The Diagnostic Value Of Urinary MiR-106B-25 MicroRNA Cluster In Bladder Cancer

BackgroundBladder cancer (BCa) is one of the most common urogenital cancers. About 70% of patients are initially diagnosed with non-muscle-invasive BCa (NMIBC). The recurrence rate for these tumors ranges from 50% to 70%, and 10-15% progress to muscle invasion over a 5-year period. Early diagnosis and surveillance have major importance in improving survival of patients with BCa. Surveillance strategies for BCa recurrence have historically relied on the diagnostic combination of cystoscopy and urinary cytology. However, the cystoscopic approach is invasive, uncomfortable and costly. Urinary cytology has the advantage of being non-invasive with a high specificity (90-95%), but it has low sensitivity (30-40%). Therefore, there is a pressing need for new urine biomarkers that may help in BCa detection and surveillance. Cell-free microRNAs (miRNAs) stably and abundantly exist in body fluids and emerging evidence suggests cell-free miRNAs as a novel class of non-invasive disease biomarkers. The miR-106b-25 cluster consists of three highly conserved miRNA (miR-106b, miR-93, and miR-25), and is a paralog of miR-17-92 cluster, a known oncogene. The miR-106b-25 cluster has been reported to be up-regulated in several types of cancers, including BCa. A large volume of experimental data has demonstrated the oncogenic role of the miR-106b-25 cluster in cancers. Therefore, in this study, we hypothesized that the quantitative detection of the oncogenic miR-106b-25 cluster in urine supernatant could be a useful clinical noninvasive biomarker for BCa.MethodsThis study was divided into three parts:(1) In order to determine of appropriate urinary miRNAs, we initially measured the urinary levels of three members of the miR-106b-25 cluster (miR-106b, miR-93 and miR-25) in 20 BCa patients and 20 healthy control subjects by quantitative reverse transcription polymerase chain reaction (qRT-PCR) in preliminary tests. (2) Validation study on the clinical application of urinary candidate miRNAs by comparing 112 BCa patients with 78 controls, and the areas under the receiver operating characteristic (ROC) curve of candidate miRNAs were analyzed. (3) Evaluation of whether the urinary candidate miRNAs could monitor tumor dynamics by comparison of urinary candidate miRNAs levels in 20 paired urine samples in 20 BCa patients before and 14days after TURBT.Results(1) In preliminary tests, our data demonstrated that the urinary levels of miR-106b were significantly higher in BCa patients than in healthy control subjects (P<0.001). However, the urinary expression levels of miR-93 (P= 0.645) and miR-25 (P= 0.281) were similar between BCa patients and healthy control subjects. Therefore, miR-106b was subjected to be the candidate miRNA.(2) The validation study demonstrated that the urinary levels of miR-106b were significantly higher in BCa patients when compared to controls (P<0.001). Next, we examined the correlation between the expressions of miR-106b with clinicopathological characteristics. Among BCa patients, the level of urinary miR-106b was associated with advanced tumor stage. The urinary miR-106b levels were higher in patients with invasive disease, compared with noninvasive disease (P=0.006). However, no significant association was found between miR-106b expression and age, gender, histological grade or lymph nodes metastasis. ROC curve analyses illustrated that urinary miR-106b was a potential biomarker for differentiating BCa from controls with an AUC (the areas under the ROC curve) of 0.802 (95%CI:0.753-0.872). At the cut-off value of 0.975, the sensitivity was 76.8% and the specificity was 72.4%.(3) The miR-106b levels were measured in paired pre- and post-operative urine samples from 20 BCa patients who underwent TURBT treatment. It was found that the levels of urinary miR-106b were significantly reduced in postoperative urine samples when compared to the preoperative samples (P=0.007). With regard to the monitoring of cancer, in one representative patient with recurrence, a re-elevation of the urinary miR-106b level was found at recurrence after surgery.Conclusion(1) Urinary cell-free miRNAs such as miR-106b might provide a useful biomarker for cancer detection and monitoring tumor dynamics in BCa patients postoperatively.(2) The level of urinary miR-106b was associated with increased risk of BCa presence and advanced tumor stage, suggested that miR-106b plays an important role in the tumorigenesis and progression of BCa.