MicroRNA-550a-3-5p controls the brain metastasis of lung cancer by directly targeting YAP1

Background This study aimed to explore the potential regulatory mechanisms of brain metastasis and to identify novel underlying targets of lung cancer with brain metastasis. Methods Exosomes were isolated from the plasma of lung cancer patients with or without brain metastasis and low or high metastatic lung cancer cells, and small RNA from plasma-derived exosomes were sequenced. Differentially expressed miRNAs (DE-miRNAs) were identified. Human brain microvascular endothelial cells (HBMECs) were transfected with miR-550a-3-5p mimics or inhibitors and exosomes. Cell viability, migration, and apoptosis/cycle were determined using Cell Counting Kit-8 (CCK-8), Transwell, and flow cytometry, respectively. Western blotting was used to measure the expression of the associated proteins. Finally, a dual-luciferase reporter gene assay was performed to confirm the miR-550a-3-5p target. Results Transmission electron microscopy, NanoSight, and western blotting showed that exosomes were successfully isolated and cell-derived exosomes could be taken up by HBMECs. Sequencing identified 22 DE-miRNAs which were enriched in the MAPK, chemokine, PPAR, and Wnt signaling pathways. MiR-550a-3-5p was significantly enriched in brain metastatic exosomes. Cellular experiments showed that miR-550a-3-5p and exosome enrichment significantly inhibited cell viability and migration, promoted apoptosis, and regulated the cell cycle of HBMECs compared with the controls (P < 0.05). Compared with the controls, high levels of both miR-550a-3-5p and exosomes markedly upregulated cleaved-PARP expression, but downregulated the expression of pRB, CDK6, YAP1, CTGF, and CYR61 (P < 0.05). Finally, YAP1 was confirmed to bind directly to miR-550a-3-5p. Conclusion Our results indicate that miR-550a-3-5p and YAP1 may be novel potential targets for controlling brain metastasis.