Expression of programmed death ligand 1 in lung adenocarcinoma and its significance

Objective To investigate the expression of programmed death ligand 1 (PD-L1) in lung adenocarcinoma tissues and its correlation with clinicopathological features of patients. Methods A total of 141 paraffin-embedded specimens of patients with newly diagnosed lung adenocarcinoma by pathology from January to August 2018 in the Affiliated Nanjing Drum Tower Hospital of Nanjing University Medical School were collected. The expression of PD-L1 in the tumor cells (TC) and tumor-infiltrating immune cells (IC) were detected by immunohistochemistry EnVision staining. Based on the percentage of expression, PD-L1 in TC and IC were divided into TC3 (≥50%), TC2 (≥5% and <50%), TC1 (≥1% and <5%), and TC0 (<1%); IC3 (≥10%), IC2 (≥5% and <10%), IC1 (≥1% and <5%), and IC0 (<1%). Results PD-L1 expression was positive in 90 cases, and the positive rate was 63.8% (90/141) at a TC1 or IC1 threshold. When a TC3 or IC3 threshold was applied, PD-L1 expression was positive in 17 cases, and the positive rate was 12.1% (17/141). In the TC1 or IC1 threshold group, PD-L1 expressions were different in patients with different sex, nerve invasion and pleural invasion, and the differences were statistically significant (all P < 0.05). While in the TC3 or IC3 threshold group, PD-L1 expressions were different in patients with different cell differentiation, clinical stage, lymphocyte infiltration, vascular invasion and nerve invasion, and the differences were statistically significant (all P < 0.05). In both TC1 or IC1 threshold group and TC3 or IC3 threshold group, PD-L1 expression was associated with nerve invasion (both P < 0.05). Conclusions PD-L1 expression is associated with nerve invasion. PD-L1 inhibitors expect to be used as a potential treatment strategy for recurrent and progressive lung adenocarcinoma patients with high level expression of PD-L1. Key words: Lung adenocarcinoma; Programmed death ligand 1; Clinicopathologic features