Functional roles of exosomal miRNAs in multi-drug resistance in cancer chemotherapeutics

Recent understanding of different molecular aspects of tumor initiation and progression has led to the discovery of a growing list of drugs. While these drugs have shown promising effects on tumor cells, their widespread usage has been hampered by the acquisition of drug resistance in a subpopulation of tumor cells. A differential pattern in the secretion of specialized vesicles named "exosomes" in drug-resistant cancer cells have recently received much attention. In addition, microRNAs (miRNAs) have been shown to be enriched in exosomes. Exosomal miRNAs (also known as exo-miRs) could be shuttled to recipient cells and play a role in the regulation of post-transcriptional gene expression, which may exert certain effects on cancer drug resistance. Here, we have reviewed the role of exo-miRs in chemotherapeutic resistance in different cancer types. Besides, studies which have focused on predictive role of circulating exo-miRs in cancer drug resistance are reviewed.