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.
McIntyre
B S
BS
Hormonal Carcinogenesis Laboratory, College of Pharmacy, Washington State University, Pullman 99164-6510.
Birkenfeld
H P
HP
Sylvester
P W
PW
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