bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2021‒10‒10
twenty-nine papers selected by
Paolo Gallipoli
Barts Cancer Institute, Queen Mary University of London

  1. Leukemia. 2021 Oct 06.
      The independent prognostic impact of specific dysplastic features in acute myeloid leukemia (AML) remains controversial and may vary between genomic subtypes. We apply a machine learning framework to dissect the relative contribution of centrally reviewed dysplastic features and oncogenetics in 190 patients with de novo AML treated in ALFA clinical trials. One hundred and thirty-five (71%) patients achieved complete response after the first induction course (CR). Dysgranulopoiesis, dyserythropoiesis and dysmegakaryopoiesis were assessable in 84%, 83% and 63% patients, respectively. Multi-lineage dysplasia was present in 27% of assessable patients. Micromegakaryocytes (q = 0.01), hypolobulated megakaryocytes (q = 0.08) and hyposegmented granulocytes (q = 0.08) were associated with higher ELN-2017 risk. Using a supervised learning algorithm, the relative importance of morphological variables (34%) for the prediction of CR was higher than demographic (5%), clinical (2%), cytogenetic (25%), molecular (29%), and treatment (5%) variables. Though dysplasias had limited predictive impact on survival, a multivariate logistic regression identified the presence of hypolobulated megakaryocytes (p = 0.014) and micromegakaryocytes (p = 0.035) as predicting lower CR rates, independently of monosomy 7 (p = 0.013), TP53 (p = 0.004), and NPM1 mutations (p = 0.025). Assessment of these specific dysmegakarypoiesis traits, for which we identify a transcriptomic signature, may thus guide treatment allocation in AML.
  2. Blood. 2021 Oct 03. pii: blood.2021013156. [Epub ahead of print]
      Majority of RUNX1 mutations in AML are missense or deletion-truncation and behave as loss-of-function mutations. Following standard therapy, AML patients expressing mtRUNX1 exhibit inferior clinical outcome than those without mutant RUNX1. Studies presented here demonstrate that as compared to AML cells lacking mtRUNX1, their isogenic counterparts harboring mtRUNX1 display impaired ribosomal biogenesis and differentiation, as well as exhibit reduced levels of wild-type RUNX1, PU.1 and c-Myc. Compared to AML cells with only wild-type RUNX1, AML cells expressing mtRUNX1 were also more sensitive to the protein translation inhibitor homoharringtonine (omacetaxine) and BCL2 inhibitor venetoclax. HHT treatment repressed enhancers and their BRD4 occupancy, as well as was associated with reduced levels of c-Myc, c-Myb, MCL1 and Bcl-xL. Consistent with this, co-treatment with omacetaxine and venetoclax or BET inhibitor induced synergistic in vitro lethality in AML expressing mtRUNX1. Compared to each agent alone, co-treatment with omacetaxine and venetoclax or BET inhibitor also displayed improved in vivo anti-AML efficacy, associated with improved survival of immune depleted mice engrafted with AML cells harboring mtRUNX1. These findings highlight superior efficacy of omacetaxine-based combination therapies for AML harboring mtRUNX1.
  3. Blood Adv. 2021 Oct 06. pii: bloodadvances.2021005614. [Epub ahead of print]
      Drug resistance and relapse are common challenges in acute myeloid leukemia (AML), particularly in an aggressive subset bearing internal tandem duplications (ITD) of the FLT3 receptor (FLT3-ITD+). The tyrosine kinase inhibitor gilteritinib is approved for the treatment of relapse/refractory AML with FLT3 mutations, yet resistance to gilteritinib remains a clinical concern of which the underlying mechanisms remain incompletely understood. Using transcriptomic analyses and functional validation studies, we identified the calcium-binding proteins, S100A8 and S100A9 (S100A8/A9), as contributors to gilteritinib resistance in FLT3-ITD+ AML. Exposure of FLT3-ITD+ AML cells to gilteritinib increased S100A8/A9 expression in vivo and in vitro, decreased free calcium levels, and genetic manipulation of S100A9 was associated with altered sensitivity to gilteritinib. Using a transcription factor screen, we identified the transcriptional corepressor BCL6, as a regulator of S100A9 expression, and found that gilteritinib decreased BCL6 binding to the S100A9 promoter, thereby increasing S100A9 expression. Furthermore, pharmacological inhibition of BCL6 accelerated the growth rate of gilteritinib-resistant FLT3-ITD+ AML cells, suggesting that S100A9 is a functional target of BCL6. These findings shed light on mechanisms of resistance to gilteritinib through regulation of a target that can be therapeutically exploited to enhance gilteritinib's anti-leukemic effects.
  4. Neoplasia. 2021 Sep 30. pii: S1476-5586(21)00077-4. [Epub ahead of print]23(11): 1101-1109
      Myelodysplastic syndromes (MDS) are clonal hematopoietic disorders with heterogeneous presentation, ranging from indolent disease courses to aggressive diseases similar to acute myeloid leukemia (AML). Approximately 90% of MDS patients harbor recurrent mutations , which - with the exception of mutated SF3B1 -have not (yet) been included into the diagnostic criteria or risk stratification for MDS. Accumulating evidence suggests their utility for diagnostic workup, treatment indication and prognosis. Subsequently, in patients with unexplained cytopenia or dysplasia identification of these mutations may lead to earlier diagnosis. The acquisition and expansion of additional driver mutations usually antecedes further disease progression to higher risk MDS or secondary AML and thus, can be clinically helpful to detect individuals that may benefit from aggressive treatment approaches. Here, we review our current understanding of somatic gene mutations, gene expression patterns and flow cytometry regarding their relevance for disease evolution from pre-neoplastic states to MDS and potentially AML.
    Keywords:  Clonal architecture; Clonal evolution; Measurable residual disease; Molecular targets; Myelodysplastic syndrome; Residual disease
  5. JCI Insight. 2021 Oct 08. pii: e138478. [Epub ahead of print]6(19):
      Myelodysplastic syndromes (MDS) are hematopoietic stem and progenitor cell (HSPC) malignancies characterized by ineffective hematopoiesis and an increased risk of leukemia transformation. Epigenetic regulators are recurrently mutated in MDS, directly implicating epigenetic dysregulation in MDS pathogenesis. Here, we identified a tumor suppressor role of the acetyltransferase p300 in clinically relevant MDS models driven by mutations in the epigenetic regulators TET2, ASXL1, and SRSF2. The loss of p300 enhanced the proliferation and self-renewal capacity of Tet2-deficient HSPCs, resulting in an increased HSPC pool and leukemogenicity in primary and transplantation mouse models. Mechanistically, the loss of p300 in Tet2-deficient HSPCs altered enhancer accessibility and the expression of genes associated with differentiation, proliferation, and leukemia development. Particularly, p300 loss led to an increased expression of Myb, and the depletion of Myb attenuated the proliferation of HSPCs and improved the survival of leukemia-bearing mice. Additionally, we show that chemical inhibition of p300 acetyltransferase activity phenocopied Ep300 deletion in Tet2-deficient HSPCs, whereas activation of p300 activity with a small molecule impaired the self-renewal and leukemogenicity of Tet2-deficient cells. This suggests a potential therapeutic application of p300 activators in the treatment of MDS with TET2 inactivating mutations.
    Keywords:  Epigenetics; Hematology; Leukemias
  6. Biol Pharm Bull. 2021 Oct 01.
      Fms-like tyrosine kinase 3 (FLT3) and isocitrate dehydrogenase 1/2 (IDH1/2) mutations drive malignancy in acute myeloid leukemia (AML), which accounts for approximately 40% of AML cases. Treatment with FLT3 or IDH1/2 inhibitors is used for such patients; however, it is not considered for most patients with AML who lack mutations on the respective genes. In this study, p90 ribosomal S6 kinase (RSK) was found to serve as a new therapeutic target in various AMLs with or without FLT3 mutations. BI-D1870, a potent inhibitor of RSK, significantly suppressed the proliferation of AML cell lines, among which three encoded wild-type FLT3 and three contained FLT3 driver mutations, compared with chronic myeloid leukemia K562 cells or other adherent cancer cells. BI-D1870 inhibited protein synthesis by dephosphorylating the p70 S6 kinase and eukaryotic initiation factor 4E-binding protein 1 in all AML cells except KG-1a cells. Meanwhile, the expression of microtubule-associated protein light chain 3B-I and -II increased in KG-1a cells treated with BI-D1870. BI-D1870 induced caspase-dependent apoptosis in all AML cells, including KG-1a cells. We next investigated the synergistic effect of BI-D1870 with cytarabine, a traditional anticancer drug used in AML. Synergistic effects of BI-D1870 and cytarabine were not observed in any of the cell lines. The findings suggested that BI-D1870 alone exerts an adequate antiproliferative effect on AML with or without FLT3 mutations and serves as a novel AML therapeutic agent.
    Keywords:  BI-D1870; FLT3; acute myeloid leukemia; p90RSK; protein synthesis
  7. Blood Adv. 2021 Oct 08. pii: bloodadvances.2021004322. [Epub ahead of print]
      WT1 overexpression is frequently identified in acute myeloid leukemia (AML) and has been reported as a potential marker for measurable residual disease (MRD) monitoring. Here, we evaluated the value of post-induction WT1 MRD level as a prognostic factor, as well as the interaction between post-induction WT1 MRD response and the effect of allogeneic stem cell transplantation (allo-SCT) in first complete remission (CR). In the ALFA-0702 trial, AML patients aged 18 to 59 years had a prospective quantification of WT1 MRD. Occurrence of a WT1 MRD ratio >2.5% in bone marrow or >0.5% in peripheral blood was defined as MRDhigh, while ratio under these thresholds was defined as MRDlow. The prognostic value of MRD after induction chemotherapy was assessed in 314 patients in first CR by comparing the risk of relapse, the relapse-free survival (RFS) and the overall survival (OS). Interaction between MRD response and allo-SCT effect was evaluated in patients by comparing the influence of allo-SCT on the outcomes of patients with MRDhigh and MRDlow. We showed that MRDhigh patients after induction had a higher risk of relapse and a shorter RFS and OS. MRD response remained of strong prognostic value in the subset of 225 patients with intermediate/unfavorable-risk AML, eligible for allo-SCT, since MRDhigh patients had a significantly higher risk of relapse resulting in worse RFS and OS. Effect of allo-SCT was higher in MRDlow patients than in MRDhigh patients but not statistically different. Early WT1 MRD response highlight a population of high-risk patients in need of additional therapies.
  8. Blood Adv. 2021 Oct 05. pii: bloodadvances.2021005538. [Epub ahead of print]
      Venetoclax (ven) + azacitidine (aza) is the standard of care for newly-diagnosed acute myeloid leukemia (AML) patients who are not candidates for intensive chemotherapy (IC). Some patients who are IC candidates instead receive ven/aza. We retrospectively analyzed newly-diagnosed AML patients who received ven/aza (N=143) or IC (N=149), to compare outcomes and seek variables that could predict response to one or the other therapy, and ascertain whether treatment recommendations can be refined. The response rate for ven/aza was 76.9% and 70.5% for IC. The median overall survival (OS) for IC was 884 days compared to 483 for ven/aza (p=0.0020). A propensity-matched cohort was utilized to compare outcomes in the setting of equivalent baseline variables, and when matched for age, biological risk, and transplantation, the median OS was 705 days for IC and not reached for ven/aza (p=0.0667). Variables that favored response to ven/aza over IC included older age, secondary AML and RUNX1 mutations. AML M5 favored response to IC over ven/aza. In the propensity-matched cohort analyzing OS, older age, adverse risk and RUNX1 mutations favored ven/aza over IC, while intermediate risk favored IC over ven/aza. In conclusion, IC patients have improved OS compared to ven/aza. However, in a propensity-matched cohort of patients with equivalent baseline factors, there was a trend toward a favorable OS for ven/aza. Specific variables, such as reported here for the first time RUNX1 mutations, can be identified that favor ven/aza or IC, helping to guide treatment decisions for patients who may be eligible candidates for either therapy.
  9. Blood Cancer J. 2021 Oct 04. 11(10): 164
      To investigate the efficacy and toxicities of CPX-351 outside a clinical trial, we analyzed 188 patients (median age 65 years, range 26-80) treated for therapy-related acute myeloid leukemia (t-AML, 29%) or AML with myelodysplasia-related changes (AML-MRC, 70%). Eighty-six percent received one, 14% two induction cycles, and 10% received consolidation (representing 22% of patients with CR/CRi) with CPX-351. Following induction, CR/CRi rate was 47% including 64% of patients with available information achieving measurable residual disease (MRD) negativity (<10-3) as measured by flow cytometry. After a median follow-up of 9.3 months, median overall survival (OS) was 21 months and 1-year OS rate 64%. In multivariate analysis, complex karyotype predicted lower response (p = 0.0001), while pretreatment with hypomethylating agents (p = 0.02) and adverse European LeukemiaNet 2017 genetic risk (p < 0.0001) were associated with lower OS. Allogeneic hematopoietic cell transplantation (allo-HCT) was performed in 116 patients (62%) resulting in promising outcome (median survival not reached, 1-year OS 73%), especially in MRD-negative patients (p = 0.048). With 69% of patients developing grade III/IV non-hematologic toxicity following induction and a day 30-mortality of 8% the safety profile was consistent with previous findings. These real-world data confirm CPX-351 as efficient treatment for these high-risk AML patients facilitating allo-HCT in many patients with promising outcome after transplantation.
  10. Blood Adv. 2021 Oct 04. pii: bloodadvances.2021004908. [Epub ahead of print]
      A potent graft-versus-leukemia (GVL) response is crucial in preventing relapse, the major impediment to successful allogeneic hematopoietic cell transplantation (HCT). In preclinical studies, Type-1 interferon (IFNα) enhanced cross-presentation of leukemia specific antigens by CD8α dendritic cells (DCs) and amplified GVL. This observation was translated into a proof-of-concept phase I/II clinical trial with long-acting IFNα (pegIFNα) in patients undergoing HCT for high-risk acute myeloid leukemia (AML). Patients with treatment resistant AML not in remission or poor risk leukemia were administered four dosages of pegIFNα every 14 days beginning at day -1 before HCT. Dose selection was established by adaptive design that continuously assessed the probability of dose limiting toxicities throughout the trial. Efficacy was evaluated by determining the six-month incidence of relapse at the maximum tolerated dose (MTD). Thirty-six patients (median age of 60 years) received pegIFNα treatment. Grade 3 or greater SAEs occurred in 25% of patients establishing 180mcg as the MTD. In phase II, the incidence of relapse was 39% at six-months, which was sustained through one-year post HCT. The incidence of transplant-related mortality was 13% and severe grade III-IV acute GVHD occurred in 11%. Paired blood samples from donors and recipients after HCT indicated elevated levels of Type-1 IFN with cellular response, persistence of cross-presenting DCs and circulating leukemia antigen specific T cells. These data suggest that prophylactic administration of pegIFNα is feasible in the peri-HCT period. In high-risk AML, increased toxicity was not observed with preliminary evidence for reduction in leukemia relapse after HCT.
  11. Blood Adv. 2021 Oct 07. pii: bloodadvances.2021004962. [Epub ahead of print]
      During the last decade, numerous studies have been carried out to exploit the complexity of genomic and transcriptomic lesions driving acute myeloid leukemia (AML) initiation. These studies have helped improve risk classification and treatment options. Detailed molecular characterization of longitudinal AML samples are, however, sparse, meanwhile relapse and therapy resistance represent the main challenge in AML care. To this end, we performed transcriptome-wide RNA sequencing of longitudinal diagnosis, relapse and/or primary resistant samples from 47 adult and 23 pediatric AML patients with known mutational background. Gene expression analysis revealed the association of short event-free survival with overexpression of GLI2 and IL1R1, as well as downregulation of ST18. Moreover, CR1-downregulation and DPEP1-upregulation were associated with AML relapse both in adults and children. Finally, machine learning and network-based analysis identified overexpressed CD6 and downregulated INSR as highly co-predictive genes depicting important relapse-associated characteristics among adult AML patients. Our findings point towards the importance of a tumor-promoting inflammatory environment in leukemia progression, as indicated by several of the herein identified differentially expressed genes. Together, this knowledge provides the foundation for novel personalized drug targets and has the potential to maximize the benefit of current treatments, to improve cure rates in AML.
  12. Cancer Treat Res. 2021 ;181 57-73
      Acute myeloid leukemia (AML) is predominantly a disease of older adults and the majority of affected patients succumb to the disease. After decades of slow progress, the last 5 years have witnessed remarkable progress in AML therapy with the approval of multiple highly active and well-tolerated novel therapies. Notable among these are agents targeting driver mutations including FLT3, IDH1/2 as well as the Bcl-2 inhibitor venetoclax. The combination of hypomethylating agents with venetoclax is highly active in AML and has become the standard of care for older patients as well as those with comorbidities. As a result of these advances, a larger proportion of AML patients now achieve complete remissions enabling them to undergo allogeneic hematopoietic cell transplantation with curative intent. Progress is also being made in the field of monoclonal antibodies targeting leukemia antigens and other immunotherapies and many such agents are currently under active investigation.
    Keywords:  Acute myeloid leukemia; Bcl-2; FLT3; IDH; Mutation; Treatment
  13. Blood. 2021 Oct 08. pii: blood.2020010405. [Epub ahead of print]
      Mixed-phenotype acute leukemia is a rare subtype of leukemia in which both myeloid and lymphoid markers are co-expressed on the same malignant cells. The pathogenesis is largely unknown, and the treatment is challenging. We previously reported the specific association of the recurrent t(8;12)(q13;p13) chromosomal translocation, creating ETV6-NCOA2 fusion, with T/myeloid leukemias. Here we report that ETV6-NCOA2 initiates T/myeloid leukemia in preclinical models; ectopic expression of ETV6-NCOA2 in mouse bone-marrow hematopoietic progenitors induced T/myeloid lymphoma accompanied by spontaneous Notch1 activating mutations. Similarly, co-transduction of human cord-blood CD34+ progenitors with ETV6-NCOA2 and a non-transforming NOTCH1 mutant induced T/myeloid leukemia in immunodeficient mice; the immunophenotype and gene expression pattern was similar to that of patient-derived ETV6-NCOA2 leukemias. Mechanistically, we show that ETV6-NCOA2 forms a transcriptional complex with ETV6 and the histone acetyltransferase p300, leading to de-repression of ETV6 target genes. The expression of ETV6-NCOA2 in human and mouse non-thymic hematopoietic progenitor cells induces transcriptional dysregulation, which activates a lymphoid program while failing to repress the expression of myeloid genes such as CSF1 and MEF2C. The ETV6-NCOA2 induced arrest at early-immature T-cell developmental stage. The additional acquisition of activating NOTCH1 mutations transforms the early-immature ETV6-NCOA2 cells into T/myeloid leukemias. Here, we describe the first preclinical model to depict the initiation of T/myeloid leukemia by a specific somatic genetic aberration.
  14. Blood Adv. 2021 Oct 06. pii: bloodadvances.2021005566. [Epub ahead of print]
      Adding the selective BCL-2 inhibitor venetoclax to reduced intensity conditioning (RIC) chemotherapy (fludarabine and busulfan, FluBu2) may enhance anti-leukemic cytotoxicity and thereby reduce the risk of post-transplant relapse. This phase 1 study investigated the recommended phase 2 (RP2D) of venetoclax, a BCL-2 selective inhibitor, when added to FluBu2 in adult patients with high risk acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and MDS/myeloproliferative neoplasms (MPN) undergoing transplant. Patients received dose-escalated venetoclax (200-400 mg daily starting day -8 for 6-7 doses) in combination with fludarabine 30 mg/m2/day for four doses and busulfan 0.8 mg/kg twice daily for eight doses on day -5 to -2 (FluBu2). Transplant related-toxicity was evaluated from the first venetoclax dose on day -8 to +28. Twenty-two patients were treated. At study entry, 5 MDS and MDS/MPN patients had 5-10% marrow blasts and 18/22 (82%) had a persistent detectable mutation. Grade 3 adverse events included mucositis, diarrhea and liver transaminitis (N=3 each). Neutrophil/platelet recovery and acute/chronic GVHD rates were similar to standard FluBu2. No DLTs were observed. The RP2D of venetoclax was 400 mg daily for 7 doses. With a median follow-up of 14.7 months (8.6-24.8 months), median overall survival was not reached, and progression free survival was 12.2 months (95% CI: 6.0 months, not estimable). In high risk AML, MDS, and MDS/MPN patients, adding venetoclax to FluBu2 was feasible and safe. To further address relapse risk, assessment of maintenance therapy after venetoclax plus FluBu2 transplant is on-going. This study was registered at as #NCT03613532.
  15. Blood. 2021 Oct 05. pii: blood.2021011563. [Epub ahead of print]
      Proton export is often considered a detoxifying process in animal cells with monocarboxylate symporters co-exporting excessive lactate and protons during glycolysis or the Warburg effect. Here we report a novel mechanism by which lactate/H+ export is sufficient to induce cell growth. Increased lactate/proton export induces intracellular alkalization that selectively activates catalysis by key metabolic gatekeeper enzymes, HK1/PKM2/G6PDH, thereby enhancing glycolytic and pentose phosphate pathway carbon flux. The result is increased nucleotide levels, NADPH/NADP+ ratio and cell proliferation. Simply increasing the lactate/proton symporter, MCT4, or sodium-proton antiporter, NHE1 was sufficient to increase intracellular-pH (pHi) and give normal hematopoietic cells a significant competitive growth advantage in vivo. This process does not require additional cytokine triggers and is exploited in malignancy where leukemogenic mutations epigenetically increase MCT4. Inhibiting MCT4 decreased intracellular pH, carbon flux and eliminated acute myeloid leukemia-initiating-cells without cytotoxic chemotherapy. Intracellular alkalization is a primitive mechanism by which proton partitioning can directly reprogram carbon metabolism for cell growth.
  16. Leuk Res. 2021 Sep 22. pii: S0145-2126(21)01714-8. [Epub ahead of print]110 106713
      Leukemia stem cells utilize cell adhesion molecules like CXCR4/CXCL12 to home to bone marrow stromal niches where they are maintained in a dormant, protected state. Dociparstat sodium (DSTAT, CX-01) is a low anticoagulant heparin with multiple mechanisms of action, including inhibition of the CXCR4/CXCL12 axis, blocking HMGB1, and binding platelet factor 4 (PF-4). We conducted a pilot study adding DSTAT to azacitidine for patients with AML or MDS unresponsive to or relapsed after prior hypomethylating agent therapy, hypothesizing that DSTAT may improve response rates. Twenty patients were enrolled, with a median of 2 prior lines of therapy and 6 cycles of prior hypomethylating agents. Among fifteen patients evaluable for response, there was 1 complete remission, and 3 marrow complete remissions, for a response rate of 27 % among evaluable patients (20 % overall). Hematologic improvement was observed in 5 additional patients. The median overall survival for all enrolled patients was 205 days (95 % CI 119-302). While cytopenias and infections were common, these were not out of proportion to what would be expected in this population of patients undergoing treatment with azacitidine alone. In summary, this trial demonstrated the feasibility of combining DSTAT with azacitidine, with several responses observed, suggesting this combination warrants further study.
    Keywords:  Azacitidine; CX-01; CXCL12; CXCR4; DSTAT; Dociparstat sodium
  17. Semin Cancer Biol. 2021 Oct 01. pii: S1044-579X(21)00247-9. [Epub ahead of print]
      Transcriptional profiling of acute leukemia, specifically by RNA-sequencing or whole transcriptome sequencing (WTS), has provided fundamental insights into its underlying disease biology and allows unbiased detection of oncogenic gene fusions, as well as of gene expression signatures that can be used for improved disease classification. While used as a research tool for many years, RNA-sequencing is becoming increasingly used in clinical diagnostics. Here, we highlight key transcriptomic studies of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) that have improved our biological understanding of these heterogeneous malignant disorders and have paved the way for translation into clinical diagnostics. Recent single-cell transcriptomic studies of ALL and AML, which provide new insights into the cellular ecosystem of acute leukemia and point to future clinical utility, are also reviewed. Finally, we discuss current challenges that need to be overcome for a more wide-spread adoption of RNA-sequencing in clinical diagnostics and how this technology significantly can aid the identification of genetic alterations in current guidelines and of newly emerging disease entities, some of which are critical to identify because of the availability of targeted therapies, thereby paving the way for improved precision medicine of acute leukemia.
    Keywords:  Acute lymphoblastic leukemia; Acute myeloid leukemia; Classification; Diagnostics; Gene fusions; Precision medicine; RNA-sequencing; Whole transcriptome sequencing
  18. Blood Adv. 2021 Oct 07. pii: bloodadvances.2021005509. [Epub ahead of print]
      Cytomegalovirus (CMV) reactivation is a frequent complication after allogeneic hematopoietic cell transplantation (HCT), whose impact on clinical outcome, in particular on leukemic relapse is controversial. We retrospectively analyzed 687 HCT recipients with acute myeloid leukemia (AML) and ciclosporin-based immunosuppression to better understand the differential impact of CMV on transplant outcomes depending on AML disease stage and in-vivo T-cell depletion with anti-thymocyte globulin (ATG). Without ATG, CMV reactivation associated with significantly reduced relapse, yet its effect was more pronounced for advanced disease AML (p=0.0002) than for patients in first complete remission (CR1, p=0.0169). Depending on the disease stage, ATG exposure abrogated relapse protection following CMV reactivation in advanced stages (p=0.796), while it inverted its effect into increased relapse for CR1 patients (p=0.0428). CMV reactivation was associated with significantly increased non-relapse mortality in CR1 patients without ATG (p=0.0187), but not in those with advanced disease and ATG. Following CMV reactivation, only patients with advanced disease had significantly higher event-free survival rates as compared to patients without CMV. Overall, our data suggest that both ATG and disease stage modulate the impact of post-HCT CMV reactivation in opposite directions, revealing a level of complexity that warrants future studies regarding the interplay between anti-virus and anti-tumor immunity.
  19. Cancer Discov. 2021 Oct 06. pii: candisc.1513.2020. [Epub ahead of print]
      Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive leukemia of plasmacytoid dendritic cells (pDCs). BPDCN occurs at least three times more frequently in men than women, but the reasons for this sex bias are unknown. Here, studying genomics of primary BPDCN and modeling disease-associated mutations, we link acquired alterations in RNA splicing to abnormal pDC development and inflammatory response through Toll-like receptors. Loss-of-function mutations in ZRSR2, an X chromosome gene encoding a splicing factor, are enriched in BPDCN and nearly all mutations occur in males. ZRSR2 mutation impairs pDC activation and apoptosis after inflammatory stimuli, associated with intron retention and inability to upregulate the transcription factor IRF7. In vivo, BPDCN-associated mutations promote pDC expansion and signatures of decreased activation. These data support a model in which male-biased mutations in hematopoietic progenitors alter pDC function and confer protection from apoptosis, which may impair immunity and predispose to leukemic transformation.
  20. Blood. 2021 Oct 05. pii: blood.2021012788. [Epub ahead of print]
      Cholesterol is a vital lipid for cellular functions. It is necessary for membrane biogenesis, cell proliferation and differentiation. In addition to maintaining cell integrity and permeability, increasing evidence indicates a strict link between cholesterol homeostasis, inflammation and haematological tumors. This makes cholesterol homeostasis an optimal therapeutic target for hematopoietic malignancies. Manipulating cholesterol homeostasis either interfering with its synthesis or activating the reverse cholesterol transport via the engagement of liver X receptors (LXRs), affects the integrity of tumor cells both in vitro and in vivo. Cholesterol homeostasis has also been manipulated to restore antitumor immune responses in preclinical models. These observations have prompted clinical trials in acute myeloid leukemia (AML) to test the combination of chemotherapy with drugs interfering with cholesterol synthesis, i.e. statins. We review the role of cholesterol homeostasis in hematopoietic malignancies, as well as in cells of the tumor microenvironment, and discuss the potential use of lipid modulators for therapeutic purposes.
  21. Blood Adv. 2021 Oct 07. pii: bloodadvances.2021004735. [Epub ahead of print]
      Black and Hispanic children with acute myeloid leukemia (AML) have worse outcomes compared to White children. AML is a heterogeneous disease with numerous genetic subtypes in which these disparities have not been specifically investigated. In this study, we used the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) database to examine the association of race-ethnicity with leukemia cytogenetics, clinical features, and survival outcomes within major cytogenetic subgroups of pediatric AML. Compared to White non-Hispanic patients, t(8;21) AML was more prevalent among Black (OR, 2.22; 95% CI, 1.28-3.74) and Hispanic patients (OR, 1.74; 95% CI, 1.05-2.83). The poor prognosis KMT2A rearrangement t(6;11)(q27;q23) was more prevalent among Black patients (OR, 6.12; 95% CI, 1.81-21.59). Among those with KMT2Ar AML, Black race was associated with inferior event-free survival (EFS) (HR, 2.31; 95% CI, 1.41-3.79) and overall survival (OS) (HR, 2.54; 1.43-4.51). Hispanic patients with KMT2Ar AML also had inferior EFS (HR, 2.20; 95% CI, 1.27-3.80) and OS (HR, 2.07; 95% CI, 1.09-3.93). Similarly, among patients with t(8;21) or inv(16) AML (i.e., core binding factor AML), Black patients had inferior outcomes (EFS HR, 1.93; 95% CI, 1.14-3.28 and OS HR, 3.24; 95% CI, 1.60-6.57). This disparity was not detected among patients receiving gemtuzumab ozogamicin. In conclusion, racial-ethnic disparities in survival outcomes among young people with AML are prominent and vary across cytogenetic subclasses. Future studies should explore the socioeconomic and biologic determinants of these disparities.
  22. Blood Adv. 2021 Oct 06. pii: bloodadvances.2020004041. [Epub ahead of print]
      Mechanisms underlying the resistance of Acute Lymphoblastic Leukemia (ALL) blasts to L-asparaginase are still incompletely known. Here we demonstrate that human primary bone marrow mesenchymal stromal cells (MSCs) successfully adapt to L-asparaginase and markedly protect leukemic blasts from the enzyme-dependent cytotoxicity through an amino acid trade-off. ALL blasts synthesize and secrete glutamine, thus increasing extracellular glutamine availability for stromal cells. In turn, MSCs use glutamine, either synthesized through Glutamine Synthetase (GS) or imported, to produce asparagine, which is then extruded to sustain asparagine-auxotroph leukemic cells. GS inhibition prevents mesenchymal cells adaptation to L-asparaginase, lowers glutamine secretion by ALL blasts, and markedly hinders the protection exerted by MSCs on leukemic cells. The pro-survival amino acid exchange is hindered by the inhibition or silencing of the asparagine efflux transporter SNAT5, which is induced in mesenchymal cells by ALL blasts. Consistently, primary MSCs from ALL patients express higher levels of SNAT5 (p < 0.05), secrete more asparagine (p < 0.05), and protect leukemic blasts (p < 0.05) better than MSCs isolated from healthy donors. In conclusion, ALL blasts arrange a pro-leukemic amino acid trade-off with bone marrow mesenchymal cells, which depends on GS and SNAT5 and promotes leukemic cell survival during L-asparaginase treatment.
  23. Nucleic Acids Res. 2021 Oct 04. pii: gkab871. [Epub ahead of print]
      KRAS-activating mutations are oncogenic drivers and are correlated with radioresistance of multiple cancers, including colorectal cancer, but the underlying precise molecular mechanisms remain elusive. Herein we model the radiosensitivity of isogenic HCT116 and SW48 colorectal cancer cell lines bearing wild-type or various mutant KRAS isoforms. We demonstrate that KRAS mutations indeed lead to radioresistance accompanied by reduced radiotherapy-induced mitotic catastrophe and an accelerated release from G2/M arrest. Moreover, KRAS mutations result in increased DNA damage response and upregulation of 53BP1 with associated increased non-homologous end-joining (NHEJ) repair. Remarkably, KRAS mutations lead to activation of NRF2 antioxidant signaling to increase 53BP1 gene transcription. Furthermore, genetic silencing or pharmacological inhibition of KRAS, NRF2 or 53BP1 attenuates KRAS mutation-induced radioresistance, especially in G1 phase cells. These findings reveal an important role for a KRAS-induced NRF2-53BP1 axis in the DNA repair and survival of KRAS-mutant tumor cells after radiotherapy, and indicate that targeting NRF2, 53BP1 or NHEJ may represent novel strategies to selectively abrogate KRAS mutation-mediated radioresistance.
  24. Cancer Discov. 2021 Oct 07. pii: candisc.0508.2021. [Epub ahead of print]
      Mutations in splicing factors (SFs) are the predominant class of mutations in myelodysplastic syndrome (MDS), but convergent downstream disease drivers remain elusive. To identify common direct targets of mis-splicing by mutant U2AF1 and SRSF2, we performed RNA-Seq and eCLIP in human hematopoietic stem/progenitor cells (HSPCs) derived from isogenic induced pluripotent stem cell (iPSC) models. Integrative analyses of alternative splicing and differential binding converged on a long isoform of GNAS (GNAS-L), promoted by both mutant factors. MDS population genetics, functional and biochemical analyses support that GNAS-L is a driver of MDS and encodes a hyperactive long form of the stimulatory G protein alpha subunit, Gas-L, that activates ERK/MAPK signaling. SF-mutant MDS cells have activated ERK signaling and consequently are sensitive to MEK inhibitors. Our findings highlight an unexpected and unifying mechanism by which SRSF2 and U2AF1 mutations drive oncogenesis with potential therapeutic implications for MDS and other SF-mutant neoplasms.
  25. Cancer Treat Res. 2021 ;181 45-55
      Acute promyelocytic leukemia (APL) is a rare but highly curable form of acute myeloid leukemia (AML) whose genetic hallmark is the balanced reciprocal translocation t(15;17)(q22;q12) which fuses the promyelocytic leukemia (PML) and retinoic acid receptor alpha (RARα) genes (Wang and Chen in Blood 111:2505-2515, 2008; Lallem and-Breitenbach et al. in J Exp Med 189:1043-1052, 1999). It is a rare disease and accounts for 5-10% of adult AML with an estimated incidence of 0.1/100,000 in Western countries (Sant et al. in Blood 116:3724-3734, 2010). In the United States, 600-800 new cases are diagnosed every year although the incidence appears increased in patients originating from Latin America (Douer in Best Pract Res Clin Haematol 16:357-367, 2003). Notably, the median age at diagnosis is approximately 40 years which is significantly lower than in AML where the median age is 68 years.
  26. Leuk Lymphoma. 2021 Oct 05. 1-10
      We recently reported an early hospital discharge (EHD) care strategy following intensive acute myeloid leukemia (AML)-like chemotherapy is safe. To evaluate its impact on infectious outcomes, we compared all adults treated from 8/1/2014 to 7/31/2018 discharging within 72 h of completing chemotherapy (EHD) with hospitalized patients (controls) across 354 induction and 259 post-remission cycles. While overall outcomes were similar, gram-positive bacteremias were more common in EHD patients than control (p<.001), although they received fewer days of IV antimicrobials (p< .001). Notably, cumulative infection risks in EHD patients were similar after induction and post-remission therapy. In multivariable analysis, only EHD status was independently associated with risk for gram-positive bacteremia (p= .01), whereas the only independent risk factor for fungal infection was fluconazole (vs. posaconazole) use (p< .001). The observation of increased rates of gram-positive bacteremias with EHD identifies improvements in catheter management as one area to further increase the safety of this care approach.
    Keywords:  Infectious complications; acute myeloid leukemia; early hospital discharge; myeloid leukemias and dysplasias
  27. Nat Med. 2021 Oct 07.
      Germline SAMD9 and SAMD9L mutations (SAMD9/9Lmut) predispose to myelodysplastic syndromes (MDS) with propensity for somatic rescue. In this study, we investigated a clinically annotated pediatric MDS cohort (n = 669) to define the prevalence, genetic landscape, phenotype, therapy outcome and clonal architecture of SAMD9/9L syndromes. In consecutively diagnosed MDS, germline SAMD9/9Lmut accounted for 8% and were mutually exclusive with GATA2 mutations present in 7% of the cohort. Among SAMD9/9Lmut cases, refractory cytopenia was the most prevalent MDS subtype (90%); acquired monosomy 7 was present in 38%; constitutional abnormalities were noted in 57%; and immune dysfunction was present in 28%. The clinical outcome was independent of germline mutations. In total, 67 patients had 58 distinct germline SAMD9/9Lmut clustering to protein middle regions. Despite inconclusive in silico prediction, 94% of SAMD9/9Lmut suppressed HEK293 cell growth, and mutations expressed in CD34+ cells induced overt cell death. Furthermore, we found that 61% of SAMD9/9Lmut patients underwent somatic genetic rescue (SGR) resulting in clonal hematopoiesis, of which 95% was maladaptive (monosomy 7 ± cancer mutations), and 51% had adaptive nature (revertant UPD7q, somatic SAMD9/9Lmut). Finally, bone marrow single-cell DNA sequencing revealed multiple competing SGR events in individual patients. Our findings demonstrate that SGR is common in SAMD9/9Lmut MDS and exemplify the exceptional plasticity of hematopoiesis in children.
  28. Blood Adv. 2021 Oct 08. pii: bloodadvances.2021005300. [Epub ahead of print]
      Acquired genetic mutations can confer resistance to arsenic trioxide (ATO) in the treatment of acute promyelocytic leukemia (APL). However, such resistance-conferring mutations are rare and do not explain most disease recurrence seen in the clinic. We have generated stable ATO-resistant promyelocytic cell lines that are also less sensitive to ATRA and the combination of ATO and ATRA compared to the sensitive cell line. Characterization of these in-house generated resistant cell lines showed significant differences in immunophenotype, drug transporter expression, anti-apoptotic protein dependence, and PML-RARA mutation. Gene expression profiling revealed prominent dysregulation of the cellular metabolic pathways in these ATO resistant APL cell lines. Glycolytic inhibition by 2-DG was sufficient and comparable to the standard of care (ATO) in targeting the sensitive APL cell line. 2-DG was also effective in the in vivo transplantable APL mouse model; however, it did not affect the ATO resistant cell lines. In contrast, the resistant cell lines were significantly affected by compounds targeting the mitochondrial respiration when combined with ATO, irrespective of the ATO resistance-conferring genetic mutations or the pattern of their anti-apoptotic protein dependency. Our data demonstrate that the addition of mitocans in combination with ATO can overcome ATO resistance. We further show that this combination has the potential in the treatment of non-M3 AML and relapsed APL. The translation of this approach in the clinic needs to be explored further.