An In Vivo CRISPR Screening Platform for Prioritizing Therapeutic Targets in AML

CRISPR-Cas9-based genetic screens have successfully identified cell type-dependent liabilities in cancer, including acute myeloid leukemia (AML), a devastating hematologic malignancy with poor overall survival. Because most of these screens have been performed in vitro using established cell lines, evaluating the physiologic relevance of these targets is critical. We have established a CRISPR screening approach using orthotopic xenograft models to validate and prioritize AML-enriched dependencies in vivo, including in CRISPR-competent AML patient-derived xenograft (PDX) models tractable for genome editing. Our integrated pipeline has revealed several targets with translational value, including SLC5A3 as a metabolic vulnerability for AML addicted to exogenous myo-inositol and MARCH5 as a critical guardian to prevent apoptosis in AML. MARCH5 repression enhanced the efficacy of BCL2 inhibitors such as venetoclax, further highlighting the clinical potential of targeting MARCH5 in AML. Our study provides a valuable strategy for discovery and prioritization of new candidate AML therapeutic targets. SIGNIFICANCE: There is an unmet need to improve the clinical outcome of AML. We developed an integrated in vivo screening approach to prioritize and validate AML dependencies with high translational potential. We identified SLC5A3 as a metabolic vulnerability and MARCH5 as a critical apoptosis regulator in AML, both of which represent novel therapeutic opportunities.This article is highlighted in the In This Issue feature, p. 275

Vitamin D Receptor Controls Cell Stemness in Acute Myeloid Leukemia and in Normal Bone Marrow.

Vitamin D (VD) is a known differentiating agent, but the role of VD receptor (VDR) is still incompletely described in acute myeloid leukemia (AML), whose treatment is based mostly on antimitotic chemotherapy. Here, we present an unexpected role of VDR in normal hematopoiesis and in leukemogenesis. Limited VDR expression is associated with impaired myeloid progenitor differentiation and is a new prognostic factor in AML. In mice, the lack of Vdr results in increased numbers of hematopoietic and leukemia stem cells and quiescent hematopoietic stem cells. In addition, malignant transformation of Vdr-/- cells results in myeloid differentiation block and increases self-renewal. Vdr promoter is methylated in AML as in CD34+ cells, and demethylating agents induce VDR expression. Association of VDR agonists with hypomethylating agents promotes leukemia stem cell exhaustion and decreases tumor burden in AML mouse models. Thus, Vdr functions as a regulator of stem cell homeostasis and leukemic propagation

Epitope-engineered human hematopoietic stem cells are shielded from CD123-targeted immunotherapy

Targeted eradication of transformed or otherwise dysregulated cells using monoclonal antibodies (mAb), antibody-drug conjugates (ADC), T cell engagers (TCE), or chimeric antigen receptor (CAR) cells is very effective for hematologic diseases. Unlike the breakthrough progress achieved for B cell malignancies, there is a pressing need to find suitable antigens for myeloid malignancies. CD123, the interleukin-3 (IL-3) receptor alpha-chain, is highly expressed in various hematological malignancies, including acute myeloid leukemia (AML). However, shared CD123 expression on healthy hematopoietic stem and progenitor cells (HSPCs) bears the risk for myelotoxicity. We demonstrate that epitope-engineered HSPCs were shielded from CD123-targeted immunotherapy but remained functional, while CD123-deficient HSPCs displayed a competitive disadvantage. Transplantation of genome-edited HSPCs could enable tumor-selective targeted immunotherapy while rebuilding a fully functional hematopoietic system. We envision that this approach is broadly applicable to other targets and cells, could render hitherto undruggable targets accessible to immunotherapy, and will allow continued posttransplant therapy, for instance, to treat minimal residual disease (MRD)

Régulation des voies de signalisation P13K/Akt et mTOR dans les leucémies aiguës myéloïdes (implications physiopathologiques et thérapeutiques)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Etude des effets du composé BEZ235, inhibiteur double des kinases PI3K et mTOR dans les leucémies aiguës myéloïdes

PARIS-BIUP (751062107) / SudocSudocFranceF

Lymphomes B diffus à grandes cellules primitifs osseux (une étude rétrospective sur 41 patients)

PARIS7-Xavier Bichat (751182101) / SudocSudocFranceF

Intérêt thérapeutique de la metformine dans les leucémies aigues myéloïdes

Les leucémies aigues myéloïdes (LAM) résultent de l'acquisition d'un avantage de prolifération et/ou de survie de progéniteurs myéloïdes immatures. L'activation de voies de signalisation intracellulaires, comme mTORC1, PI3K/Akt ou ERK/MAPK, contribue à ce processus. La voie mTORC1 (mammalian Target Of Rapamycin Complex 1) est constitutivement activée dans la plupart des échantillons de LAM et favorise la croissance cellulaire via le contrôle de la synthèse protéique. Cette voie est inhibée de manière physiologique par la kinase dépendant de l'AMP (ou AMPK) en réponse à une déprivation énergétique de la cellule. Nous avons ainsi étudié la capacité d'un agoniste pharmacologique de l'AMPK, la metformine, à inhiber la voie mTORC 1 dans les LAM.Nos résultats, essentiellement obtenus à partir d'échantillons de cellules primaires de LAM, montrent que la metformine active de manière très spécifique l'axe LKB 1/AMPK, ce qui se traduit par une inhibition des cibles de mTOR, la P70S6K et surtout le régulateur traductionnel 4E-BPI. L'accumulation de formes déphosphorylées de 4E BPI inhibe la traduction cap dépendante des ARNm, ce qui se traduit par une diminution de l'expression de protéines oncogéniques comme c-Myc, Cycline D1 et Bcl-xL.La metformine induit d'importants effets anti-leucémiques ex vivo, réduisant la prolifération cellulaire, inhibant la capacité clonogénique et induisant l'apoptose caspase dépendante des blastes de LAM. Cette molécule induit en revanche peu d'effets sur les cellules hématopoïétiques normales immatures CD34+ ex vivo, suggérant un index thérapeutique favorable dans le système hématopoïétique. De plus, la metformine réduit la croissance tumorale de la lignée leucémique humaine MV4-11 transplantée dans des souris nude sans effet toxique majeur chez ces animaux, démontrant son efficacité in vivo.L'utilisation thérapeutique de la metformine ou d'autres agonistes de l'AMPK peut ainsi être envisagée chez des patients atteints de LAM. éventuellement en traitement adjuvant à la chimiothérapie conventiokelle.ROUEN-BU Médecine-Pharmacie (765402102) / SudocSudocFranceF

Efficacité et tolérance de l'association fludarabine et cyclophosphamide dans la maladie de Waldenström chez 49 patients

PARIS-BIUM (751062103) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocSudocFranceF