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.
Chemico-biological interactions 2010 Jul 29; In press
Gomez-Sarosi L LA, Strasberg-Rieber M, Rieber M
Instituto Venezolano de Investigaciones CientÃficas (IVIC), CMBC, Tumor Cell Biology Laboratory, Apartado 20632, Caracas, 1020A Venezuela.
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 8-fold 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.
Keywords: melanoma