Expression profiles and functional associations of endogenous androgen receptor and caveolin-1 in prostate cancer
Nigel C Bennett1, John D Hooper, David W Johnson
1Centre for Kidney Disease Research, School of Medicine, University of Queensland, Translational Research Institute, Woolloongabba, Brisbane, Australia.
Background:
In prostate cancer (PCa) patients, the protein target for androgen deprivation and blockade therapies is androgen receptor (AR). AR interacts with many proteins that function to either co-activate or co-repress its activity. Caveolin-1 (Cav-1) is not found in normal prostatic epithelium, but is found in PCa, and may be an AR co-regulator protein.
Methods:
We investigated cell line-specific signatures and associations of endogenous AR and Cav-1 in six PCa cell lines of known androgen sensitivity: LNCaP (androgen sensitive); 22Rv1 (androgen responsive); PC3, DU145, and ALVA41 (androgen non-reliant); and RWPE1 (non-malignant). Protein and mRNA expression profiles were compared and electron microscopy used to identify cells with caveolar structures. For cell lines expressing both AR and Cav-1, knockdown techniques using small interfering RNA against AR or Cav-1 were used to test whether diminished expression of one affected the other. Co-sedimentation of AR and Cav-1 was used to test their association. A reporter assay for AR genomic activity was utilized following Cav-1 knockdown.
Results:
AR-expressing LNCaP and 22Rv1 cells had low endogenous Cav-1 mRNA and protein. Cell lines that expressed little or no AR (DU145, PC3, ALVA41, and RWPE1) expressed high endogenous levels of Cav-1. AR knockdown in LNCaP cells had little effect on Cav-1, but Cav-1 knockdown inhibited AR expression and genomic activity.
Conclusions:
These data show endogenous AR and Cav-1 mRNA and protein expression is inversely related in PCa cells, with Cav-1 acting on the androgen/AR signaling axis possibly as an AR co-activator, demonstrated by diminished AR genomic activity following Cav-1 knockdown.
Insights
Androgen receptor (AR) and Caveolin-1 (Cav-1) expression are inversely related in prostate cancer cells. Cav-1 knockdown reduces AR activity, suggesting Cav-1 may co-activate AR signaling.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Prostate cancer (PCa) therapies target the androgen receptor (AR).
- Caveolin-1 (Cav-1) is upregulated in PCa and may regulate AR activity.
- AR interacts with co-activator and co-repressor proteins.
Purpose of the Study:
- To investigate the relationship between AR and Cav-1 expression in PCa cell lines.
- To determine if Cav-1 influences AR activity.
Main Methods:
- Assessed AR and Cav-1 mRNA and protein expression in six PCa cell lines.
- Utilized electron microscopy to identify caveolar structures.
- Performed AR and Cav-1 knockdown experiments and a reporter assay for AR genomic activity.
Main Results:
- AR-expressing cell lines showed low Cav-1, while AR-low/negative cell lines showed high Cav-1.
- Cav-1 knockdown, but not AR knockdown, inhibited AR expression and genomic activity.
- AR and Cav-1 co-sedimentation indicated a physical association.
Conclusions:
- Endogenous AR and Cav-1 expression are inversely correlated in PCa cells.
- Cav-1 appears to act as an AR co-activator, modulating the androgen/AR signaling axis.
- Cav-1 knockdown diminishes AR genomic activity, supporting its role in AR signaling.
