A MicroRNA expression profile defining the invasive bladder tumor phenotype.

Objective: The purpose of this study was to identify microRNA (miRNA) involved in the transition between the noninvasive and invasive urothelial carcinoma of the bladder (UCB) phenotype.

Methods: Differential expression of miRNA was identified in a microarray format between noninvasive and invasive UCB cell lines and confirmed using quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) within this cell panel. Normalization of qRT-PCR with miR-222 was established from the microarray data and validated within a panel of 57 UCB tumors (26 noninvasive lesions (Ta/G1) and 31 invasive lesions (T2-T4). Pre-miR constructs were transfected into appropriate UCB cell lines to establish a change in invasive potential.

Results: Differential expression of miRNAs was identified from microarray analysis and included reduced expression associated with miR-30b, miR-31, miR-141, miR-200a, miR-200b, miR-200c, miR-205, miR-21 in invasive lesions and elevated miR-99a in noninvasive UCB lesions. Reduced invasion potential was recorded in UM-UC-3, following pre-miR transfection, in all UCB cell lines with the exception of UM-UC-3/miR-30b transfectants. Our results identify a panel of miRNA modulated and expressed in invasive UCB tumors and demonstrates a role for them in the invasive phenotype.

Conclusions: The diagnostic test, based on the three most discriminatory miRNAs in our panel (miR-200c, miR-141, and miR-30b), showed a sensitivity of 100% and a specificity of 96.2%. Such a panel of miRNAs has the potential to identify invasive bladder tumors misclassified in pathologic assessment of bladder biopsy specimens.