remains the major challenge for successful treatment of acute myeloid leukemia (AML). Although recent mouse studies suggest that treatment response of genetically and immunophenotypically indistinguishable AML can be influenced by their different cells of origin, corresponding evidence in human disease is still largely lacking. By combining prospective disease modeling using highly purified human hematopoietic stem or progenitor cells with retrospective deconvolution study of leukemia stem cells (LSCs) from primary patient samples, we identified human hematopoietic stem cells (HSCs) and common myeloid progenitors (CMPs) as two distinctive origins of human AML driven by Mixed Lineage Leukemia (MLL) gene fusions (MLL-AML). Despite LSCs from either MLL-rearranged HSCs or MLL-rearranged CMPs having a mature CD34-/lo/CD38+ immunophenotype in both a humanized mouse model and primary patient samples, the resulting AML cells exhibited contrasting responses to chemotherapy. HSC-derived MLL-AML was highly resistant to chemotherapy and expressed elevated amounts of the multispecific anion transporter ABCC3. Inhibition of ABCC3 by shRNA-mediated knockdown or with small-molecule inhibitor fidaxomicin, currently used for diarrhea associated with Clostridium difficile infection, effectively resensitized HSC-derived MLL-AML toward standard chemotherapeutic drugs. This study not only functionally established two distinctive origins of human LSCs for MLL-AML and their role in mediating chemoresistance but also identified a potential therapeutic avenue for stem cell-associated treatment resistance by repurposing a well-tolerated antidiarrhea drug already used in the clinic.
  4. Br J Haematol. 2021 Feb 22.
      Clonal haematopoiesis (CH) in patients with acute myeloid leukaemia (AML) may persist beyond attaining complete remission. From a consecutive cohort of 67 patients with nucleophosmin 1-mutated (NPM1mut ) AML, we identified 50 who achieved NPM1mut clearance and had parallel multicolour flow cytometry (MFC) and next generation sequencing (NGS). In total, 13 (26%) cleared all mutations, 37 (74%) had persistent CH frequently involving DNA methyltransferase 3α (DNMT3A,70%), tet methylcytosine dioxygenase 2 (TET2, 27%), isocitrate dehydrogenase 2 (IDH2, 19%) and IDH1 (11%). A small number (<1%) of aberrant CD34+ myeloblasts, but immunophenotypically different from original AML blasts [herein referred to as a pre-leukaemic (PL) phenotype], was detected in 17 (49%) patients with CH, but not in any patients with complete clearance of all mutations (P = 0·0037). A PL phenotype was associated with higher mutation burden (P = 0·005). Persistent IDH2 and serine and arginine-rich splicing factor 2 (SRSF2) mutations were exclusively observed in PL+ CH+ cases (P = 0·016). Persistent dysplasia was seen exclusively in cases with a PL+ phenotype (29% vs. none; P = 0·04). The PL+ phenotype did not correlate with age, intensity of induction therapy or relapse-free survival. Post-remission CH in the setting of NPM1mut clearance is common and may result in immunophenotypic changes in myeloid progenitors. It is important to not misinterpret these cells as AML measurable residual disease (MRD).
    Keywords:  AML; Clonal hematopoiesis; MRD; NPM1
  5. Blood Cells Mol Dis. 2021 Feb 20. pii: S1079-9796(21)00015-2. [Epub ahead of print]88 102549
      Wilms tumor 1 (WT1) gene is commonly mutated in acute myeloid leukemia (AML), particularly in younger age population. The mechanism through which WT1 mutations drive leukemogenesis have not been fully elucidated; however, recent studies reported an association with the epigenetic pathway. Here, we studied the phenotypic characteristics and somatic mutational profile of 114 WT1-mutant AML patients and focused on potential WT1 gene relations to other cooperative genomic events that may impact disease prognosis. Invariant phenotypic and genomic associations of WT1 mutations in AML were uncovered and rigorously described. Our findings help improving the current understanding and definition of WT1-mutant AML patients' characteristics and clinical outcomes.
    Keywords:  Acute myeloid leukemia; Clinical associations; WT1 mutations
  6. Am J Hematol. 2021 Feb 24.
      Differentiation Syndrome (DS) has been identified in a subset of patients undergoing treatment with novel classes of differentiating therapies for acute myeloid leukemia (AML) such as IDH and FLT3 inhibitors. While DS is a well-known treatment-related complication in acute promyelocytic leukemia (APL), efforts are still ongoing to standardize diagnostic and treatment parameters for DS in AML. Though the rates of incidence vary, many of the signs and symptoms of DS are common between APL and AML. DS can lead to fatal complications in AML, but prompt management is usually effective and rarely necessitates interruption or discontinuation of AML therapy. This article is protected by copyright. All rights reserved.
  7. Curr Hematol Malig Rep. 2021 Feb 25.
      PURPOSE OF REVIEW: The advent of several targeted agents has revolutionized the treatment of acute myeloid leukemia (AML) in recent times; however, majority of patients are still not cured. In the ongoing quest for rationally targeted treatment strategies in AML, scientific endeavors have focused on identifying new antigen targets on the leukemic cells for therapeutic exploitation including strategies to directly deliver toxins into the leukemic blasts as well as strategies that harness host immunity to favorably impact clinical outcomes. Gemtuzumab ozogamicin, a CD33 directed antibody-drug conjugate, has provided the proof of concept for the potential efficacy of monoclonal antibody-based therapies in AML. This article provides an overview of immunologically relevant antigen targets expressed on the leukemic cells and synopsizes the clinical results evaluating targeted antibody-based therapeutic approach in AML.RECENT FINDINGS: AML blasts and leukemic stem cells express several antigens, including CD33, CD47, CD70, CD123, and CLEC12A. The past several years have seen the burgeoning of cell-specific immunotherapy concepts, including checkpoint inhibitors, antibody-toxin conjugates, and bispecific antibodies in the treatment of AML. The first-in-class anti-CD47 antibody magrolimab and anti-CD70 antibody cusatuzumab in combination with hypomethylating agent (HMA) azacitidine, in newly diagnosed AML, and flotetuzumab, a bispecific DART® (dual-affinity retargeting) antibody to CD3ε and CD123 as salvage option in relapsed/refractory AML appear promising. The development of antibody-based immunotherapeutic approach in AML has been encouraging. Ongoing research will define the choice of an appropriate complementary therapeutic agent in antibody-based combination therapy, and whether one or more than one antigen should be simultaneously targeted. Further studies will likely refine the role of antibody-based therapy in post hematopoietic cell transplant setting.
    Keywords:  Acute myeloid leukemia; CD123; CD33; CD47; CD70
  8. Leukemia. 2021 Feb 23.
      Mutations in the gene encoding the transcription factor CCAAT/enhancer-binding protein alpha (C/EBPα) occur in 10-15% of acute myeloid leukemia (AML). Frameshifts in the CEBPA N-terminus resulting in exclusive expression of a truncated p30 isoform represent the most prevalent type of CEBPA mutations in AML. C/EBPα p30 interacts with the epigenetic machinery, but it is incompletely understood how p30-induced changes cause leukemogenesis. We hypothesized that critical effector genes in CEBPA-mutated AML are dependent on p30-mediated dysregulation of the epigenome. We mapped p30-associated regulatory elements (REs) by ATAC-seq and ChIP-seq in a myeloid progenitor cell model for p30-driven AML that enables inducible RNAi-mediated knockdown of p30. Concomitant p30-dependent changes in gene expression were measured by RNA-seq. Integrative analysis identified 117 p30-dependent REs associated with 33 strongly down-regulated genes upon p30-knockdown. CRISPR/Cas9-mediated mutational disruption of these genes revealed the RNA-binding protein MSI2 as a critical p30-target. MSI2 knockout in p30-driven murine AML cells and in the CEBPA-mutated human AML cell line KO-52 caused proliferation arrest and terminal myeloid differentiation, and delayed leukemia onset in vivo. In summary, this work presents a comprehensive dataset of p30-dependent effects on epigenetic regulation and gene expression and identifies MSI2 as an effector of the C/EBPα p30 oncoprotein.
  9. Haematologica. 2021 Feb 25.
      DDX41 mutations are associated with hematologic malignancies including myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), but the incidence in idiopathic cytopenia of undetermined significance (ICUS) is unknown. We investigated the incidence, genetic characteristics, and clinical features of DDX41 mutations in Korean patients with ICUS, MDS, or AML. We performed targeted deep sequencing of 61 genes including DDX41 in 457 patients with ICUS (n=75), MDS (n=210), or AML (n=172). The germline DDX41 mutations with causality were identified in 28 (6.1%) patients, of whom 27 (96.4%) had somatic mutations in the other position of DDX41. Germline origins of the DDX41 mutations were confirmed in all of the 11 patients who performed germline-based testing. Of the germline DDX41 mutations, p.V152G (n=10) was most common, followed by p.Y259C (n=8), p.A500fs (n=6), and p.E7* (n=3). Compared with non-mutated patients, DDX41-mutated patients showed male predominance, old age, normal karyotype, low leukocyte count, and hypocellular marrow at diagnosis. Three of the 4 ICUS patients with germline DDX41 mutations progressed to MDS. DDX41 mutations in Korean patients showed a high incidence and distinct mutation patterns, in that p.V152G was a unique germline variant. ICUS harboring germline DDX41 mutations may be regarded as a hereditary myeloid neoplasm. Germline DDX41 mutations are not uncommon and should be explored when treating the patients with myeloid malignancies.
  10. Biochem Biophys Res Commun. 2021 Feb 18. pii: S0006-291X(21)00210-2. [Epub ahead of print]547 162-168
      Although acute myeloid leukemia (AML) is a highly heterogeneous disease with diverse genetic subsets, one hallmark of AML blasts is myeloid differentiation blockade. Extensive evidence has indicated that differentiation induction therapy represents a promising treatment strategy. Here, we identified that the pharmacological inhibition of the mitochondrial electron transport chain (ETC) complex III by antimycin A inhibits proliferation and promotes cellular differentiation of AML cells. Mechanistically, we showed that the inhibition of dihydroorotate dehydrogenase (DHODH), a rate-limiting enzyme in de novo pyrimidine biosynthesis, is involved in antimycin A-induced differentiation. The activity of antimycin A could be reversed by supplement of excessive amounts of exogenous uridine as well as orotic acid, the product of DHODH. Furthermore, we also found that complex III inhibition exerts a synergistic effect in differentiation induction combined with DHODH inhibitor brequinar as well as with the pyrimidine salvage pathway inhibitor dipyridamole. Collectively, our study uncovered the link between mitochondrial complex III and AML differentiation and may provide further insight into the potential application of mitochondrial complex III inhibitor as a mono or combination treatment in differentiation therapy of AML.
    Keywords:  Acute myeloid leukemia; Differentiation therapy; Mitochondrial ETC complex III; Pyrimidine biosynthesis
  11. Ther Adv Hematol. 2021 ;12 2040620720986646
      Venetoclax in combination with hypomethylating agents (HMAs) or low-dose cytarabine (LDAC) has demonstrated exceptional activity in elderly and unfit patients with newly diagnosed acute myeloid leukemia (AML). Notably, the safety profile of venetoclax-based induction regimens was favorable, with a low rate of early treatment-related mortality, even in frail study participants. Thus, the introduction of venetoclax has transformed the landscape of AML therapy in elderly patients. Given these promising results, venetoclax in combination with other agents is now being studied as a frontline therapy in younger patients with AML, as well as in relapsed/refractory AML patients. Here, we review clinical data for venetoclax-based therapy in AML, both from prospective as well as retrospective studies, and highlight ongoing novel studies of venetoclax-containing regimens and discuss future research directions.
    Keywords:  acute myeloid leukemia; combinatorial regimens; venetoclax
  12. Blood Cancer J. 2021 Feb 22. 11(2): 41
      Progress in the understanding of the biology and therapy of acute myeloid leukemia (AML) is occurring rapidly. Since 2017, nine agents have been approved for various indications in AML. These included several targeted therapies like venetoclax, FLT3 inhibitors, IDH inhibitors, and others. The management of AML is complicated, highlighting the need for expertise in order to deliver optimal therapy and achieve optimal outcomes. The multiple subentities in AML require very different therapies. In this review, we summarize the important pathophysiologies driving AML, review current therapies in standard practice, and address present and future research directions.
  13. Leukemia. 2021 Feb 23.
      Infants with KMT2A-rearranged acute lymphoblastic leukemia (KMT2A-r ALL) have a poor prognosis. KMT2A-r ALL overexpresses FLT3, and the FLT3 inhibitor (FLT3i) lestaurtinib potentiates chemotherapy-induced cytotoxicity in preclinical models. Children's Oncology Group (COG) AALL0631 tested whether adding lestaurtinib to post-induction chemotherapy improved event-free survival (EFS). After chemotherapy induction, KMT2A-r infants received either chemotherapy only or chemotherapy plus lestaurtinib. Correlative assays included FLT3i plasma pharmacodynamics (PD), which categorized patients as inhibited or uninhibited, and FLT3i ex vivo sensitivity (EVS), which categorized leukemic blasts as sensitive or resistant. There was no difference in 3-year EFS between patients treated with chemotherapy plus lestaurtinib (n = 67, 36 ± 6%) vs. chemotherapy only (n = 54, 39 ± 7%, p = 0.67). However, for the lestaurtinib-treated patients, FLT3i PD and FLT3i EVS significantly correlated with EFS. For FLT3i PD, EFS for inhibited/uninhibited was 59 ± 10%/28 ± 7% (p = 0.009) and for FLTi EVS, EFS for sensitive/resistant was 52 ± 8%/5 ± 5% (p < 0.001). Seventeen patients were both inhibited and sensitive, with an EFS of 88 ± 8%. Adding lestaurtinib did not improve EFS overall, but patients achieving potent FLT3 inhibition and those whose leukemia blasts were sensitive FLT3-inhibition ex vivo did benefit from the addition of lestaurtinib. Patient selection and PD-guided dose escalation may enhance the efficacy of FLT3 inhibition for KMT2A-r infant ALL.
  14. Blood Adv. 2021 Feb 23. 5(4): 1110-1121
      Lenalidomide, an antineoplastic and immunomodulatory drug, has therapeutic activity in acute myeloid leukemia (AML), but definitive studies about its therapeutic utility have been lacking. In a phase 3 study, we compared 2 induction regimens in newly diagnosed patients age 18 to 65 years with AML: idarubicine-cytarabine (cycle 1) and daunorubicin and intermediate-dose cytarabine (cycle 2) without or with lenalidomide (15 mg orally on days 1-21). One final consolidation cycle of chemotherapy or autologous stem cell transplantation (auto-SCT) or allogeneic SCT (allo-SCT) was provided according to a prognostic risk and minimal residual disease (MRD)-adapted approach. Event-free survival (EFS; primary end point) and other clinical end points were assessed. A second random assignment in patients in complete response or in complete response with incomplete hematologic recovery after cycle 3 or auto-SCT involved 6 cycles of maintenance with lenalidomide (10 mg on days 1-21) or observation. In all, 392 patients were randomly assigned to the control group, and 388 patients were randomly assigned to lenalidomide induction. At a median follow-up of 41 months, the study revealed no differences in outcome between the treatments (EFS, 44% ± 2% standard error and overall survival, 54% ± 2% at 4 years for both arms) although in an exploratory post hoc analysis, a lenalidomide benefit was suggested in SRSF2-mutant AML. In relation to the previous Dutch-Belgian Hemato-Oncology Cooperative Group and Swiss Group for Clinical Cancer Research (HOVON-SAKK) studies that used a similar 3-cycle regimen but did not pursue an MRD-guided approach, these survival estimates compare markedly more favorably. MRD status after cycle 2 lost prognostic value in intermediate-risk AML in the risk-adjusted treatment context. Maintenance with lenalidomide showed no apparent effect on relapse probability in 88 patients randomly assigned for this part of the study.
  15. Hemasphere. 2021 Mar;5(3): e532
      The nutritional status at diagnosis, as well as weight loss during chemotherapy, are important factors for morbidity and mortality in cancer patients. They might also influence outcomes in patients with acute myeloid leukemia (AML) receiving allogeneic hematopoietic stem cell transplantation (HSCT). We evaluated the body mass index (BMI) at diagnosis, prior to HSCT, and the BMI difference (ΔBMI = BMIHSCT-BMIdiagnosis) in 662 AML patients undergoing allogeneic HSCT. Patients being obese at AML diagnosis had significantly higher nonrelapse mortality (NRM) and shorter overall survival (OS) after HSCT, but no distinct cumulative incidence of relapse than nonobese patients. Weight loss during chemotherapy (ΔBMI > -2) was a strong predictor for higher NRM and shorter OS in univariate and multivariate analyses. These results were observed across all European LeukemiaNet (ELN) 2017 risk groups but especially in patients with favorable or intermediate ELN2017 risk and patients transplanted in morphologic complete remission. Only in patients being obese at AML diagnosis, weight loss did not result in adverse outcomes. ΔBMI > -2 represents a strong, independent, and modifiable risk factor for AML patients treated with HSCT. Nutritional monitoring and supplementation during disease course might improve patients' outcomes.
  16. Blood. 2021 Feb 22. pii: blood.2020009564. [Epub ahead of print]
      Genes encoding B lineage restricted transcription factors are frequently mutated in B-lymphoid leukemias, suggesting a close link between normal and malignant B-cell development. One of these transcription factors is Early B cell Factor 1 (EBF1), a protein of critical importance for lineage specification and survival of B-lymphoid progenitors. Here, we report that impaired EBF1 function in mouse B-cell progenitors results in reduced expression of Myc. Ectopic expression of MYC partially rescued B-cell expansion in the absence of EBF1 both in vivo and in vitro. Using chromosome conformation analysis in combination with ATAC-seq, ChIP-seq and reporter gene assays, we identified six EBF responsive enhancer elements within the Myc locus. CRISPR-Cas9 mediated targeting of EBF1 binding sites identified one element of key importance for Myc expression and pro-B cell expansion. These data provide evidence that Myc is a direct target of EBF1. Furthermore, ChIP-seq analysis revealed that several regulatory elements in the Myc locus are targets of PAX5. However, ectopic expression of PAX5 in EBF1 deficient cells inhibits the cell cycle and reduces Myc expression, suggesting that EBF1 and PAX5 act in an opposing manner to regulate Myc levels. This hypothesis is further substantiated by the finding that Pax5 inactivation reduces requirements for EBF1 in pro-B cell expansion. The binding of EBF1 and PAX5 to regulatory elements in the human MYC gene in a B-ALL cell line indicate that the EBF1:PAX5:MYC regulatory loop is conserved and may control both normal and malignant B-cell development.
  17. Am J Hematol. 2021 Feb 24.
      Molecular classification of acute myeloid leukemia (AML) aids prognostic stratification and clinical management. Our aim in this study is to identify transcriptome-wide mRNAs that are specific to each of the molecular subtypes of AML. We analyzed RNA-sequencing data of 955 AML samples from three cohorts, including the BeatAML project, the Cancer Genome Atlas, and a cohort of Swedish patients to provide a comprehensive transcriptome-wide view of subtype-specific mRNA expression. We identified 729 subtype-specific mRNAs, discovered in the BeatAML project and validated in the other two cohorts. Using unique proteomics data, we also validated the presence of subtype-specific mRNAs at the protein level, yielding a rich collection of potential protein-based biomarkers for the AML community. To enable the exploration of subtype-specific mRNA expression by the broader scientific community, we provide an interactive resource to the public. This article is protected by copyright. All rights reserved.
  18. Blood. 2021 Feb 22. pii: blood.2020007489. [Epub ahead of print]
      Mitochondria of hematopoietic stem cells (HSCs) play crucial roles in regulating cell fate and preserving HSC functionality and survival. However, the mechanism underlying its regulation remains poorly understood. Here, we identify transcription factor TWIST1 as a novel regulator of HSC maintenance through modulating mitochondrial function. We demonstrate that Twist1 deletion results in a significantly decreased lymphoid-biased (Ly-biased) HSC frequency, markedly reduced HSC dormancy and self-renewal capacities, and skewed myeloid differentiation in steady-state hematopoiesis. Twist1-deficient HSCs are more compromised in tolerance of irradiation and 5-fluorouracil-induced stresses, and exhibit typical phenotypes of senescence. Mechanistically, Twist1 deletion induces transactivation of voltage-gated calcium channel (VGCC) Cacna1b which exhausts Ly-biased HSCs, impairs genotoxic hematopoietic recovery, and enhances mitochondrial calcium levels, metabolic activity, and reactive oxygen species production. Suppression of VGCC by a calcium channel blocker largely rescues the phenotypic and functional defects in Twist1-deleted HSCs under both steady-state and stress conditions. Collectively, our data, for the first time, characterize TWIST1 as a critical regulator of HSC function acting through the CACNA1B/Ca2+/mitochondria axis, and highlight the importance of Ca2+ in HSC maintenance. These observations provide new insights into the mechanisms for the control of HSC fate.
  19. Cell Death Dis. 2021 Feb 24. 12(2): 208
      Chronic myeloid leukemia (CML) is characterized by the accumulation of malignant and immature white blood cells which spread to the peripheral blood and other tissues/organs. Despite the fact that current tyrosine kinase inhibitors (TKIs) are capable of achieving the complete remission by reducing the tumor burden, severe adverse effects often occur in CML patients treated with TKIs. The differentiation therapy exhibits therapeutic potential to improve cure rates in leukemia, as evidenced by the striking success of all-trans-retinoic acid in acute promyelocytic leukemia treatment. However, there is still a lack of efficient differentiation therapy strategy in CML. Here we showed that MPL, which encodes the thrombopoietin receptor driving the development of hematopoietic stem/progenitor cells, decreased along with the progression of CML. We first elucidated that MPL signaling blockade impeded the megakaryocytic differentiation and contributed to the progression of CML. While allogeneic human umbilical cord-derived mesenchymal stem cells (UC-MSCs) treatment efficiently promoted megakaryocytic lineage differentiation of CML cells through restoring the MPL expression and activating MPL signaling. UC-MSCs in combination with eltrombopag, a non-peptide MPL agonist, further activated JAK/STAT and MAPK signaling pathways through MPL and exerted a synergetic effect on enhancing CML cell differentiation. The established combinational treatment not only markedly reduced the CML burden but also significantly eliminated CML cells in a xenograft CML model. We provided a new molecular insight of thrombopoietin (TPO) and MPL signaling in MSCs-mediated megakaryocytic differentiation of CML cells. Furthermore, a novel anti-CML treatment regimen that uses the combination of UC-MSCs and eltrombopag shows therapeutic potential to overcome the differentiation blockade in CML.
  20. Exp Hematol. 2021 Feb 19. pii: S0301-472X(21)00089-8. [Epub ahead of print]
      Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome/myeloproliferative neoplasm overlap syndrome characterized by monocytic proliferation in the presence of dysplastic bone marrow changes, inflammatory symptoms and propensity for transformation to AML, with a poor prognosis and limited treatment options. Unlike the α and β isoforms, the PI3K-δ signaling protein is predominantly expressed by hematopoietic cells and therefore has garnered interest as a potential target for the treatment of lymphomas and leukemias. We revealed a pattern of increased PIK3CD : PIK3CA ratio in monocytic M5 AML patients and cell lines and this ratio correlated with responsiveness to pharmacological PI3K-δ inhibition in vitro . As CMML is a disease defined by monocytic clonal proliferation, we tested the PI3K-δ inhibitor, umbralisib, as a single agent, and in combination with the JAK1/2 inhibitor, ruxolitinib in CMML. Our ex vivo experiments with primary CMML patient samples showed synergistic inhibition of viability and clonogenicity with this combination. Phospho-specific flow cytometry revealed that dual inhibition had the unique ability to decrease STAT5, ERK, AKT and S6 phosphorylation simultaneously, which offers a mechanistic hypothesis for the enhanced efficacy of the combination treatment. These preclinical data demonstrate promising activity by co-inhibition of PI3K-δ and JAK1/2 and support the use of ruxolitinib + umbralisib combination therapy in CMML under active clinical investigation.
    Keywords:  Chronic myelomonocytic leukemia; JAK/STAT; PI3K
  21. Hematology. 2021 Dec;26(1): 256-260
      Fms-like tyrosine kinase 3 (FLT3) is one of the most frequently mutated genes in acute myelogenous leukemia (AML) and the mutation is associated with poor prognosis of patients. Two distinct types of activating mutations have been identified in AML samples. One is internal tandem duplications in the juxtamembrane domain (FLT3-ITD) and the other is point mutations in the tyrosine kinase domain (FLT3-TKD). Gilteritinib is a FLT3 inhibitor that inhibits both FLT3-ITD and FLT3-TKD. It was reported that differentiation of leukemic blasts accompanied by differentiation syndrome occurs in some patients treated with gilteritinib. However, information about the precise clinical course is limited, and appropriate management of differentiation syndrome has not been established. We report a case of relapsed AML with FLT3-ITD that was treated with gilteritinib. Analysis of the FLT3-ITD variant allele frequency (VAF) revealed that FLT3-ITD VAF was not decreased despite achievement of complete remission with incomplete hematologic recovery. Remarkable increases of monocytes and granulocytes accompanied by differentiation syndrome were observed at 6 months after the initiation of gilteritinib treatment. Intermittent chemotherapy with low-dose cytarabine and mitoxantrone was effective for reducing myelomonocytosis and resolving differentiation syndrome.
    Keywords:  Acute myelogenous leukemia; FLT3 inhibitor; Fms-like tyrosine kinase 3; differentiation syndrome; gilteritinib; internal tandem duplication; normal karyotype; variant allele frequency
  22. Nat Commun. 2021 02 23. 12(1): 1248
      Mutations in human equilibrative nucleoside transporter 3 (ENT3) encoded by SLC29A3 results in anemia and erythroid hypoplasia, suggesting that ENT3 may regulate erythropoiesis. Here, we demonstrate that lysosomal ENT3 transport of taurine-conjugated bile acids (TBA) facilitates TBA chemical chaperone function and alleviates endoplasmic reticulum (ER) stress in expanding mouse hematopoietic stem and progenitor cells (HSPCs). Slc29a3-/- HSPCs accumulate less TBA despite elevated levels of TBA in Slc29a3-/- mouse plasma and have elevated basal ER stress, reactive oxygen species (ROS), and radiation-induced apoptosis. Reintroduction of ENT3 allows for increased accumulation of TBA into HSPCs, which results in TBA-mediated alleviation of ER stress and erythroid apoptosis. Transplanting TBA-preconditioned HSPCs expressing ENT3 into Slc29a3-/- mice increase bone marrow repopulation capacity and erythroid pool size and prevent early mortalities. Together, these findings suggest a putative role for a facilitative lysosomal transporter in the bile acid regulation of ER stress in mouse HSPCs which may have implications in erythroid biology, the treatment of anemia observed in ENT3-mutated human genetic disorders, and nucleoside analog drug therapy.
  23. Cell Stem Cell. 2021 Feb 22. pii: S1934-5909(21)00018-7. [Epub ahead of print]
      The implications of stem cell heterogeneity for disease pathogenesis and therapy are poorly defined. JAK2V617F+ myeloproliferative neoplasms (MPNs), harboring the same mutation in hematopoietic stem cells (HSCs), display diverse phenotypes, including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). These chronic malignant disorders are ideal models to analyze the pathological consequences of stem cell heterogeneity. Single-cell gene expression profiling with parallel mutation detection demonstrated that the megakaryocyte (Mk)-primed HSC subpopulation expanded significantly with enhanced potential in untreated individuals with JAK2V617F+ ET, driven primarily by the JAK2 mutation and elevated interferon signaling. During treatment, mutant HSCs were targeted preferentially in the Mk-primed HSC subpopulation. Interestingly, homozygous mutant HSCs were forced to re-enter quiescence, whereas their heterozygous counterparts underwent apoptosis. This study provides important evidence for the association of stem cell heterogeneity with the pathogenesis and therapeutic response of a malignant disease.
    Keywords:  JAK2V617F; MPN; hematopoietic stem cells; heterogeneity; inflammation; interferon; megakaryocyte lineage priming; pathogenesis; single cell RNA-Seq; therapeutic response
  24. Blood Adv. 2021 Feb 23. 5(4): 1102-1109
      At diagnosis of chronic-phase chronic myeloid leukemia (CML), there are conflicting data as to whether additional cytogenetic abnormalities (ACAs) beyond a standard Philadelphia (Ph) translocation confer a higher risk of subsequent disease progression. In the United Kingdom SPIRIT2 trial comparing imatinib 400 mg daily with dasatinib 100 mg daily, diagnostic karyotypes were available in 763 of the 814 patients recruited. Of these, 27 had ACAs in either/both the original 4 major route group (trisomy 8 or 19, iso17q or a second Ph) or the 5 additional lesions recently described (trisomy 21, 3q26.2, monosomy 7/7q-, 11q23, and complex karyotypes), and their progression rate was significantly higher (22.2%) than in patients without one of these ACAs (2.2%; P < .001). Patients with ACAs had worse progression-free survival (PFS; hazard ratio [HR], 5.21; 95% confidence interval [CI], 2.59-10.50; P < .001) and freedom from progression (FFP; HR, 12.66; 95% CI, 4.95-32.37; P < .001) compared with patients without ACAs. No association was seen between the Sokal or European Treatment and Outcome Study long-term survival (ELTS) scores and the presence of ACAs. Univariate analysis showed that higher Sokal and ELTS scores and the presence of ACAs were associated with poorer PFS, though only ACAs and high-risk ELTS scores were associated with poorer FFP. Multivariable models identified both the Sokal/ELTS score and ACAs as significant independent factors for PFS but only ELTS score and ACAs as significant independent factors for FFP. The data support the view that certain ACAs are predictive of disease progression independently of Sokal or ELTS scores.
  25. Clin Cancer Res. 2021 Feb 25. pii: clincanres.4271.2020. [Epub ahead of print]
      On November 28, 2018, the Food and Drug Administration approved gilteritinib (Xospata; Astellas, Northbrook, IL), a small molecule FMS-like tyrosine kinase 3 (FLT3) inhibitor, for treatment of relapsed or refractory (R/R) acute myeloid leukemia (AML) with a FLT3 mutation as detected by an FDA-approved test. In the ADMIRAL Study, patients were randomized 2:1 to receive gilteritinib or standard chemotherapy and stratified by response to first-line treatment and intensity of prespecified chemotherapy. Efficacy was established on interim analysis based on complete remission (CR)+CR with partial hematologic recovery (CRh) rate, duration of CR+CRh, and conversion from transfusion dependence (TD) to transfusion independence (TI) in 138 patients in the gilteritinib arm. With median follow-up of 4.6 months (95% CI 2.8-15.8 months) at interim analysis, the CR+CRh rate was 21% (95% confidence interval [CI], 15%-29%), median duration of CR+CRh was 4.6 (range, 0.1-15.8+) months, and conversion from TD to TI was 31%. Revised labeling approved May 29, 2019 included the results of the final analysis, showing an improvement in overall survival (OS) with gilteritinib compared to chemotherapy (hazard ratio [HR] 0.64 [95% CI 0.49-0.83], 1-sided p=0.0004); median OS 9.3 months vs 5.6 months). The OS benefit was observed in both high and low chemotherapy intensity subgroups. Labeling includes a boxed warning for differentiation syndrome (DS) and warnings for posterior reversible encephalopathy syndrome, QT prolongation, pancreatitis, and embryo-fetal toxicity. Safe use requires frequent monitoring of electrocardiograms and blood chemistries. Assessments of long-term safety are pending.
  26. Ther Adv Hematol. 2021 ;12 2040620720986643
      Background: Currently, the goal of chronic myeloid leukemia (CML) treatment is normal survival and good quality of life without life-long treatment, namely, "treatment-free remission" (TFR). At present, approximately only 50% of patients with CML with a deep molecular response are able to discontinue tyrosine kinase inhibitor (TKI) without experiencing molecular relapse [MR; loss of major molecular response (MMR)]. In addition, prior interferon (IFN) treatment is associated with a higher rate of TFR.Methods: We aimed to evaluate the feasibility of TKI discontinuation in Chinese patients with CML and determine whether IFN could prevent MR when used after TKI discontinuation in patients with 0.0032% <BCR-ABL IS ⩽0.1%. Therefore, we retrospectively analyzed the data of patients with CML who discontinued TKI treatment at our center.
    Results: Forty-nine patients who discontinued TKI therapy after achieving MR 4.5 were included in this study, and the median follow-up time from TKI discontinuation was 27 (7, 75) months. Nineteen patients eventually lost MMR, and the TFR rate of the 49 patients was 67% (95% confidence interval 53.6%, 80.3%) at 12 months. The duration of MR 4.5 ⩾54 months and duration of imatinib ⩾85 months were significantly associated with a higher TFR rate. Of the 22 patients with 0.0032% <BCR-ABL IS ⩽0.1%, 12 received IFN-α treatment. The median IFN-α therapy duration was nine (2, 18) months, and three patients eventually lost MMR. Three patients discontinued IFN-α after 2, 2.5, and 10 months, and maintained MMR for 9, 8, and 11 months after IFN discontinuation, respectively. Of the 10 patients not receiving IFN-α treatment, eight eventually lost MMR. The MR-free survival rate was significantly different between the patients treated with and those treated without IFN-α over 24 months (70.7% versus 15.0%, p = 0.002).
    Conclusion: These results indicate that after TKI discontinuation, IFN-α can be administered to patients with 0.0032% <BCR-ABL IS ⩽0.1%, which may help prevent MR.
    Keywords:  chronic myeloid leukemia; discontinuation; interferon; tyrosine kinase inhibitor
  27. Eur J Haematol. 2021 Feb 26.
      INTRODUCTION: Long-term follow-up (≥4 years) demonstrated a low incidence of cardiac and vascular treatment-emergent adverse events (TEAEs) with bosutinib treatment. We evaluated cardiac, vascular, hypertension, and effusion TEAEs after ≥7 years of follow-up in patients with Philadelphia chromosome-positive (Ph+) leukemia.METHODS: This retrospective analysis of a phase I/II study and its on-going extension study included data from patients with chronic phase chronic myeloid leukemia (CML) treated with bosutinib after resistance/intolerance to imatinib (CP2L) or to imatinib plus dasatinib and/or nilotinib (CP3L), and those with accelerated/blast phase CML or acute lymphoblastic leukemia after treatment with, at a minimum, imatinib (ADV).
    RESULTS: In all, 570 patients were treated with bosutinib; median treatment duration was 11.1 months (range: 0.03-133.1). The incidence of cardiac, vascular, hypertension, and effusion-related TEAEs was 10.9%, 8.8%, 9.1% and 13.3%, respectively. Few patients had maximum grade 3-4 TEAEs (cardiac, 3.9%; vascular, 4.0%; hypertension, 3.0%; effusion, 4.6%). Grade 5 TEAEs occurred in the cardiac (0.7%) and vascular (1.8%) clusters only. In years 5-7, fewer than 5% of patients each year had newly occurring cardiac, vascular, hypertension, or effusion TEAEs. The exposure-adjusted TEAE rates (patients with TEAEs/total patient-year) pooled across CP2L, CP3L, and ADV cohorts were: cardiac, 0.044; vascular, 0.035; hypertension, 0.038; and effusion, 0.056, of which, correspondingly, 0.9%, 1.2%, 0%, and 2.1% required treatment discontinuation.
    CONCLUSIONS: The incidence of cardiac, hypertension, vascular, and effusion events was low in patients with Ph+ CML resistant or intolerant to prior therapy who were treated with bosutinib.
    Keywords:  bosutinib; cardiovascular events; chronic myeloid leukemia; clinical trial; effusion events; tyrosine kinase inhibitor
  28. Front Oncol. 2020 ;10 610820
      TP53 is a key tumor suppressor gene with protean functions associated with preservation of genomic balance, including regulation of cellular senescence, apoptotic pathways, metabolism functions, and DNA repair. The vast majority of de novo acute myeloid leukemia (AML) present unaltered TP53 alleles. However, TP53 mutations are frequently detected in AML related to an increased genomic instability, such as therapy-related (t-AML) or AML with myelodysplasia-related changes. Of note, TP53 mutations are associated with complex cytogenetic abnormalities, advanced age, chemoresistance, and poor outcomes. Recent breakthroughs in AML research and the development of targeted drugs directed at specific mutations have led to an explosion of novel treatments with different mechanisms. However, optimal treatment strategy for patients harboring TP53 mutations remains a critical area of unmet need. In this review, we focus on the incidence and clinical significance of TP53 mutations in de novo and t-AML. The influence of these alterations on response and clinical outcomes as well as the current and future therapeutic perspectives for this hardly treatable setting are discussed.
    Keywords:  TP53 mutations; acute myeloid leukemia; decitabine; poor outcome; venetoclax (BCL-2 inhibitor)