Functional significance of aberrantly expressed microRNAs in prostate cancer.

microRNAs, a class of small non-coding 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 microRNAs contribute to prostate cancer development, progression and metastasis. Based on reports describing microRNA expression signatures, several differentially expressed microRNAs have been discovered. In the present review, eight genome-wide microRNA expression signatures were used to select aberrantly expressed microRNAs (i.e. upregulated and downregulated microRNAs) in prostate cancer clinical specimens. Also, we mapped these selected microRNAs in the human genome. Interestingly, some clustered microRNAs, such as miR-221/222, miR-143/145, miR-23b/27b/24-1 and miR-1/133a, are frequently downregulated in cancer tissues, and recent studies have shown that these clustered microRNAs function as tumor suppressors. We also discuss the functional significance of the differentially expressed microRNAs and the molecular pathways/targets regulated by these microRNAs. These recent findings of microRNAs in prostate cancer will facilitate the development of effective strategies for microRNA-based therapeutics for the treatment of prostate cancer.