Knockdown of long non-coding RNA MALAT1 increases the blood-tumor barrier permeability by up-regulating miR-140

The blood-tumor barrier (BTB) forms a major obstacle in brain tumor therapy by preventing the delivery of sufficient quantities of therapeutic drugs. Long non-coding RNAs (lncRNAs) play important roles in both normal development and diseases including cancer. Here, we elucidated the expression of lncRNA metastasis associated lung adenocarcinoma transcript 1 (MALAT1) and defined its functional role in the regulation of BTB function as well as its possible molecular mechanisms. Our results proved that MALAT1 expression was up-regulated in brain microvessels of human glioma and glioma endothelial cells (GECs) which were obtained by co-culturing endothelial cells with glioma cells. Functionally, knockdown of MALAT1 resulted in an impairment and increased the permeability of BTB as well as decreased the expression of ZO-1, occludin and claudin-5 in GECs. Further, there was reciprocal repression between MALAT1 and miR-140, and miR-140 mediated the effects that MALAT1 knockdown exerted. Mechanistic investigations defined that nuclear factor YA (NFYA), a CCAAT box-binding transcription factor, was a direct and functional downstream target of miR-140, which was involved in the MALAT1 knockdown induced regulation of BTB function. Furthermore, NFYA could up-regulate the promoter activities and bind to the promoters of ZO-1, occludin and claudin-5 in GECs. Taken together, we have demonstrated the fact that knockdown of MALAT1 resulted in the increased permeability of BTB, which might contribute to establishing potential therapeutic strategies for human gliomas.