High-Level Expression of microRNA-21 in Peripheral Blood Mononuclear Cells Is a Diagnostic and Prognostic Marker in Prostate Cancer

Aims: Our study aimed to evaluate the diagnostic and prognostic values of microRNA-21 (miR-21) expression levels in peripheral blood mononuclear cells (PBMCs) for prostate cancer (PCa). Methods: Between February 2010 and June 2014, 75 consecutive patients with localized PCa confirmed by radical prostatectomy and biopsy were enrolled as the case group. Among them, 25 patients were confirmed with recurrence or metastasis (R/M) (PCa with R/M group) and 50 patients without R/M (PCa without R/M group). During the same period, 75 healthy volunteers were enrolled as the control group. Blood was collected from all subjects, and PBMCs were isolated. Relative miR-21 expression levels from the PBMCs were determined by fluorescence real-time quantitative polymerase chain reaction (RT-qPCR). Results: The relative miR-21 expression levels in the preoperative case group was significantly higher than that in the postoperative case group and the control group (both p<0.001). miR-21 expression levels were associated with tumor differentiation, clinical stage, and lymph node metastasis (all p<0.001). Furthermore, miR-21 expression levels in PCa patients with R/M were significantly higher than that in PCa patients without R/M and healthy controls (both p<0.001). Receiver operating characteristic (ROC) curve analysis revealed that the cut-off point of miR-21 for diagnosis of PCa was 0.9 with a sensitivity of 87.5% and a specificity of 85.7%. Conclusions: Our study demonstrates that high miR-21 expression levels in PBMCs were correlated with the presence, recurrence, and metastasis of PCa and that this may be a useful biomarker for screening PCa and monitoring the risk of PCa recurrence and metastasis.