title: Prognostic value of PD-L1 and PD-1 expression in pulmonary neuroendocrine tumors.
abstract: OBJECTIVE
  Programmed death 1 (PD-1) receptor and its ligand, programmed death ligand-1 (PD-L1), play critical roles in the immune invasion of various tumors. This study aimed to explore the clinical significance of PD-L1/PD-1 expression in the progression of pulmonary neuroendocrine tumors (PNETs).
  
  
  METHODS
  The expression of PD-L1 and PD-1 in 80 patients diagnosed with PNETs were investigated. Immunohistochemical analysis was performed on 80 formalin-fixed paraffin-embedded tissue specimens from PNETs and 20 corresponding cancer-adjacent tissue specimens.
  
  
  RESULTS
  Tissues from PNETs had higher levels of PD-L1 (58.8%) and PD-1 (51.3%) compared to the cancer-adjacent tissues (25% and 20%, respectively). Meanwhile, PD-L1 expression was associated with PD-1 expression (P=0.007). PD-L1 expression was significantly associated with histological type (P=0.014) and tumor stage (P=0.014). Univariate analyses showed that the overall survival time of PNETs patients was significantly associated with PD-L1 expression in cancer cells (P=0.003), PD-1 expression in tumor-infiltrating lymphocytes (P=0.001), tumor node metastasis stage (P<0.05), and distant metastasis (P<0.001). Additionally, multivariate analysis revealed that PD-L1 expression, PD1 expression, and distant metastasis of PNETs were independently associated with survival time. Moreover, Kaplan-Meier survival curves analysis revealed that patients with negative PD-L1 and PD-1 expression had better prognoses.
  
  
  CONCLUSIONS
  Data suggested that PD-L1 and PD-1 can be useful prognostic biomarkers for survival and can pave the way toward new immunotherapy regimens against PNETs through targeting the PD-L1/PD-1 pathway.
authors: Department of Medical Oncology.
authors: Yangwei
authors: Y
authors: Fan
authors: Department of Medical Oncology.
authors: Ke
authors: K
authors: Ma
authors: Department of Medical Oncology.
authors: Chuying
authors: C
authors: Wang
authors: Department of Medical Oncology.
authors: Jing
authors: J
authors: Ning
authors: Department of Medical Oncology.
authors: Yuan
authors: Y
authors: Hu
authors: Department of Medical Oncology.
authors: Danfeng
authors: D
authors: Dong
authors: Department of Medical Oncology.
authors: Xuyuan
authors: X
authors: Dong
authors: Department of Nuclear Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, People's Republic of China.
authors: Qianqian
authors: Q
authors: Geng
authors: Department of Medical Oncology.
authors: Enxiao
authors: E
authors: Li
authors: Department of Medical Oncology.
authors: Yinying
authors: Y
authors: Wu
keywords: PD-1; PD-L1; prognosis; pulmonary neuroendocrine tumors