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

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.