Promoting effect of croton oil on the induction of cervical and vaginal cancers with herpes simplex virus types 1 and 2 in mice.

Hybrid Swiss virgin mice (Kuan-min strain) were challenged intravaginally with uv-inactivated herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2) twice a week for 16 times and subsequently with croton oil or control medium twice a week for 27 times. After a period of 180 days the exposure to HSV-2 plus control medium induced premalignant and malignant lesions of the cervix and vagina in 50.0% of the mice. The exposure to HSV-2 plus croton oil induced similar lesions in 78.2% of the mice. The exposure to HSV-1 combined with either control medium or croton oil induced lesions in 37.2 and 58.3% of the mice, respectively. No malignant lesions were found in the control mice. These results reveal that (1) HSV-1 and HSV-2 have a similar oncogenic potential, and (2) croton oil can promote the induction of cervical and vaginal cancers with HSV-1 and HSV-2. Additionally, these results suggest that the virus-induced carcinogenesis of cervix and vagina might be similar to the classical two-stage carcinogenesis model. This animal model seems to be more suitable for studying the prevention and treatment of cervical and vaginal cancers because the period of this experiment is significantly shorter than that of experiments reported by other investigators and the frequency of the malignant lesion is significantly higher than or similar to that of the same lesion reported in other experiments.