Relevance of α-1 adrenoreceptor antagonist Doxazosin and PI3K pathway in prostate cancer progression: An assessment of in vitro mechanisms.
Article published in Urologia Polska 2008/61/Supl. 1.

authors

Maciej Salagierski, Hanna Romańska, Rachel Bruton, Zulfigar Gulzar, Paul Abel, Marek Sosnowski, El-Nasir Lalani

I Klinika Urologii UM w Łodzi
Department of Pathology, University of Birmingham, UK
Department of Surgery, Imperial College, Hammersmith Campus, London, UK

summary

Introduction.

Hormone refractory prostate cancer (PCa) is a lethal disease. It is believed that a progression to this final stage of cancer is related to the activation of alternative, androgen-independent cell signaling pathways. It has been postulated that androgen ablation therapy leads to the activation of PI3K/PTEN/AKT pathway and Bcl-2 upregulation. Doxazosin, a selective α-1 adrenoreceptor antagonist, widely used in the management of benign prostatic hyperplasia has been recently demonstrated to induce apoptosis in PCa cells in vitro and in vivo. The mechanism of its action still remains unknown.

Objectives.

The aim of our study was to assess a correlation between doxazosin- induced cell death, PI3K pathway and Bcl-2 expression in PCa cells.

Materials and methods.

An in vitro model mimicking the natural progression of PCa was used in the study. Du 145 [AR(-), Bcl-2(-)], the parental cell line derived from PCa brain metastases, was transfected with 1) an androgen receptor (AR)- Dar 19 [AR(+) Bcl-2(-)]) or 2) Bcl-2- Dkc 9 [AR(-), Bcl-2(+)]. MTT assay was used to examine the effect of doxazosin (25μM - 75 μM) on cell growth (24- 120 h). The effect of doxazosin (50μM, 24 h) on basal and EGF- induced (50 ng/ml) p-AKT expression was assessed using Western blotting. Specificity of doxazosin activity was confirmed with a specific PI3K /PTEN/AKT pathway inhibitor, LY294002 (10 μM, 50 minutes).

Results.

Doxazosin treatment (25 μM) led to a statistically significant (56%; p<0.01) death of Du 145 cells and at the concentration of 75 μM or higher resulted in an almost complete (97%; p<0.01) apoptosis. The agent proved less potent in both transfected cells. Doxazosin (25 μM and 75 μM) induced 23% (p>0.05), 97 % (p<0.01) of Dar 19 and 8% (p>0.05), 90% (p<0.01) of Dkc 9 cell death, respectively. Doxazosin (50 μM, 24 h) completely abrogated (Du 145) or decreased (Dar 19 and Dkc 9) constitutive expression of p-AKT and downregulated its EGF- induced levels. Its effect on decreasing both constitutive and EGF- induced p-AKT expression was the greatest in parental Du 145 cells. LY294002 was shown to completely inhibit EGF- induced AKT phosphorylation.

Conclusions.

1. Doxazosin- induced cell death appears to be at least partially attributable to the inhibition of PI3K/PTEN/AKT pathway. 2. Androgen independent Du 145 [AR(-), Bcl-2(-)] cells are most susceptible to the cell death induced by doxazosin. 3. Bcl-2 or AR overexpression partially protects PCa cells from doxazosin- induced apoptosis.