The oncoprotein H-RasV12 increases mitochondrial metabolism

Background: Neoplastic cells increase glycolysis in order to produce anabolic precursors and energy within the hypoxic environment of a tumor. Ras signaling is activated in several cancers and has been found to regulate metabolism by enhancing glycolytic flux to lactate. We examined the effects of sequential immortalization and H-Ras^V12-transformation of human bronchial epithelial cells on the anabolic fate of fully-labeled ¹³C-glucose-derived carbons using two-dimensional total correlated spectroscopic analysis-nuclear magnetic resonance spectroscopy (2D TOCSY-NMR). Results: We found that the introduction of activated H-Ras^V12 into immortalized human bronchial epithelial cells unexpectedly increased tricarboxylic acid cycle activity as measured by the direct conversion of ¹³C-glucose carbons into the anabolic substrates glutamate/glutamine, aspartate and uridine. We then observed that immortalization and H-Ras^V12-transformation of bronchial epithelial cells caused a stepwise increase in oxygen consumption, a global measure of electron transport chain activity. Importantly, ectopic expression of H-Ras^V12 sensitized immortalized cells to the ATP-depleting and cytotoxic effects of electron transport perturbation using the complex I inhibitor rotenone. Conclusion: Taken together, these data indicate that the oncoprotein H-Ras^V12 increases mitochondrial metabolism and provide new rationale for the targeting of the tricarboxylic acid cycle and electron transport chain as anti-neoplastic strategies.