Abstract 3796: Inhibition of mitochondrial respiration synergizes with tyrosine kinase inhibitors to eliminate Bcr-Abl+ leukemia

Abstract

Abstract Bcr-Abl kinase inhibitors are the standard therapy for chronic myelogenous leukemia (CML). While effective in controlling disease in chronic phase, these inhibitors often fail to completely eliminate Bcr-Abl+ CML cells and also fail to achieve durable remissions for advanced CML and Bcr-Abl+ acute lymphoblastic leukemias (ALL). Our lab employed a large-scale synthetic lethal shRNA screen to identify genes involved in CML survival upon treatment with the Bcr-Abl kinase inhibitor imatinib (IM) [Cancer Cell. 2010;18(1):74-87]. This screen identified several genes involved in energy utilization including a component of pyruvate dehydrogenase, dihydrolipoyllysine-residue acetyltransferase. This target was identified by two independent shRNAs, each underrepresented over 22 fold in treated cells compared to untreated. CML proliferation depends on Bcr-Abl-driven glycolysis for energy production. Upon IM treatment, I hypothesized that these cells are forced to rely on other sources of energy including the TCA cycle and mitochondrial respiration, and that targeting alternative energy production pathways will enhance IM-mediated elimination of CML cells. Thus, I predicted that inhibition of mitochondrial respiration by knockdown or pharmacologic inhibition would cooperate with tyrosine kinase inhibitors to eliminate Bcr-Abl+ leukemias. My experiments have shown that knocking down pyruvate dehydrogenase in human blast crisis Bcr-Abl+ CML cells (K562) greatly sensitizes cells to IM in vitro. Conversely, supplementing the cell culture media with increasing concentrations of methyl-pyruvate protects K562 cells from IM treatment. Moreover, I find that the mitochondrial ATP-synthase inhibitor Oligomycin A also synergizes with IM to kill CML cells in vitro. In addition, inhibition of mitochondrial respiration with Oligomycin A enhances elimination of Bcr-Abl+ cells by a Bcr-Abl tyrosine kinase inhibitor in vivo and prolongs disease-free survival in a mouse model of Bcr-Abl+ B-ALL. The drug doses of Oligomycin A used are over 100-fold below the LD50, and have no apparent adverse effects on these mice. Targeting mitochondrial metabolism as an adjuvant drug therapy may prevent the survival of residual Bcr-Abl+ CML cells upon tyrosine kinase inhibitor treatment. *This project is supported in part by pre-doctoral fellowship number F31CA157166 from the National Cancer Institute. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3796. doi:10.1158/1538-7445.AM2011-3796