Expression Characteristics And Clinical Significance Of PD-L1 In The Tumor Microenvironment Of Non-small Cell Lung Cancer

Part â…°Expression characteristics and clinical significance of PD-L1in patients with non-small cell lung cancer cellsObjective: To detect the expression of negative costimulatory molecule PD-L1 in tumor tissues from patients with non-small cell lung cancer(NSCLC), and analyze its clinical significance and biological function on T cell proliferation.Methods: 102 tumor- and corresponding nontumor- tissues were collected from patients with newly diagnosed NSCLC by operation in First Affiliated Hospital of Soochow University. The expression of PD-L1 on these tissue specimens was examined by immunohistochemistry technique. The clinical significance was subsequently evaluated based on the levels of PD-L1 protein in patients with NSCLC. The frequency of tumor tissue-infiltrating CD3+T cells and CD8+T cell was detected by flow cytometry, and the relationship with tumor PD-L1 was analyzed. The effect of PD-L1 expressed by lung cancer cell A549 on T cell proliferation was investigated in vitro by using a PD-L1 blocking antibody.Results: The positive staining of PD-L1 was found in 62 tumor-tissue specimens from the detected 102 samples(60.78%). However, none of the detected corresponding nontumor tissue specimens denonstrated obvious expression of PD-L1. Statistics analysis indicated that the levels of PD-L1 expressed in tumor tissues was related with the state of the lymph node metastasis and advanced clinical stage( P<0.01, respectively), but not with the difference in gender, age, tumor size, pathological types or degree of differentiation( P>0.05, respectively). More importantly, the follow-up data analysis showed that high expression of PD-L1 was a poor prognostic indicator. It can be concluded that patients with low level of PD-L1 has a longer survival time compared with those with high level of PD-L1(P <0.05). Further analysis indicated that tumor tissue with higher expression of PD-L1 has lower level of tumor tissue-infiltrating CD8+T cells( P<0.05). Functional test also showed that blocking PD-1/PD-L1 signal can significantly improve the proliferation of T cells in vitro(P <0.05).Conclusion: PD-L1 as a tumor-associated gene could be expressed on tumor cells but not on pulmonary epithelial cells in patients with NSCLC. Additionally, as a potential prognostic molecule, it could be applied in clinical diagnosis of NSCLC.Part â…±Abnormal expression of PD-L1 on tumor-tissue infiltrating monocytes/macrophage from patients with NSCLC and its clinical significanceObjective:Tumor associated macrophages( TAM) is a group of solid tumor-infiltrating myeloid-derived cells, which is characterized by CD45+ CD14+ phenotype. As a type of antigen-presenting cells, TAM plays an important role in tumor immune escape and tumoral angiogenesis. This study aims to analyze the expression of PD-L1 on monocytes/macrophage in different tissues from patients with NSCLC, and investigate its clinical significance.Methods: The tumor tissue samples from 60 patients with NSCLC were collected by operation. The corresponding nontumor tissue samples and the peripheral blood samples were also collected. And another 7-paired lymph nodes with or without tumor metastasis were also included in this study. The expression of PD-L1 on monocytes/macrophages was detected through flow cytometry. The clinical significance of PD-L1 expression on TAM was estimates by statistical analysis. To investigate the dynamic expression of PD-L1 on CD11b+F4/80+ mocrophage, a tumor-bearing mouse model with lung cancer cell line LLC were established. Six days after the implantation of LLC cells, with the growing of the tumor, 3 mice as a group were euthanized every five days. The blood, spleen and tumor tissue were collected and the dynamic expression levels of PD-L1 on macrophage cells were examined by flow cytometry. Besides, PD-L1 blocking m Ab were performed to analyze the biofunction of PD-L1 expressed by macrophage in T cell proliferation.Results: The levels of PD-L1 on macrophage from tumor-tissue significantly increased compared with those from corresponding nontumor tissue(P<0.01); the levels of PD-L1 in tumor-metastatic lymph nodes were notably higher compared to tumor-free lymph nodes(P<0.01). The statistical analysis indicated that the levels of PD-L1 on TAM were correlated with lymph node metastasis and later clinical stage(P<0.05, respectively), but not with other characteristics, such as age, gender and pathological differentiation(P>0.05, respectively). In addition, we found that PD-L1 on the blood monocytes, spleen-macrophage and tumor-infiltrating macrophage all gradually increased with the tumor growth. These data further confirmed that abnormally high expression of PD-L1 on macrophage was correlated with tumor progression. Furthermore, we blocked PD-L1 pathway by using a special antibody against PD-L1 in co-culture of monocytes and autologous T cells(P<0.01). We found that T cell proliferative suppression was effectively reversed by blocking PD-1/PD-L1 signal.Conclusion:Our data revealed that PD-L1 was dominantly high expressed on macrophage from tumor-tissue compared to corresponding nontumor-tissue. The increase in the level of PD-L1 in NSCLC patients is a poor prognostic indicator, and may affect immunosuppressive properties through PD-L1/PD-1 pathway.