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Androgen receptor and prostate cancer invasion
Lorella Bonaccorsi1, Monica Muratori, Vinicio Carloni
1Dipartimento di Fisiopatologia Clinica, Unità di Andrologia, Università di Firenze, Firenze, Italy. l.bonaccorsi@dfc.unifi.if
Abstract:
Evidence indicates that androgen-sensitive prostate cancer cells have a lower malignant potential. We previously demonstrated that expression of androgen receptor (AR) by transfection of the androgen-independent prostate cancer cell line PC3 decreases invasion and adhesion of these cells through modulation of alpha6beta4 expression. Treatment with the androgen further reduced adhesion and invasion of the cells without, however, modifying alpha6beta4. Here we investigated whether the androgen has a direct effect on alpha6beta4-EGF receptor (EGFR) interaction and signalling leading to invasion of these cells. Immunoconfocal microscopy demonstrated that in control cells (PC3-Neo), alpha6beta4 and EGFR colocalize and redistribute in response to epidermal growth factor (EGF). In PC3-AR cells colocalization and redistribution between the two molecules was reduced and abolished by pre-treatment with R1881. Co-immunoprecipitation studies demonstrated that tyrosine phosphorylation of beta4 in response to EGF was reduced in PC3-AR cells compared to PC3-Neo. Immunoconfocal and co-immunoprecipitation studies demonstrated colocalization at membrane level and co-immunoprecipitation of EGFR and AR, indicating an interaction between the two proteins. PI3K activity, a key signalling pathway for invasion of these cells, was decreased in PC3-AR cells in response to EGF and further reduced by treatment with R1881. EGFR internalization was strongly reduced in PC3-AR compared with PC3-Neo cells and was reduced by treatment with R1881. In conclusion, the expression of AR by transfection in PC3 cells confers a less malignant phenotype by interfering with EGFR--alpha6beta4 interaction and signalling leading to invasion through a mechanism involving an interaction between the classic AR and EGFR.
Insights
Androgen receptor (AR) expression in prostate cancer cells reduces invasion by interfering with the interaction between epidermal growth factor receptor (EGFR) and alpha6beta4. This finding suggests AR influences cancer malignancy.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Androgen-sensitive prostate cancer cells exhibit lower malignancy.
- Androgen receptor (AR) expression in PC3 cells reduces invasion and adhesion.
- Androgen treatment further decreases invasion without altering alpha6beta4 levels.
Purpose of the Study:
- Investigate the direct effect of androgens on alpha6beta4-epidermal growth factor receptor (EGFR) interaction and signaling in prostate cancer cell invasion.
- Determine the role of AR in modulating EGFR-mediated signaling pathways crucial for cell invasion.
Main Methods:
- Immunoconfocal microscopy to assess protein colocalization and redistribution.
- Co-immunoprecipitation to analyze protein interactions and tyrosine phosphorylation.
- Measurement of phosphatidylinositol 3-kinase (PI3K) activity.
- Assessment of EGFR internalization.
Main Results:
- AR expression reduced alpha6beta4 and EGFR colocalization and redistribution in response to EGF.
- Tyrosine phosphorylation of beta4 and PI3K activity were decreased in AR-expressing cells.
- AR interacted with EGFR at the membrane level.
- EGFR internalization was significantly reduced in AR-expressing cells.
Conclusions:
- AR expression in PC3 cells confers a less malignant phenotype.
- AR interferes with EGFR-alpha6beta4 interaction and signaling pathways leading to invasion.
- A mechanism involving AR and EGFR interaction underlies the reduced invasiveness.