Endocrine Abstracts

Extracellular vesicles (EVs) are membrane-bound vesicles which are release by most, if not all, cell types into the extracellular space. They may be divided into two types: microvesicles which are shed directly from the plasma membrane; and exosomes which are released via multivesicular bodies. Although initially thought to be cellular junk, EVs represent an important mode of intercellular communication and are highly conserved across species. This is achieved through the transfer of nucleic acids, proteins and lipids which effect changes in physiological and pathological processes in recipient and parent cells. The removal of unwanted cellular components via EV release is important in maintaining cellular homeostasis, while plasma EVs play an important role in maintaining vascular integrity by contributing to haemostasis. EVs are also important in innate and adaptive immune responses. However, it is the role of EVs in cancer that has been most widely studied and best understood. The transfer of oncogenic receptors and nucleic acids from tumour cells to normal cells can result in oncogenic transformation. EVs also play an important role in metastasis and angiogenesis. As the composition of EVs reflect the phenotype and function of their parent cell, their analysis as biomarkers of disease has generated a great deal of attention and circulating EVs are increasingly being used as “liquid biopsies” in a variety of pathological conditions. This work has been hampered by the small size of EVs and the unpredictable expression of marker present on the parent cell. Consequently, there has been an explosion in techniques for the isolation and characterisation of EVs which poses challenges for standardisation. Finally, the potential of EVs for drug delivery or therapeutic agents in their own right is starting to be realised, with the first clinical trials being developed over the last few years.