THE ROLE OF MAMMARY STROMA IN MODULATING THE PROLIFERATIVE RESPONSE TO OVARIAN HORMONES IN THE NORMAL MAMMARY-GLAND

Postnatal mammary gland development is highly dependent on the ovarian steroids, estrogen and progesterone. However, evidence from both in v itro and in vivo studies indicates that steroid-induced development oc curs indirectly, requiring stromal cooperation in epithelial prolifera tion and morphogenesis. Stromal cells appear to influence epithelial c ell behavior by secretion of growth factors and/or by altering the com position of the extracellular matrix in which epithelial cells reside. This review will discuss the requirement for stromal tissue in modula ting proliferative responses to ovarian hormones during postnatal deve lopment and the potential role of the EGF IGF, HGF and FGF(3) growth f actor families. Additionally, the roles of extracellular matrix protei ns, including fibronectin, collagens and laminin, will be summarized.