The emerging role of extracellular vesicle-derived miRNAs: implication in cancer progression and stem cell related diseases.

Cells release into the extracellular environment, diverse types of membrane vesicles of endosomal and plasma membrane origin called exosomes and microvesicles. A number of studies indicate that these extracellular vehicles (EVs) mediate the interaction between cancer cells and their microenvironment; and thereby, play a critical role in the development of cancers. EVs contain cargo which consist of proteins, lipids, mRNAs, and miRNAs that can be delivered to different types of cells in nascent as well as distal locations. Discovery of this latter cargo has drawn an increasing amount of attention, due to their altering effects on the transcriptome, proteins, and subsequent cellular characteristics in recipient cells. Cancer cell derived exosomes (CCEs) have been identified in body fluids of cancer patients including urine, plasma and saliva. Because CCE content largely depends on tumor type and stage, they invariably lend great potential in serving as prognostic and diagnostic markers. Notably, accumulating evidence demonstrates that EV-derived miRNAs have key roles in regulating various aspects of cellular homeostasis, including proliferation, survival, migration, metastasis, and the immune system etc. More recently, diagnostic and therapeutic exploitation of stem cells derived EVs are under investigation. This review aims to summarize recent advances in EV-derived miRNAs in a variety of tumor types, and suggests that these cancer-derived exosomal miRNAs play a critical role in regulating cellular functions in surrounding and distant locations. It also discusses the role of adverse environmental exposure in altering stem cell exosomal miRNA profiling, which we believe leads to changes in the extracellular environment as well as a diverse range of biological processes.