A novel DNA lesion in neoplastic livers of feral fish: 2,6-diamino-4-hydroxy-5-formamidopyrimidine.

DNA from neoplastic hepatic tissues of feral fish environmentally exposed to carcinogens was shown to contain the guanine-derived lesion 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua). This modification of DNA appears to arise from the attack of the hydroxyl radical at C-8 of guanine. Concentrations of the lesion ranged from 0.97 to 5.11 nmol/mg DNA. FapyGua was not detected in nonneoplastic tissue and has not been previously reported to occur in the DNA of animal tissues. The present findings support the view that reactive oxygen species damage DNA in living systems and thus may play an important role in the formation of neoplastic tissues.