• Nyall R London, Lisa M Rooper, Justin A Bishop, Haiying Xu, Lydia J Bernhardt, Masaru Ishii, Christine L Hann, Janis M Taube, Evgeny Izumchenko, Daria A Gaykalova, and Gary L Gallia.
• Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland, USA.
• World Neurosurg. 2020 Mar 1; 135: e187-e193.

BackgroundProgrammed cell death ligand 1 (PD-L1) is a transmembrane glycoprotein that interacts with the receptor programmed cell death 1 (PD-1) to suppress T-cell activation, reduce adjacent tissue damage, and promote tolerance to self-antigens. Tumors may express PD-L1 as a mechanism to evade immune detection. Recent clinical trials have demonstrated the efficacy of PD-L1/PD-1 antagonists through activation of tumor-infiltrated CD8+ T cells. The aim of this study was to determine the expression pattern of PD-L1 and PD-1 in olfactory neuroblastoma (ONB) tumor cells and to determine the presence of PD-1+ and CD8+ lymphocytes in the ONB immune microenvironment.MethodsImmunohistochemistry for expression of PD-L1, PD-1, and CD8 was performed on paraffin-embedded ONB tissue.ResultsOf the 10 primary site ONB samples, 4 demonstrated positive PD-L1 expression. Of PD-L1+ tumors, the 2 highest expressing samples were found to contain PD-1+ tumor cells. Of the 4 available metastatic samples, all of which arose from PD-L1- primary site ONB, 3 were positive for PD-L1 and contained PD-1+ tumor cells. PD-L1+ primary and metastatic tumors also demonstrated increased PD-1+ infiltrating lymphocytes in the tumor and stroma (11.6- and 4.62-fold increase) compared with PD-L1- samples (P < 0.05 and P = 0.068 respectively). PD-L1+ specimens demonstrated increased CD8+ lymphocytes in the tumor and stroma (7.46- and 2.14-fold increase) compared with PD-L1- tumors (P < 0.05 for both).ConclusionsThese data demonstrate that a proportion of ONB primary and metastatic tumors express PD-L1 and possess an associated tumor and stromal infiltrate of PD-1+ and CD8+ lymphocytes.Copyright © 2019 Elsevier Inc. All rights reserved.

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