Epidermal growth factor stimulation of human breast cancer cells in culture

Epidermal growth factor (EGF), a polypeptide found in human and animal blood and secretions, has been found to stimulate a variety of tissues in vitro including normal and malignant rodent mammary epithelium and human breast epithelial cells and fibroadenoma. We have studied the influence of EGF on malignant human breast tissue with a model system comprising human breast carcinoma cells growing in tissue culture. EGF stimulated growth of MCF-7 cells in serum-free medium. After 7 days in culture, a 2-fold increase in cell number and DNA content and a 3-fold increase in total protein were observed in cells incubated with EGF (10 ng/ml). As little as 0.01 ng/ml of EGF stimulated growth; 10 ng/ml was maximal. EGF effects on growth were noted for cells plated at a high as well as sparse (cloning) density. EGF also stimulated the rates of thymidine, uridine, and leucine incorporation into macromolecules in a dose- and time-dependent fashion. Stimulation of uridine and leucine incorporation was evident by 3 hr, whereas EGF stimulation of thymidine incorporation was delayed until 12 to 18 hr. EGF increased the proportion of cells active in DNA synthesis by nearly 2-fold. The combination of optimal concentrations of insulin (also a growth factor for these cells) and EGF did not stimulate growth above that seen with either hormone alone, suggesting a common step in their mechanism of action. The EGF effect was not dependent on the presence of serum and was not enhanced by dexamethasone as reported for other types of cells. EGF had no effect on another human breast cancer cell line, the MDA-231. These studies suggest that growth of some human breast cancers may be influenced by EGF.