Higher Tumor to Benign Ratio of the Androgen Receptor mRNA Expression Associates with Prostate Cancer Progression after Radical Prostatectomy

Abstract

Alterations of androgen receptor (AR) functions caused by overexpression, amplification, or mutation have been described in a significant subset of advanced prostate cancer (CaP). Because AR mutations or amplification are rare in early stage CaP, we hypothesized that altered AR expression in prostate tumor cells may provide a prognostic indicator of disease progression. RNA from laser capture microdissected (LCM) tumor and benign epithelial cells from radical prostatectomy specimens of 115 hormone-naive patients were studied. Expression of AR and GAPDH genes were measured by duplex quantitative real-time polymerase chain reaction (RT-PCR) in 230 specimens. A ratio of the expression of AR gene, normalized to GAPDH gene expression in the same specimens, was compared in tumor and benign epithelial cells (tumor-to-benign ratio) and correlated with clinicopathologic features. Paired t test analysis revealed a 62% lower AR expression in tumor tissue compared with benign tissue (P = 0.0005). However, multivariate Cox proportional hazards regression analysis of time to PSA recurrence revealed that higher tumor cell associated AR expression (continuous, log-transformed), significantly increases odds of prostate-specific antigen (PSA) recurrence (P = 0.0139) when controlling for age at surgery, race, time from diagnosis to surgery, risk stratification, pathologic T stage, Gleason sum, and margin status. Quantitative determination of AR gene expression levels in prostate epithelial cells may be useful for predicting PSA recurrence. This study supports the accumulating data suggesting that gain of AR function may contribute to CaP progression.