The endothelium is the critical barrier that controls transendothelial communications. Blood vessels in cancer tissue are poorly developed and highly permeable. However, it is poorly understood how circulating cancer cells released through these "leaky" vessels break the intact vasculature of remote organs to metastasize. We investigated the roles of cancer cell-derived extracellular vesicles (CEVs) in regulating cancer metastasis by analyzing samples from gastric cancer patients, performing in vitro experiments, and studying mouse models. We made several novel observations. First, the rate of metastasis was closely associated with plasma levels of CEVs in patients with gastric cancer. Second, cultured endothelial cells endocytosed CEVs, resulting in cytoskeletal rearrangement, low expression of the junction proteins cadherin and CD31, and forming large intercellular gaps to allow the transendothelial migration of cancer cells. The dynamin inhibitor Dynasore prevented these CEV-induced changes of endothelial cells by blocking CEVs endocytosis. Third, CEVs disrupted the endothelial barrier of cancer-bearing mice to promote cancer metastasis. Finally, lactadherin promoted the clearance of circulating CEVs to reduce metastasis. These results demonstrate the essential role of CEVs in promoting the metastasis of gastric cancer.
Keywords: Cytoskeleton; Endothelial permeability; Extracellular vesicle-scavenging factor; Microvesicle endocytosis; Pulmonary metastasis.
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