PD-L1 expression and CD8+ infiltration shows heterogeneity in juvenile recurrent respiratory papillomatosis

Introduction: Tumor immunotherapy have broadened therapeutic options for tumor treatment. The role of immune function in juvenile recurrent respiratory papillomatosis (JRRP) has not been investigated. Applying immunoblockade inhibitors as a novel disease treatment is unclear. Our study, for the first time, evaluates immune infiltration and immuno-suppressive molecule expression in JRRP. Our study provides insights in possibly treating this disease with tumor immunotherapies. We aimed to determine expression of programmed death-ligand 1 (PD-L1), a cancer escape protein, and presence of CD8+ T cell infiltration in tumor microenvironment.

Material and methods: Seven patients with JRRP (mean age: 7.43; age range 3-17) in this study routinely have their tumors surgical debulked at Massachusetts Eye and Ear Infirmary. Following surgery, samples were de-identified and sent to pathology where they were stained and analyzed.

Results: Six out of seven patients expressed PD-L1 on tumor cells to various extents. Three patients showed concurrent PD-L1 expression on tumor cells and abundant CD8+ tumor infiltrating lymphocytes as well as PD-L1+ stromal lymphocytes, while PD-L1 expression on tumor cells were not associated with CD8+ tumor infiltrating T cells nor PD-L1+ stromal lymphocytes in the other three patients. HPV 6/11 and p16 was detected in all the patients. There appeared to be no correlation between either PD-L1 expression and CD8+ infiltration and clinical severity as measured by both the number of surgeries per year or Derkay score.

Conclusions: Despite a small cohort, the expression of p16 and HPV 6/11 in all of the patients confirms the tissues were HPV tumor cells. PD-L1 expression was detected in the vast majority of tumor samples, while inflammatory cell compartments showed a higher degree of variation. Expression of PD-L1 on tumor cells but not inflammatory cells raises the possibility of a tumor cell intrinsic manner of PD-L1 expression. In contrast, a group of patients showed PD-L1 positivity in both tumor and inflammatory cells along with abundant CD8+ tumor infiltrating lymphocytes, suggesting adoptive immune resistance in these tumors and potential benefits from tumor immunotherapy.