microRNAs and Prostate Cancer.

microRNAs are noncoding RNAs that are important for embryonic stem cell development and epithelial to mesenchymal transition (EMT). Tumor cells hijack EMT and stemness to grow and metastasize to distant organs including bone. In the tumor microenvironment, tumor cells interact with the stromal fibroblasts at the primary and metastatic sites and this interaction leads to tumor growth, EMT, and bone metastasis. Tumor-stromal interactions are a dynamic process that involves both cell-cell communications and extracellular vesicles and soluble factors. Growing body of evidence suggests that microRNAs are part of the payload that comprises the extracellular vesicles. microRNAs induce reactive stroma and thus convert normal stroma into tumor-associated stroma to promote aggressive tumorigenicity in vitro and in vivo. Landmark published studies demonstrate that expression of specific microRNAs of DLK1-DIO3 stem cell cluster correlates with patient survival in metastatic prostate cancer. Thus, microRNAs mediate tumor growth, EMT, and metastasis through cell intrinsic mechanisms and extracellular communications and could be novel biomarkers and therapeutic targets in bone metastatic prostate cancer.