Expression of PD-L1 in plasma exosomes of NSCLC patients and its associations with PD-L1 expression of corresponding tumour tissues

Abstract

Background: The aim of this study was to research whether there was expression of PD-L1 in plasma exosome of NSCLC patients and whether its expression can partly represent PD-L1 expression of corresponding lung tumor tissues. Methods: Plasma was collected before and after surgery of NSCLC patients with stage II to stage III. Plasma of NSCLC patients with stage IV was also collected before and after anti-PD-1/PD-L1 therapy. Digital PCR was used to detect PD-L1 and β-actin mRNA expression of plasma exosomes. Expression of PD-L1 in tumor tissues was determined by immunohistochemical staining (22C3). Pearson correlation analysis and wilcoxon rank sum test was performed by SPSS 22.0. Results: A total of 126 patients (54 patients with surgery and 72 patients with non-surgery therapy) were participated in this study. Exosomal PD-L1 expression can be detected in all plasma samples. Exosomal expression of PD-L1 calculated by both absolute quantification method and relative quantification method showed a positive correlation with PD-L1 expression of tumor tissues (absolute quantification method: r2=0.289, P=0.001; relative quantification method: r2=0.547, P=0.000). However, expression of exosomal PD-L1 calculated by relative quantification calculation showed higher correlation. Exosomal PD-L1 expression significantly decreased after surgery (P<0.001) and three patients who showed good response (PR) to anti-PD-1/PD-L1 therapy also showed significantly decreasing exosomal PD-L1 expression after anti-PD-1/PD-L1 therapy (P<0.001). Conclusions: Plasma exosomes of NSCLC patients contains substantial expression of PD-L1. Plasma exosomal PD-L1 expression showed high correlation with PD-L1 expression of tumor tissues. Exosomal PD-L1 expression could represent PD-L1 expression of tumor tissues and might be a potential predictive marker for anti-PD-1/ PD-L1 therapy.