Inhibitory effects of biochanin A on benzo(a)pyrene induced carcinogenesis in mice.

Biochanin A was studied for its capacity to inhibit benzo(a)pyrene (BP) induced neoplasia in female Swiss Webster mice. To investigate the effect of biochanin A on the initiation step, biochanin A (500 mg/kg) was administered orally 48 hours prior to BP (3 mg/mouse), which was also given orally. This sequence of biochanin A and BP administration was repeated once a week for a total of 4 weeks. At 26 weeks after the last treatment, all the mice were sacrificed. To investigate the effect of biochanin A on the promotion step, a single subcutaneous injection of 0.5 mg of BP was given within 24 hours after birth, and biochanin A (0.125 mg/mouse) was injected intraperitoneally 3 times a week for 6 weeks after weaning. In the initiation protocol, the concomitant administration of biochanin A showed significant inhibition of the mean number of lung tumors (P less than 0.001) and the incidence of carcinoma of the forestomach (P less than 0.02). In the promotion protocol, biochanin A significantly inhibited the incidence (P less than 0.01) and the multiplicity (P less than 0.001) of pulmonary adenoma, compared with the group treated with BP alone. These results suggest that biochanin A inhibitory potential in the initiation, as well as in the promotion step of BP carcinogenesis in female Swiss-Webster mice.