title: Disulfiram induces apoptosis in human melanoma cells: a redox-related process.
abstract: Melanoma is highly resistant to conventional chemotherapy. We have demonstrated that redox regulation in melanoma cells is aberrant, and redox-modulating agents can induce cell apoptosis. We have currently explored the effect of disulfiram (DSF), a member of the dithiocarbamate family, on apoptosis of melanoma cells in vitro. Human metastatic melanoma cells c81-46A, c81-61, and c83-2C were treated with DSF and apoptosis measured. DSF, at a dose of 25-50 ng/ml, consistently caused a 4-6-fold increase in apoptosis. The same dose of DSF did not significantly affect apoptosis in melanocytes. Coincubation of N-acetyl-cysteine reversed the DSF-induced apoptosis. Buthionine sulfoximine (BSO), an inhibitor of gamma-glutamyl-cysteine synthetase, as a single agent caused a approximately 2-fold increase in apoptosis when incubated with melanoma cells for 4 days. BSO slightly enhanced the level of apoptosis induced by DSF (4-10% higher than DSF alone). Intracellular glutathione was remarkably depleted with BSO treatment. DSF did not cause glutathione depletion; however, the ratio of reduced and oxidized glutathione was significantly decreased (14% of control), and N-acetyl-cysteine partially restored the ratio to 30% of control. There was a transient (2-fold) elevation of intracellular superoxide level after 24 h of DSF treatment (before the overt apoptosis). The intracellular H2O2 level progressively decreased with time. DSF decreased the mitochondrial membrane polarization in a time-dependent manner, and there was a significant inverse correlation between apoptosis and mitochondrial membrane polarization. We propose that DSF-induced apoptosis is redox related but involves a different mechanism from BSO-induced apoptosis in tumor cells. Our findings have provided new data for additional understanding of drug-induced apoptosis in melanoma cells and suggests an alternative therapeutic approach to melanoma.
authors.affiliation: Department of Medicine, Chao Family Comprehensive Cancer Center, College of Medicine, University of California, Irvine, 101 City Drive South, Building 23, Suite 403, Orange, CA 92868, USA.
authors.forename: Dazhi
authors.initials: D
authors.lastname: Cen
authors.forename: Rachel I
authors.initials: RI
authors.lastname: Gonzalez
authors.forename: Julie A
authors.initials: JA
authors.lastname: Buckmeier
authors.forename: Ravi S
authors.initials: RS
authors.lastname: Kahlon
authors.forename: Nilou B
authors.initials: NB
authors.lastname: Tohidian
authors.forename: Frank L
authors.initials: FL
authors.lastname: Meyskens
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D004221:Disulfiram / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005978:Glutathione / Q000032:analysis; D008544:Melanocytes / Q000737:chemistry / Q000187:drug effects; D008545:Melanoma / Q000188:drug therapy / Q000473:pathology*; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D009362:Neoplasm Metastasis; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D000964:Antimetabolites, Antineoplastic; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D019328:Buthionine Sulfoximine; D005978:Glutathione; D004221:Disulfiram