Abstract 994: Monitoring glucose, glutamine and fatty acid metabolism to determine metabolic vulnerability of tumor cells in vitro

Abstract

Abstract Tumor cells display a metabolism that is strikingly different from that of the normal tissue from which they originated. This metabolic alteration results from activation of oncogenes and/or loss of tumor suppressor genes controlling cellular metabolic pathways as well as adaptation to their microenvironments and provides energy and cellular building blocks, allowing tumor cells to proliferate and survive. The altered metabolism of glucose and glutamine are becoming one of the hallmarks of tumor cells. We present a method that enables rapid assessment of the ability of tumor cells to catabolize the three major nutrient substrates, glucose, glutamine and fatty acids in a microplate using the XF Extracellular Flux Analyzer. Cellular oxygen consumption rate is used as an indicator of substrate oxidation by the mitochondrial respiratory chain upon substrate addition and extracellular acidification rate upon glucose addition is used as an indicator of glycolysis. Furthermore, the maximal capacity of glycolysis and of mitochondrial substrate oxidation is determined by forcing one of the two energy-producing pathways to operate at maximum. In addition, pharmacological inhibition of distinct metabolic pathways allows us to discern the biochemical pathways used, i.e., whether glutamine is metabolized through aminotransferase or glutamate dehydrogenase. Using this approach, we have demonstrated that the nutrient levels in culture medium can markedly shift the ability of cancer cells to use glucose for glycolysis versus oxidation of glutamine and fatty acids and is accompanied by modulation of cell proliferation rate. For example, excessive nutrients induced activation of fatty acid oxidation and enhanced glutamine oxidation in myc-expressing SF188 glioblastoma cells. This shift in substrate use also sensitized these cells to inhibition of fatty acid oxidation. We observed a concomitant increase in the maximal capacity of the mitochondrial respiratory chain with elevated substrate oxidation. In contrast, the apparent glycolysis rate of SF188 cells was much reduced but the glycolytic capacity was retained, which implies these cells have the flexibility to channel glucose to either energy or building block production required for cell mass duplication. We suggest that this type of dynamic analysis provides a rapid means to determine the ability of various types of tumor cells to use glucose, glutamine and fatty acids as well as the maximal capacity of the machineries of glycolysis and substrate oxidation, which may be indicative of metabolic vulnerability and therefore targets of intervention of a particular tumor cell type. 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 994. doi:10.1158/1538-7445.AM2011-994