血管的通透性在癌细胞的扩散中起着至关重要的作用，促进癌细胞的远处转移。众所周知，小细胞外囊泡（sEV）可穿过血管壁促进各种癌症的转移。然而，异常糖复合物对肿瘤血管中 sEV 的作用仍不清楚。我们的研究发现，肌层浸润性膀胱癌（BLCA）中岩藻糖基转移酶 VII (FUT7) 及其产物唾液酸化 Lewis X (sLeX) 水平升高，其中高水平的 sLeX 促进 BLCA 细胞的生长和侵袭。进一步研究表明，sLeX 富含 BLCA 衍生的 sEV。 sLeX 修饰的 sEV 通过破坏人脐静脉内皮细胞 (HUVEC) 的紧密连接来增加血管通透性。使用糖蛋白质组学方法，我们将整合素 α3 (ITGA3) 鉴定为 BLCA 细胞及其 sEV 中带有 sLeX 的糖蛋白。从机械角度来看，sLeX 修饰通过防止 ITGA3 在溶酶体中降解来稳定 ITGA3。携带 sLeX 修饰的 ITGA3 的 sEV 可以被 HUVEC 有效内化，导致紧密连接蛋白表达减少。相反，在 sLeX 修饰的 sEV 中沉默 ITGA3 可恢复紧密连接蛋白，并通过抑制 MAPK 途径降低血管通透性。此外，HUVEC 中 ITGA3 Asn 265 的 sLeX 修饰促进了 Ser/Thr 残基的 occludin 去磷酸化，随后诱导其导入蛋白 α1 介导的核转位，从而导致紧密连接的破坏。我们的研究结果提出了一种破坏转移性微环境形成并预防恶性膀胱癌扩散的潜在策略。© 2024。作者获得 Springer Nature B.V. 的独家许可。

The permeability of blood vessels plays a crucial role in the spread of cancer cells, facilitating their metastasis at distant sites. Small extracellular vesicles (sEVs) are known to 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 remains unclear. Our study found elevated levels of fucosyltransferase VII (FUT7) and its product sialyl Lewis X (sLeX) in muscle-invasive bladder cancer (BLCA), with high levels of sLeX promoting the growth and invasion of BLCA cells. Further investigation revealed that sLeX was enriched in sEVs derived from BLCA. sLeX-decorated sEVs increased blood vessel permeability by disrupting the tight junctions of human umbilical vein endothelial cells (HUVECs). Using the glycoproteomics approach, we identified integrin α3 (ITGA3) as a sLeX-bearing glycoprotein in BLCA cells and their sEVs. Mechanically, sLeX modification stabilized ITGA3 by preventing its degradation in lysosomes. sEVs carrying sLeX-modified ITGA3 can be effectively internalized by HUVECs, leading to a decrease in the expression of tight junction protein. Conversely, silencing ITGA3 in sLeX-decorated sEVs restored tight junction proteins and reduced blood vessel permeability by inhibiting the MAPK pathway. Moreover, sLeX-modification of ITGA3 at Asn 265 in HUVECs promoted occludin dephosphorylation at Ser/Thr residues, followed by inducing its importin α1-mediated nuclear translocation, which resulted in the disruption of tight junctions. Our findings suggest a potential strategy for disrupting the formation of a metastatic microenvironment and preventing the spread of malignant bladder cancer.© 2024. The Author(s), under exclusive licence to Springer Nature B.V.