BCL-2 Inhibitor ABT-737 Effectively Targets Leukemia-Initiating Cells with Differential Regulation of Relevant Genes Leading to Extended Survival in a NRAS/BCL-2 Mouse Model of High Risk-Myelodysplastic Syndrome.

Petra Gorombei,Pierre De La Grange,Marika Pla,Jacqueline Boultwood,Anne Janin,Niclas Setterblad,Saravanan Ganesan,Rose Ann Padua,Christine Chomienne,Andrea Pellagatti,Marina Konopleva,Satyananda Patel,Mathieu Chiquet,Fabien Guidez,Pierre Fenaux,Michael Andreeff,Carole Le Pogam,Laura Guerenne,Nader Omidvar,Patricia Krief,Laure Goursaud,Lionel Adès,Robert R West ,Stéphanie Beurlet ,Maria Elena Noguera ,Laure Sarda‐Mantel ,P Merlet ,Christophe Lebœuf ,Nilgün Solak Tekin

doi:10.3390/ijms221910658

Abstract

AbastractDuring transformation, myelodysplastic syndromes (MDS) are characterized by reducing apoptosis of bone marrow (BM) precursors. Mouse models of high risk (HR)-MDS and acute myelogenous leukemia (AML) post-MDS using mutant NRAS and overexpression of human BCL-2, known to be poor prognostic indicators of the human diseases, were created. We have reported the efficacy of the BCL-2 inhibitor, ABT-737, on the AML post-MDS model; here, we report that this BCL-2 inhibitor also significantly extended survival of the HR-MDS mouse model, with reductions of BM blasts and lineage negative/Sca1+/KIT+ (LSK) cells. Secondary transplants showed increased survival in treated compared to untreated mice. Unlike the AML model, BCL-2 expression and RAS activity decreased following treatment and the RAS:BCL-2 complex remained in the plasma membrane. Exon-specific gene expression profiling (GEP) of HR-MDS mice showed 1952 differentially regulated genes upon treatment, including genes important for the regulation of stem cells, differentiation, proliferation, oxidative phosphorylation, mitochondrial function, and apoptosis; relevant in human disease. Spliceosome genes, found to be abnormal in MDS patients and downregulated in our HR-MDS model, such as Rsrc1 and Wbp4, were upregulated by the treatment, as were genes involved in epigenetic regulation, such as DNMT3A and B, upregulated upon disease progression and downregulated upon treatment.

Highlights

Myelodysplastic syndromes (MDS) are clonal stem cell disorders characterized by ineffective hematopoiesis leading to blood cytopenias, bone marrow (BM) dysplasia, and an increased risk of developing acute myelogenous leukemia (AML)
We have previously shown that ABT-737 is efficacious in our mouse model of AML post-MDS [9]; in this present study, we assessed the effect of ABT-737 on survival and leukemia-initiating cells (LICs) in our preclinical mouse model of HR-MDS
ABT-737 treatment was initiated after confirming the presence of transgenes by genotyping, expression of human BCL-2 (hBCL-2) by flow cytometry and disease monitoring by measuring blood counts; 64 mice with thrombocytopenia were recruited and followed for survival

Summary

Introduction

Myelodysplastic syndromes (MDS) are clonal stem cell disorders characterized by ineffective hematopoiesis leading to blood cytopenias, bone marrow (BM) dysplasia, and an increased risk of developing acute myelogenous leukemia (AML). The RAS family of genes encodes for GTP-binding proteins located in the plasma membrane, where they play a role in the transduction of signals from membrane receptors. Activating mutations of the NRAS oncogene, found in a wide range of human hematological malignancies, are observed in 5 to 30% of HR-MDS patients, often as an early event. There is a predominance of NRAS mutations at codon 12 [2], and overall, 78% of patients had one or more oncogene mutations, including K and N RAS [3]. The mutation renders the active RAS-GTP conformation insensitive to the GTPase activating protein (GAP) and results in constitutive signaling cascades, such as the MAP kinase pathway

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