Cell-free microRNAs in urine as diagnostic and prognostic biomarkers of bladder cancer.

miRNAs are small, non-coding RNAs that play important roles in various biological processes. The aims of our study were to investigate whether cell-free miRNAs can be measured in urine samples and might be an accurate biomarker of bladder cancer. Datasets of GSE20418 and GSE19717 were used for analysis, and two miRNAs, miR-145 and miR-200a, were selected for study. A total of 207 patients with primary transitional cell carcinoma of the urinary bladder and 144 healthy normal controls were enrolled. Using quantitative PCR, the levels of miR-145 and miR-200a in urine were measured and compared with the clinicopathological features of bladder cancer. According to our experiments, cell-free miRNAs were present in urine and were stable. Assessment of miR-145 levels was able to distinguish bladder cancer patients from non-cancer controls (77.8% sensitivity and 61.1% specificity for NMIBC, AUC 0.729; 84.1 and 61.1% for MIBC, respectively, AUC 0.790) and showed good correlation with grade (p=0.048). In addition, miR-200a was shown to be an independent predictor of NMIBC recurrence by multivariate analysis (OR 0.449, 95% CI 0.239‑0.842, p=0.013). A higher risk of recurrence was observed among patients with a lower miR-200a level compared to patients with higher miR-200a levels (log-rank test, p=0.040). Urinary cell-free miRNAs show promise as noninvasive biomarkers for diagnosis and recurrence of bladder cancer.