Role of Epidermal Growth Factor Receptors and Their Ligands in Normal MammaryEpithelial and Breast Cancer Cells

摘要

The mechanisms of action of, and the factors that control the response(s)(type/magnitude) induced by epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) in normal mammary epithelial cells (MEC), and breast cancer cells are not yet fully understood. Comparative studies were carried out to determine whether EGF and TGF-alpha play distinct roles in regulating the development of normal MEC. Cell proliferation was analyzed using an MTT assay and by measuring 3H-thymidine incorporation. Functional differentiation was monitored using a casein ELISA protocol. Morphogenesis was monitored by light microscopic examination of the individual mammary epithelial organoids. Elaboration of matrix-degrading metalloproteinases was evaluated by zymogram analysis. Extensive cell proliferation, functional differentiation, and branching alveolar morphogenesis were observed when the MEC were cultured within a reconstituted basement membrane (RBM) in the presence of ALV Media with either 10 ng/ml mouse EGF (mEGF), 1 or 10 ng/ml human recombinant EGF (hrEGF), 1 or 10 ng/ml human recombinant TGF-a (hrTGF-alpha, or the combination of 10 ng/ml mEGF and hrTGF-a at 1 or 10 ng/ml). Both hrEGFand hrTGF-alpha appeared to enhance the secretion of an approx. 92 kDa matrix-degrading metalloproteinase when MEC were cultured within the RBM in the presence of ALV Media without hydrocortisone. Our preliminary studies suggest that it will be possible to take advantage of the recent upgrade to our model system which will allow for the examination of epithelial cell-specific effects when MEC are cultured alone and physiological effects when MEC are co-cultured with primary mammary stromal cells.