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

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.