Serum MiRNA-21: Elevated Levels in Patients with Metastatic Hormone-refractory Prostate Cancer and Potential Predictive Factor for the Efficacy of Docetaxel-based Chemotherapy

Background: miR-21 has been recognized as an "onco-microRNA" with the activity of negatively modulating the expression of tumor-suppressor genes. However, its role in prostate cancer (CaP) has not been well-documented. We designed this study to assess the potential function of serum miR-21 in the progression of CaP.

Methods: Serum samples of 56 patients, including 20 patients with localized CaP, 20 with androgen-dependent prostate cancer (ADPC), 10 with hormone-refractory prostate cancer (HRPC), and 6 with benign prostatic hyperplasia (BPH), were collected for the measurement of miR-21. The 10 HRPC patients were administered docetaxel-based chemotherapy. Quantification of miR-21 was assayed by specific TaqMan qRT-PCR.

Results: Serum miR-21 level was found to correlate to serum PSA level in patients with ADPC and HRPC, P = 0.012 and 0.049, respectively. There was no significant difference in serum miR-21 level between BPH, localized CaP and ADPC with PSA level <4 ng/ml. Higher levels of miR-21 were detected in patients with HRPC and ADPC with PSA level >4 ng/ml. Six of the 10 HRPC patients reached partial remission with a decreased PSA level of >50% after chemotherapy. Serum miR-21 levels were higher in patients who were resistant to docetaxel-based chemotherapy when compared to those sensitive to chemotherapy, P = 0.032.

Conclusions: Serum miR-21 levels are elevated in HRPC patients, especially in those resistant to docetaxel-based chemotherapy. It may be applicable as a marker to indicate the transformation to hormone refractory disease, and a potential predictor for the efficacy of docetaxel-based chemotherapy.