HPV frequency in oral cavity and oropharynx cancers and its association with immune checkpoint inhibitors

Objectives: The prevalence of human papillomavirus (HPV) associated oropharyngeal squamous cell carcinomas (SqCCs) varies ethnically and geographically and has better prognostic features compared to HPV negative cases. Escaping from the immune system is one of the important mechanisms in the development of oropharyngeal SCC. The interaction of programmed cell death receptor 1 (PD-1) and its ligand (PD-L1) causes T cell suppression. In our study, we aimed to evaluate the frequency of HPV and its relation with PD-1/PD-L1, which is closely related to lymphoid tissue and important in prognosis and treatment in oral cavity and oropharynx SCCs. Method: We retrospectively investigated the presence of HPV in sections prepared from paraffin blocks of biopsy and excision materials by immunohistochemical staining method with p16 antibody and HPV in-situ hybridization (ISH) method in our series of 70 patients diagnosed with oral (SqHC). We also evaluated PD-L1 expression in tumor cells and PD-1 expression in lymphoid cells in the tumor microenvironment by immunohistochemically staining method. Results: HPV positivity was detected in three tumors, two in the oropharynx and one lateral to the tongue. PD-L1 positivity was observed in 45 (64.3%) cases. PD-1 expression was moderate or severe in 75.6% of PD-L1 positive cases and 24% of PD-L1 negative cases and this ratio was statistically significant. PD-L1 positivity was detected in only one of the 3 HPV positive cases. There was no significant difference in overall survival in PD-L1 positive patients compared to PD-L1 negative ones. Discussion: PD-1 or PD-L1 expression can be observed in oral cavity and oropharynx SCC regardless of HPV status. Although HPV positivity is frequently reported to be associated with good prognosis, studies are limited especially in our country. The prognostic and predictive importance of these biomarkers should be supported by more comprehensive studies.