Abstract 1248: Enhanced glutamine metabolism contributes to docetaxel resistance in DU145 prostate cancer cells

Abstract

Abstract Chemotherapeutic resistance is one of the major factors contributing to cancer mortality. Although evidence supports a mechanistic link between metabolic enzyme polymorphisms and drug sensitivity, little is known about the metabolic changes tumor cells undergo when treated with a chemotherapeutic agent. Moreover, the metabolic consequences of exposure to these agents may provide essential adaptive functions contributing to chemotherapeutic resistance. Here we used metabolic flux analysis to identify metabolic changes accompanying and potentially accounting for docetaxel resistance in DU145 prostate cancer cells. We focused on the utilization of glucose and glutamine, the two most abundant extracellular nutrients, which together account for the bulk of carbon and nitrogen metabolism in tumor cells. Docetaxel resistant (DOCETR) cells consumed glutamine more avidly and secreted glutamate and ammonia at a greater rate than sensitive parental cells. Surprisingly, contribution of glutamine carbon into the TCA cycle was unchanged in DOCETR cells despite the higher glutamine utilization. Transfer of glutamine carbon into both the intracellular and extracellular glutamate pools, on the other hand, was higher in DOCETR cells, indicating that the DOCETR cells had an increased ability to convert glutamine to glutamate and then to secrete the glutamate. Accordingly, these cells also had increased expression and activity of glutaminase, the major enzyme responsible for glutamine deamidation. Because glutaminase activity does not yield energy unless the resulting glutamate is further oxidized, we hypothesized that this metabolic transition served a non-bioenergetic role, possibly supporting enhanced rates of glutathione synthesis for modification and secretion of docetaxel. Consistent with this idea, DOCETR cells displayed an increase in de novo synthesis of glycine, which is required for the production of glutathione. Importantly, a glutaminase inhibitor re-sensitized DOCETR cells to docetaxel, strongly suggesting that their enhanced glutamine metabolism was involved in resistance to the drug. We speculate that alterations in glutamine metabolism provide a general and targetable mechanism for xenobiotic resistance in cancer cells. 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 1248. doi:10.1158/1538-7445.AM2011-1248