Increased expression of estrogen-related receptor α (ERRα) is a negative prognostic predictor in human prostate cancer

The nuclear receptor ERR alpha (estrogen-related receptor alpha) is known to modulate the estrogen-signaling pathway, but the biological significance of ERRa in the prostate remains unclear. We investigated the expression of ERRa in human prostate tissues and cancer cell lines to evaluate the potential roles of the receptor in prostate cancer (PC). Western blot analysis of ERR alpha was performed in three cell lines of human PC (LNCaP, DU145 and PC-3). The expressions of ERR alpha in cancerous lesions (n = 106) and benign foci (n = 99) of 106 surgically obtained prostate specimens were evaluated by immunohistochemistry. The relationships between the ERR alpha expression and clinicopathological features were evaluated. Western blot analysis using the polyclonal anti-ERR alpha antibody detected a 52 kD band in all three PC cell lines. Positive immunostaining of ERR alpha in the nuclei was found in 73 (69%) cancerous and 47 (47.5%) benign epithelium, whereas the stromal tissues were negative for ERR alpha. 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 ERR alpha expression and poor cancer-specific survival (p = 0.0141 and 0.0367, respectively). The enhanced expression of ERR alpha might play a role in the development of human PC and serve as a significant prognostic factor for the disease. (c) 2007 Wiley-Liss, Inc.