Effects of the differentiating agents (inducers) dimethylacetamide, di- and tetramethylurea on epidermal tumor promotion by retinyl (vitamin A) acetate and croton oil in hamster cheek pouch.

The cell-differentiating agents (inducers) dimethylacetamide, dimethylurea and tetramethylurea significantly lowered the yields and/or incidences of total tumors, benign plaques, benign hyperkeratotic lesions and advanced tumors promoted by retinyl acetate or croton oil after initiation by 7,12-dimethylbenz(a)anthracene. The percentage of plaques was increased by the inducers suggesting that they inhibited progression of plaques to more advanced tumors. These results suggest that topical application of inducers might have therapeutic potential in epidermal carcinoma.