Extracellular vesicles derived from lung cancer cells exposed to intermittent hypoxia upregulate programmed death ligand 1 expression in macrophages
Yuanling Liu, Minzhen Lu, Jianan Chen, Siqi Li, Yiyu Deng, Shifang Yang, Qiong Ou, Jing Li, Ping Gao, Zeru Luo, Ping Yuan, Jianlong Tan, Xinglin Gao
Abstract
Abstract Purpose Intermittent hypoxia (IH), a hallmark of obstructive sleep apnea (OSA), compromises immune surveillance through the upregulation of programmed cell death-1 ligand (PD-L1). Tumor-released extracellular vesicles (EVs) have been reported to modulate immunosuppressive activities. We investigated whether or not EVs derived from intermittent hypoxic lung cancer cells can alter the expression of PD-L1 in macrophages. Methods The expression of PD-L1 + monocytes from 40 patients with newly diagnosed non-small-cell lung cancer (NSCLC) and with ( n =21) or without ( n =19) OSA were detected. Plasma EVs isolated from NSCLC patients with moderate–severe OSA ( n =4) and without OSA ( n =4) were co-cultured with macrophages. A549 cells were exposed to normoxia or IH (48 cycles of 5 min of 1% O 2 hypoxia, followed by 5 min of normoxia). EVs were isolated from cell supernatant and were co-cultured with macrophages differentiated from THP-1. PD-L1 and hypoxia-inducible factor-1 α (HIF-1α) expressions were measured by flow cytometry, immunofluorescence, and Western blot analysis. Results PD-L1 + monocytes were elevated in NSCLC patients with OSA and increased with the severity of OSA and nocturnal desaturation. PD-L1 + macrophages were induced by EVs from NSCLC patients with OSA and positively correlated with HIF-1α expressions. EVs from IH-treated A549 can promote PD-L1 and HIF-1α expression in macrophages and the upregulation of PD-L1 expression was reversed by specific HIF-1α inhibitor. Conclusion IH can enhance the function of EVs derived from lung cancer cells to aggravate immunosuppressive status in macrophages. HIF-1α may play an important role in this process.