bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2021‒06‒13
28 papers selected by
Paolo Gallipoli
Barts Cancer Institute, Queen Mary University of London

  1. Hemasphere. 2021 Jun;5(6): e578
      Driver mutations occur in Janus kinase 2 (JAK2), thrombopoietin receptor (MPL), and calreticulin (CALR) in BCR-ABL1 negative myeloproliferative neoplasms (MPNs). From mutations leading to one amino acid substitution in JAK2 or MPL, to frameshift mutations in CALR resulting in a protein with a different C-terminus, all the mutated proteins lead to pathologic and persistent JAK2-STAT5 activation. The most prevalent mutation, JAK2 V617F, is associated with the 3 entities polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF), while CALR and MPL mutations are associated only with ET and MF. Triple negative ET and MF patients may harbor noncanonical mutations in JAK2 or MPL. One major fundamental question is whether the conformations of JAK2 V617F, MPL W515K/L/A, or CALR mutants differ from those of their wild type counterparts so that a specific treatment could target the clone carrying the mutated driver and spare physiological hematopoiesis. Of great interest, a set of epigenetic mutations can co-exist with the phenotypic driver mutations in 35%-40% of MPNs. These epigenetic mutations, such as TET2, EZH2, ASXL1, or DNMT3A mutations, promote clonal hematopoiesis and increased fitness of aged hematopoietic stem cells in both clonal hematopoiesis of indeterminate potential (CHIP) and MPNs. Importantly, the main MPN driver mutation JAK2 V617F is also associated with CHIP. Accumulation of several epigenetic and splicing mutations favors progression of MPNs to secondary acute myeloid leukemia. Another major fundamental question is how epigenetic rewiring due to these mutations interacts with persistent JAK2-STAT5 signaling. Answers to these questions are required for better therapeutic interventions aimed at preventing progression of ET and PV to MF, and transformation of these MPNs in secondary acute myeloid leukemia.
  2. Clin Cancer Res. 2021 Jun 08.
      PURPOSE: Biomarkers of response and resistance to FLT3 tyrosine kinase inhibitors (TKI) are still emerging, and optimal clinical combinations remain unclear. The purpose of this study is to identify co-occurring mutations that influence clinical response to the novel FLT3 inhibitor pexidartinib (PLX3397).EXPERIMENTAL DESIGN: We performed targeted sequencing of pretreatment blasts from 29 patients with FLT3 internal tandem duplication (ITD) mutations treated on the phase I/II trial of pexidartinib in relapsed/refractory FLT3-ITD+ acute myeloid leukemia (AML). We sequenced 37 samples from 29 patients with available material, including 8 responders and 21 non-responders treated at or above the recommended phase II dose of 3,000 mg.
    RESULTS: Consistent with other studies, we identified mutations in NRAS, TP53, IDH2, and a variety of epigenetic and transcriptional regulators only in non-responders. Among the most frequently mutated genes in non-responders was Cyclin D3 (CCND3). A total of 3 individual mutations in CCND3 (Q276*, S264R, and T283A) were identified in 2 of 21 non-responders (one patient had both Q276* and S264R). No CCND3 mutations were found in pexidartinib responders. Expression of the Q276* and T283A mutations in FLT3-ITD MV4;11 cells conferred resistance to apoptosis, decreased cell-cycle arrest, and increased proliferation in the presence of pexidartinib and other FLT3 inhibitors. Inhibition of CDK4/6 activity in CCND3 mutant MV4;11 cells restored pexidartinib-induced cell-cycle arrest but not apoptosis.
    CONCLUSIONS: Mutations in CCND3, a gene not commonly mutated in AML, are a novel cause of clinical primary resistance to FLT3 inhibitors in AML and may have sensitivity to CDK4/6 inhibition.
  3. Blood Cancer J. 2021 Jun 07. 11(6): 111
      About 25% of patients with acute myeloid leukemia (AML) harbor FMS-like tyrosine kinase 3 (FLT3) internal tandem duplication (ITD) mutations and their prognosis remains poor. Gilteritinib is a FLT3 inhibitor approved by the US FDA for use in adult FLT3-mutated relapsed or refractory AML patients. Monotherapy, while efficacious, shows short-lived responses, highlighting the need for combination therapies. Here we show that gilteritinib and CUDC-907, a dual inhibitor of PI3K and histone deacetylases, synergistically induce apoptosis in FLT3-ITD AML cell lines and primary patient samples and have striking in vivo efficacy. Upregulation of FLT3 and activation of ERK are mechanisms of resistance to gilteritinib, while activation of JAK2/STAT5 is a mechanism of resistance to CUDC-907. Gilteritinib and CUDC-907 reciprocally overcome these mechanisms of resistance. In addition, the combined treatment results in cooperative downregulation of cellular metabolites and persisting antileukemic effects. CUDC-907 plus gilteritinib shows synergistic antileukemic activity against FLT3-ITD AML in vitro and in vivo, demonstrating strong translational therapeutic potential.
  4. Clin Lymphoma Myeloma Leuk. 2021 May 11. pii: S2152-2650(21)00181-6. [Epub ahead of print]
      BACKGROUND: FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) is a molecular genetic alteration significantly affecting the clinical outcome in patients with acute myeloid leukemia (AML). FLT3-ITD mutations are characterized by variable mutant-to-wild allelic ratios (ARs) and sizes of the duplicated sequences. The size of the inserted sequence may vary from a few to hundreds of nucleotides. The aim of this work was to determine the impact of FLT3-ITD ARs, FLT3-ITD allelic frequency (AF), and allele size in de novo AML.PATIENTS AND METHODS: We studied 117 patients with FLT3-ITD gene mutation-positive AML, dividing them into those with low ARs and those with high ARs (>0.64) and examined their prognostic impact.
    RESULTS: High FLT3-ITD AR ≥ 0.64 and AF ≥ 0.5 were significantly associated with a lower overall survival compared with lower AR (median 0.625 vs. 1.020 months, respectively; P = .041) and AF (median 0.493 vs. 0.954 months, respectively; P = .009). NPM1 mutation had no favorable impact on the low-level FLT3-ITD group.
    CONCLUSION: Initial high total leukocyte count, FLT3-ITD AF, and splenomegaly are independent prognostic factors for poor outcome in FLT3-ITD-positive AML.
    Keywords:  Acute myeloid leukemia; Allelic ratio; FMS-like tyrosine kinase 3; NPM1; Prognosis
  5. Blood Adv. 2021 Jun 08. 5(11): 2539-2549
      The clinicopathologic features of DNA methyltransferase 3A (DNMT3A)-mutated de novo acute myeloid leukemia (AML), and the significance of variant type, variant allele frequency (VAF), and multiple concomitant DNMT3A mutations, remain poorly defined. We examined 104 DNMT3A-mutated de novo AML patients from 2 major centers. Most (82%) had normal karyotype (NK); R882H variants were frequent(38%). The most commonly comutated genes included nucleophosmin (NPM1; 53%), Fms-related tyrosine kinase 3 (FLT3)-internal tandem duplication (25%), IDH1 (23%), IDH2 (23%), and TET2 (21%). Patients with high DNMT3A VAF at diagnosis (≥44%; DNMT3AHIGH) had more significant leukocytosis and higher blast counts in peripheral blood and bone marrow. DNMT3AHIGH cases were associated with much shorter event-free survival (EFS; 14.1 vs 56.8 months) and overall survival (OS; 18.3 months vs not reached) compared with cases of patients with low DNMT3A (DNMT3ALOW). Thirteen patients had 2 DNMT3A variants and similar VAFs at diagnosis that tracked together at multiple time points after chemotherapy and/or stem cell transplantation (SCT). In multivariable analyses performed in NK patients who received standard induction chemotherapy, presence of 2 DNMT3A mutations (hazard ratio [HR] = 3.192; P = .038) and SCT in first complete remission (HR = 0.295; P = .001) independently affected EFS; increasing marrow blast percentage (HR = 1.026; P = .025), high DNMT3A VAF (HR = 3.003; P = .010), and 2 DNMT3A mutations (HR = 4.816; P = .020) had independent effects on OS. These data support the adverse prognostic significance of DNMT3AHIGH reveal a novel association between 2 concomitant DNMT3A mutations and inferior outcome in DNMT3A-mutated de novo AML with a NK.
  6. Nat Cancer. 2020 Apr;1(4): 410-422
      Aggressive myeloid leukemias such as blast crisis chronic myeloid leukemia and acute myeloid leukemia remain highly lethal. Here we report a genome-wide in vivo CRISPR screen to identify new dependencies in this disease. Among these, RNA-binding proteins (RBPs) in general, and the double-stranded RBP Staufen2 (Stau2) in particular, emerged as critical regulators of myeloid leukemia. In a newly developed knockout mouse, loss of Stau2 led to a profound decrease in leukemia growth and improved survival in mouse models of the disease. Further, Stau2 was required for growth of primary human blast crisis chronic myeloid leukemia and acute myeloid leukemia. Finally, integrated analysis of CRISPR, eCLIP and RNA-sequencing identified Stau2 as a regulator of chromatin-binding factors, driving global alterations in histone methylation. Collectively, these data show that in vivo CRISPR screening is an effective tool for defining new regulators of myeloid leukemia progression and identify the double-stranded RBP Stau2 as a critical dependency of myeloid malignancies.
  7. Acta Haematol. 2021 Jun 08. 1-7
      INTRODUCTION: Achievement of an initial complete remission (CR) following induction chemotherapy is tightly correlated with survival in acute myeloid leukemia (AML) patients, yet patients in CR with incomplete hematologic recovery (CRi) still experience improved outcomes compared with nonresponding patients. Whether CRi predicts prognosis in patients referred to an allogeneic stem cell transplantation (allo-SCT) is incompletely defined. In this analysis, we evaluated whether clinical outcomes of transplanted AML patients in CR and CRi were significantly different.METHODS: A retrospective single-center analysis of all de novo AML patients who underwent an allo-SCT between 2001 and 2015. The cohort included all adult patients with AML who underwent a first allo-SCT either in first or second CR or CRi at the time of transplantation.
    RESULTS: The study cohort included 186 CR patients and 44 CRi patients. In univariate analysis, CRi was associated with inferior 3-year survival and 3-year nonrelapse mortality (NRM) compared to CR (41 vs. 62%; p = 0.022 and 27 vs. 10%; p = 0.006, respectively). In multivariate analysis, CRi was associated with decreased rates of survival (hazard ratio [HR] 2.01; 95% CI, 1.24-3.25; p = 0.005) and NRM (HR, 3.5; 95% CI, 1.6-7.8; p = 0.002).
    CONCLUSION: CRi in transplanted AML patients is potentially a potent predictor of increased NRM and survival.
    Keywords:  Acute myeloid leukemia; Allogeneic stem cell transplantation; Complete remission
  8. iScience. 2021 May 21. 24(5): 102435
      In an attempt to unravel functionality of the non-canonical PRC1.1 Polycomb complex in human leukemogenesis, we show that USP7 and TRIM27 are integral components of PRC1.1. USP7 interactome analyses show that PRC1.1 is the predominant Polycomb complex co-precipitating with USP7. USP7 inhibition results in PRC1.1 disassembly and loss of chromatin binding, coinciding with reduced H2AK119ub and H3K27ac levels and diminished gene transcription of active PRC1.1-controlled loci, whereas H2AK119ub marks are also lost at PRC1 loci. TRIM27 and USP7 are reciprocally required for incorporation into PRC1.1, and TRIM27 knockdown partially rescues USP7 inhibitor sensitivity. USP7 inhibitors effectively impair proliferation in AML cells in vitro, also independent of the USP7-MDM2-TP53 axis, and MLL-AF9-induced leukemia is delayed in vivo in human leukemia xenografts. We propose a model where USP7 counteracts TRIM27 E3 ligase activity, thereby maintaining PRC1.1 integrity and function. Moreover, USP7 inhibition may be a promising new strategy to treat AML patients.
    Keywords:  Cancer; Cell Biology; Molecular Biology
  9. Cancer Discov. 2021 Jun 08. pii: candisc.0145.2021. [Epub ahead of print]
      Lineage ambiguous leukemias are high-risk malignancies of poorly understood genetic basis. Here, we describe a distinct subgroup of acute leukemia with expression of myeloid, T lymphoid and stem cell markers driven by aberrant allele-specific deregulation of BCL11B, a master transcription factor responsible for thymic T-lineage commitment and specification. Mechanistically, this deregulation was driven by chromosomal rearrangements that juxtapose BCL11B to super-enhancers active in hematopoietic progenitors, or focal amplifications that generate a super-enhancer from a non-coding element distal to BCL11B. Chromatin conformation analyses demonstrate long range interactions of rearranged enhancers with the expressed BCL11B allele, and association of BCL11B with activated hematopoietic progenitor cell cis-regulatory elements, suggesting BCL11B is aberrantly co-opted into a gene regulatory network that drives transformation by maintaining a progenitor state. These data support a role for ectopic BCL11B expression in primitive hematopoietic cells mediated by enhancer hijacking as an oncogenic driver of human lineage ambiguous leukemia.
  10. Front Oncol. 2021 ;11 665291
      Despite significant recent advances in our understanding of the biology and genetics of acute myeloid leukemia (AML), current AML therapies are mostly based on a backbone of standard chemotherapy which has remained mostly unchanged for over 20 years. Several novel therapies, mostly targeting neomorphic/activating recurrent mutations found in AML patients, have only recently been approved following encouraging results, thus providing the first evidence of a more precise and personalized approach to AML therapy. Rewired metabolism has been described as a hallmark of cancer and substantial evidence of its role in AML establishment and maintenance has been recently accrued in preclinical models. Interestingly, unique metabolic changes are generated by specific AML recurrent mutations or in response to diverse AML therapies, thus creating actionable metabolic vulnerabilities in specific patient groups. In this review we will discuss the current evidence supporting a role for rewired metabolism in AML pathogenesis and how these metabolic changes can be leveraged to develop novel personalized therapies.
    Keywords:  acute myeloid leukemia; drug resistance; leukemic stem cell; metabolism; personalized therapy
  11. Front Oncol. 2021 ;11 677833
      The clinically ideal time point and optimal approach for the assessment of measurable residual disease (MRD) in patients with acute myeloid leukemia (AML) are still inconclusive. We investigated the clinical value of multiparameter flow cytometry-based MRD (MFC MRD) after induction (n = 492) and two cycles of consolidation (n = 421). The latter time point was proved as a superior indicator with independent prognostic significance for both relapse-free survival (RFS, HR = 3.635, 95% CI: 2.433-5.431, P <0.001) and overall survival (OS: HR = 3.511, 95% CI: 2.191-5.626, P <0.001). Furthermore, several representative molecular MRD markers were compared with the MFC MRD. Both approaches can establish prognostic value in patients with NPM1 mutations, and FLT3, C-KIT, or N-RAS mutations involved in kinase-related signaling pathways, while the combination of both techniques further refined the risk stratification. The detection of RUNX1-RUNX1T1 fusion transcripts achieved a considerable net reclassification improvement in predicting the prognosis. Conversely, for patients with biallelic CEBPA or DNMT3A mutations, only the MFC method was recommended due to the poor prognostic discriminability in tracking mutant transcripts. In conclusion, this study demonstrated that the MFC MRD after two consolidation cycles independently predicted clinical outcomes, and the integration of MFC and molecular MRD should depend on different types of AML-related genetic lesions.
    Keywords:  acute myeloid leukemia; measurable residual disease; molecular markers; multiparameter flow cytometry; prognosis
  12. Ann Hematol. 2021 Jun 10.
      Resistance remains the major clinical challenge for the therapy of Philadelphia chromosome-positive (Ph+) leukemia. With the exception of ponatinib, all approved tyrosine kinase inhibitors (TKIs) are unable to inhibit the common "gatekeeper" mutation T315I. Here we investigated the therapeutic potential of crizotinib, a TKI approved for targeting ALK and ROS1 in non-small cell lung cancer patients, which inhibited also the ABL1 kinase in cell-free systems, for the treatment of advanced and therapy-resistant Ph+ leukemia. By inhibiting the BCR-ABL1 kinase, crizotinib efficiently suppressed growth of Ph+ cells without affecting growth of Ph- cells. It was also active in Ph+ patient-derived long-term cultures (PD-LTCs) independently of the responsiveness/resistance to other TKIs. The efficacy of crizotinib was confirmed in vivo in syngeneic mouse models of BCR-ABL1- or BCR-ABL1T315I-driven chronic myeloid leukemia-like disease and in BCR-ABL1-driven acute lymphoblastic leukemia (ALL). Although crizotinib binds to the ATP-binding site, it also allosterically affected the myristol binding pocket, the binding site of GNF2 and asciminib (former ABL001). Therefore, crizotinib has a seemingly unique double mechanism of action, on the ATP-binding site and on the myristoylation binding pocket. These findings strongly suggest the clinical evaluation of crizotinib for the treatment of advanced and therapy-resistant Ph+ leukemia.
    Keywords:  Allosteric inhibition; BCR-ABL1; Compound mutations; Crizotinib; Philadelphia chromosome–positive leukemia; TKI resistance
  13. Oncogene. 2021 Jun 08.
      Artificial intelligence (AI) is about to make itself indispensable in the health care sector. Examples of successful applications or promising approaches range from the application of pattern recognition software to pre-process and analyze digital medical images, to deep learning algorithms for subtype or disease classification, and digital twin technology and in silico clinical trials. Moreover, machine-learning techniques are used to identify patterns and anomalies in electronic health records and to perform ad-hoc evaluations of gathered data from wearable health tracking devices for deep longitudinal phenotyping. In the last years, substantial progress has been made in automated image classification, reaching even superhuman level in some instances. Despite the increasing awareness of the importance of the genetic context, the diagnosis in hematology is still mainly based on the evaluation of the phenotype. Either by the analysis of microscopic images of cells in cytomorphology or by the analysis of cell populations in bidimensional plots obtained by flow cytometry. Here, AI algorithms not only spot details that might escape the human eye, but might also identify entirely new ways of interpreting these images. With the introduction of high-throughput next-generation sequencing in molecular genetics, the amount of available information is increasing exponentially, priming the field for the application of machine learning approaches. The goal of all the approaches is to allow personalized and informed interventions, to enhance treatment success, to improve the timeliness and accuracy of diagnoses, and to minimize technically induced misclassifications. The potential of AI-based applications is virtually endless but where do we stand in hematology and how far can we go?
  14. Leuk Res. 2021 Jun 06. pii: S0145-2126(21)00139-9. [Epub ahead of print]109 106638
      Cytoplasmic vacuoles, which are a morphological feature of dysplasia, can be observed under a microscope at initial diagnosis. Recently, this typical morphological feature has been found to be associated with impaired survival. To investigate the clinical significance of the grading of blasts with vacuoles in acute myeloid leukemia (AML), we retrospectively studied 152 patients newly diagnosed with non-M3 AML. The patients were categorized into three groups according to the percentage of blasts with vacuoles (>20 %, 11-20 %, 0-10 %). A high percentage of blasts with vacuoles (>20 %) was positively associated with the European Leukemia Net (2017-ELN) high-risk AML, a complex karyotype, TP53 and IDH1/2 mutations, and CD71 expression and negatively associated with the ELN low-risk category. Importantly, patients who had a higher percentage of blasts with vacuoles had a lower complete remission rate in response to first-cycle induction chemotherapy. The overall survival and event-free survival of patients who had a higher percentage of blasts with vacuoles were significantly shorter. Moreover, multivariate analysis showed that blast vacuolization was an independent high prognostic factor for AML. In conclusion, a higher percentage of leukemic blasts with vacuoles predicts worse outcomes in AML and may have potential as a prognostic marker.
    Keywords:  Acute myeloid leukemia; Clinical outcome; Gene mutation; Immunophenotype; Leukemic blasts; Vacuoles
  15. Blood. 2021 Jun 11. pii: blood.2019004638. [Epub ahead of print]
      EZH2, the enzymatic component of PRC2, has been identified as a key factor in hematopoiesis. EZH2 loss of function mutations have been found in myeloproliferative neoplasms, more particularly in myelofibrosis, but the precise function of EZH2 in megakaryopoiesis is not fully delineated. Here, we show that EZH2 inhibition by small molecules and shRNA induces MK commitment by accelerating lineage marker acquisition without change in proliferation. Later in differentiation, EZH2 inhibition blocks proliferation, polyploidization and decreases proplatelet formation. EZH2 inhibitors similarly reduce MK polyploidization and proplatelet formation in vitro and platelet level in vivo in a JAK2V617F background. In transcriptome profiling, the defect in proplatelet formation was associated with an aberrant actin cytoskeleton regulation pathway, whereas polyploidization was associated with an inhibition of expression of genes involved in DNA replication and repair, and an upregulation of CDK inhibitors, more particularly CDKN1A and CDKN2D. The knockdown of CDKN1A and at a lesser extend of CDKN2D could partially rescue the percentage of polyploid MKs. Moreover, H3K27me3 and EZH2 ChIP assays revealed that only CDKN1A is a direct EZH2 target while CDKN2D expression is not directly regulated by EZH2 suggesting that EZH2 controls MK polyploidization directly through CDKN1A and indirectly through CDKN2D.
  16. Front Immunol. 2021 ;12 653030
      DNA (cytosine-5)-methyltransferase 3A (DNMT3A)-mutated acute myeloid leukemia (AML) has a poor prognosis, but the exact mechanism is still unclear. Here, we aimed to explore the mechanism of immune escape in AML with DNMT3A mutation. We constructed a DNMT3A knockout clone and DNMT3A-R882H-mutated clones. RNA-seq results showed that transcription factors and macrophage inflammatory proteins were significantly downregulated in the DNMT3A mutant clones. KEGG enrichment and gene set enrichment analysis (GSEA) showed that a large number of genes were enriched in inflammatory immune-related pathways, such as the toll-like receptor signaling pathway. Therefore, we co-cultured AML cells with macrophages. The DNMT3A-mutated AML cells attenuated M1 macrophage polarization and resisted its killing effect in vitro and in vivo. In xenografts, the tumor volumes in the experimental group were significantly larger than those in the control group, and the proportion of M2 macrophages was significantly higher. After the co-culture, the increase in pro-inflammatory cytokine expression in the mutant cells was significantly lower than that in the control group, while that in immunosuppressive factors was not significantly different. In co-cultivated supernatants, the concentration of inflammatory factors in the experimental group was significantly lower than that in the control group, while that of immunosuppressive factors was significantly higher. Resistin significantly promoted the expression of inflammatory proteins in AML cells. It relieved the inhibitory effect of DNMT3A mutation, promoted the phenotypic recovery of the co-cultured macrophages, eliminated resistance, and regulated the immune microenvironment. Thus, resistin may serve as an ancillary drug for patients with DNMT3A-mutated AML.
    Keywords:  AML; DNMT3A; epigenetics; immune escape; immune microenvironment; macrophage polarization
  17. Sci Rep. 2021 Jun 09. 11(1): 12148
      Peposertib (M3814) is a potent and selective DNA-PK inhibitor in early clinical development. It effectively blocks non-homologous end-joining repair of DNA double-strand breaks (DSB) and strongly potentiates the antitumor effect of ionizing radiation (IR) and topoisomerase II inhibitors. By suppressing DNA-PK catalytic activity in the presence of DNA DSB, M3814 potentiates ATM/p53 signaling leading to enhanced p53-dependent antitumor activity in tumor cells. Here, we investigated the therapeutic potential of M3814 in combination with DSB-inducing agents in leukemia cells and a patient-derived tumor. We show that in the presence of IR or topoisomerase II inhibitors, M3814 boosts the ATM/p53 response in acute leukemia cells leading to the elevation of p53 protein levels as well as its transcriptional activity. M3814 synergistically sensitized p53 wild-type, but not p53-deficient, AML cells to killing by DSB-inducing agents via p53-dependent apoptosis involving both intrinsic and extrinsic effector pathways. The antileukemic effect was further potentiated by enhancing daunorubicin-induced myeloid cell differentiation. Further, combined with the fixed-ratio liposomal formulation of daunorubicin and cytarabine, CPX-351, M3814 enhanced the efficacy against leukemia cells in vitro and in vivo without increasing hematopoietic toxicity, suggesting that DNA-PK inhibition could offer a novel clinical strategy for harnessing the anticancer potential of p53 in AML therapy.
  18. Nat Struct Mol Biol. 2021 Jun;28(6): 487-500
      Fanconi anemia (FA) is a devastating hereditary disease characterized by bone marrow failure (BMF) and acute myeloid leukemia (AML). As FA-deficient cells are hypersensitive to DNA interstrand crosslinks (ICLs), ICLs are widely assumed to be the lesions responsible for FA symptoms. Here, we show that FA-mutated cells are hypersensitive to persistent replication stress and that FA proteins play a role in the break-induced-replication (BIR)-like pathway for fork restart. Both the BIR-like pathway and ICL repair share almost identical molecular mechanisms of 53BP1-BRCA1-controlled signaling response, SLX4- and FAN1-mediated fork cleavage and POLD3-dependent DNA synthesis, suggesting that the FA pathway is intrinsically one of the BIR-like pathways. Replication stress not only triggers BMF in FA-deficient mice, but also specifically induces monosomy 7, which is associated with progression to AML in patients with FA, in FA-deficient cells.
  19. Blood. 2021 Jun 11. pii: blood.2021011694. [Epub ahead of print]
      Treatment outcomes for pediatric patients with acute myeloid leukemia (AML) have continued to lag behind outcomes reported for children with acute lymphoblastic leukemia (ALL), in part because of the heterogeneity of the disease, a paucity of targeted therapies, and the relatively slow development of immunotherapy compared to ALL. In addition, we have reached the limits of treatment intensity and, even with outstanding supportive care, it is highly unlikely that further intensification of conventional chemotherapy alone will impact relapse rates. However, comprehensive genomic analyses and a more thorough characterization of the leukemic stem cell have provided insights that should lead to tailored and more effective therapies in the near future. In addition, new therapies are finally emerging, including the BCL-2 inhibitor venetoclax, CD33 and CD123-directed chimeric antigen receptor T cell therapy, CD123-directed antibody therapy, and menin inhibitors. Here we present four cases to illustrate some of the controversies regarding the optimal treatment of children with newly diagnosed or relapsed AML.
  20. Front Oncol. 2021 ;11 674720
      Tumor cells require a higher supply of nutrients for growth and proliferation than normal cells. It is well established that metabolic reprograming in cancers for increased nutrient supply exposes a host of targetable vulnerabilities. In this article we review the documented changes in expression patterns of amino acid metabolic enzymes and transporters in myeloid malignancies and the growing list of small molecules and therapeutic strategies used to disrupt amino acid metabolic circuits within the cell. Pharmacological inhibition of amino acid metabolism is effective in inducing cell death in leukemic stem cells and primary blasts, as well as in reducing tumor burden in in vivo murine models of human disease. Thus targeting amino acid metabolism provides a host of potential translational opportunities for exploitation to improve the outcomes for patients with myeloid malignancies.
    Keywords:  amino acids; metabolism; myeloid dysplasia; myeloid neoplasia; therapy
  21. J Clin Oncol. 2021 Jun 09. JCO2003380
      PURPOSE: Allogeneic hematopoietic cell transplantation (HCT) is the only potentially curative therapy for myelodysplastic syndromes (MDS), although it is infrequently offered to older patients. The relative benefits of HCT over non-HCT therapy in older patients with higher-risk MDS have not been defined.METHODS: We conducted a multicenter biologic assignment trial comparing reduced-intensity HCT to hypomethylating therapy or best supportive care in subjects 50-75 years of age with intermediate-2 or high-risk de novo MDS. The primary outcome was overall survival probability at 3 years. Between January 2014 and November 2018, we enrolled 384 subjects at 34 centers. Subjects were assigned to the Donor or No-Donor arms according to the availability of a matched donor within 90 days of study registration.
    RESULTS: The median follow-up time for surviving subjects was 34.2 months (range: 2.3-38 months) in the Donor arm and 26.9 months (range: 2.4-37.2 months) in the No-Donor arm. In an intention-to-treat analysis, the adjusted overall survival rate at 3 years in the Donor arm was 47.9% (95% CI, 41.3 to 54.1) compared with 26.6% (95% CI, 18.4 to 35.6) in the No-Donor arm (P = .0001) with an absolute difference of 21.3% (95% CI, 10.2 to 31.8). Leukemia-free survival at 3 years was greater in the Donor arm (35.8%; 95% CI, 29.8 to 41.8) compared with the No-Donor arm (20.6%; 95% CI, 13.3 to 29.1; P = .003). The survival benefit was seen across all subgroups examined.
    CONCLUSION: We observed a significant survival advantage in older subjects with higher-risk MDS who have a matched donor identified and underwent reduced-intensity HCT, when compared with those without a donor. HCT should be included as an integral part of MDS management plans in fit older adults with higher-risk MDS.
  22. Blood. 2021 Jun 10. pii: blood.2020006846. [Epub ahead of print]
      CRLF2-rearranged (CRLF2r) acute lymphoblastic leukemia (ALL) comprises over half of Philadelphia chromosome-like (Ph-like) ALL, is associated with poor outcome in children and adults. Overexpression of CRLF2 results in activation of JAK-STAT and parallel signaling pathways in experimental models, but existing small molecule inhibitors of Janus kinases show variable and limited efficacy. Here we evaluated the efficacy of proteolysis-targeting chimeras (PROTACs) directed against Janus kinases. Solving the structure of type I JAK inhibitors ruxolitinib and baricitinib bound to the JAK2 tyrosine kinase domain enabled the rational design and optimization of multiple series of cereblon (CRBN)-directed JAK PROTACs utilizing derivatives of JAK inhibitors, linkers and CRBN-specific molecular glues. The resulting JAK PROTACs were evaluated for target degradation, and activity tested in a panel of leukemia/lymphoma cell lines and xenograft models of kinase-driven ALL. Multiple PROTACs were developed that degraded Janus kinases and potently killed CRLF2--rearranged cell lines, the most active of which also degraded the known CRBN neosubstrate GSPT1, and suppressed proliferation of CRLF2-rearranged ALL in vivo. While dual JAK/GSPT1-degrading PROTACs were most potent, development and evaluation of multiple PROTACs in an extended panel of xenografts identified a potent JAK2-degrading GSPT1-sparing PROTAC that demonstrated efficacy in the majority of the kinase-driven xenografts which were otherwise unresponsive to type I JAK inhibitors. Together, these data show the potential of JAK-directed protein degradation as a therapeutic approach in JAK-STAT-driven ALL, and highlight the interplay of Janus kinase and GSPT1 degradation activity in this context.
  23. Immunity. 2021 May 28. pii: S1074-7613(21)00209-0. [Epub ahead of print]
      A common metabolic alteration in the tumor microenvironment (TME) is lipid accumulation, a feature associated with immune dysfunction. Here, we examined how CD8+ tumor infiltrating lymphocytes (TILs) respond to lipids within the TME. We found elevated concentrations of several classes of lipids in the TME and accumulation of these in CD8+ TILs. Lipid accumulation was associated with increased expression of CD36, a scavenger receptor for oxidized lipids, on CD8+ TILs, which also correlated with progressive T cell dysfunction. Cd36-/- T cells retained effector functions in the TME, as compared to WT counterparts. Mechanistically, CD36 promoted uptake of oxidized low-density lipoproteins (OxLDL) into T cells, and this induced lipid peroxidation and downstream activation of p38 kinase. Inhibition of p38 restored effector T cell functions in vitro, and resolution of lipid peroxidation by overexpression of glutathione peroxidase 4 restored functionalities in CD8+ TILs in vivo. Thus, an oxidized lipid-CD36 axis promotes intratumoral CD8+ T cell dysfunction and serves as a therapeutic avenue for immunotherapies.
    Keywords:  CD36; CD8(+) T cells; lipid peroxidation; oxidized lipids; tumor microenvironment
  24. Hemasphere. 2021 Jun;5(6): e572
      Patients with relapsed or refractory (r/r) acute myeloid leukemia (AML) have a poor prognosis and treatment remains challenging. For the majority of r/r patients, allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment approach. Salvage therapy is given in order to reduce the leukemia load prior to transplantation. Patients achieving complete remission prior to allogeneic HSCT have a more favorable outcome. Intensive salvage regimens commonly consist of an anthracycline and high-dose cytarabine backbone. Donor lymphocyte infusions have shown efficacy in patients relapsing after allogeneic HSCT. For patients who cannot be intensively treated (eg, elderly AML patients), outcome is generally very poor and combinations with novel agents are currently under investigation. Mutational analysis should be repeated at the time of relapse to identify aberrations that can be targeted with new agents. For r/r AML patients with mutated fms-related tyrosine kinase 3 (FLT3), gilteritinib has shown superior results to intensive salvage regimens. The US Food and Drug Administration (FDA) and European Medicines Agency (EMA) approved gilteritinib for FLT3 mutated r/r AML patients. Ivosidenib and enasidenib, inhibitors for mutated isocitrate dehydrogenase (IDH) 1 and 2, respectively, have received approval for IDH1/IDH2 mutated r/r AML by the FDA (not EMA). APR-246 restores the function of mutated TP53 and early study results are promising. Other agents targeting CD47, menin, neural-precursor-cell-expressed developmentally down-regulated 8, as well as bispecific antibodies or chimeric antigen receptor T cells are under investigation. Further trials are needed to understand how to best combine novel agents with each other or with chemotherapy.
  25. Bone Marrow Transplant. 2021 Jun;56(6): 1272-1280
      We retrospectively compared outcomes of a large series of adult patients with APL in CR2 receiving alloHSCT (n = 228) or autoHSCT (n = 341) reported to the European Society for Blood and Marrow Transplantation from January 2004 to December 2018. The 2-year cumulative incidence of non-relapse mortality was significantly higher for alloHSCT 17.3% (95% CI 12.5-22.8) compared with autoHSCT 2.7% (95% CI 1.2-5) (p = 0.001), while differences in relapse rate were not significant (28% versus 22.9%; p = 0.28). Leukemia-free survival (LFS) and overall survival (OS) favored autoHSCT with 74.5% (95% CI 69-79.2) and 82.4% (95% CI 77.3-86.5) compared with alloHSCT with 54.7% (95% CI 47.5-61.3) (p = 0.001) and 64.3% (95% CI 57.2-70.6), respectively (p = 0.001 and p = 0.001). Multivariable analysis showed significantly worse LFS after alloHSCT (HR 0.49; 95% CI 0.37-0.67; p < 0.0001), older age (p = 0.001), and shorter time from diagnosis to transplant (p = 0.00015). Similar results were obtained for OS. The study shows that autoHSCT resulted in better survival outcomes (LFS and OS) for APL in CR2. These results were mainly due to reduced NRM in the autoHSCT as compared to alloHSCT.
  26. Cell Rep. 2021 Jun 08. pii: S2211-1247(21)00562-3. [Epub ahead of print]35(10): 109212
      Obesity is an established risk factor for cancer in many tissues. In the mammalian intestine, a pro-obesity high-fat diet (HFD) promotes regeneration and tumorigenesis by enhancing intestinal stem cell (ISC) numbers, proliferation, and function. Although PPAR (peroxisome proliferator-activated receptor) nuclear receptor activity has been proposed to facilitate these effects, their exact role is unclear. Here we find that, in loss-of-function in vivo models, PPARα and PPARδ contribute to the HFD response in ISCs. Mechanistically, both PPARs do so by robustly inducing a downstream fatty acid oxidation (FAO) metabolic program. Pharmacologic and genetic disruption of CPT1A (the rate-controlling enzyme of mitochondrial FAO) blunts the HFD phenotype in ISCs. Furthermore, inhibition of CPT1A dampens the pro-tumorigenic consequences of a HFD on early tumor incidence and progression. These findings demonstrate that inhibition of a HFD-activated FAO program creates a therapeutic opportunity to counter the effects of a HFD on ISCs and intestinal tumorigenesis.
    Keywords:  Apc; Cpt1a; Ppar; fatty acid oxidation; high-fat diet; intestinal stem cells