ObjectiveTo investigate the function of tumor cell extracellular vesicles (EVs) derived long non-coding RNA X-inactive specific transcript (XIST) in non-small cell lung cancer (NSCLC) brain metastasis and to clarify its specific mechanism. MethodsEVs were isolated from A549 cells, and transmission electron microscopy, nanoparticle tracking, and western blotting were used to detect morphology and particle size of EVs. Human brain microvascular endothelial cells (HBMEC) and astrocytes were used to construct an in vitro blood–brain barrier (BBB) model. The BBB model was treated with EVs for 24 h. PKH67 staining was performed to examine EV engulfment by HBMEC and astrocytes. RT-qPCR was used to examine XIST, miR-19b-3p, and epsin 2 (EPN2) mRNA expression. Expression of EPN2 and tight junction (TJ) proteins such as claudin-5, occludin, and ZO-1 were measured using western blotting. Transepithelial electrical resistance (TEER), rhodamine-dextran, and immunofluorescence staining were performed to explore the effects of EVs and XIST on the BBB. Transwell assay was used to evaluate the invasive ability of A549 and H1299 cells. Dual-luciferase and immunoprecipitation assays were used to verify binding between miR-19b-3p, XIST, and EPN2. The Interactive Video Information System was used to observe brain metastasis of xenografts in BALB/c nude mice. ResultsA549 cell-derived EVs exhibited typical characteristics of EVs. HBMEC ingested EVs in the BBB model. EVs treatment decreased TEER and TJ protein level and increased the permeability to rhodamine-dextran. XIST was overexpressed in A549 and H1299 cells. Knockdown of XIST in A549 cell-derived EVs alleviated BBB damage and reduced NSCLC cell invasion. In vivo, XIST inhibition repressed NSCLC brain metastasis by ameliorating the BBB. Mechanistically, XIST sponged miR-19b-3p and positively regulated EPN2 expression. miR-19b-3p inhibition weakened the protective effect of XIST inhibition on the BBB. ConclusionA549 cells EVs-derived XIST inhibition ameliorates BBB injury and inhibits NSCLC brain metastasis by regulating the miR-19b-3p/EPN2 axis.
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