Potentiating effect of vitamin a on 9-10 dimethyl 1-2 benzanthracene—carcinogenesis in the hamster cheek pouch

Hamster cheek pouches were painted three times weekly for 2 to 12 weeks with 0.5% 9-10 dimethyl 1-2 benzanthracene (DMBA) and/or 10% vitamin A dissolved in liquid paraffin. With vitamin A alone, foci of acanthosis first appeared after 4 weeks. After DMBA alone for 6 weeks intraepithelial carcinoma was present. However, after only 4 weeks application of the combination of DMBA and vitamin A, intraepithelial carcinomas were found and after 6 weeks infiltrating carcinomas were present. After 8 weeks infiltrating carcinomas were also present in pouches treated with DMBA alone but at this stage, as well as after 10 and 12 weeks, the combination of DMBA and vitamin A had induced more anaplastic and larger tumors than DMBA alone. These findings may be the result of an addition of the epithelial hyperplasia effected by vitamin A and the carcinogenic effect of DMBA. Alternatively, the increased permeability of cellular and subcellular membranes induced by vitamin A may facilitate the entry of DMBA into the cells, thus potentiating its carcinogenic effect.