VITAMIN-A, DIFFERENTIATION AND CANCER

Retinoids, which are derivatives of vitamin A, have a variety of effec ts on normal cellular differentiation and on the process of carcinogen esis. A number of novel endogenous retinol metabolites have been ident ified recently. The response of many cell types to retinoid treatment is mediated by retinoid receptors, and involves changes in gene expres sion, cell growth and cell differentiation. The gene encoding one of t he retinoic acid receptors is disrupted by the chromosome translocatio ns associated with acute promyelocytic leukemia, and the expression of another is altered in epithelial tumors; both of these findings have important implications for the use of retinoids as anti-carcinogenic a gents. It has been demonstrated recently that certain homeobox genes a re regulated by retinoids; these genes may also prove to be useful age nts for anti-carcinogenic therapies.