Fig. 5. EGFR ligand-induced ER-a downregulation is prevented by the specific EGFR inhibitor gefitinib in BT474 breast cancer cells. After 24-h serum starvation, we pretreated cells with or without 10 mM gefitinib for 30 min and then treated cells with 50 ng/ml TGFA (A, C) and EGF (B, D). Levels of p-, t-EGFR, p-, t-ERK and ER-a protein were detected by western blots (A, B). Levels of ER-a mRNA were detected by real-time PCR (C, D). Results are representative of three independent experiments. Values are mean ± SEM. * P<0.05 vs. (-) control, f P<0.05 vs. TGFA- or EGF-treated cells.