Programmed death-1 (PD-1), programmed death-ligand 1 (PD-L1), and EBV-encoded RNA (EBER) expression in Hodgkin lymphoma

Programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) are new targets in cancer immunotherapy. PD-1 protein is an immune checkpoint expressed in many tumors. Epstein-Barr virus (EBV) is present in malignant Hodgkin/Reed-Sternberg (HRS) cells in approximately 40-50 % of Hodgkin lymphoma (HL). The aim of this study is to evaluate the clinical and prognostic importance of PD-1 and/or PD-L1 in HL and also to determine the association between EBV-encoded RNA (EBER) and PD-1/PD-L1. Formalin-fixed, paraffin-embedded tissue samples from 87 cases with HL were analyzed in this study. Immunohistochemical staining was performed to detect the PD-1 and PD-L1 expressions. Chromogenic in situ hybridization for EBER was performed using fluorescein-labeled oligonucleotide probes. PD-1 and PD-L1 expressions were found in 20 % of the cases. The EBER positivity was found in 40 cases (45 %). It has been found that co-expression of PD-1 and PD-L1 was associated with shorter survival although PD-1 or PD-L1 expressions were not found to be related with survival. Overall survival (OS) and disease-free survival (DFS) in cases without PD-1 and PD-L1 expressions were 135 and 107 months, respectively. OS and DFS in cases with co-expression for PD-1 and PD-L1 were 24 and 20 months, respectively, and these differences were found to be statistically significant for both OS and DFS (p = 0.002 and p = 0.003, respectively). Cox regression analysis showed that co-expression of PD-1 and PD-L1 was found to be an independent risk factor for prognosis (OR 6.9, 95 % CI 1.9-24.3). Targeting PD-1 and/or PD-L1 is meaningful due to the 20 % expression of each in HL, and we did not find an important association between PD-1 and PD-L1 and EBER expression in HL. Very poor outcome in cases with co-expression of PD-1/PD-L1 suggests new avenues to detect the new prognostic markers and also therapeutic approaches in HL.