Abstract
The nuclear receptor ERRα (estrogen‐related receptor α) is known to modulate the estrogen‐signaling pathway, but the biological significance of ERRα in the prostate remains unclear. We investigated the expression of ERRα in human prostate tissues and cancer cell lines to evaluate the potential roles of the receptor in prostate cancer (PC). Western blot analysis of ERRα was performed in three cell lines of human PC (LNCaP, DU145 and PC‐3). The expressions of ERRα in cancerous lesions (n = 106) and benign foci (n = 99) of 106 surgically obtained prostate specimens were evaluated by immunohistochemistry. The relationships between the ERRα expression and clinicopathological features were evaluated. Western blot analysis using the polyclonal anti‐ERRα antibody detected a 52 kD band in all three PC cell lines. Positive immunostaining of ERRα in the nuclei was found in 73 (69%) cancerous and 47 (47.5%) benign epithelium, whereas the stromal tissues were negative for ERRα. The mean immunoreactivity score (IR score) of the cancerous lesions (3.5 ± 2.6) was significantly higher than that of the benign foci (1.8 ± 2.1) (p < 0.0001). The IR score of the cancerous lesions significantly correlated with the Gleason score (p = 0.0135). Univariate and multivariate hazard analyses revealed significant correlations between elevated ERRα expression and poor cancer‐specific survival (p = 0.0141 and 0.0367, respectively). The enhanced expression of ERRα might play a role in the development of human PC and serve as a significant prognostic factor for the disease. © 2006 Wiley‐Liss, Inc.