Association of microRNA-21 expression with clinicopathological characteristics and the risk of progression in advanced prostate cancer patients receiving androgen deprivation therapy

BACKGROUND Despite androgen deprivation therapy (ADT) remains the mainstay therapy for advanced prostate cancer (PCa), the patients have widely variable durations of response to ADT. Unfortunately, there is limited knowledge of pre‐treatment prognostic factors for response to ADT. Recently, microRNA‐21 (miR‐21) has been reported to play an important role in development of castration resistance of CaP. However, little is known about the expression of miR‐21 in advanced PCa biopsy tissues, and data on its potential predictive value in advanced PCa are completely lacking. METHODS In this study, paraffin‐embedded prostate carcinoma tissues obtained by needle biopsy from 85 advanced PCa patients were evaluated for the expression levels of miR‐21 by quantitative real‐time PCR (qRT‐PCR). In situ hybridization (ISH) analysis was performed to further confirm the qRT‐PCR results. Kaplan–Meier analysis and Cox proportional hazards regression models were performed to investigate the correlation between miR‐21 expression and time to progression of advanced PCa patients. RESULTS Compared with adjacent non‐cancerous prostate tissues, the expression level of miR‐21 was significantly increased in PCa tissues (PCa vs. non‐cancerous prostate: 1.3273 ± 0.3207 vs. 0.9970 ± 0.2054, P