Increased expression of IRF8 in tumor cells inhibits the generation of Th17 cells and predicts unfavorable survival of diffuse large B cell lymphoma patients

// Weijie Zhong 1 , Xin Xu 1, 3 , Zhigang Zhu 1 , Qinghua Du 2 , Hong Du 4 , Li Yang 2, 6 , Yanying Ling 5 , Huabao Xiong 3 and Qingshan Li 2 1 Department of Hematology & Oncology, Guangzhou First People’s Hospital, Guangzhou Medical University, Guangzhou, China 2 Department of Hematology, Guangzhou First People’s Hospital, Guangzhou Medical University, Guangzhou, China 3 Immunology Institute, Mount Sinai School of Medicine, New York, NY, USA 4 Department of Pathology, Guangzhou First People’s Hospital, Guangzhou Medical University, Guangzhou, China 5 Department of Laboratory, Guangzhou First People’s Hospital, Guangzhou Medical University, Guangzhou, China 6 Collaborative Innovation Center for Cancer Medicine, State Key Laboratory of Oncology in South China, Guangdong Esophageal Cancer Institute, Cancer Center, Sun Yat-Sen University, Guangzhou, China Correspondence to: Qingshan Li, email: drliqingshang@126.com Keywords: Interferon regulatory factor 8, Th17 cells, lymphoma, large B cell, diffuse Received: October 26, 2016     Accepted: April 18, 2017     Published: May 08, 2017 ABSTRACT The immunological pathogenesis of diffuse large B cell lymphoma (DLBCL) remains elusive. Searching for new prognostic markers of DLBCL is a crucial focal point for clinical scientists. The aim of the present study was to examine the prognostic value of interferon regulatory factor 8 (IRF8) expression and its effect on the development of Th17 cells in the tumor microenvironment of DLBCL patients. Flow cytometry, immunohistochemistry, and quantitative real-time PCR were used to detect the distribution of Th17 cells and related cytokines and IRF8 in tumor tissues from DLBCL patients. Two DLBCL cell lines (OCI-LY10 and OCI-LY1) with IRF8 knockdown or overexpression and two human B lymphoblast cell lines were co-cultured with peripheral blood mononuclear cells (PBMCs) in vitro to determine the effect of IRF8 on the generation of Th17 cells. Quantitative real-time PCR and Western blotting were used to investigate the involvement of retinoic acid receptor-related orphan receptor gamma t (RORγt) in the effect of IRF8 on Th17 cell generation. The survival of 67 DLBCL patients was estimated using the Kaplan-Meier method and log-rank analysis. The percentage of Th17 cells was lower in DLBCL tumor tissues than in PBMCs and corresponding adjacent benign tissues. Relative expression of interleukin (IL)-17A was lower, whereas that of interferon (IFN)-γ was higher in tumor tissues than in benign tissues. Co-culture with DLBCL cell lines inhibited the generation of Th17 cells in vitro . IRF8 upregulation was detected in DLBCL tumor tissues, and it was associated with decreased DLBCL patient survival. Investigation of the underlying mechanism suggested that IRF8 upregulation in DLBCL, through an unknown mechanism, inhibited Th17 cell generation by suppressing RORγt in neighboring CD4+ T cells. Tumor cells may express soluble or membrane-bound factors that inhibit the expression of RORγt in T cells within the tumor microenvironment. Our findings suggest that IRF8 expression could be a prognostic factor for DLBCL.