MicroRNAs and miRceptors: a new mechanism of action for intercellular communication.

MicroRNAs (miRs) are small non-coding RNAs (ncRNAs) that control the expression of target genes by modulating (usually inhibiting) their translation into proteins. This 'traditional' mechanism of action of miRs has been recently challenged by new discoveries pointing towards a role of miRs as 'hormones', capable of binding to proteic receptors (miRceptors) and triggering their downstream signalling pathways. These findings harbour particular significance within the tumour microenvironment (TME), defined as the variety of non-cancerous cells surrounding cancer cells, but are relevant also for other diseases. In recent years it has become clearer that the TME does not passively assist the growth of cancer cells but contributes to its biology. Some of the mediators of the intercellular communication between cancer cells and TME are miRs shuttled within exosomes, a subtype of cellular released extracellular vesicles. This article will highlight the most recent findings on the biological implications of miR-miRceptor interactions for the biology of the TME and other diseases, and will provide some perspectives on the future development of this fascinating research.This article is part of the discussion meeting issue 'Extracellular vesicles and the tumour microenvironment'.