Inhibition of experimental oral carcinogenesis by topical beta carotene

beta-Carotene was found to significantly inhibit the formation of 7,12-dimethylbenz[a]anthracene (DMBA)-induced squamous cell carcinoma of hamster buccal pouch when applied topically on days alternate to the application of 0.25% DMBA in heavy mineral oil thrice weekly for 22 weeks. An initial experiment utilized 40 male young adult Syrian hamsters divided into four equal groups. Group 1 had DMBA applied to left buccal pouches thrice weekly. Group 2 had DMBA applied as in group 1 but also beta-carotene thrice weekly on days alternate to the DMBA application. Group 3 animals were painted with only beta-carotene and group 4 animals were untreated controls. In a second experiment with 80 animals, beta-carotene was found to inhibit oral carcinogenesis in an initiation--promotion hamster buccal pouch system using 0.1% DMBA as initiator and 40% benzoyl peroxide as promoter. beta-Carotene inhibited both initiation and promotion.