Expression of epidermal growth factor (EGF) and the EGF receptor in human tissues

The EGF-EGF receptor system has been widely examined for signal transduction, control of cell growth and differentiation, and in vivo physiological function and carcinogenesis. The localization of EGF receptors in vivo led to the idea that the system is operative in proliferation and differentiation of cells and tissues. However, a consensus for its distribution and function in human tissues has not yet been determined because of discrepancies in the reported results. Using a highly specific monoclonal antibody against the EGF receptor, we examined various tissues of an infant and adults as well as embryonal carcinoma. We observed restricted localization of EGF receptors in basal cells of epithelial tissues and duct cells of secretory tissues. Fibroblasts express a high level of EGF receptors when they are rapidly growing. Using the monoclonal anti-EGF antibodies, we observed that EGF is localized to differentiated cells rather than to stem cells such as glandular tissues. We also observed that some cells express both EGF and the EGF receptor. All histochemical results indicated that in epidermis and various glandular tissues, EGF may be expressed in differentiating cells derived from the stem cells expressing EGF receptors.