MicroRNAs: Key Players in Bladder Cancer.

Bladder cancer (BC) is the second highest morbid malignancy of the urinary tract and the fifth most common cancer worldwide. BC is highly malignant with significant morbidity and mortality, especially muscle-invasive BC (MIBC), which has a poor prognosis and frequently recurs after the first resection. Therefore, more sensitive diagnostic tools and effective therapeutic methods are urgently needed. MicroRNAs (miRNAs) are small noncoding RNAs that regulate the expression of protein-coding genes by repressing their translation or cleaving RNA transcripts in a sequence-specific manner. miRNAs play very important roles in regulating genes related to tumorigenesis, tumor development, progression, metastasis and angiogenesis. With the rapid development of high-throughput sequencing technology, an increasing number of miRNAs with aberrant expression between either BC patients and healthy volunteers or between BC tumor tissues and matched peripheral control tissues have been recently examined. The tumor etiopathogenesis must be determined to promote the development of new markers as diagnostic and prognostic tools and targets for bladder tumor therapy, it is therefore vital to elucidate the function of miRNAs with aberrant expression in BC. In the present study, we examined the published data of BC-related miRNAs by reviewing their expression levels, possible functions, potential target genes, related molecular regulatory networks, candidate markers for prognosis and diagnosis, and prospective therapeutic cases, and we summarized the status of research on BC-related miRNAs in recent years.