Mutation of Succinate Dehydrogenase Subunit C Results in Increased O2, Oxidative Stress, and Genomic Instability

Mutations in genes coding for succinate dehydrogenase (SDH) subunits are believed to contribute to cancer and aging, but the mechanism for this is unclear. Hamster fibroblasts expressing a mutation in SDH subunit C (SDHC; B9) showed 3-fold increases in dihydroethidine and dichlorodihydrofluor-escein (CDCFH2) oxidation indicative of increased steady-state levels of O2 and H2O2, increases in glutathione/glutathione disulfide (indicative of oxidative stress), as well as increases in superoxide dismutase activity, relative to parental B1 cells. B9 cells also showed characteristics associated with cancer cells, including aneuploidy, increases in glucose consumption, and sensitivity to glucose deprivation–induced cytotoxicity. Expression of wild-type (WT) human SDHC in B9 cells caused prooxidant production, glucose consumption, sensitivity to glucose deprivation–induced cytotoxicity, and aneuploidy to revert to the WT phenotype. These data show that SDHC mutations cause increased O2 production, metabolic oxidative stress, and genomic instability and that mutations in genes coding for mitochondrial electron transport chain proteins can contribute to phenotypic changes associated with cancer cells. These results also allow for the speculation that DNA damage to genes coding for electron transport chain proteins could result in a ‘‘mutator phenotype’ ’ by increasing steady-state levels of O