Circulating microRNAs (miRNA) in serum of patients with prostate cancer.

OBJECTIVES

To analyze circulating microRNAs (miRNA) in serum as non-invasive biomarker in patients with localized prostate cancer (PCA), benign prostate hyperplasia (BPH) and healthy individuals (HI).

METHODS

Total RNA was isolated from serum samples and the circulating levels of different RNA species (miRNA, miR-16; small nuclear RNA, RNU1A-1; messenger RNA, HPRT1), as well as of 4 oncogenic miRNAs (miR-26a, miR-32, miR-195, miR-let7i), were determined using a quantitative real-time polymerase chain reaction. We also evaluated miRNA levels in a second cohort of 10 PCA patients in cancer/nonmalignant tissue, and pre- and post-prostatectomy serum samples.

RESULTS

The levels of miR-16 and RNU1A-1 were reliably measured, whereas HPRT1 levels were often below the detection limit of our assay. Circulating oncogenic miRNA levels were different, and especially the miR-26a level allowed sensitive (89%) discrimination of PCA and BPH patients at a moderate specificity (56%; area under the curve [AUC]: 0.703); the analysis of oncogenic miRNAs in combination increased the diagnostic accuracy (sensitivity: 78.4%; specificity: 66.7%; AUC: 0.758). Despite the low number of patients limiting the statistical power of the study, we observed correlations with clinical-pathologic parameters: miR-16, miR-195, and miR-26a were significantly correlated with surgical margin positivity; miR-195 and miR-let7i were significantly correlated with the Gleason score. Tissue miRNA levels were correlated with preprostatectomy miRNA levels in serum, and serum miRNA decreased after prostatectomy, thereby indicating tumor-associated release of miRNA.

CONCLUSIONS

Tumor-associated miRNAs in serum allow noninvasive discrimination of PCA and BPH.