Cancer-associated extracellular vesicles (EVs) are intimately involved in establishment of tumor microenvironment and occurrence of metastasis. However, previous studies have mainly relied on experiments with cultured cell lines or mouse models, making it difficult to gain a full understanding of EV functions in human body. Hence, we extracted EVs directly from surgically resected viable clear cell renal cell carcinoma (ccRCC) tissues and adjacent normal renal tissues (n = 20). Quantitative LC/MS analysis identified 3,871 tissue-exudative EV (Te-EV) proteins, among which azurocidin (AZU1) was highly enriched in tumor Te-EVs (p = 2.85 × 10 , fold-change = 31.59). Importantly, AZU1 content was also significantly higher in serum EVs from ccRCC patients compared to those from healthy donors. We further found that ccRCC-derived EVs had AZU1-dependent membrane permeabilizing activity for the vascular endothelial cell layer. Thus Te-EVs should be ideal resource for investigation of physiological EV functions.

Azurocidin (AZU1) is an antimicrobial protein secreted by neutrophils that acts as a chemoattractant for monocytes and macrophages and a permeabilizer of vascular endothelial cells. We previously identified AZU1 to be specifically present in extracellular vesicles (EVs) obtained from renal cell carcinoma (RCC) tissues. Here, we examined the relationship between Nlinked glycosylation and AZU1 loading into small EVs (SEVs). Inhibition of N-linked glycosylation by introducing mutations in three glycosylation sites inhibited AZU1 loading into SEVs. Furthermore, SEVs released from AZU1-wild-type cells increased the Ca 2+ concentration in endothelial cells and the endothelial permeability, whereas SEVs released from AZU1-mutant cells had no significant effect. Anti-AZU1 antibodies diminished the effect of SEVs on endothelial cell sheets. Collectively, we found that N-linked glycosylation of AZU1 directs its loading into SEVs, thereby enabling AZU1positive SEVs to function as potent permeabilizers of endothelial cells and leading to enhanced transendothelial migration of RCC cells.