CHARACTERIZATION OF EPIDERMAL GROWTH-FACTOR RECEPTOR AND ACTION ON HUMAN-BREAST CANCER-CELLS IN CULTURE

Abstract

Epidermal growth factor (EGF) may play a role in regulating growth of breast cancer cells in vivo. The action of EGF on breast cancer cells was examined in vitro and the EGF receptor was characterized as a model system for its action in vivo. All of the 14 [human] breast cancer cell lines [MDA-MB-231 cells, BT-474 cells, BT-20 cells, MDA-MB-453 cells, BT-549 cells, MDA-MB-330 cells, HSO-578T cells, T-47D cells, HBL-100 cells, MDA-MB-175 cells, MCF-7 cells, MDA-MB-157 cells, ZR-75-1 cells and MDA-MB-436 cells] which grow attached to culture dishes specifically bound EGF, including 1 purportedly normal breast line (HBL-100). The 1 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 .apprx. 10,000 EGF binding sites/cell. Scatchard analysis of EGF binding to 4 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 h at 37.degree., followed by a progressive loss of cell-associated radioactivity, 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 MW 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. EGF receptors are consistently expressed by breast cells grown attached to a surface but 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.