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Elevation of mouse mammary tumor virus envelope glycoprotein (Gp52) by growth factors
1Department of Microbiology, Texas Tech University Health Sciences Center, Lubbock 79430.
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.
Insights
Epidermal growth factor (EGF) increases mouse mammary tumor virus glycoprotein (gp52) release in cell cultures. This suggests growth factors may influence viral production and shed gp52 levels in tumors.
Area of Science:
- Molecular Biology
- Virology
- Cell Biology
Background:
- Mouse mammary tumor virus (MMTV) is a retrovirus associated with mammary tumors.
- Viral glycoprotein (gp52) is a key component of MMTV and can be detected extracellularly.
- Polypeptide growth factors regulate cellular functions, including proliferation and differentiation.
Purpose of the Study:
- To investigate the effect of different polypeptide growth factors on MMTV gp52 release.
- To determine if epidermal growth factor (EGF) influences extracellular gp52 levels in MMTV-producing and non-producing cells.
Main Methods:
- Murine mammary tumor cells (C3H Mm5mt/cl and B9) were cultured in serum-free conditions.
- Cells were treated with various growth factors, including EGF, fibroblast growth factor, and platelet-derived growth factor.
- Extracellular levels of virion-associated and soluble gp52 were measured.
Main Results:
- Epidermal growth factor (EGF) significantly elevated extracellular gp52 levels in both producer and nonproducer cells.
- Fibroblast growth factor showed a less pronounced effect, while platelet-derived growth factor had no significant impact on gp52 release.
- EGF and fibroblast growth factor were more mitogenic and stimulated cell growth more effectively than platelet-derived growth factor.
Conclusions:
- EGF quantitatively influences the extracellular levels of MMTV gp52.
- These findings suggest that growth factors like EGF may play a role in regulating MMTV production.
- EGF may also affect the shedding of gp52 as a soluble tumor marker.