Stromal-derived miR-486-5p promotes metastasis of non-small-cell lung cancer cells by targeting the CADM1/tight junctions axis in vascular endothelial cells

Serum microRNA has been demonstrated as a noninvasive predictor for the progression of non-small-cell lung cancer (NSCLC). The role of microRNA-486-5p (miR-486-5p) in NSCLC seems to be paradoxical. On the one hand, elevated expression of miR-486-5p in serum is associated with unfavorable survival; on the other hand, miR-486-5p was notably reduced in NSCLC tissues and acted as a tumor-suppressor to inhibit NSCLC metastasis. The expression of miR-486-5p was analyzed in serum and tissue samples and their relationship was explored. The miR-486-5p-expressing cells were isolated by fluorescent-activated cell sorting. The downstream target of miR-486-5p was identified by bioinformatics prediction and experimental confirmation. Functional studies of miR-486-5p on NSCLC metastasis were determined by endothelial permeability assay and trans-endothelial invasion assay. We found that the expression of miR-486-5p was remarkably increased in serum, while dramatically downregulated in tumor tissues of NSCLC. However, the level of miR-486-5p in serum was positively correlated with that in tumor tissues. Next, we identified CD31⁺ vascular endothelial cells in the lung stroma as miR-486-5p-expressing cells. According to bioinformatics prediction, quantitative real-time reverse transcription PCR, luciferase reporter assay, and western blot, miR-486-5p directly targeted the cell adhesion molecule 1/tight junctions axis in vascular endothelial cells. In addition, endothelial permeability assay and trans-endothelial invasion assay confirmed that miR-486-5p promoted NSCLC metastasis. Highly elevated expression of miR-486-5p in CD31⁺ vascular endothelial cells increased vascular permeability and promoted NSCLC metastasis. In conclusion, stromal-derived miR-486-5p is responsible for the paradoxical effect of miR-486-5p in serum and tumor tissue.