miRNAs in prostate cancer: Intercellular and extracellular communications

Prostate cancer is the most prevalent male cancer in Western Europe and North America. Although new drugs were recently approved, clinical challenges such as accurately predicting and screening drug-resistant prostate cancer remain. microRNAs are short noncoding RNA molecules that participate in gene regulation at the post-transcriptional level by targeting messenger RNAs. There is accumulating evidence that intracellular microRNAs play important roles as promoters or inhibitors of prostate cancer progression. Additionally, recent studies showed that microRNAs are encapsulated in extracellular vesicles and shuttled into the extracellular space. Transfer of extracellular microRNAs contributes to intercellular communication between prostate cancer cells and components of the tumor microenvironment, which can promote prostate cancer progression. Furthermore, due to their encapsulation in extracellular vesicles, extracellular microRNAs can be stably present in body fluids which contain high levels of RNase. Thus, circulating microRNAs have great potential as noninvasive diagnostic and prognostic biomarkers for prostate cancer. Here, we summarize the roles of intracellular and extracellular microRNAs in prostate cancer progression and discuss the potential of microRNA-based therapeutics as a novel treatment strategy for prostate cancer.