Growth-inhibitory and growth-stimulatory effects of epidermal growth factor on human breast cancer cell line, MDA.MB.436: dependence on culture conditions.

Epidermal growth factor (EGF) is growth inhibitory for some cell lines, especially those having over-expressed EGF receptors. We have examined the effects of murine EGF on the growth of the human breast cancer cell line, MDA.MB.436, which has low numbers of EGF receptors. In the presence or absence of serum a 6 day exposure to 0.1 ng/ml EGF causes inhibition of growth if the culture medium is left unchanged during the course of the experiment but the same concentration of EGF causes stimulation above control if the EGF-containing medium is replaced daily. A 1 day exposure to 0.1 ng/ml followed by return to control medium has no effect on subsequent growth. The cells do not synthesize EGF receptor binding activity and added EGF is degraded within 2 days, suggesting that the inhibitory effects of EGF persist in its absence.