The selective prolyl hydroxylase inhibitor IOX5 stabilizes HIF-1α and compromises development and progression of acute myeloid leukemia.

Acute myeloid leukemia (AML) is a largely incurable disease, for which new treatments are urgently needed. While leukemogenesis occurs in the hypoxic bone marrow, the therapeutic tractability of the hypoxia-inducible factor (HIF) system remains undefined. Given that inactivation of HIF-1α/HIF-2α promotes AML, a possible clinical strategy is to target the HIF-prolyl hydroxylases (PHDs), which promote HIF-1α/HIF-2α degradation. Here, we reveal that genetic inactivation of Phd1/Phd2 hinders AML initiation and progression, without impacting normal hematopoiesis. We investigated clinically used PHD inhibitors and a new selective PHD inhibitor (IOX5), to stabilize HIF-α in AML cells. PHD inhibition compromises AML in a HIF-1α-dependent manner to disable pro-leukemogenic pathways, re-program metabolism and induce apoptosis, in part via upregulation of BNIP3. Notably, concurrent inhibition of BCL-2 by venetoclax potentiates the anti-leukemic effect of PHD inhibition. Thus, PHD inhibition, with consequent HIF-1α stabilization, is a promising nontoxic strategy for AML, including in combination with venetoclax.

Molecular MRD is strongly prognostic in patients with NPM1-mutated AML receiving venetoclax-based nonintensive therapy.

ABSTRACT: Assessment of measurable residual disease (MRD) by quantitative reverse transcription polymerase chain reaction is strongly prognostic in patients with NPM1-mutated acute myeloid leukemia (AML) treated with intensive chemotherapy; however, there are no data regarding its utility in venetoclax-based nonintensive therapy, despite high efficacy in this genotype. We analyzed the prognostic impact of NPM1 MRD in an international real-world cohort of 76 previously untreated patients with NPM1-mutated AML who achieved complete remission (CR)/CR with incomplete hematological recovery following treatment with venetoclax and hypomethylating agents (HMAs) or low-dose cytarabine (LDAC). A total of 44 patients (58%) achieved bone marrow (BM) MRD negativity, and a further 14 (18%) achieved a reduction of ≥4 log10 from baseline as their best response, with no difference between HMAs and LDAC. The cumulative rates of BM MRD negativity by the end of cycles 2, 4, and 6 were 25%, 47%, and 50%, respectively. Patients achieving BM MRD negativity by the end of cycle 4 had 2-year overall of 84% compared with 46% if MRD was positive. On multivariable analyses, MRD negativity was the strongest prognostic factor. A total of 22 patients electively stopped therapy in BM MRD-negative remission after a median of 8 cycles, with 2-year treatment-free remission of 88%. In patients with NPM1-mutated AML attaining remission with venetoclax combination therapies, NPM1 MRD provides valuable prognostic information.

C/EBPα Confers Dependence to Fatty Acid Anabolic Pathways and Vulnerability to Lipid Oxidative Stress-Induced Ferroptosis in FLT3-Mutant Leukemia.

Although transcription factor CCAAT-enhancer binding protein α (C/EBPα) is critical for normal and leukemic differentiation, its role in cell and metabolic homeostasis is largely unknown in cancer. Here, multiomics analyses uncovered a coordinated activation of C/EBPα and Fms-like tyrosine kinase 3 (FLT3) that increased lipid anabolism in vivo and in patients with FLT3-mutant acute myeloid leukemia (AML). Mechanistically, C/EBPα regulated the fatty acid synthase (FASN)-stearoyl-CoA desaturase (SCD) axis to promote fatty acid (FA) biosynthesis and desaturation. We further demonstrated that FLT3 or C/EBPα inactivation decreased monounsaturated FA incorporation to membrane phospholipids through SCD downregulation. Consequently, SCD inhibition enhanced susceptibility to lipid redox stress that was exploited by combining FLT3 and glutathione peroxidase 4 inhibition to trigger lipid oxidative stress, enhancing ferroptotic death of FLT3-mutant AML cells. Altogether, our study reveals a C/EBPα function in lipid homeostasis and adaptation to redox stress, and a previously unreported vulnerability of FLT3-mutant AML to ferroptosis with promising therapeutic application. SIGNIFICANCE: FLT3 mutations are found in 30% of AML cases and are actionable by tyrosine kinase inhibitors. Here, we discovered that C/EBPα regulates FA biosynthesis and protection from lipid redox stress downstream mutant-FLT3 signaling, which confers a vulnerability to ferroptosis upon FLT3 inhibition with therapeutic potential in AML. This article is highlighted in the In This Issue feature, p. 1501.

Mannose metabolism inhibition sensitizes acute myeloid leukaemia cells to therapy by driving ferroptotic cell death.

Resistance to standard and novel therapies remains the main obstacle to cure in acute myeloid leukaemia (AML) and is often driven by metabolic adaptations which are therapeutically actionable. Here we identify inhibition of mannose-6-phosphate isomerase (MPI), the first enzyme in the mannose metabolism pathway, as a sensitizer to both cytarabine and FLT3 inhibitors across multiple AML models. Mechanistically, we identify a connection between mannose metabolism and fatty acid metabolism, that is mediated via preferential activation of the ATF6 arm of the unfolded protein response (UPR). This in turn leads to cellular accumulation of polyunsaturated fatty acids, lipid peroxidation and ferroptotic cell death in AML cells. Our findings provide further support to the role of rewired metabolism in AML therapy resistance, unveil a connection between two apparently independent metabolic pathways and support further efforts to achieve eradication of therapy-resistant AML cells by sensitizing them to ferroptotic cell death.

Vitamin B5 and succinyl-CoA improve ineffective erythropoiesis in SF3B1-mutated myelodysplasia.

Patients with myelodysplastic syndrome and ring sideroblasts (MDS-RS) present with symptomatic anemia due to ineffective erythropoiesis that impedes their quality of life and increases morbidity. More than 80% of patients with MDS-RS harbor splicing factor 3B subunit 1 (SF3B1) mutations, the founder aberration driving MDS-RS disease. Here, we report how mis-splicing of coenzyme A synthase (COASY), induced by mutations in SF3B1, affects heme biosynthesis and erythropoiesis. Our data revealed that COASY was up-regulated during normal erythroid differentiation, and its silencing prevented the formation of erythroid colonies, impeded erythroid differentiation, and precluded heme accumulation. In patients with MDS-RS, loss of protein due to COASY mis-splicing led to depletion of both CoA and succinyl-CoA. Supplementation with COASY substrate (vitamin B5) rescued CoA and succinyl-CoA concentrations in SF3B1mut cells and mended erythropoiesis differentiation defects in MDS-RS primary patient cells. Our findings reveal a key role of the COASY pathway in erythroid maturation and identify upstream and downstream metabolites of COASY as a potential treatment for anemia in patients with MDS-RS.

A Phase I/II Open-Label Study of Molibresib for the Treatment of Relapsed/Refractory Hematologic Malignancies.

PURPOSE: Molibresib is a selective, small molecule inhibitor of the bromodomain and extra-terminal (BET) protein family. This was an open-label, two-part, Phase I/II study investigating molibresib monotherapy for the treatment of hematological malignancies (NCT01943851). PATIENTS AND METHODS: Part 1 (dose escalation) determined the recommended Phase 2 dose (RP2D) of molibresib in patients with acute myeloid leukemia (AML), Non-Hodgkin lymphoma (NHL), or multiple myeloma. Part 2 (dose expansion) investigated the safety and efficacy of molibresib at the RP2D in patients with relapsed/refractory myelodysplastic syndrome (MDS; as well as AML evolved from antecedent MDS) or cutaneous T-cell lymphoma (CTCL). The primary endpoint in Part 1 was safety and the primary endpoint in Part 2 was objective response rate (ORR). RESULTS: There were 111 patients enrolled (87 in Part 1, 24 in Part 2). Molibresib RP2Ds of 75 mg daily (for MDS) and 60 mg daily (for CTCL) were selected. Most common Grade 3+ adverse events included thrombocytopenia (37%), anemia (15%), and febrile neutropenia (15%). Six patients achieved complete responses [3 in Part 1 (2 AML, 1 NHL), 3 in Part 2 (MDS)], and 7 patients achieved partial responses [6 in Part 1 (4 AML, 2 NHL), 1 in Part 2 (MDS)]. The ORRs for Part 1, Part 2, and the total study population were 10% [95% confidence interval (CI), 4.8-18.7], 25% (95% CI, 7.3-52.4), and 13% (95% CI, 6.9-20.6), respectively. CONCLUSIONS: While antitumor activity was observed with molibresib, use was limited by gastrointestinal and thrombocytopenia toxicities. Investigations of molibresib as part of combination regimens may be warranted.

Mutational synergy during leukemia induction remodels chromatin accessibility, histone modifications and three-dimensional DNA topology to alter gene expression.

Altered transcription is a cardinal feature of acute myeloid leukemia (AML); however, exactly how mutations synergize to remodel the epigenetic landscape and rewire three-dimensional DNA topology is unknown. Here, we apply an integrated genomic approach to a murine allelic series that models the two most common mutations in AML: Flt3-ITD and Npm1c. We then deconvolute the contribution of each mutation to alterations of the epigenetic landscape and genome organization, and infer how mutations synergize in the induction of AML. Our studies demonstrate that Flt3-ITD signals to chromatin to alter the epigenetic environment and synergizes with mutations in Npm1c to alter gene expression and drive leukemia induction. These analyses also allow the identification of long-range cis-regulatory circuits, including a previously unknown superenhancer of Hoxa locus, as well as larger and more detailed gene-regulatory networks, driven by transcription factors including PU.1 and IRF8, whose importance we demonstrate through perturbation of network members.

The Role of Metabolism in the Development of Personalized Therapies in Acute Myeloid Leukemia.

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.

Design, implementation and clinical utility of next generation sequencing in myeloid malignancies: acute myeloid leukaemia and myelodysplastic syndrome.

Next generation sequencing (NGS) based technology has contributed enormously to our understanding of the biology of myeloid malignancies including acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS). Assessment of clinically important mutations by NGS is a powerful tool to define diagnosis, determine prognostic risk, monitor measurable residual disease and uncover predictive mutational markers/therapeutic targets, and is now a routine component in the workup and monitoring of haematological disorders. There are many technical challenges in the design, implementation, analysis and reporting of NGS based results, and expert interpretation is essential. It is vital to distinguish relevant somatic disease associated mutations from those that are known polymorphisms, rare germline variants and clonal haematopoiesis of indeterminate potential (CHIP) associated variants. This review highlights and addresses the technical and biological challenges that should be considered before the implementation of NGS based testing in diagnostic laboratories and seeks to outline the essential and expanding role NGS plays in myeloid malignancies. Broad aspects of NGS panel design and reporting including inherent technological, biological and economic considerations are covered, following which the utility of NGS based testing in AML and MDS are discussed. In current practice, patient care is now strongly shaped by the results of NGS assessment and is considered a vital piece of the puzzle for clinicians as they manage these complex haematological disorders.

Bone Marrow Mesenchymal Stem Cells Support Acute Myeloid Leukemia Bioenergetics and Enhance Antioxidant Defense and Escape from Chemotherapy.

Like normal hematopoietic stem cells, leukemic stem cells depend on their bone marrow (BM) microenvironment for survival, but the underlying mechanisms remain largely unknown. We have studied the contribution of nestin+ BM mesenchymal stem cells (BMSCs) to MLL-AF9-driven acute myeloid leukemia (AML) development and chemoresistance in vivo. Unlike bulk stroma, nestin+ BMSC numbers are not reduced in AML, but their function changes to support AML cells, at the expense of non-mutated hematopoietic stem cells (HSCs). Nestin+ cell depletion delays leukemogenesis in primary AML mice and selectively decreases AML, but not normal, cells in chimeric mice. Nestin+ BMSCs support survival and chemotherapy relapse of AML through increased oxidative phosphorylation, tricarboxylic acid (TCA) cycle activity, and glutathione (GSH)-mediated antioxidant defense. Therefore, AML cells co-opt energy sources and antioxidant defense mechanisms from BMSCs to survive chemotherapy.

Does Outcome/Survival of Patients With Myelodysplastic Syndromes Should Be Predicted by Reduced Levels of ADAMTS-13? Results From a Pilot Study.

INTRODUCTION: Von Willebrand factor (vWF) cleaving protease ADAMTS-13 has a key role for maintaining normal size of vWF. A deficiency or dysfunction of vWF cleaving protease is associated with ultra large vWF multimers and thrombotic microangiopathy. Patients with cancers have reduced levels of vWF cleaving protease. In this pilot study, we have evaluated whether or not deficiencies of ADAMTS-13 were present in myelodysplastic syndromes (MDS). Moreover, we assessed if a reduction in basal levels of ADAMTS-13 may play a role in the prognosis of MDS. PATIENTS AND METHODS: We measured and compared the levels of vWF cleaving protease ADAMTS-13 in 100 patients with MDS and 35 healthy controls. Patients were divided into 2 groups according to the International Prognostic Scoring System: group I consisting of 44 patients with low-risk MDS and group II of 56 patients with high-risk MDS. Patients with high-risk and low-risk MDS presented significantly lower levels of ADAMTS-13 than controls (P < .001 and P = .0177, respectively). High-risk patients had significantly lower levels of ADAMTS-13 when compared with the low-risk group (P < .001). RESULTS: We found that reduced levels of ADAMTS-13 have a relationship with overall survival (P < .001). Statistical analysis showed that ADAMTS-13 correlates with cytogenetics (P < .001) and a tendency of slight correlation with platelet count and basal levels of ADAMTS-13 (R, 0.35; P value, 0.001). Moreover, we found that levels of ADAMTS-13 have correlation with response to treatment (P < .001). CONCLUSIONS: ADAMTS-13 in MDS might represent a surrogate marker of prognosis, response to therapy, or disease progression. Further studies are needed.

Cohesin-dependent regulation of gene expression during differentiation is lost in cohesin-mutated myeloid malignancies.

Cohesin complex disruption alters gene expression, and cohesin mutations are common in myeloid neoplasia, suggesting a critical role in hematopoiesis. Here, we explore cohesin dynamics and regulation of hematopoietic stem cell homeostasis and differentiation. Cohesin binding increases at active regulatory elements only during erythroid differentiation. Prior binding of the repressive Ets transcription factor Etv6 predicts cohesin binding at these elements and Etv6 interacts with cohesin at chromatin. Depletion of cohesin severely impairs erythroid differentiation, particularly at Etv6-prebound loci, but augments self-renewal programs. Together with corroborative findings in acute myeloid leukemia and myelodysplastic syndrome patient samples, these data suggest cohesin-mediated alleviation of Etv6 repression is required for dynamic expression at critical erythroid genes during differentiation and how this may be perturbed in myeloid malignancies.

Contrasting requirements during disease evolution identify EZH2 as a therapeutic target in AML.

Epigenetic regulators, such as EZH2, are frequently mutated in cancer, and loss-of-function EZH2 mutations are common in myeloid malignancies. We have examined the importance of cellular context for Ezh2 loss during the evolution of acute myeloid leukemia (AML), where we observed stage-specific and diametrically opposite functions for Ezh2 at the early and late stages of disease. During disease maintenance, WT Ezh2 exerts an oncogenic function that may be therapeutically targeted. In contrast, Ezh2 acts as a tumor suppressor during AML induction. Transcriptional analysis explains this apparent paradox, demonstrating that loss of Ezh2 derepresses different expression programs during disease induction and maintenance. During disease induction, Ezh2 loss derepresses a subset of bivalent promoters that resolve toward gene activation, inducing a feto-oncogenic program that includes genes such as Plag1, whose overexpression phenocopies Ezh2 loss to accelerate AML induction in mouse models. Our data highlight the importance of cellular context and disease phase for the function of Ezh2 and its potential therapeutic implications.

Prognostic Models Turn the Heat(IT)up on FLT3ITD -Mutated AML.

The presence of internal tandem duplications (ITD) in the FLT3 receptor tyrosine kinase gene have long been known to confer a poor prognosis in patients with acute myeloid leukemia. Now, specific structural features of the ITDs are also suggested to alter patient outcome, including sensitivity to targeted therapies, prompting their evaluation in therapeutic algorithms.See related article by Schwartz et al., p. 573.