Independent verification of circulating miRNA as diagnostic biomarkers for urothelial carcinoma

Urothelial carcinoma (UC) is an umbrella term for bladder cancers (BCa) and upper‐tract urothelial carcinoma (UTUC), with BCa and UTUC sometimes detected concomitantly. The methods of detection for UC are often inaccurate or highly invasive, and, therefore, are thought to be unsatisfactory. Previously, we reported seven serum miRNAs as diagnostic markers for BCa. Here, we re‐evaluated potential diagnostic miRNAs in different institutions. We prospectively analyzed serum samples obtained from 126 UC patients (BCa: 106 samples; UTUC: 14 samples; UTUC with BCa: six samples) and 50 noncancer controls by microarray analysis. We randomly assigned these samples into a training or a validation set. Biomarker candidate miRNAs were selected based on cross‐validation scores in the training set of samples, with diagnostic power confirmed in the validation set. Among the diagnostic miRNAs identified in this way, miR‐1343‐5p and miR‐6087 had been identified as potential diagnostic miRNAs in our previous study. In addition, we evaluated the association between the serum levels of identified miRNAs and the presence of UC risk conditions. The expression levels of several miRNAs correlate with the risk factors in participants without UC, which may be explained by the presence of a microscopic tumor or a precancerous lesion. In conclusion, we identified two robust miRNA diagnostic markers for UC detection. Further functional analysis is required to elucidate the mechanism by which alterations in the expression of these miRNAs occur. The methods of detection for urothelial carcinoma are often inaccurate or highly invasive, and, therefore, are thought to be unsatisfactory. In the present study, we prospectively evaluated the expression of circulating miRNAs in urothelial carcinoma patients, identifying miR‐1343 and miR‐6087, as reliable diagnostic markers for urothelial carcinoma.