Glutathione depletion induced by c-Myc downregulation triggers apoptosis on treatment with alkylating agents. Neoplasia 2004, 6, 195–206. © 2014 by the authors; licensee MDPI

Here we investigate the mechanism(s) involved in the c-Myc–dependent drug response of melanoma cells. By using three M14-derived c-Myc low-expressing clones, we demonstrate that alkylating agents, cispla-tin and melphalan, trigger apoptosis in the c-Myc antisense transfectants, but not in the parental line. On the contrary, topoisomerase inhibitors, adriamycin and camptothecin, induce apoptosis to the same extent regardless of c-Myc expression. Because we previ-ously demonstrated that c-Myc downregulation de-creases glutathione (GSH) content, we evaluated the role of GSH in the apoptosis induced by the different drugs. In control cells treated with one of the alkylat-ing agents or the others, GSH depletion achieved by L-buthionine-sulfoximine preincubation opens the apoptotic pathway. The apoptosis proceeded through early Bax relocalization, cytochrome c release, and concomitant caspase-9 activation, whereas reactive oxygen species production and alteration of mitochon-dria membrane potential were late events. That GSH was determining in the c-Myc –dependent drug-induced apoptosis was demonstrated by altering the intracellular GSH content of the c-Myc low-expressing cells up to the level of controls. Indeed, GSH ethyl ester–mediated increase of GSH abrogated apopto-sis induced by cisplatin and melphalan by inhibition of Bax/cytochrome c redistribution. The relationship among c-Myc, GSH content, and the response to al-kylating agent has been also evaluated in the M14 Myc overexpressing clones as well as in the melanoma JR8 c-Myc antisense transfectants. All together, these results demonstrate that GSH plays a key role in governing c-Myc–dependent drug-induced apoptosis