Monoclonal antibodies against epidermal growth factor receptor induce prolactin synthesis in cultured rat pituitary cells (GH3)

Abstract

The addition of epidermal growth factor (EGF) to cultured rat pituitary cells (GH3) leads to increased synthesis of prolactin and to partial inhibition of cell proliferation. Monoclonal antibodies generated against EGF receptor from human epidermoid carcinoma (A-431) cells were used to characterize the EGF receptor kinase system of GH3 cells and to investigate the role of the hormone-receptor complex in the expression of the prolactin gene in these cells. The EGF receptor of GH3 cells is a 170,000-dalton protein associated with a protein kinase. It is similar but not identical to the EGF receptor identified in other tisses. The immunoprecipitated membrane receptor is phosphorylated on both serine and tyrosine residues. The monoclonal antibody denoted 2G2-IgM binds to EGF receptor on GH3 cells. Like EGF, the monoclonal antibody induced the synthesis of prolactin and morphological changes in these cells. Hence, EGF receptor in GH3 cells, when properly triggered, contains all of the biological attributes necessary for the induction of EGF-induced gene expression and morphological changes in GH3 cells.