Transformation of rat tracheal epithelial cells in culture by chemicals and radiation

A serum-free culture system has previously been described for the proliferation of rat tracheal epithelial (RTE) cells at clonal density. Using this culture system, preneoplastic variants of RTE cells can be induced following exposure of normal RTE cells to carcinogens. Selection for variants is imposed after carcinogen treatment by switching cultures from serum-free medium which is permissive for the proliferation of normal RTE cells to serum-containing medium which is permissive only for preneoplastic enhanced growth (EG) variants and results in the terminal squamous differentiation of normal RTE cells. EG variants continue to proliferate in serum-containing selective medium forming large colonies of small cells with increased nuclear to cytoplasmic ratios which appear hyperchromatic after staining. Using colony forming assays, RTE cells exhibit a dose-dependent decrease in survival following exposure to direct acting chemical carcinogens such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and benzo[a]pyrene diolepoxide (BPDE) and in response to radiation such as gamma rays or X-rays