Abstract
BackgroundThis study aimed to explore the potential regulatory mechanisms of brain metastasis and to identify novel underlying targets of lung cancer with brain metastasis.MethodsExosomes 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.ResultsTransmission 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.ConclusionOur results indicate that miR-550a-3-5p and YAP1 may be novel potential targets for controlling brain metastasis.
Highlights
This study aimed to explore the potential regulatory mechanisms of brain metastasis and to identify novel underlying targets of lung cancer with brain metastasis
Characterization of plasma‐derived exosomes and lung cancer cell‐derived exosomes Exosomes were extracted from the plasma of lung cancer patients with or without brain metastasis and high or low metastatic lung cancer cells, and characterized using NTA, TEM, and western blotting
NTA results showed that the major peaks of substances isolated from the plasma of lung cancer patients with or without brain metastasis and high or low metastatic lung cancer cells were approximately 94 nm or 90 nm and 95 nm or 99 nm, respectively (Fig. 1B)
Summary
This study aimed to explore the potential regulatory mechanisms of brain metastasis and to identify novel underlying targets of lung cancer with brain metastasis. Brain metastasis is an important cause of morbidity and mortality in lung cancer patients [2]. 10–15% of lung cancer patients are diagnosed with brain metastasis and approximately 40% develop. Treatment for patients diagnosed with early stage lung cancer usually involves surgical resection with occasional adjuvant radiotherapy or chemotherapy [6]. Once patients develop lung cancer with brain metastasis, radical treatment becomes almost impossible, and the focus shifts to life-prolonging treatments, primarily systemic chemotherapy [1, 7]. The survival of lung cancer patients with brain metastasis remains low, limited to weeks or months [4]. The molecular mechanisms that can inhibit the progression of lung cancer metastases have not been identified, there is an urgent need to identify new targets for the prevention and control of brain metastasis of lung cancer
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