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.