Relative tumor initiating activity of benzo[ a]fluoranthene, benzo[ b]fluoranthene, naphtho[1,2- b]fluoranthene and naphtho[2,1- a]fluoranthene on mouse skin

Abstract

The tumor-initiating activities of benzo[ a]fluoranthene (BaF), benzo[ b]fluoranthene (BbF), naphtho[1,2- b]fluoranthene (NbF) and naphtho[2,1- a]fluoranthene (NaF) were evaluated on the skin of female CD-1 mice. Each of these polycyclic aromatic hydrocarbons was assayed at total initiation doses of 1.0 and 4.0 μmol/mouse. These hydrocarbons were applied in 10 subdoses administered every other day. Promotion commenced 10 days after the last initiator dose and consisted of thrice weekly application of 2.5 μg of tetradecanoylphorbol acetate for 20 weeks. BbF was the most potent tumor initiator inducing a 100% incidence of tumor-bearing mice with an average of 8.5 tumors per mouse at a total initiator dose of 1.0 μmol. NaF was slightly more active as a tumor initiator than either NbF or BaF. NaF induced a 90% incidence of tumor-bearing mice with an average of 5.9 tumors per mouse at a total initiator dose of 1.0 μmol. BaF and NbF at a total initiator dose of 4.0 μmol exhibited similar tumor-initiating activity with both inducing a 90% incidence of tumor-bearing mice with an average of 4.3 and 6.6 tumors per mouse, respectively. However, at a total initiator dose of 1.0 μmol, BaF and NbF induced a 95% and 65% incidence of tumor-bearing mice with an average of 3.3 and 2.5 tumors per mouse, respectively.