Lina Quan¹, Xue Chen¹, Yan Zhang², Xiuchen Guo¹, Shujie Yan¹, Yue Liu¹, Aichun Liu¹

¹Hematology department, Harbin Medical University Cancer Hospital, ²Radiotherapy department, Harbin Medical University Cancer Hospital.

Objective:Epstein–Barr virus-positive diffuse large B-cell lymphoma (EBV+DLBCL) is an aggressive malignancy that is largely resistant to current therapeutic regimens and is an attractive target for immune-based therapies. Anti-programmed death-1 (PD-1) antibodies showed encouraging results both in preclinical models and in advanced solid and hematological malignancies, but its efficacy against EBV+DLBCL is unknown. Method:1) The expression of PD-L1 on a panel of lymphoma cell lines and primary lymphoma specimens were detected with flowcytometry. 2) Effector memory T cells and T cells exhaustion in DLBCL microenvironment were detected using CD3, CD4, CD8, CD45RA, CD62L, PD-1, CTLA-4, and CD45RO with flowcytometry. 3) Co-culture experiment using T cells and lymphoma cell lines including EBV+DLBCL and EBV-DLBCL [including germinal center B-cell like (GCB)-DLBCL and non-GCB-DLBCL] in vitro were conducted, respectively. The expression of PD-1, CFSE-labeled proliferation and cytokine secretion were observed before and after adding PD-1 blockade antibody. Result: 1) PD-L1 was expressed by EBV-positive cell lines, non-GCB- DLBCL cell lines but not by GCB-DLBCL cell lines. In primary lymphoma specimens, results were consistent to cell lines, PD-L1 was expressed by most of EBV+DLBCL and non-GCB-DLBCL, but not by GCB-DLBCL. 2) T cells in DLBCL microenvironment displayed effector memory phenotypic traits (CD45RA-CD62L-) with increased expression of PD-1. 3) Tumor cells augmented the expression of PD-1 in activated T cells, decreased the proliferation of T cells, and had influence on the secretion of cytokines. Through PD-1 blockade these functions could be restored; moreover, the effects of PD-1 blockade on antitumor immunity showed that it was more effective in EBV+DLBCL than in EBV-DLBCL in vitro. Conclusion: T-cell exhaustion and immune escape in microenvironment is one of the mechanisms of DLBCL; furthermore, PD-1 blockade provides a more efficacious immunotherapeutic method for EBV+DLBCL.

Key Words: T cell exhaustion  EBV positive DLBCL  microenvironment