Retinoids and mammary gland differentiation

Certain retinoids serve as effective chemopreventive agents against breast cancer. The effective retinoids are also antiproliferative agents for the mammary gland both in vivo and in vitro. N-(4-hydroxyphenyl)retinamide (HPR) can inhibit the occurrence of hyperplastic alveolar nodules in C3H mice in vivo and 7,12-dimethylbenz[a]anthracene-induced nodule-like alveolar lesions in vitro. Moreover, HPR can also inhibit the phorbol ester-induced promotion of hyperplastic alveolar nodule development in vitro. HPR is metabolized by the mammary gland in vitro and one of the metabolites competes for the cytosolic retinoic acid-binding protein although the metabolite is not all-trans-retinoic acid.