Abstract 2311: Targeting EMT and MET breast cancer stem cell states through simultaneous inhibition of glycolytic and antioxidant pathways
Authors: Luo Ming , Davis April , McDermott Sean , Jiagge Evelyn , Brooks Michael , Gheordunescu Elizabeth , Luther Tahra , Clouthier Shawn G. , Conley Sarah , Spitz Douglas R. , Wicha Max S. 
Published: August 2015

Abstract
Cancer stem cells (CSCs) drive tumor growth as well as mediating metastasis and treatment resistance. In breast cancer (BC), CSCs exist in alternative mesenchymal (EMT) and epithelial (MET)-like states characterized by the expression of CD44+CD24- and aldehyde dehydrogenase (ALDH) respectively. BCSCs display phenotypic plasticity allowing them to transition between EMT and MET states in a process regulated by the tumor microenvironment. The plasticity of BCSCs suggests that it may be necessary to simultaneously target alternative BCSC states to achieve maximal eradication of these cell populations. In order to develop strategies to target these BCSC states, we measured the cellular bioenergetics of EMT and MET BCSCs compared to non-stem bulk tumor cells as well as the sensitivity of distinct BCSC states to inhibitors of glucose and hydroperoxide metabolism. Using a Seahorse XCF instrument, we found that both MET and EMT BCSCs display higher glycolytic potential than bulk tumor cells. Increased glycolysis correlated with elevated expression of hexokinase 2, a rate limiting glycolytic enzyme in cancer. Interestingly, the glycolytic inhibitor, 2-deoxyglucose (2DG), specifically inhibited EMT BCSCs in a dose dependent fashion; however, MET BCSCs were completely refractory to this treatment. Proteomic and RNA-seq analyses revealed that two important arms of hydroperoxide metabolism, the thioredoxin- and glutathione-mediated antioxidant pathways, were robustly up-regulated in MET BCSCs, suggesting that these cells are rendered resistant to glycolysis inhibition via an enhanced anti-oxidant defense. Pharmacologic inhibition of this antioxidant defense by Auranofin (an inhibitor of thioredoxin reductase) is sufficient to deplete MET BCSCs in SUM149 BC cells which were rescued by NAC, a ROS scavenger, or catalase, a specific enzyme capable of degrading intracellular H2O2. Finally, administration of 2DG together with Auranofin and BSO (an inhibitor of glutathione metabolism) synergistically suppressed tumor growth in a patient derived xenograft (PDX) model by suppressing both EMT and MET BCSCs. This study suggests that utilizing metabolic inhibition to simultaneously target EMT and MET BCSCs is a viable therapeutic strategy with important clinical implications.
Citation Format: Ming Luo, April Davis, Sean McDermott, Evelyn Jiagge, Michael Brooks, Elizabeth Gheordunescu, Tahra Luther, Shawn G. Clouthier, Sarah Conley, Douglas R. Spitz, Max S. Wicha. Targeting EMT and MET breast cancer stem cell states through simultaneous inhibition of glycolytic and antioxidant pathways. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2311. doi:10.1158/1538-7445.AM2015-2311