Expression of Peroxisome Proliferator Activated Receptor gamma in Prostatic Adenocarcinoma

Peroxisome proliferator-activated receptor gamma (PPAR-gamma), a ligand-activated transcription factor has been investigated as the target for cancer treatment as well as metabolic disorders. Recent studies have demonstrated that PPAR-gamma ligands are anti-tumorigenic in prostate cancer due to anti-proliferative and pro-differentiation effects. The aim of this study was to validate PPAR-gamma expression in malignant and benign prostate tissues by immunohistochemistry and quantitative real-time polymerase chain reaction (PCR). A total of 730 prostatic adenocarcinomas (PCAs) including 63 whole sections from radical prostatectomy specimens and tissue microarrays containing 667 PCAs were subject to immunostaining for two PPAR-gamma antibodies. Twenty-five benign prostate tissues and PCAs were selected for investigating mRNA expression by quantitative real-time PCR. 10.7% of PCAs (78/730) showed cytoplasmic immunoreactivity of PPAR-gamma and no nuclear immunoreactivity was noted in PCAs. Most benign prostatic glands showed negative immunoreactivity of PPAR-gamma except for variable weak cytoplasmic staining in some glands. Nuclear immunoreactivity of PPAR-gamma was noted some central zone and verumontanum mucosal epithelium. The constitutive PPAR-gamma mRNA showed significantly lower level in PCAs compared to that in the benign tissues. There was no difference of PPAR-gamma mRNA expression between low (<= 7) and high (> 7) Gleason score groups. There was no association of PPAR-gamma mRNA level or cytoplasmic immunostaining with Gleason grade or pathologic stage. Our study supported the evidence of extra-nuclear localization and nongenomic actions of PPAR-gamma. Further studies are needed to assess the functional role of PPAR-gamma and to validate its therapeutic implication in prostate cancer.