Targeting the dysfunctional mitochondrial respiration in drug resistant B-cell acute lymphoblastic leukemia

Abstract

Tel. (304) 293-7206 21 22 Keywords: B-cell acute lymphoblastic leukemia, mitochondrial respiration, pyrvinium 23 pamoate, drug resistance, nanoparticles, co-culture model. 24 225 Abstract Reprogramming of cellular pathways is a crucial mechanism of drug resistance 26 and survival in refractory acute lymphoblastic leukemia (ALL) cells. In the present study, 27 we performed an unbiased gene expression analysis and identified a dysfunctional 28 mitochondrial respiration program in drug-resistant ALL cells grown in a co-culture system 29 with bone marrow stromal cells (BMSC). Specifically, the activity of the complexes within 30 the electron transport chain was significantly downregulated, correlated with decreased 31 mitochondrial mass and ATP production in drug-resistant ALL cells. To validate 32 mitochondrial respiration as a druggable target, we utilized pyrvinium pamoate (PP), a 33 known inhibitor of mitochondrial respiration and documented its anti-leukemic activity in 34 several ALL cell lines grown alone or in co-culture with BMSC. To increase the 35 bioavailability profile of PP, we successfully encapsulated PP in a nanoparticle drug 36 delivery system and demonstrated that it retained its anti-leukemic activity in a 37 hemosphere assay. PP anti-leukemic activity was decreased by the addition of sodium 38 pyruvate, and furthermore, PP was found to have an additive anti-leukemic effect when 39 used in combination with rotenone, a mitochondrial complex I inhibitor with activity similar 40 to PP on the mitochondrial respiration. Importantly, PP's cell death activity was found to 41 be specific for leukemic cells as primary normal immune cells were resistant to PP-42 mediated cell death. In conclusion, we have demonstrated that PP is a novel therapeutic 43 lead compound that counteracts the respiratory reprogramming found in refractory ALL 44 cells. 45 46 47 3 48 Introduction 49 B lineage acute lymphoblastic leukemia (ALL) originates from differentiation arrest 50 followed by uncontrolled proliferation of the immature B lymphoid cells, resulting in 51 accumulation within the bone marrow (BM) [1]. This rapid accumulation of the leukemic 52 blast cells leads to the "hijacking" of the BM niche and the impairment of steady state 53 hematopoiesis. Thus, coincident with progression of disease, there is a collapse of the 54 functional integrity of the hematopoietic system [2]. The drivers of the disease have not 55 yet been fully elucidated, but are known to include changes in chromosomal number 56 (hyperdiploidy, hypodiploidy, trisomy 4 and 10 and intrachromosomal amplification of 57 chromosome 21) or chromosomal translocation (MLL-AF4, ETV6-RUNX1, E2A-PBX1 58 and BCR-ABL1) [3]. Fortunately, irrespective of the genesis of the disease, there has 59 been continuous improvement in prognosis in both children and adults, with most 60 achieving complete remission following treatment using the present standard-of-care [4].61 However, disease relapse does occur in specific patients, and often the emerging disease 62 will mani...