Transition mutation in codon 248 of the p53 tumor suppressor gene induced by reactive oxygen species and a nitric oxide-releasing compound

Exposing the human bronchial epithelial cell line BEAS2B to the nitric oxid e (NO) donor sodium 1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DEA/NO) a t an initial concentration of 0.6 mM while generating superoxide ion at the rate of 1 mu M/min with the hypoxanthine/xanthine oxidase (HX/XO) system i nduced C:G-->T:A transition mutations in codon 248 of the p53 gene. This pa ttern of mutagenicity was not seen by 'fish-restriction fragment length pol ymorphism/polymerase chain reaction' (fish-RFLP/PCR) on exposure to DEA/NO alone, however, exposure to HX/XO led to various mutations, suggesting that co-generation of NO and superoxide was responsible for inducing the observ ed point mutation. DEA/NO potentiated the ability of HX/XO to induce lipid peroxidation as well as DNA single- and double-strand breaks under these co nditions, while 0.6 mM DEA/NO in the absence of HX/XO had no significant ef fect on these parameters. The results show that a point mutation seen at hi gh frequency in certain common human tumors can be induced by simultaneous exposure to reactive oxygen species and a NO source.