Mitochondria-mediated oxidative stress and cancer therapy

Most cancer cells demonstrate increased rates of glucose metabolism when compared to normal cells. Glucose metabolism leads to the formation of pyruvate and NADPH both of which function in the cellular detoxification of hydroperoxides. Therefore, tumor cells may increase their metabolism of glucose as a compensatory mechanism to protect against hydroperoxides generated as byproducts of mitochondrial metabolism. Recent studies have shown that glucose deprivation preferentially induces cytotoxicity and oxidative stress in human cancer cells, relative to normal cells. Mitochondria have been hypothesized to be the site of prooxidant production during glucose deprivation. The preferential cytotoxicity and oxidative stress seen during glucose deprivation in cancer cells, relative to normal cells, has been hypothesized to have implications in designing more effective combined modality cancer therapies involving inhibitors of glycolytic metabolism and agents that enhance ROS production. Many drugs currently used to treat cancer cells (i.e., ionizing radiation, Cisplatin, Doxorubison, and azidothymidine, etc.) have been proposed to increase superoxide and hydrogen peroxide production and could also be combined with inhibitors of glucose metabolism and peroxide detoxification. The application of these findings to developing new combined modality cancer therapy protocols will be discussed as well as the clinical implications of using glucose metabolism and FDG-PET imaging to predict tumor responses to therapy.