Promoting activity of 3-tert-butyl-4-hydroxyanisole (BHA) in BALB/3T3 cell transformation

3-Tert-butyl-4-hydroxyanisole (BHA), a synthetic antioxidant, is an initiator in the transformation of BALB/3T3 mouse embryo cells, when cells are treated first with the chemical and then with a tumor promoter, 12-O-tetradecanoylphorbol-13-acetate. In the present study, BHA was examined for its promoting activity in BALB/3T3 cell transformation. BHA in a range of 5-20 microg/ml enhanced transformation induced by a subthreshold dose of 3-methylcholanthrene (MCA, 0.1 microg/ml) in a dose-dependent manner. Statistically significant increases were noted in the proportion of dishes with transformed foci in the cultures treated with 10 and 20 microg/ml BHA following MCA as compared to the cultures treated with MCA alone. When BHA was applied to the cultures both on initiating and promoting stages in the absence of another initiator or promoter, however, BHA did not increase the transformation frequency, suggesting that the transforming activities of BHA are too weak and require combination with a potent initiator or promoter to attain complete transformation in this assay system. BHA did not increase postconfluent cell density nor induce DNA synthesis in density-arrested cells, suggesting that cell proliferation is excluded from the causal events of transformation enhancement by BHA in BALB/3T3 cells.