A method for detecting carcinogenic organic chemicals using mammalian cells in culture

A method for testing organic chemicals for their carcinogenic potential is described. Baby hamster kidney cells (BHK-21/C1 13) were exposed to different doses of test compound in liquid tissue culture medium containing rat liver post-mitochondrial supernatant and cofactors (S-9 mix) to aid metabolism, but without serum. Survival of cells following exposure to the compound was assessed by cloning in liquid growth medium. Transformation was assessed by colony growth in semi-solid agar. The dose-response curve for survival was used to determine the LC50 of the compound. A dose-response curve for transformation was constructed and a 5-fold increase in transformation frequency at the LC50 was regarded as a positive test result. The method may also be used for testing gaseous compounds. Cells grown in monolayers and overlaid with serum-free medium and S-9 mix were exposed to vinyl chloride gas mixed with air. After exposure, the treated cells were trypsinized, resuspended in growth medium, and survival and transformation assays performed. The methods described are illustrated by examples taken from an evaluation study using 120 compounds and found to be more than 90% accurate in distinguishing between carcinogens and non-carcinogens.