Exosomes from Intermittent Hypoxia Treated Lung Adenocarcinoma Cell Line Up-regulate Programmed Death Ligand 1 Expression through HIF-1a Pathway in Macrophages

Abstract

Rationale: Intermittent hypoxia (IH), a hallmark of Obstructive sleep apnea (OSA), compromises immune surveillance through the upregulation of the programmed cell death-1 ligand (PD-L1). Exosomes released by cancer cells may cause immunosuppression, however, it is unknown whether IH can alter the expression of PD-L1 in macrophage by tumor-derived exosomes. Methods: Adenocarcinoma cell line A549 cells were exposed to condition of normoxia (21% O2, 5% CO2, and balance N2) or IH (48 cycles of 5 min of hypoxia [1% O2, 5% CO2 and balance N2] followed by 5 min of normoxia. Exosomes were isolated from the cell supernatant of A549 cells cultured in normoxia condition (Exo-con) or A549 cells exposed to IH (Exo-IH). Macrophages differentiated from THP-1 cells respectively were co-cultured with Exo-con, Exo-IH or Exo-IH (10 ug/ml) combined with BAY87-2243(HIF-1α inhibitor, 10μM)] and PBS for 48 hours before evaluation of PD-L1 and hypoxia-inducible factor-1(HIF-1α) expression. Result: Exosomes from IH treated A549 cells can upregulate PD-L1 and HIF-1α expression in macrophages. Specific HIF-1α inhibitor BAY87-2243 inhibited the upregulation of PD-L1 expression in the Exo-IH Group. Conclusion: Exosomes from intermittent hypoxia treated lung adenocarcinoma cell line up-regulate PD-L1 expression through HIF-1α pathway in macrophages.