Cell-to-cell miRNA transfer: from body homeostasis to therapy

The role of non-protein coding RNAs (ncRNAs), microRNAs (miRNAs) in particular, as fine-tuners of both pathological and physiological processes is no longer a matter of debate. With the recent discovery of miRNAs in a wide variety of body fluids and considering them as tools employed in horizontal gene transfer between cells, a new horizon opens in the field of diagnosis and therapeutics. Circulating miRNAs not only enable the communication among cells, but also provide insight into the pathological and physiological state of the originating cells. In this review we summarize the recent advances made in this field, arguing for compelling translation of miRNAs into clinical practice. Moreover, we provide overview of their characteristics and how they impact the evolution of tumor microenvironment and cell-to-cell communication, advancing the idea that miRNAs may function as hormones.