Effects of estrogen, epidermal growth factor, and transforming growth factor-α on the growth of human breast epithelial cells in primary culture

Abstract

Since 17β-estradiol (E 2)-stimulated growth in human breast cancer cell lines has been shown to be accompanied by increased production of epidermal growth factor (EGF) and transforming growth factor-α (TGF-α) and their receptor, we investigated the effects of E 2 and these growth factors on the growth of human breast epithelial cells (HBEC) in primary culture. HBEC from normal, benign, and malignant tissues were cultured in serum-free medium [DME:F12(1:1), 5 mg/ml BSA, 10 ng/ml cholera toxin, 0.5 μg/ml cortisol, 10 μg/ml insulin] in the presence and absence of E 2, EGF, and TGF-α. Tritiated-thymidine ([ 3H]TdR) incorporation into DNA was used as a measure of cell growth. E 2 did not stimulate growth of any of the cultures at all concentrations examined (10 −9 to 10 −6 M). In contrast, EGF ranging from 1 to 100 ng/ml consistently increased the growth of cells of all three breast tissue types in a dose-dependent manner. The EGF stimulation was inhibited by MAb 528, a monoclonal antibody against the EGF receptor. TGF-α was equally or more effective in stimulating proliferation, although its dose-response range was different than that of EGF. E 2 and EGF together acted in a synergistic manner in 50% of the samples examined. These studies suggest that E 2 can exert effects on HBEC growth via modulation of the cells' response to EGF.