Expression profile and in vitro blockade of programmed death-1 in human papillomavirus-negative head and neck squamous cell carcinoma

ABSTRACT Background Treatment with a blocking programmed death‐1 (αPD‐1) antibody recently showed clinical efficacy for various tumor types. In this study, we characterized the expression profile of PD‐1/programmed death‐ligand‐1 (PD‐L1) and the potential of PD‐1 blockade in human papillomavirus (HPV)‐negative head and neck squamous cell carcinoma (HNSCC). Methods Lymphocytes from peripheral blood, draining lymph nodes, and the tumor were phenotyped for PD‐1 expression, and their proliferative activity was assessed in the presence of blocking αPD‐1 treatment. Primary tumor expression of PD‐L1 was also analyzed using immunohistochemistry (IHC). Results Lymphocyte PD‐1 expression was abundant with highest expression in the tumor, and in vitro mixed lymphocyte reaction demonstrated that PD‐1 blockade could induce T cell proliferation. Furthermore, tumor cells were found to have 3 distinct patterns of PD‐L1 expression with over 78% of the specimens demonstrating strong PD‐L1 positivity. Conclusion Our data strongly supports the use of αPD‐1 blockade in patients with HPV‐negative HNSCC that are refractory to standard treatments. © 2014 Wiley Periodicals, Inc. Head Neck 37: 1088–1095, 2015