Background: Programmed cell death ligand 1 (PD-L1) is widely known as an immune checkpoint molecule in tumor cells. Osteopontin (OPN) is expressed by both tumor cells and tumor-associated macrophages (TAMs), and both autocrine and paracrine of OPN are considered to be involved in tumor metastasis, proliferation and immunosuppression. However, little is known about the relationship between OPN expressed in TAMs (TOPN) and PD-L1 in non-small cell lung cancer (NSCLC).
Methods: Tissue microarray was used to detect the expression of TOPN, TAMs and PD-L1 by multiple quantitative fluorescence staining in 509 NSCLC patients undergoing complete pulmonary resection. The correlations between TOPN, PD-L1 and clinicopathological data were analyzed. An in vitro coculture system was established to investigate the crosstalk between TOPN and neoplastic PD-L1. In vivo, the intrinsic features of PD-L1 in NSCLC xenografts were evaluated after being coinjected with OPN-positive TAMs, and a series of key cytokines and chemokines were detected in the tumor microenvironment.
Results: A positive association between the TOPN and PD-L1 expression in tumor tissues from 509 patients with NSCLC was verified. In addition, TOPN and PD-L1 were independent prognostic factors for overall survival (OS) and disease-free survival (DFS) of NSCLC patients. Moreover, TOPN upregulated PD-L1 expression in NSCLC cells through the nuclear factor-κB (NF-κB) pathway in vitro TOPN induced the PD-L1 expression promoted the tumor growth in tumor-bearing mice, altering immune-related cytokines and chemokines.
Conclusions: TOPN regulates PD-L1 expression through the NF-κB pathway in NSCLS, which is a potential independent biomarker and target for prognosis as well as immunotherapy.
Keywords: PD-L1; non-small cell lung cancer (NSCLC); osteopontin (OPN); tumor microenvironment; tumor-associated macrophages (TAMs).
© 2021 The Authors. Thoracic Cancer published by China Lung Oncology Group and John Wiley & Sons Australia, Ltd.