High expression of PD-L1 in lung cancer may contribute to poor prognosis and tumor cells immune escape through suppressing tumor infiltrating dendritic cells maturation

The immunohistochemical analysis was used to evaluate the expression of PD-L1 in 109 non-small cell lung cancer (NSCLC) tissues and para-tumor tissues. Associations between expressed PD-L1 and tumor histological types, degree of differentiation, and lymph node metastasis were calculated, and overall survival was assessed. Meanwhile, immunohistochemistry and immunofluorescence double labeling technique were performed to detect the expressions of PD-L1, CD1α, and CD83 on TIDC of 20 lung cancer tissues, and the expression of PD-L1 in CD1α⁺DCs and CD83⁺DCs and their significances were also explored. We found that the expression rate of PD-L1 in NSCLC was associated with histological types and overall survival. Patients with either adenocarcinoma or survival time after surgery less than 3 years showed higher expression rate of PD-L1. Furthermore, Cox model analysis indicated that PD-L1 might be regarded as a poor prognostic factor. PD-L1 could be also detected in CD1α⁺ immature DC in NSCLC, indicating that as a class of key anti-tumor immunocyte in tumor microenvironment, DC expressing PD-L1 itself might play an important role in keeping its immature status and contributing to tumor cells immune escape and disease progression.