Aim/Background: Solid tumors have been shown to evade host antitumor immunity through upregulation of the immune checkpoint PD-1/PD-L1 pathway. However, CD47, an antiphagocytic ligand expressed on tumor cells, represents another cell surface molecule promoting tumor immune evasion via targeting the innate immune system. We investigated whether PD-L1 and CD47 are co-expressed in early stage non-small cell lung cancer (NSCLC).
Methods: Resected tumor and matched adjacent normal tissue from 84 stage I-III NSCLCs (42 adenocarcinomas [Adeno]; 42 squamous cell carcinomas [SqCC]) were processed to single cell suspensions, stained with a panel of antibodies (CD45, CD31, CD14, EpCAM, CD73, CD90, PD-L1, CD47) and subjected to multicolor flow cytometric analysis. In parallel, the phenotype of tumor infiltrating lymphocytes (TILs) was also performed using CD19, CD45RO, CD3, CD4, CD8, PD-1, CD127 and CD107a. In a subset of patients, expression of PD-L1 and CD47 was confirmed via immunohistochemistry.
Results: PD-L1 expression on tumor epithelium (EpCAM+) was increased in both Adeno (p = 0.0295) and SqCC (p = 0.0016) patients. CD47 was also upregulated on the tumor EpCAM+ fraction in SqCC (p = 0.05) but not in Adeno patients (p = 0.124). An increase in the tumor mesenchymal fraction in both Adeno (p = 0.015) and SqCC (p = 0.027) patients was found that showed an enhanced expression of PD-L1 but not CD47. Immunohistochemical analysis confirmed coexpression of PD-L1 and CD47 in a subset of patients. Finally, there was an increase in CD4+PD-1hi TILs in Adeno patients, whereas a decrease in CD127 expression was found on CD8+ TILs (p < 0.0001) with a CD107aloPD1hi phenotype in both histological subtypes.
Conclusions: We detected PD-L1 expression in different compartments in a subset of patients with early stage Adeno and SqCC, whereas CD47 expression was restricted to the tumor epithelial compartment in SqCC patients only. These differences may be related to the intragraft immune priming inside the tumor microenvironment. Further study is required to determine whether dual targeting of PD-L1 and CD47 in the perioperative setting represents a promising therapeutic strategy to reinvigorate TILs in affected patients.
Legal entity responsible for the study: N/A
Funding: Inselspital, University Hospital of Bern, Division of Thoracic Surgery
Disclosure: All authors have declared no conflicts of interest.
