Differentiated tumor immune microenvironment of Epstein-Barr virus-associated and negative gastric cancer: implication in prognosis and immunotherapy

// Jing Ma 1, * , Jianhui Li 2, * , Yiming Hao 1, * , Yongzhan Nie 1 , Zengshan Li 1, 3 , Meirui Qian 1 , Qiaoyi Liang 4 , Jun Yu 4 , Musheng Zeng 5 and Kaichun Wu 1 1 Fourth Military Medical University, State Key Laboratory of Cancer Biology & Institute of Digestive Diseases, Xijing Hospital, Xi'an, Shaanxi, China 2 Department of Infectious Diseases, Tangdu Hospital Affiliated to the Fourth Military Medical University, Xi'an, Shaanxi, China 3 The Pathology Department, Fourth Military Medical University, Xi'an, Shaanxi, China 4 Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China and The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, Guangdong, China 5 State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Experimental Research, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, China * These authors have contributed equally to this work Correspondence to: Kaichun Wu, email: kaicwu@fmmu.edu.cn Keywords: gastric cancer, tumor microenvironment, Epstein-Barr virus, tumor-infiltrating lymphocytes, immune checkpoint Received: November 14, 2016 Accepted: March 01, 2017 Published: May 16, 2017 ABSTRACT Epstein-Barr virus-associated gastric cancer (EBVaGC) has been proposed to be a distinct subtype with a specific immune microenvironment. Here, we evaluated tumor-infiltrating T-cell subsets and the expression of programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) in 571 gastric cancers (GCs). Tissue microarrays were stained using EBER in situ hybridization for EBV and using immunohistochemistry for CD4, CD8, Foxp3, PD-1 and PD-L1. GCs were categorized into four types based on CD8 + infiltration and PD-L1 expression. The 5-year overall survival (OS) was evaluated according to EBV infection, T-cell subsets, PD-1 and PD-L1 expression and immune types. Thirty-two (5.3%) EBVaGCs were identified, which were more prevalent for CD8 + (p<0.001) and Foxp3 + (p=0.020) cell infiltration than EBV-negative GCs (EBVnGCs), suggesting a better 5-year OS (p=0.003). CD8 + (p=0.001) and Foxp3 + (p=0.018) cell infiltration was associated with better 5-year OS, whereas PD-L1 expression correlated with a poor 5-year OS (p=0.002). EBVaGC and EBVnGC had heterogeneous immune microenvironment, with CD8 + PD-L1 - GC exhibiting the best 5-year OS (p<0.001). GC was an immune ignorant dominant tumor and poor to no T-cell infiltration. An immune type classification algorithm can provide prognostic information and a rational basis for immunotherapy.