Fig. (4) rhEGF-induced changes in expression of EGFR, Ki67, and PCNA with respect to time.The cells were incubated for 18-24 hours in serum-free media (0.5% FBS) and treated with rhEGF (10nM) for 5 min, 4, 24, 48, or 72 hours. Ki67 significantly decreased in cancer cell lines and increased in the normal fibroblasts.