Abstract
miRNAs are small noncoding RNAs with critical roles in a large variety of biological processes such as development and tumorigenesis. miRNA expression profiling has been reported to be a powerful tool to classify tissue samples, including cancers, based on their developmental lineage. In this study, we have profiled the expression of miRNAs in bladder carcinoma in situ (CIS) and distinct cell compartments of the normal bladder, namely umbrella and basal-intermediate urothelial cells, as well as the muscularis propria. We identified several miRNAs differentially expressed between umbrella and basal-intermediate cells (miR-133a, miR-139-3p, miR-142-3p, miR-199b-5p, and miR-221). In situ hybridization confirmed the expression of miR-133a and miR-139-3p in umbrella cells, and miR-142-3p in basal-intermediate cells. Strikingly, miRNA expression levels of CIS most closely resembled the miRNA profile of umbrella cells. Finally, we examined well-established umbrella and basal-intermediate cell immunohistochemical biomarkers in an independent series of CIS samples. Again, this analysis revealed the significant expression of umbrella-specific markers in CIS when compared to non-CIS lesions. Overall, our studies represent a comprehensive and accurate description of the different miRNAs expressed in CIS tumors and three distinct histological areas of the urinary bladder. Notably, this study provides evidence of the possible origin relationship between CIS and normal umbrella cells.