Aberrant expression of microRNAs in bladder cancer.

MicroRNAs (miRNAs), a class of small noncoding RNAs, regulate protein-coding gene expression by repressing translation or cleaving RNA transcripts in a sequence-specific manner. A growing body of evidence suggests that miRNAs contribute to bladder cancer development, progression and metastasis. Genome-wide miRNA expression signatures have been used to rapidly and precisely identify aberrant miRNA expression in bladder cancer. Based on reports describing miRNA signatures, several downregulated and upregulated miRNAs have been discovered. Examination of the differential expression of miRNAs between clinical bladder cancer and normal bladder tissue has led to the elucidation of 11 miRNA expression signatures. miRNAs downregulated in bladder cancer, such as miR-145, miR-143 and miR125b, are known to be tumour suppressors, whereas upregulated miRNAs, such as miR-183, miR-96, miR17-5p and miR-20a are oncogenic. Several studies have demonstrated the potential of miRNAs for providing prognostic information. miR-145 is the most frequently downregulated miRNA in bladder cancer and has been shown to significantly inhibit proliferation, migration and invasion. Understanding the role of differentially expressed miRNAs, as well as their molecular targets, in bladder cancer will provide an effective and promising strategy for miRNA-based therapeutics for the treatment of bladder cancer.