Modulatory effects of snuff, retinoic acid, and beta-carotene on DMBA-induced hamster cheek pouch carcinogenesis in relation to keratin expression.

The hamster cheek pouch (HCP) serves as an excellent model system not only for the studies on initiation and promotion but also for the modulation of experimental oral carcinogenesis. In our studies, HCPs treated with 7,12-dimethylbenz[a]anthracene (DMBA) showed both cheek pouch and stomach papillomas. Utilizing this model system, we tested and compared the modulatory effects of snuff, retinoic acid, and beta-carotene on the incidence of tumors and the keratin expression pattern. HCPs treated with snuff, either alone or in combination with DMBA, resulted in stomach papillomas. HCPs treated with snuff showed no cheek pouch tumors, and those treated with snuff and DMBA showed only 10-15% tumor incidence. Both beta-carotene and retinoic acid showed a total inhibition of DMBA-induced carcinogenesis in the HCP as well as in the stomach. The keratin expression pattern showed alterations depending on the experimental conditions.