title: Glutathione depletion induced by c-Myc downregulation triggers apoptosis on treatment with alkylating agents.
abstract: 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, cisplatin 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 previously demonstrated that c-Myc downregulation decreases 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 alkylating 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 mitochondria 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 apoptosis induced by cisplatin and melphalan by inhibition of Bax/cytochrome c redistribution. The relationship among c-Myc, GSH content, and the response to alkylating 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.
authors.affiliation: Experimental Chemotherapy Laboratory, Experimental Research Center, Regina Elena Cancer Institute, Rome 00158, Italy. biroccio@ifo.it
authors.forename: Annamaria
authors.initials: A
authors.lastname: Biroccio
authors.forename: Barbara
authors.initials: B
authors.lastname: Benassi
authors.forename: Francesco
authors.initials: F
authors.lastname: Fiorentino
authors.forename: Gabriella
authors.initials: G
authors.lastname: Zupi
mesh_terms: D000477:Alkylating Agents / Q000494:pharmacology*; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002166:Camptothecin / Q000494:pharmacology; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005019:Ethyl Ethers / Q000494:pharmacology; D005978:Glutathione / Q000172:deficiency / Q000378:metabolism*; D006801:Humans; D008545:Melanoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D008558:Melphalan / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D059003:Topoisomerase Inhibitors
chemical_list: D000477:Alkylating Agents; D018906:Antineoplastic Agents, Alkylating; D004791:Enzyme Inhibitors; D005019:Ethyl Ethers; C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; D059003:Topoisomerase Inhibitors; D019328:Buthionine Sulfoximine; D004317:Doxorubicin; D005978:Glutathione; D002945:Cisplatin; D008558:Melphalan; D002166:Camptothecin