Inhibitors of glucose and hydroperoxide metabolism potentiate 17AAG-induced cancer cell killing via metabolic oxidative stress

17-Allylamino-17-demethoxygeldanamycin (17AAG) is an experimental chemotherapeutic agent, believed to form free radicals in vivo, and cancer cell resistance to 17AAG is believed to be a thiol-dependent process. Inhibitors of thiol-dependent hydroperoxide metabolism [L-buthionine-S,R-sulfoximine (BSO) and auranofin (AUR)] were combined with the inhibitor of glucose metabolism [2-deoxy-D-glucose (2DG)] to determine if 17AAG-mediated cancer cell killing could be enhanced. When 2DG (20 mM, 24 h), BSO (1 mM, 24 h), and auranofin (500 nM, 3 h) were combined with 17AAG, they significantly increased cell killing in three human cancer cell lines (PC-3, SUM159, MDA-MB-231), relative to 17AAG alone. Increases in toxicity seen with this drug combination also correlated with increased glutathione (GSH) and thioredoxin (Trx) oxidation and depletion. Furthermore, treatment with the thiol antioxidant, N-acetyl cysetine (NAC, 15 mM, 24 h), was able to significantly protect from drug-induced toxicity and ameliorate GSH oxidation, Trx oxidation, and Trx depletion. These data strongly support the hypothesis that simultaneous inhibition of GSH and Trx dependent metabolism is necessary to sensitize human cancer cells to 2DG + 17AAG-mediated cancer cell killing by enhancing thiol-dependent oxidative stress and suggest that simultaneous targeting of both GSH and Trx metabolism could represent an effective strategy for chemo-sensitization in human cancer cells.