Compared with that in the PBS and HK1 exosome-treated groups, ZO-1, VE-cadherin, occludin and claudin-5 expression were significantly reduced in endothelial cells positive for CD31 (Fig. 2A and Supplementary Fig. S4), and much more dextran extravasated from the blood circulation into the interstitial space of lung and liver in NPC43 exosome-treated group (Fig. 2B), indicating that the vasculature in mice treated with exosomes derived from EBV-positive NPC cells exhibited higher permeability. Here, HK1 is linked to nasopharyngeal carcinoma.