title: H(2)O(2) preferentially synergizes with nitroprusside to induce apoptosis associated with superoxide dismutase dysregulation in human melanoma irrespective of p53 status: Antagonism by o-phenanthroline.
abstract: The pro-oxidant hydrogen peroxide (H(2)O(2)) is converted to a reactive oxygen species by transition metals like iron. Since mutations in the p53 tumor suppressor gene contribute to drug resistance, we used genetically-matched human C8161 melanoma harbouring wt or DN-R175H mutant p53, to investigate the influence of p53 status on the potentiation of H(2)O(2) toxicity by: (a) intact sodium nitroprusside or nitroferricyanide (SNP), (b) its light-exhausted NO-depleted form (lex-SNP), (c) potassium ferricyanide, or (d) ferric ammonium sulphate. Whereas single treatments with SNP or H(2)O(2) were partly cytotoxic, preferentially potentiation of H(2)O(2) toxicity was evidenced with intact or lex-SNP. No comparable increase of H(2)O(2) toxicity was induced by ferricyanide, ferric ammonium sulphate or S-nitroso-N-acetyl penicillamine (SNAP), a known NO donor lacking iron. Immune blotting revealed apoptosis-associated PARP cleavage induced by [SNP+H(2)O(2)] irrespective of p53 status. This correlated with an eightfold induction of [Mn-SOD; SOD2] in wt p53 melanoma cells, and with a super-induction of the same enzyme reciprocal with loss of [Cu,Zn-SOD; SOD1], in mutant p53 cells. All these changes were antagonized by the anti-oxidant N-acetylcysteine or the iron chelator o-phenanthroline. We hypothesize that superoxide dismutase imbalance and iron-dependent redox changes involving OH species generated from a Fenton reaction between [SNP+H(2)O(2)], may be important in this anti-tumor activity. Although tumor drug resistance is frequently associated with DN-p53 mutations, our data shows for the first time the preferential ability of SNP to enhance H(2)O(2) toxicity, irrespective of p53 status.
authors.affiliation: Instituto Venezolano de Investigaciones Científicas (IVIC), CMBC, Tumor Cell Biology Laboratory, Apartado 20632, Caracas, 1020A, Venezuela.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Gomez-Sarosi
authors.forename: Mary
authors.initials: M
authors.lastname: Strasberg-Rieber
authors.forename: Manuel
authors.initials: M
authors.lastname: Rieber
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D004357:Drug Synergism; D005838:Genotype; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008545:Melanoma / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D009599:Nitroprusside / Q000494:pharmacology*; D010618:Phenanthrolines / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D010618:Phenanthrolines; D016159:Tumor Suppressor Protein p53; D009599:Nitroprusside; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; C025205:1,10-phenanthroline