Co-expression of PD-1 and PD-L1 predicts poor outcome in nasopharyngeal carcinoma

Jianwei Zhang, Wenfeng Fang, Tao Qin, Yunpeng Yang, Shaodong Hong, Wenhua Liang, Yuxiang Ma, Hongyun Zhao, Yan Huang, Cong Xue, Peiyu Huang, Zhihuang Hu, Yuanyuan Zhao, Li Zhang

Tumor immune evasion is a hallmark of cancer. The programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) pathway has been suggested to play an important role in T cell tolerance and tumor immune escape. In this study, we aimed to evaluate the correlation between the expression of PD-1/PD-L1 and the post-treatment outcome in patients with nasopharyngeal carcinoma (NPC). Formalin-fixed, paraffin-embedded tissue biopsies from 139 patients with histological diagnosis of NPC treated with conventional chemoradiotherapy were studied. By using immunohistochemistry staining, expressions of PD-1 on tumor-infiltrating lymphocyte and PD-L1 on tumor tissue were detected. The staining results were evaluated with H-score. The correlation between PD-1/PD-L1 expression and clinical characteristics and post-treatment outcome were analyzed. PD-1(+) immune cell were present in 52 of these 139 tumors (37.4 %). PD-L1 expression was detected in 132 patients (95.0 %), which located on tumor tissue. High expression of PD-L1 (median H-score >35) in tumor tissue significantly correlated with a poor prognosis of disease-free survival (P = 0.009). Co-expression of PD-1 and PD-L1 in NPC at diagnosis correlated with the poorest prognosis of disease-free survival (P = 0.038). PD-1/PD-L1 co-expression reflected the selective suppression of cytotoxic lymphocytes in the tumor microenvironment and predicted recurrence and metastasis of NPC after conventional therapies. Blocking this pathway in patients with co-expression of PD-1/PD-L1 provides a potential therapy target for NPC.