OBJECTIVETo evaluate the correlation between programmed death-ligand 1 (PD-L1) expression in primary lung cancer cells, tumor associated macrophages (TAM) and patients' clinicopathological characteristics.

METHODSFrom 2008 to 2010, 208 non-small cell lung cancer patients who underwent surgery or CT-guided biopsy were recruited from Huadong Hospital, Fudan University. Immunohistochemistry staining was performed to evaluate the PD-L1 expression in both primary lung cancer cells and CD68 positive TAM. The relationship between PD-L1 expression and the clinical pathology was evaluated using χ(2) test. Spearman's rank correlations were used to determine the correlation between PD-L1 expression in tumor cells and macrophages.

RESULTSPositive PD-L1 expression in primary cancer cells was found in 136 (65.3%) patients, which were negatively correlated with lymph node metastasis (P=0.009) and smoking history (P=0.036). Besides, TAM with PD-L1 expression (found in 116 patients) was positively associated with smoking history (P=0.034), well-differentiation (P=0.029) and negative lymph node metastasis (P=0.0096). A correlation between PD-L1 expression in primary tumor cells and non-small cell lung cancer associated macrophages was found (r=0.228, P=0.021).

CONCLUSIONPD-L1, secreted from TAM, might induce cancer cells apoptosis, and decrease lymph node metastasis.