Expression of PD-1/PD-L1 in lung adenocarcinoma and correlation with epidermal growth factor receptor mutation status

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Objective: To investigate the expression of programmed cell death-1(PD-1) and programmed cell death-ligand 1(PD-L1) in lung adenocarcinoma in correlation with clinical pathological parameters, especially with regard to different epidermal growth factor receptor (EGFR) mutation status. Methods: One hundred and nine cases of lung adenocarcinoma were collected during the period from Aug. 2010 to Jan. 2016, including 51 cases of EGFR wild type and 58 cases of EGFR mutations. Immunohistochemistry was used to detect PD-1/PD-L1 protein expression. Chi-square test was used to analyze the correlation between PD-1 and PD-L1 expression, and in correlation with clinicopathological parameters. All statistical analyses run by SAS 9.1 software. Results: The positive rates of PD-1 and PD-L1 expression were 68.8% (75/109) and 27.5% (30/109), respectively, with significant correlation between the two (P<0.05). PD-1 and PD-L1 expression rates were higher in 51 cases with EGFR wild type status (74.5% and 39.2%) than those in 58 EGFR mutation cases (63.8% and 17.2%); PD-1 expression was significantly associated with age (P<0.05); that of PD-L1 was closely correlated with histological type, tumor size, lymph node metastasis and EGFR status (P<0.05). Conclusions: PD-1 and PD-L1 expression profiles and their correlation with EGFR mutations are different from those with native EGFR. PD-L1 overexpression is closely correlated with larger tumor size and lymph node metastasis, suggesting it is a high-grade marker for lung adenocarcinoma.