Initiating activity of 3-tert-butyl-4-hydroxyanisole (3-BHA) and its metabolites in two-stage transformation of BALB/3T3 cells.

3-tert-Butyl-4-hydroxyanisole (3-BHA) and its metabolites, tert-butyl-1,4-benzoquinone (BQ) and 3-tert-butyl-5-methoxy-1,2-benzoquinone (BHAoQ), were tested for initiating activity in a two-stage transformation assay using BALB/3T3 cells. Cells were treated first with a test chemical and then with the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA). In the absence of TPA the test chemicals did not induce cell transformation. With the promoting treatment, 3-BHA and BQ induced dose-dependent cell transformation. There were statistically significant increases in the proportion of dishes with transformed foci in the cultures treated with 30 micrograms/ml 3-BHA plus TPA (15 of 24 dishes, P less than 0.005) and with 0.4 microgram/ml BQ plus TPA (12 of 22 dishes, P less than 0.02) as compared to the cultures treated with DMSO plus TPA (5 of 24 dishes). BHAoQ caused a non-significant increase in transformation frequency in the presence of TPA. In conclusion, 3-BHA and BQ had an initiating activity in the cell transformation system and the potency of BQ was approximately 100 times higher than that of 3-BHA.