Relationship between epidermal growth factor receptor levels, autophosphorylation and mitogenic-responsiveness in normal mouse mammary epithelial cells in vitro.
Mammary epithelial cells were isolated from mid-pregnant BALB/c mice, grown within collagen gels and maintained on DME/F12 (1:1) media containing 10% bovine calf serum and 10 micrograms/ml insulin. Initial time-course and dose-response studies showed that epidermal growth factor (EGF)-induced autophosphorylation of the EGF-receptor (EGF-R) in these cells was maximal 5 min after exposure to 75 ng/ml EGF. Mammary epithelial cells displaying little or no growth during their first 2 days in primary culture cells were found to contain low levels of EGF-R. However, EGF-induced autophosphorylation of the EGF-R in these cells was extremely intense. Subsequent studies demonstrated that during the proliferative and plateau phases of growth, EGF-R levels progressively increased, while conversely EGF-induced autophosphorylation of the EGF-R decreased over time in primary culture. These results demonstrate that EGF-R levels and autophosphorylation do not show a direct correlation with mammary epithelial cell mitogen-responsiveness. Intense EGF-R autophosphorylation appears to be required for initiating growth, but sustained mammary epithelial cell proliferation occurs when EGF-R autophosphorylation is low. This inverse relationship between EGF-R levels and autophosphorylation may reflect changes in receptor affinity and function during the various phases of mammary epithelial cell growth in primary culture.
Hormonal Carcinogenesis Laboratory, College of Pharmacy, Washington State University, Pullman 99164-6510.
B S
BS
McIntyre
H P
HP
Birkenfeld
P W
PW
Sylvester
D000818:Animals; D015153:Blotting, Western; D002452:Cell Count; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004847:Epithelial Cells; D004848:Epithelium / Q000737:chemistry / Q000187:drug effects; D066246:ErbB Receptors / Q000032:analysis / Q000378:metabolism*; D005260:Female; D008321:Mammary Glands, Animal / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D008934:Mitogens / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D011247:Pregnancy; D015398:Signal Transduction; D013997:Time Factors
D017077:Culture Media, Conditioned; D008934:Mitogens; D004815:Epidermal Growth Factor; D066246:ErbB Receptors