Role of epidermal-growth-factor receptor in tumor progression in transformed human mammary epithelial cells

The presence of epidermal-growth-factor receptors (EGFR) and of its ligands (TGFalpha and amphiregulin) in breast-cancer tissues suggests that they play a paracrine/autocrine role in tumor growth or progression. This hypothesis was tested on 3 cell lines, S2T2, NS2T2A and NS2T2A1. These epithelial cells are derived from a normal human breast-epithelial-cell culture transformed by SV40-T Ag, are of the same clonal origin, have respectively increasing levels of EGFR, TGFalpha, amphiregulin and of thymidine-kinase activity associated with increasing tumorigenic potential in nude mice (tumor intake and tumor volume). The monoclonal antibody MAb 425, which blocks ligands interaction with EGFR, reduced by more than 90% anchorage-independent growth of the most tumorigenic cells, NS2T2A1. Another anti-EGFR MAb, 528, reduced to 25% of controls the mean tumor mass after NS2T2A1 grafting in mice. Anti-sense RNA expression of EGFR in these cells confirmed the importance of this receptor in tumor progression, since it reduced significantly the tumor volume and tumor weight of NS2T2A1 cells to 16% of those in mock-transfected control cells.