Extracellular vesicles (EVs) are lipid bilayer-bound vesicles secreted by cells. Subtypes of EVs such as microvesicles and exosomes are further categorized mainly by their different biogenesis mechanisms. EVs have been revealed to play an important role in disease diagnosis and intercellular communication. Despite the wide interest in EVs, the technologies for the purification and enrichment of EVs are still in their infancy. The isolation of EVs, especially exosomes, is inherently challenging due to their small size and heterogeneity. In this review, we mainly introduce the advances of techniques in isolating microvesicles and exosomes according to their approaches. Also, we discuss the limitations of currently reported technologies in terms of their specificity and efficiency, and provide our thoughts about future developments of EV purification and enrichment technology.

Cancer cells in secondary tumors are found to form metastases more efficiently as compared to their primary tumor counterparts. This is partially due to the unfavorable microenvironments encountered by metastasizing cancer cells that result in the survival of a more metastatic phenotype from the original population. However, the role of deleterious mechanical stresses in this change of metastatic potential is unclear. Here, by forcing cancer cells to flow through small capillary-sized constrictions, it is demonstrated that mechanical deformation can select a tumor cell subpopulation that exhibits resilience to mechanical squeezing-induced cell death. Transcriptomic profiling reveals up-regulated proliferation and DNA damage response pathways in this subpopulation, which are further translated into a more proliferative and chemotherapy-resistant phenotype. These results highlight a potential link between the microenvironmental physical stresses and the enhanced malignancy of metastasizing cancer cells which may be utilized as a therapeutic strategy in preventing the metastatic spread of cancer cells.

Exosomes are extracellular vesicles of endosome origin secreted by various cells. The exosomal cargo, especially proteins and microRNAs, have been extensively investigated for their roles in intercellular communication and as biomarkers for clinical applications. However, the understanding of types and functions of exosomal mRNAs remains limited. Here, we evaluated the mRNAs of 61 hypoxia-targeted genes in exosomes by quantitative reverse transcription PCR (RT-qPCR). Among these 61 mRNAs, 14.8% of them were detected in the MCF10A-derived exosomes, 42.6% in the MCF7-derived exosomes, and 49.2% in the MDA-MB-231-derived exosomes, many of which are differentially regulated in response to hypoxic stress in a cell-line dependent manner. Consequently, 30 exosomal mRNAs are identified as cancer related biomarkers as they are present in cancer cell-derived exosomes and absent in MCF10A-derived exosomes. Co-culture of MDA-MB-231 cells with HUVECs shows uptake of MDA-MB-231 secreted exosomes by the Human umbilical vein endothelial cells (HUVECs). Subsequently, the cancer exosomal VEGFA mRNAs were translated within the HUVECs into proteins that promoted VEGFR-dependent angiogenesis. This finding provides novel insights into how cancer cells can directly contribute towards angiogenesis. RNA-seq also shows that cancer exosomes can upregulate epithelial-mesenchymal transition-related and metabolism-related genes. The transcripts of these genes are found present in the cancer exosomes, suggesting that the uptake of exosomal mRNAs at least partially contributed to the upregulation of the corresponding mRNAs. This study shows that cancer exosomes harbor diverse mRNAs, some of which can act as promising biomarkers as well as contribute towards reprogramming of recipient cells.