Cancer cells, relative to normal cells, demonstrate increased sensitivity to
glucose-deprivation-induced cytotoxicity. To determine whether oxidative stress mediated by O(2)(*-) and hydroperoxides contributed to the differential susceptibility of human epithelial
cancer cells to
glucose deprivation, the oxidation of DHE (
dihydroethidine; for O(2)(*-)) and CDCFH(2) [5- (and 6-)carboxy-2',7'-dichlorodihydrofluorescein diacetate; for hydroperoxides] was measured in human colon and
breast cancer cells (HT29, HCT116, SW480 and MB231) and compared with that in normal human cells [FHC cells, 33Co cells and HMECs (human mammary epithelial cells)].
Cancer cells showed significant increases in DHE (2-20-fold) and CDCFH(2) (1.8-10-fold) oxidation, relative to normal cells, that were more pronounced in the presence of the mitochondrial electron-transport-chain blocker,
antimycin A. Furthermore, HCT116 and MB231 cells were more susceptible to
glucose-deprivation-induced cytotoxicity and oxidative stress, relative to 33Co cells and HMECs. HT29 cells were also more susceptible to 2DG (2-deoxyglucose)-induced cytotoxicity, relative to FHC cells. Overexpression of
manganese SOD (
superoxide dismutase) and mitochondrially targeted
catalase significantly protected HCT116 and MB231 cells from
glucose-deprivation-induced cytotoxicity and oxidative stress and also protected HT29 cells from 2DG-induced cytotoxicity. These results show that
cancer cells (relative to normal cells) demonstrate increased steady-state levels of ROS (
reactive oxygen species; i.e. O(2)(*-) and H(2)O(2)) that contribute to differential susceptibility to
glucose-deprivation-induced cytotoxicity and oxidative stress. These studies support the hypotheses that
cancer cells increase
glucose metabolism to compensate for excess metabolic production of ROS and that inhibition of
glucose and
hydroperoxide metabolism may provide a biochemical target for selectively enhancing cytotoxicity and oxidative stress in human
cancer cells.