A pilot study of urinary microRNA as a biomarker for urothelial cancer

MicroRNAs (miRNAs) are part of a class of small ribonucleic acid (RNAs). They are important regulatory molecules, involved in several cell processes, such as developmental timing, stem cell division and apoptosis. Dysregulated miRNAs have been identified in several human malignancies, including bladder cancer tissue samples, and may confer a "tumour signature" that can be exploited for diagnostic purposes. We report on a prospective pilot study investigating the diagnostic capability of miRNAs in the urine of patients with urothelial cancer.

Voided urine samples were collected from patients with urothelial carcinoma just prior to bladder tumour resection, as well as age-matched healthy control patients. Pathology demonstrated both low- and high-grade cancer. Total RNA was isolated and quantitative reverse transcriptase-polymerase chain reaction was performed on the RNA extracts using primers for 4 miRNAs shown previously to be dysregulated in solid urothelial carcinomas with RNU6B as the endogenous control. Standard urine cytology was performed on all samples in a blinded fashion.

Two miRNAs of interest were dysregulated in the urine from cancer patients with miR-125b showing an average 10.42-fold decrease (p < 0.01) and miR-126 showing an average 2.70-fold increase (p = 0.30) in the cancer samples compared to the normal controls. The sensitivity and specificity of the cytology on the same urine samples were 50% and 80%, respectively. Using these 2 miRNAs only, a decision-tree prediction model was generated for a validation cohort of patients yielding a specificity of 100% and a sensitivity of 80%.

This preliminary study of candidate urinary miRNA in patients with low- and high-grade urothelial cancer demonstrated a significantly improved diagnostic accuracy over cytology. These results provide rationale for further studies on discovery and validation of candidate miRNAs in voided urine and may potentially lead to the development of a non-invasive and sensitive test for bladder cancer diagnosis and prognosis.