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Increased epidermal growth factor receptor gene expression by gamma-interferon in a human breast carcinoma cell line
A W Hamburger1, G D Pinnamaneni
1University of Maryland Cancer Center, Baltimore 21201.
Abstract:
The interferons are a group of naturally occurring proteins that inhibit the growth of tumours in vivo and many transformed cell lines in vitro. The mechanisms of action of interferon, however, remain unclear. The IFN induced inhibition of growth of many epithelial cancer cell lines is associated with changes in Epidermal Growth Factor Receptor (EGFR) binding or expression. Therefore, we examined the effect of IFN treatment on the expression of EGFR in a human breast carcinoma cell line, MDA 468. We have found the IFN-gamma inhibited, in a dose dependent fashion, the growth of MDA 468 cells. IFN decreased cell surface binding of 125I-EGF to EGFR by changing receptor number rather than affinity. However, total cellular receptor protein, as measured by immunoprecipitation with monoclonal antibodies, was increased in IFN-treated cells. The half-life of the metabolically labelled receptor was unchanged by treatment with IFN. Increased amounts of EGFR mRNA were observed in MDA 468 cells treated with IFN-gamma for 3 days. The levels of mRNA increased with time in culture, reaching a peak of four times control values after 5 days of treatment. This effect was observable with as little as 10 U ml-1 of IFN-gamma. Treatment of the cells with Actinomycin D to inhibit new RNA synthesis suggested that the stability of EGFR mRNA was not enhanced in IFN-gamma treated cells. The increase in receptor mRNA induced by IFN was not inhibited by cycloheximide. These data suggest IFN-gamma can increase expression of EGFR mRNA and protein in MDA 468 cells. Increased expression of EGFR mRNA and protein by IFN-gamma is associated with inhibition of cell growth.
Insights
Interferon-gamma (IFN) inhibits breast cancer cell growth by increasing Epidermal Growth Factor Receptor (EGFR) mRNA and protein. This suggests a novel mechanism for IFN
Area of Science:
- Oncology
- Molecular Biology
- Immunology
Background:
- Interferons (IFNs) are proteins known to inhibit tumor growth.
- The precise mechanisms by which IFNs exert their anti-tumor effects are not fully understood.
- IFN-induced growth inhibition in cancer cells is often linked to alterations in Epidermal Growth Factor Receptor (EGFR) expression or binding.
Purpose of the Study:
- To investigate the effect of Interferon-gamma (IFN-gamma) on Epidermal Growth Factor Receptor (EGFR) expression in a human breast carcinoma cell line (MDA 468).
- To elucidate the molecular mechanisms underlying IFN-gamma's impact on EGFR in breast cancer cells.
Main Methods:
- Treatment of MDA 468 cells with varying doses of IFN-gamma.
- Assessment of cell growth inhibition.
- Measurement of 125I-EGF binding to cell surface EGFR.
- Quantification of total cellular EGFR protein via immunoprecipitation.
- Analysis of EGFR mRNA levels using Northern blotting or similar techniques.
- Investigation of mRNA stability using Actinomycin D.
- Assessment of protein synthesis dependence using cycloheximide.
Main Results:
- IFN-gamma demonstrated dose-dependent inhibition of MDA 468 cell growth.
- IFN-gamma reduced cell surface EGFR binding by altering receptor number, not affinity.
- Total cellular EGFR protein levels increased in IFN-gamma treated cells.
- EGFR mRNA levels significantly increased in a time-dependent manner following IFN-gamma treatment, peaking at 5 days.
- The increase in EGFR mRNA was independent of enhanced mRNA stability or new protein synthesis.
Conclusions:
- IFN-gamma treatment leads to increased expression of both EGFR mRNA and protein in MDA 468 breast carcinoma cells.
- The observed increase in EGFR expression is associated with the growth inhibitory effects of IFN-gamma.
- These findings suggest a novel mechanism for IFN-gamma's anti-cancer activity involving modulation of EGFR signaling pathways.