[Expression of PD-1 and PD-L1 in the peripheral blood of advanced non-small-cell lung cancer patients and its implications].

Objective: To investigate the expression of programmed death 1(PD-1) and programmed death ligand 1 (PD-L1) on T lymphocyte and monocyte from peripheral blood of advanced non-small-cell lung cancer (NSCLC) patients and its potential role in immune escape of NSCLC.
Methods: Forty-eight patients with advanced NSCLC (Lung Cancer Group) were included from the Department of Respiratory Diseases in The Second Affiliated Hospital of Soochow University from June 2014 to June 2015. Thirty-six healthy volunteers who received health examination at the same time, matching in sex, age were also enrolled as controls. The expression of PD-1 on peripheral blood CD4(+)T cells and CD8(+)T cells and PD-L1 on monocytes were detected by flow cytometry. Patients who received chemotherapy alone for 2-4 cycles and received sequential sampling were assessed with Response Evaluation Criteria in Solid Tumors 1.1 (RECIST 1.1). Seven cases of patients with significant response to treatment were selected as partial response (PR) group and ten patients with poor response to treatment were treated as progression disease(PD) group. The differences in the expression of PD-1 on the surface of CD4(+)T cells, CD8(+)T cells, and PD-L1 on the surface of monocyte before and after treatment were analyzed.
Results: Compared with healthy control group, PD-1 expression level on both CD4(+) T and CD8(+) T cells from peripheral blood in lung cancer group were significantly increased [(25.9±7.4)% vs (20.6±6.2)%, (19.9±9.8)% vs (14.0±5.6)%, both P<0.05]. A higher level of PD-L1 expression on monocyte in lung cancer group was also found compared with the control group [(33.1±15.1)% vs (13.6±5.3)%, P<0.001]. The expression level of PD-1 on CD4(+)T and CD8(+)T cells and PD-L1 on monocytes in lung cancer group with good response to treatment was relatively lower than the baseline level of before treatment [(22.8±8.5)% vs (25.9±7.8)%, (17.1±8.4)% vs (20.4±8.6)%, (18.1±6.9)% vs (31.3±13.2)%, all P<0.05], but in lung cancer group with poor response to treatment, it was higher than the baseline level of before treatment [(33.5±6.5)% vs (23.9±4.2)%, (25.2±9.1)% vs (19.1±8.8)%, (43.1±18.3)% vs (29.7±10.6)%, all P<0.05].
Conclusion: Abnormal expression of PD-1 and PD-L1 exists in T cells and monocytes respectively, prompting PD-1/PD-L1 pathway may inhibit T cell proliferation during the interaction of T cell and monocyte, which may lead to non-small cell lung cancer immune escape.