Dose response effect of retinyl acetate on DMBA induced carcinogenesis in the hamster cheek pouch

The role of vitamin A in the induction and growth of chemically induced tumors is still controversial. While in some studies vitamin A influenced inhibition of chemically induced tumors was observed, other studies report on an enhancing influence of this substance on tumor induction. The cheek pouch epithelium of sixty five Syrian golden hamsters was exposed to DMBA and different doses of retinyl acetate, singly and in combination with DMBA. The findings suggest that 1) a significant delay occurs in tumor induction in animals treated with DMBA in combination with a higher concentration (2.0%) of retinyl acetate, 2) retinyl acetate at lower concentration (0.5 and 1.0%) does not inhibit or delay tumor induction.