Glutathione depletion sensitizes tumor cells to oxidative cytolysis.

Activated macrophages and granulocytes lyse tumor cells in the presence of phorbol myristate acetate or antitumor antibody via the secretion of reactive oxygen intermediates, such as HzOz. We compared the lysis of GSH-depleted or normal tumor cells by oxidants generated with glucose oxidase or activated macrophages and granulocytes. Two independent methods were employed to deplete cells specifically of GSH: (1) inhibition of GSH biosynthesis with buthionine sulfoximine, a selective inhibitor of y-glutamylcysteine synthetase, and (2) treatment with l-chloro-2,4-dinitrobenzene (CDNB), which covalently binds GSH as catalyzed by endogenous GSH S-transferase. Incubation of P388 lymphoma or P815 mastocytoma cells with 0.2 mM buthionine sulfoximine resulted in a 50% reduction in GSH content by 4.5-5 h and >90% depletion by 15 h. Treatment of P815 cells with CDNB for 15 min resulted in a dose-dependent loss of GSH, with a maximal depletion of approximately 70% obtained with 10 p~ CDNB. GSH depletion of P815 and P388 markedly enhanced their sensitivity to lysis by a flux of HzO2. Such cells could be lysed by dilutions of glucose oxidase and numbers of phorbol myristate acetate-stimulated granulocytes and activated macrophages which were ineffectual against untreated tumors. Recovery of tumor cell resistance to HzOz after GSH depletion by either buthionine sulfoximine or CDNB followed the same time course as resynthesis of cellular GSH. These results and the previous finding that inhibition of the GSH redox cycle of tumor cells enhances both macrophageand glucose oxidase-mediated cytolysis (Nathan, C. F., Arrick, B. A., Murray, H. W., DeSantis, N. M., and Cob , Z. A. (1981) J. Exp. Med 153,766-782) demonstrate the importance of GSH to tumor cell antioxidant defenses.