Combined inhibition of glycolysis, the pentose cycle, and thioredoxin metabolism selectively increases cytotoxicity and oxidative stress in human breast and prostate cancer

Inhibition of glycolysis using 2-deoxy-D-glucose (2DG, 20 mM, 24-48 h) combined with inhibition of the pentose cycle using dehydroepiandrosterone (DHEA, 300 mu M, 24-48 increased clonogenic cell killing in both human prostate (PC-3 and DU145) and human breast (MDA-MB231) cancer cells via a mechanism involving thiol-mediated oxidative stress. Surprisingly, when 2DG + DHEA treatment was combined with an inhibitor of glutathione (GSH) synthesis (L-buthionine sulfoximine; BSO, 1 mM) that depleted GSH > 90% of control, no further increase in cell killing was observed during 48 h exposures. In contrast, when an inhibitor of thioredoxin reductase (TrxR) activity (Auranofin; Au, 1 mu M), was combined with 2DG I DHEA or DHEA-alone for 24 h, clonogenic cell killing was significantly increased in all three human cancer cell lines. Furthermore, enhanced clonogenic cell killing seen with the combination of DHEA I Au was nearly completely inhibited using the thiol antioxidant, N-acetylcysteine (NAC, 20 mM). Redox Western blot analysis of PC-3 cells also supported the conclusion that thiorecloxin-1 (Trx-1) oxidation was enhanced by treatment DHEA+Au and inhibited by NAC. Importantly, normal human mammary epithelial cells (1-IMEC) were not as sensitive to 2DG, DHEA, and Au combinations as their cancer cell counterparts (MDA-MB-231). Overall, these results support the hypothesis that inhibition of glycolysis and pentose cycle activity, combined with inhibition of Trx metabolism, may provide a promising strategy for selectively sensitizing human cancer cells to oxidative stress-induced cell killing. (C) 2014 The Authors. Published by Elsevier B.V.