title: Elevation of mouse mammary tumor virus envelope glycoprotein (Gp52) by growth factors.
abstract: Murine mammary tumor cells (C3H Mm5mt/cl and B9) were grown in serum-free culture to examine the effects of different polypeptide growth factors on viral glycoprotein (gp52) release into extracellular culture fluids. Epidermal growth factor (EGF) elevated extracellular virion-associated and soluble gp52 levels of mouse mammary tumor virus producer and nonproducer cells. While EGF effectively and consistently elevated gp52 levels at 20 ng/ml, fibroblast growth factor was less effective, and platelet-derived growth factor failed to elevate gp52 levels. Growth factors, EGF and fibroblast growth factor, stimulated cell growth to a greater degree than platelet-derived growth factor and were also more consistently mitogenic. The EGF-mediated elevation in gp52 was statistically significant as compared to controls; however, increases were smaller in magnitude than those obtained with the classical glucocorticoid stimulator, dexamethasone. The results demonstrate that EGF can quantitatively influence extracellular levels of gp52 detected in viral particle and virus-free soluble antigen fractions. These in vitro findings suggest that growth factors such as EGF may play a role in determining tumor cell levels of mouse mammary tumor virus production and levels of gp52 shed as a soluble marker for tumor.
authors.affiliation: Department of Microbiology, Texas Tech University Health Sciences Center, Lubbock 79430.
authors.forename: E M
authors.initials: EM
authors.lastname: Ritzi
authors.forename: E B
authors.initials: EB
authors.lastname: Walthall
mesh_terms: D000818:Animals; D000957:Antigens, Viral, Tumor / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005346:Fibroblast Growth Factors / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology*; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism* / Q000382:microbiology; D008324:Mammary Tumor Virus, Mouse / Q000187:drug effects* / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology
chemical_list: D000957:Antigens, Viral, Tumor; D006133:Growth Substances; D010982:Platelet-Derived Growth Factor; C040612:glycoprotein 52 antigen, Mouse mammary tumor virus; D005346:Fibroblast Growth Factors; D004815:Epidermal Growth Factor; D003907:Dexamethasone