Influence of excess of retinoid on DMBA carcinogenesis.

This paper reports a study on the influence of excess of vitamin A palmitate on the induction and maintenance of oral tumors. Sixty four weanling Syrian hamsters were divided in four groups and painted three times a week, either with 0.5% DMBA or 15% vitamin A palmitate, singly or in combination. A possible mild immune response evoked by vitamin A palmitate is considered responsible for the delayed induction of the tumors. In all animals exposed to carcinogen + vitamin A the induced tumors were small in size and histologically verified as well differentiated epidermoid carcinomas. In control group with sole vitamin A palmitate application the cheek pouch showed considerably increased keratinization.