MicroRNAs in Bladder Cancer: Expression Profiles, Biological Functions, Regulation, and Clinical Implications

Bladder cancer (UBC) is a common cancer worldwide and has a high rate of recurrence and progression despite systemic therapy. The molecular mechanisms of UBC are not completely understood. MicroRNAs are noncoding RNA molecules of approximately 23 nucleotides that play important roles in multiple steps during the progression of UBC. Here, we review the expression profiles of miRNAs and their biological functions, regulation, and clinical implications in UBC. Either down-regulation or up-regulation of miRNAs occurs in UBC through epigenetic changes or defects of the biogenesis apparatus. Deregulation of miRNAs is involved in cell-cycle arrest, apoptosis, proliferation, metastasis, drug resistance, and other functions in UBC. A number of miRNAs, including urine miRNAs, have been associated with tumor type, stage, or patient survival, and miRNAs might be developed as diagnostic or prognostic markers. Better understanding of the roles of miRNAs in UBC will shed light on the molecular mechanisms of UBC.