The expression of basic fibroblast growth factor and its receptor in cell lines derived from normal human mammary gland and a benign mammary lesion
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Y Ke1, D G Fernig, M C Wilkinson
1Department of Biochemistry, University of Liverpool, UK.
Abstract:
mRNA for basic Fibroblast Growth Factor (bFGF) was expressed in a series of SV40-transformed human mammary cell lines as molecules of 7.1, 3.6, 2.0 and 1.2 kb. This expression was much weaker in those lines of epithelial morphology than in myoepithelial-like cell lines derived from them. It was confirmed, using northern hybridization to single-stranded RNA probes, that the multiple mRNAs were transcribed from the coding strand for bFGF. bFGF activity was detected in extracts of the cells and the relative amounts of activity corresponded in general to the amounts of mRNA found. Similar results were obtained from spontaneously transformed cell lines derived from a human benign breast lesion. The presence of bFGF protein in the extracts was confirmed by western blotting, which showed a band of 18-19 kDa, migrating in the same position as authentic bFGF; in addition, the myoepithelial-like cells showed prominent bands of bFGF at 24 and 26 kDa. No FGF receptor was detectable by the binding of 125I-bFGF to the SV40-transformed cell lines or to the epithelial cell lines from the benign breast lesion, but both high- and low-affinity receptors were found on myoepithelial-like cells derived from the latter. The results indicate that differentiation to the human myoepithelial-like phenotype in culture is associated with the enhanced expression of bFGF, and it is suggested that bFGF, immunocytochemically detected in the basement membrane of the human breast, may arise, at least in part, from the myoepithelial cells of the mammary parenchyma.
Insights
Myoepithelial-like cells enhance basic Fibroblast Growth Factor (bFGF) expression, suggesting a role for these cells in bFGF production within the human breast. This finding is crucial for understanding mammary gland development and function.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Basic Fibroblast Growth Factor (bFGF) plays a role in cell growth and differentiation.
- Mammary gland epithelial and myoepithelial cells have distinct functions and molecular profiles.
Purpose of the Study:
- To investigate the expression of basic Fibroblast Growth Factor (bFGF) in different human mammary cell lines.
- To determine the relationship between cell morphology, differentiation, and bFGF expression and activity.
- To explore the presence and function of FGF receptors in these cell types.
Main Methods:
- Northern hybridization to detect bFGF mRNA.
- Western blotting to confirm bFGF protein presence and size.
- 125I-bFGF binding assays to identify FGF receptors.
Main Results:
- SV40-transformed human mammary cell lines expressed multiple bFGF mRNA transcripts (7.1, 3.6, 2.0, 1.2 kb).
- Myoepithelial-like cell lines exhibited significantly higher bFGF mRNA expression and activity compared to epithelial-like cell lines.
- bFGF protein was detected in cell extracts, with myoepithelial-like cells showing additional prominent bands at 24 and 26 kDa.
- FGF receptors were detected on myoepithelial-like cells but not on SV40-transformed or benign epithelial cell lines.
Conclusions:
- Differentiation to a human myoepithelial-like phenotype in culture is associated with enhanced bFGF expression.
- Myoepithelial cells are a potential source of bFGF found in the basement membrane of the human breast.
- These findings contribute to understanding the paracrine and autocrine roles of bFGF in mammary gland biology.