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The development and survival of cancer cells require adaptive mechanisms to stress. Such adaptations can confer intrinsic vulnerabilities, enabling the selective targeting of cancer cells. Through a pooled in vivo short hairpin RNA (shRNA) screen, we identified the adenosine triphosphatase associated with diverse cellular activities (AAA-ATPase) valosin-containing protein (VCP) as a top stress-related vulnerability in acute myeloid leukemia (AML). We established that AML was the most responsive disease to chemical inhibition of VCP across a panel of 16 cancer types. The sensitivity to VCP inhibition of human AML cell lines, primary patient samples, and syngeneic and xenograft mouse models of AML was validated using VCP-directed shRNAs, overexpression of a dominant-negative VCP mutant, and chemical inhibition. By combining mass spectrometry-based analysis of the VCP interactome and phospho-signaling studies, we determined that VCP is important for ataxia telangiectasia mutated (ATM) kinase activation and subsequent DNA repair through homologous recombination in AML. A second-generation VCP inhibitor, CB-5339, was then developed and characterized. Efficacy and safety of CB-5339 were validated in multiple AML models, including syngeneic and patient-derived xenograft murine models. We further demonstrated that combining DNA-damaging agents, such as anthracyclines, with CB-5339 treatment synergizes to impair leukemic growth in an MLL-AF9-driven AML murine model. These studies support the clinical testing of CB-5339 as a single agent or in combination with standard-of-care DNA-damaging chemotherapy for the treatment of AML.

Simple Summary Acute myeloid leukemia (AML) accounts for 7.6% of hematopoietic malignancies with a long-term survival of less than 20%. Better understanding its physiopathology and finding new treatments remain important issues. In the current review, the authors discuss how genetic engineering technologies improvement allowed a better genetic characterization of AML. Such molecular dissection of the AML genome had two direct clinical impacts: a prognostic contribution by defining a new molecular classification of AML which guides therapeutic regimen intensity, and a therapeutic impact by allowing the identification of new therapeutic targets. New genome editing tools and animal models have also paved the way for a better understanding of AML leukemogenesis. Their impact is also summarized in this review. The combination of descriptive and functional genetics may ultimately be the key to improving the prognosis of this dismal disease. Abstract Over the past decades, genetic advances have allowed a more precise molecular characterization of AML with the identification of novel oncogenes and tumor suppressors as part of a comprehensive AML molecular landscape. Recent advances in genetic sequencing tools also enabled a better understanding of AML leukemogenesis from the preleukemic state to posttherapy relapse. These advances resulted in direct clinical implications with the definition of molecular prognosis classifications, the development of treatment recommendations based on minimal residual disease (MRD) measurement and the discovery of novel targeted therapies, ultimately improving AML patients’ overall survival. The more recent development of functional genomic studies, pushed by novel molecular biology technologies (short hairpin RNA (shRNA) and CRISPR-Cas9) and bioinformatics tools design on one hand, along with the engineering of humanized physiologically relevant animal models on the other hand, have opened a new genomics era resulting in a greater knowledge of AML physiopathology. Combining descriptive and functional genomics will undoubtedly open the road for an AML cure within the next decades.

Place: Oxford Publisher: Pergamon-Elsevier Science Ltd WOS:000551658300034; Phagocytes, especially neutrophils, can produce reactive oxygen species (ROS), through the activation of the NADPH oxidase (NOX2). Although this enzyme is crucial for host-pathogen defense, ROS production by neutrophils can be harmful in several pathologies such as cardiovascular diseases or chronic pulmonary diseases. The ROS production by NOX2 involves the assembly of the cytosolic subunits (p67(phox), p47(phox), and p40(phox)) and Rac with the membrane subunits (gp91(phox) and p22(phox)). Many studies are devoted to the activation of NOX2. However, the mechanisms that cause NADPH oxidase deactivation and thus terminate ROS production are not well known. Here we investigated the ability of class I phosphoinositide 3-kinases (PI3Ks) to sustain NADPH oxidase activation. The NADPH oxidase activation was triggered by seeding neutrophil-like PLB-985 cells, or human neutrophils on immobilized fibrinogen. Adhesion of the neutrophils, mediated by beta 2 integrins, induced activation of the NADPH oxidase and translocation of the cytosolic subunits at the plasma membrane. Inhibition of class I PI3Ks, and especially PI3K beta, terminated ROS production. This deactivation of NOX2 is due to the release of the cytosolic subunits, p67(phox) and p47(phox) from the plasma membrane. Overexpression of an active form of Rac 1 did not prevent the drop of ROS production upon inhibition of class I PI3Ks. Moreover, the phosphorylation of p47(phox) at S328, a potential target of kinases activated by the PI3K pathway, was unchanged. Our results indicate that the experimental downregulation of class I PI3K products triggers the plasma membrane NADPH oxidase deactivation. Release of p47(phox) from the plasma membrane may involve its PX domains that bind PI3K products.

Pour la troisième année, dans le cadre du module d’enseignement « Physiopathologie de la signalisation » proposé par l’université Paris-sud, les étudiants du Master « Biologie Santé » de l’université Paris-Saclay se sont confrontés à l’écriture scientifique. Ils ont sélectionné 8 articles scientifiques récents dans le domaine de la signalisation cellulaire présentant des résultats originaux, via des approches expérimentales variées, sur des thèmes allant des relations hôte-pathogène aux innovations thérapeutiques, en passant par la signalisation hépatique et le métabolisme. Après un travail préparatoire réalisé avec l’équipe pédagogique, les étudiants, organisés en binômes, ont ensuite rédigé, guidés par des chercheurs, une Nouvelle soulignant les résultats majeurs et l’originalité de l’article étudié. Ils ont beaucoup apprécié cette initiation à l’écriture d’articles scientifiques et, comme vous pourrez le lire, se sont investis dans ce travail avec enthousiasme ! Une de ces Nouvelles est publiée dans ce numéro, les autres le seront dans les prochains numéros de m/s.

Introduction: MPN are a heterogeneous group of chronic hematological malignancies often resulting from a combination of a driver gene mutation (JAK2, MPL or CALR) and a variety of somatic mutations harboring diverse prognosis values. A subset of MPN patients carry somatic mutations in the hematopoietic transcription factor NFE2 (nuclear factor erythroid 2) resulting in a functionally enhanced truncated form of NFE2 (Jutzi JS et al., JEM, 2013). Moreover, epigenetically induced overexpression of NFE2 has recently been reported in the majority of MPN patients (Peeken JC et al., Blood, 2018). In transgenic murine models, NFE2 overexpression results in an MPN phenotype (thrombocytosis, leukocytosis, EPO-independent colony formation, characteristic bone marrow histology and expansion of stem and progenitor compartments) and has recently been shown to predispose to the acquisition of additional genetic abnormalities and subsequent leukemic transformation (Kaufmann KB et al., JEM, 2012) (Jutzi JS et al., Blood, 2019). However, clinical impact of NFE2 mutations in MPN patients remains unknown. The aim of this study was to evaluate the phenotypic characteristics and prognostic impact of NFE2 somatic mutations in a large mono-centric cohort of MPN patients. Methods: A total of 1243 consecutive patients were diagnosed with MPN according to WHO criteria and followed in our hospital between January 2011 and May 2020. This study included 707 of them in whom a next-generation sequencing (NGS) molecular analysis targeting 36 myeloid genes was performed at diagnosis and/or during follow-up. Clinical and biological characteristics at time of diagnosis and follow-up were collected from medical charts and electronic medical records. Statistical analyses were performed using the STATA software (STATA 15.0 Corporation, College Station, TX). Results: In our cohort, 411 patients presented with polycythemia vera (PV), 577 with essential thrombocythemia (ET), 184 with primary or pre-fibrotic myelofibrosis (PMF), 59 with unclassified MPN and 12 with MDS/MPN. Median age at diagnosis was 51 years [40-63]. 73.1% patients had a JAK2V617F mutation, 14.1% a CALR mutation and 3.3% a MPL mutation. Overall, 64 (9.05%) patients harbored a NFE2 mutation with a variant allelic frequency (VAF) ≥ 0.5% and 36 had a VAF ≥ 5%, the latest were considered as NFE2 mutated for the rest of the study as VAF Conclusion: In this retrospective study we show that presence of NFE2 mutations with a VAF ≥5% is independently associated with an increased risk of leukemic transformation and shorter overall survival. These findings are in line with recently reported animal models and suggest that NFE2 mutations screening should be routinely performed in MPN patients. Disclosures Rea: Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees. Kiladjian:AOP Orphan: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Benajiba:Gilead Foundation: Research Funding.

Introduction: Next generation sequencing (NGS) studies identified additional somatic mutations impacting disease evolution and prognosis in MPN. SF3B1, a component of the U2 small nuclear ribonucleoprotein splicing complex, is frequently mutated in myelodysplastic syndromes where it has been proposed to define a new entity (Malcovati et. al. Blood 2020). In MPN, SF3B1 is mutated in approximately 10% of patients with primary myelofibrosis (PMF) and 3-5% with polycytemia vera or essential thrombocytemia (ET). Recent reports suggested that spliceosome mutations may adversely affect myelofibrosis free survival (MFS) in ET (Tefferi et. al. Br J Haematol. 2020). The main objective of this study was to evaluate the impact of the concomitant presence of driver (JAK2, MPLor CALR) and SF3B1 clonal or sub-clonal mutations on MPN phenotype and evolution in a large single center cohort of MPN patients. Methods: A total of 1243 consecutive patients were diagnosed with MPN according to WHO criteria between January 2011 and May 2020 in our center, of whom 707 had molecular analysis by NGS targeting a panel of 36 myeloid genes performed at diagnosis and/or during follow-up. Significant variants were retained with a sensitivity of 0.5%. Patients were grouped according to variant allele frequencies (VAF) determined by NGS as "driver" SF3B1mutated patients when driver and SF3B1 mutations VAF were similar (double mutated clone), and as "non-driver" SF3B1 mutants when SF3B1VAF was lower than that of the driver mutation, suggestive of a sub-clone. 4 patients with SF3B1 mutations but no driver mutation were excluded. We then compared the characteristics and outcomes of 3 groups of patients according to their SF3B1 mutational status: wild type (WT), driver and non-driver SF3B1 mutations. Results: A total of 39/703 (5.6%) patients had SF3B1 mutations, of whom 11/39 (28.2%) and 28/39 (71.8%) harbored driver and non-driver SF3B1mutations, respectively. Driver SF3B1 mutations were associated with PMF (OR 6.1, 95%CI [1.1; 33.6], p= 0.039) and MPN unclassified (OR 15.6,95%CI [1.1; 116.5], p= 0.007) subtypes, presence of immature myeloid cells ≥ 2% (OR 9.3, CI [2.6; 32.8], p= 0.001) and peripheral blasts ≥ 1% (OR 5.0,95%CI [1.0; 24.7], p= 0.047) at diagnosis (Figure A). Other variables were not significantly different between patients with driver, non-driver and WT SF3B1, including age, driver mutation type, MPN-related symptoms, cytogenetics and high molecular risk mutations (ASXL1, EZH2, SRSF2, IDH1/2or U2AF1). There was no significant difference in the response to therapy: complete hematological response was seen in 5/11 (45.5%), 10/28 (35.7%) and 327/664 (49.3%) of patients with driver, non-driver and WT SF3B1 respectively. After a median follow-up of 103.7 months IQR [47.2; 175.6], evolution to myelofibrosis occurred in 5/7 (71.4%), 6/20 (30.0%) and 99/564 (17.6%) of patients with driver, non-driver and WT SF3B1 respectively. Interestingly, driver SF3B1 but not non-driver SF3B1 mutational status adversely impacted MFS (OR 7.56,95%CI[2.95; 19.38], p Conclusion: This study in a large cohort of MPN patients highlights for the first time to our knowledge the adverse impact on MFS of SF3B1 and MPN-driver co-mutated clones. In contrast, presence of an SF3B1 mutation at sub-clonal level didn't increase the risk of MF development. In line with our findings, a recent study reported an association between rapid progression to myelofibrosis and SF3B1 mutations in patients with age-related clonal hematopoiesis (Bartels et al. Leukemia 2020). Further studies are warranted to confirm our results on independent cohorts and to investigate the mechanisms of bone marrow fibrosis development in patients with SF3B1 and MPN-drivermutations. Disclosures Rea: Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees. Kiladjian:BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; AOP Orphan: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees. Benajiba:Gilead Foundation: Research Funding.