(283f) Understanding Tumor Cell Physiology Using Metabolic Flux Analysis

During carcinogenesis tumor cells undergo a metabolic transformation to fuel their aggressive growth in the body. Unique changes in energetic and biosynthetic pathway fluxes enable cancer cells to better utilize substrates in their microenvironment but offer novel therapeutic targets as well. Here we have conducted metabolic flux analysis (MFA) using stable isotopic tracers to characterize the metabolic phenotype of lung carcinoma cell lines. Using 13C glucose and glutamine tracers we identified elevated fluxes within central carbon metabolism in A549 cells. Significant levels of reductive carboxylation were detected, and isotopomer spectral analysis (ISA) using 5-13C glutamine indicated that at least 65% of the glutamine contribution to lipogenesis proceeded through this pathway. Furthermore, relatively high fluxes were estimated through malic enzyme, which may enable tumor cells to meet the large quantify of NADPH required for fatty acid synthesis. Finally, we quantified the effects on central carbon metabolism of dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinase. Acute DCA treatment decreased lactate production of tumor cells and increased oxidative metabolism in the tricarboxylic acid (TCA) cycle. In addition, DCA caused a decrease in reductive carboxylation through isocitrate dehydrogenase as well as the contribution of this pathway to palmitate synthesis. These results highlight the utility of 13C MFA in elucidating the metabolic phenotype of tumor cells in vitro.