Papilloma and carcinoma production in DMBA-initiated, onion oil-promoted mouse skin.

Groups of 20 females Ha/ICR mice were initiated with 25 micrograms 7,12-dimethylbenz[a]anthracene (DMBA) and promoted one week later with topical treatments three times per week of 5 micrograms phorbol myristate acetate (PMA) and/or onion oil or garlic oil. Promotion was continued for 49 weeks in most experiments. Promotion was continued for 60 weeks in the experiment that evaluated the effect of time intervals between PMA and garlic oil. All experiments were conducted with 0.2 ml acetone solutions of agents. Onion oil, but not garlic oil, was a weak promoter in mouse skin. A 1-mg dose produced five papillomas in three mice and one carcinoma in 330 days (18 survivors). The 10-mg dose was more effective; it produced cumulative yields of 56 papillomas in 14 mice and 7 carcinomas in 4 mice in 345 days (14 survivors). Onion oil is neither an initiator nor a whole carcinogen. The effects of intervals between PMA and a 1-mg dose of onion or garlic oil were determined. These intervals were -2 hrs, -1 hr, -0.5 hr, +0.5 hr, +1 hr, and +2 hrs with respect to time of PMA application. Maximal inhibition of papillomas by onion oil was observed at the +0.5-hr interval and was similar to that previously reported. Garlic oil is not a promoter. It inhibited papillomas at the +0.5-hr, +1.0-hr, and +2.0-hr intervals but did not appear to affect carcinoma production.