Role of androgens in proliferation and differentiation of mouse mammary epithelial cell line HC11

Androgens have been found in mammary epithelium and in milk throughout the cycle of the mammary gland in vivo. The aim of this study was to investigat e the possible role of these substances in mammary epithelial growth and di fferentiation in the mouse HC11 cell line. Cells were stimulated with testo sterone, dihydrotestosterone, androstenedione and 5 alpha -androstane-3 alp ha ,17 beta -diol at concentrations ranging between 0.3 nM and 30 nM. Cypro terone acetate or flutamide, androgen receptor antagonists, (3 muM) were us ed to block specific androgen effects. Proliferative effects were measured by an MTT (tetrazolium blue) conversion test and [H-3]thymidine uptake. HC1 1 cells were transfected with p beta cCAT, a chimeric rat beta -casein gene promoter-chloramphenicol acetyl transferase (CAT) gene construct and CAT E LISA was used to determine gene expression. RT-PCR was performed to detect androgen receptor expression. After 24, 48 and 72 h androgens significantly (P<0.05) increased proliferation. Androgen antagonists significantly (P<0. 05) reduced the proliferative effects. Furthermore androgens potentiated th e lactogenic effect of prolactin, insulin and dexamethasone (P<0.05). Final ly, the androgen receptor gene was expressed in both proliferating and diff erentiated HC11 cells. These observations lead us to hypothesize an activit y of this class of steroids in mammary physiology. In particular, androgens stimulate cell proliferation and <beta>-casein gene expression; this influ ence appears to be mediated by androgen receptors.