Metabolic activation and DNA binding of food mutagens and other environmental carcinogens in human mammary epithelial cells

Abstract

Cultures of human mammary epithelial cells were treated with one of seven heterocyclic amine food mutagens [2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoxaline (MeIQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline (7,8-DiMeIQx), 2-amino-3,4,7,8-tetramethylimidazo[4,5-f]quinoxaline (4,7,8TriMeIQx) or 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP)], four nitropyrenes (1-nitropyrene (1-NP), 1,3-dinitropyrene (1,3-DNP), 1,6-dinitropyrene (1,6-DNP) or 1,8-dinitropyrene (1,8-DNP)I or the polycyclic aromatic hydrocarbon dibenzo[a,l]pyrene (DB[a,l]P). DNA isolated from the cultures was analysed by 32P-post-labelling and in each case the presence of carcinogen-DNA adducts was detecte. The patterns and numbers of adducts obtained when human mammary cell DNA digests were separated on polyethyleneimine-ceIlulose TLC were found to closely resemble those previously demonstrated to be present in the DNA of tissues from rodents and other primates treated with the same agents. Up to six DNA adducts were detected in human breast cells treated with IQ and MeIQ. Fewer adducts (1-3) were detected following treatment with MeIQx or its methylated derivatives, whilst PhIP gave rise to at least four distinct adduct spots. Five adduct spots were detected in breast cells treated with DB[a,l]P or with 1-NP, but fewer adduct spots were formed by 1,3-,1,6- and 1,8-DNP. These data demonstrate the ability of human breast epithelial cells to activate to DNA binding species a range of carcinogenic compounds known to be present in the human diet or to which humans are known to be exposed environmentally.