In the presence of serum (Fig. 2c, d), the cell growth stimulated with EGF was faster than that in serum-free medium (Fig. 2a, b), and the cell growth started to decelerate at day 3 and reached a plateau phase at day 4–5, indicating that EBP50 could really inhibit the EGF-induced cell proliferation in human breast cancer cell. This evidence concerns the gene NHERF1 and breast cancer.