Expression of Immune Checkpoint Regulators, Cytotoxic T-Lymphocyte Antigen-4, and Programmed Death-Ligand 1 in Epstein-Barr Virus-associated Nasopharyngeal Carcinoma

Background: Nasopharyngeal carcinoma (NPC) is the most common cancer arising from the nasopharynx with a poor prognosis. Targeting immune checkpoint is one of the new promising lines in cancer treatment. Cytotoxic T-lymphocyte antigen-4 (CTLA-4) and programmed death-ligand 1 (PD-L1) are immune checkpoints that regulate T-cell immune function. Aim: This work aimed to assess the immunohistochemical expression of PD-L1 and CTLA-4 in NPC and their ability to predict survival and response therapy and to check their validity as immunotherapy targets. Twenty-six cases of NPC were studied by immunohistochemistry for PD-L1 and CTLA-4 and by nested polymerase chain reaction followed by DNA sequencing for the presence of EBNA-1 gene of Epstein-Barr virus (EBV). All investigated cases were diagnosed and treated in the Zagazig University Hospital in the period from August 2015 to July 2018. EBNA-1 gene was identified in 84.6% of the cases. Whereas the expression of PD-L1 was noted in 46.2% of all cases studied, 54.6% of EBV-associated NPCs were found to express PD-L1. There was a significant association between PD-L1 expression and the advanced stage of the tumor (P<0.001). CTLA-4 expression was observed in 88.4% of all NPC cases as cytoplasmic staining in both tumor cells and tumor-infiltrating lymphocytes. CTLA-4 expression in lymphocytes was associated with the presence of EBV. A significant association was detected between CTLA-4 and tumor-infiltrating lymphocyte expression on one side and the stage of the tumor on the other. High expression of CTLA-4 was significantly associated with disease progression and worse overall survival. Conclusion: PD-L1 and CTLA-4 are adverse prognostic markers in NPC. The authors propose that targeted therapy against PD-L1 and CTLA-4 will be a hopeful therapy for cases of NPC with resistance to concurrent chemoradiation treatment in Egypt, especially EBV-associated cases.