Characterization of epidermal growth factor receptor and action on human breast cancer cells in culture.

Epidermal growth factor (EGF) may play a role in regulating growth of breast cancer cells in vivo. We have examined the action of EGF on breast cancer cells in vitro and characterized the EGF receptor as a model system for its action in vivo. All of the fourteen breast cancer cell lines which grow attached to culture dishes specifically bound EGF, including one purportedly normal breast line (HBL-100). The one cell line examined which grows as a suspension, DU-4475, did not express measurable levels of EGF binding. The number of EGF binding sites per cell for the different cell lines varied from 200 EGF binding sites/cell (for MDA-MB-436) to 700,000 EGF binding sites/cell (for MDA-MB-231), with most cell lines having approximately 10,000 EGF binding sites/cell. Scatchard analysis of EGF binding to four of the breast cell lines indicated a single class of high-affinity binding sites for MDA-MB-231 cells (Kd = 200 pM; n = 220 fmol of EGF bound/mg of cell protein); and for T-47D cells (Kd = 4 nM, n = 85 fmol of EGF bound/mg of cell protein) and curvilinear plots for MCF-7 cells and HBL-100 cells. The EGF binding to MDA-MB-231 cells was specific for EGF and was maximum after 2 hr at 37 degrees, followed by a progressive loss of cell-associated radio-activity, which was prevented by the action of the lysosomal inhibitory agent chloroquine. Specific covalent binding of 125I-EGF to MDA-MB-231 cells indicated that the EGF receptor had molecular weights of 165,000 and 140,000. MCF-7 cells and T-47D cells grown in serum-free medium supplemented with 10 nM EGF for 3 days had significantly increased protein, DNA, and cell number, whereas MDA-MB-231 and ZR-75-1 cells did not respond significantly to EGF. These results indicate that EGF receptors are consistently expressed by breast cells grown attached to a surface but that some cell lines expressing EGF receptors do not respond mitogenically to EGF. The biochemical characteristics of EGF receptors in MDA-MD-231 breast cells are similar to those observed for EGF receptors in other human tissues.