Abstract: Background and purpose: Liquid biopsy is a kind of blood, urine and other non-solid biological tissue sampling analysis, mainly for malignant tumor diagnosis, monitoring and predicting its prognosis. In this research, we optimized the extraction of miRNA in urine, established a standardized means of liquid biopsy, screened and verified the miRNA markers in patients with bladder cancer. Methods: From Jan. 2014 to Sept. 2015, we used miRNA microarray in six patients with bladder cancer and six healthy controls. Samples of 78 cases of bladder cancer and 23 healthy controls were tested by real-time fluorescent quantitative polymerase chain reaction (RTFQ-PCR) to verify the relationship between miRNA markers in liquid biopsy and clinical pathological parameters. The diagnostic value of miRNA markers was also analyzed and compared. Results: We screened 10 miRNAs differential expression in urine. Combined with previous literature, we selected 20 miRNAs to verify their expression levels in bladder cancers and healthy controls. miR-509-5p/miR-124 ratio in the urine was found higher in patients with bladder cancer than in healthy controls (P<0.000 1). With the rise of miR-509-5p/miR-124 ratio in urine, tumor stage and grade were also increased (P=0.003). When the cutoff was set at 0.41, the diagnostic sensitivity and specificity of miR-509-5p/miR-124 ratio were 73.1% and 82.6%, respectively. The AUC of miR-509-5p/miR-124 ratio to detect bladder cancer was 0.864, higher than that of urinary exfoliated cells (P=0.000 2). Conclusion: We optimized the extraction of miRNAs in urine, established a standardized liquid biopsy of miRNA markers. The miR-509-5p/miR-124 ratio could be an ideal diagnostic marker for bladder cancer.

Key words: Bladder cancer, miRNA, Diagnosis, Liquid biopsy