Abstract
The permeability of blood vessels plays a crucial role in the spread of cancer cells, leading to their metastasis at distant sites. Small extracellular vesicles (sEVs) contribute to the metastasis of various cancers by crossing the blood vessel wall. However, the role of abnormal glycoconjugates on sEVs in tumor blood vessels is unknown. Our study found elevated levels of fucosyltransferase VII and its product sialyl Lewis X (sLeX) in muscle-invasive bladder cancer (BLCA), and high levels of sLeX can promote growth and invasion of BLCA cells. Further study revealed that sLeX was enriched in sEVs originating from BLCA. sLeX-decorated sEVs increased blood vessel permeability by disrupting the tight junctions of human umbilical vein endothelial cells (HUVECs). Using a glycoproteomics approach, we identified integrin α3 (ITGA3) as a sLeX-bearing glycoprotein in BLCA cells and their sEVs. Mechanically, sLeX modification stabilized ITGA3 by inhibiting its degradation in lysosomes. sEVs carrying sLeX-modified ITGA3 can be effectively internalized by HUVECs, leading to decreased expression of tight junction protein. In contrast, silencing ITGA3 in sLeX-decorated sEVs restored tight junction protein and reduced blood vessel permeability by inhibiting the MAPK pathway. Moreover, ITGA3 sLeX-modification at Asn 265 in HUVECs promoted occludin dephosphorylation on Ser/Thr residues, followed by inducing its importin α1-mediated nuclear translocation and resulting destroyed tight junction. Our findings suggest a potential strategy for disrupting the formation of a metastatic microenvironment and preventing the spread of malignant bladder cancer.