[Induction of gene amplification in Djungarian hamster cells by various chemical carcinogens]

The influence of 9 different carcinogens on gene amplification was studied in DM-15 Djungarian hamster cells. The effect was assessed by resistance to colchicine or methotrexate. It was found that tumour promotors (12-0-tetradecanoylphorbol-13-acetate (TPA), mezerein, tween-80) and some carcinogens possessing both initiating and promoting activity (20-methylcholanthrene, 7,12-dimethylbenz(a)antracene, aflatoxin B1) dramatically increased the number of colchicine and methotrexate-resistant cells. 4-0-methylTPA, a non-promoting analog of TPA, and alkylating carcinogens (ethylmethanesulphonate and nitrosomethylurea) did not induce gene amplification. It was suggested that the ability of carcinogens to induce gene amplification correlated with their ability to induce the second promotion stage.