AUGMENTATION OF THE RESPONSE OF NORMAL MAMMARY EPITHELIAL-CELLS TO ESTRADIOL BY MAMMARY STROMA

Abstract

A 2-dimensional monolayer culture system is described in which mouse mammary stromal cells and colonies of normal epithelium are allowed to confront each other en bloc. Epithelial (and stromal) cell growth was inhibited by confrontation. Epithelial cell growth was reinitiated by estradiol (10-8 M) but not by dexamethasone. Reinitiated growth was inhibited by tamoxifen (10-6 M). Contact between stromal cells and epithelium was critical for the response to estradiol, and photomicrographic evidence was obtained that estradiol stimulated invasion of the stroma-epithelial interface. These observations are organized into a model for mitogenic action of estradiol that seems to reconcile observed disparities in the action of the hormone in vivo and in vitro.