Exosomes as miRNA nano shuttles dual role in tumor progression

Tumor-derived extracellular vesicles (EVs) have a pleiotropic role in cancer, interacting with target cells of the tumor microenvironment, such as fibroblasts, immune and endothelial cells. EVs can modulate tumor progression, angiogenic switch, metastasis, and immune escape. These vesicles are nano-shuttles containing a wide spectrum of miRNAs that contribute to tumor progression. MiRNAs contained in extracellular vesicles (EV-miRNAs) are disseminated in the extracellular space and are able to influence the expression of target genes with either tumor suppressor or oncogenic functions, depending on both parental and target cells. Metastatic cancer cells can balance their oncogenic potential by expressing miRNAs with oncogenic function, whilst exporting miRNAs with tumor suppressor roles out of the cells. Importantly, treatment of cancer cells with specific natural and chemical compounds could induce the elimination of miRNAs with oncogenic function, thereby reducing their aggressiveness. In this review, we discuss the mechanisms by which EV-miRNAs, acting as miRNAs with oncogenic or tumor suppressor functions, could contribute to cancer progression.