Blood exosome PD-L1 is associated with PD-L1 expression measured by immunohistochemistry, and lymph node metastasis in lung cancer

Background: Previous observations illustrated that programmed cell death ligand 1 in exosomes (Exo-PD-L1) may lead to immunosuppression. This study proposed to investigate the significance of Exo-PD-L1 and the results of PD-L1 immunohistochemistry (IHC) assay in the clinical diagnosis and treatment of lung cancer. Methods: 29 lung cancer patients were enrolled. Exosomes were extracted from the blood of patients and purified, and the extracts were identified by Western blot and transmission electron microscope. Next, the levels of Exo-PD-L1 and PD-L1 in tumor tissue were evaluated by enzyme-linked immunosorbent assay (ELISA) and IHC, respectively. The correlation between Exo-PD-L1, IHC PD-L1 status and pathological features of patients was analyzed by applying Chi-square test. After immune checkpoint inhibitor (ICI) treatment, the objective response rate (ORR) was calculated, and drug response prediction in lung cancer patients by using Exo-PD-L1 alone, IHC PD-L1 alone, and their combined detection were analyzed. Results: This study confirmed that lung cancer patients had much expression of PD-L1 in blood exosomes and that Exo-PD-L1 level was associated with IHC PD-L1 status. The expression level of Exo-PD-L1 was evidently related to the positive lymph node metastasis of lung cancer patients, while IHC PD-L1 status was not correlated with clinicopathological features of patients. Moreover, Exo-PD-L1 and IHC PD-L1 alone or their combined detection could be utilized to predict the efficacy of ICI therapy in lung cancer patients. Conclusion: The correlation between Exo-PD-L1 and IHC PD-L1 status was indicated, and Exo-PD-L1 could assist in determining the suitable lung cancer patients suitable for ICI therapy using IHC PD-L1. This study provides references for the application of Exo-PD-L1 as an effective predictor of ICI therapy.