Intermittent hypoxia enhances the tumor programmed death ligand 1 expression in a mouse model of sleep apnea.

Background: As a hallmark of obstructive sleep apnea (OSA), intermittent hypoxia (IH) promotes tumor progress. The high expression of programmed death 1 and programmed death ligand 1 (PD-L1) in tumor leads to immune evasion and subsequently aggravates tumor progress. This study aims to determine the tumor PD-L1 expression under the IH condition.

Methods: A total of 24 C57BL/6J mice were randomly assigned to the normoxia (control, CTL) group and the IH group. Mice in the IH group were subjected to the IH condition for 5 weeks. Lung cancer cells were injected into the flank of each mouse after 1 week of IH exposure. Tumor PD-L1 expression was detected by immunohistochemistry (IHC). Correlation between tumor weight, tumor volume, and expression of PD-L1 was analyzed.

Results: Compared to the CTL group, mice in the IH group had a high PD-L1 expression. The IH can enhance the tumor PD-L1 expression. Tumor weight, volume, and HIF-1α levels were closely associated with the PD-L1 expression in the IH group, while dissimilar findings were observed in the CTL group.

Conclusions: The IH enhances tumor PD-L1 expression in OSA mimicking mice. Additional studies are required to clarify the underlying mechanism.