EGF mediates multiple signals: dependence on the conditions.

Epidermal growth factor (EGF) has been reported to both increase and decrease proliferation and apoptosis. In KB cells, EGF-induced alteration in proliferation and apoptosis are concentration and time dependent. High concentrations of EGF (10(-7) and 10(-8) M) stimulated proliferation and inhibited apoptosis at 24 h, with apoptosis increasing with prolonged exposure. Low concentrations of EGF (10(-10)-10(-11) M) inhibited apoptosis without affecting proliferation. EGFR protein expression was downregulated at high and upregulated at low EGF concentrations. Significant inverse correlation was shown between EGFR expression level and apoptosis. These results suggest the EGF receptor involvement in the modulation of apoptosis and the role of EGF anti-apoptotic effects in EGF-induced apoptosis.