P16 expression and its association with PD-L1 expression and FOXP3-positive tumor infiltrating lymphocytes in head and neck squamous cell carcinoma

Backgrounds: Human papilloma virus (HPV) infection is an important factor in development and prognosis of head and neck squamous cell carcinoma (HNSCC). It is also known that HPV infection could affect anti-cancer immunity. Methods: We examined the association between cancer immunity-related molecules and HPV infection, using immunohistochemical (IHC) staining for p16, PD-L1, and FOXP3 and real-time polymerase chain reaction for HPV. Results: The IHC staining for PD-L1 was positive in 30 out of 122 cases (24.6%) and p16 showed positivity in 68 out of 122 cases (55.7%). HPV was detected in 48 out of 122 cases (39.3%). P16 expression was significantly associated with PD-L1 expression (P=0.004), HPV infection (P=0.032), and the number of FOXP3-positive tumor infiltrating lymphocytes (P=0.009). PD-L1-positive or p16-positive HNSCC showed a worse prognosis than PD-L1-negative or p16-negative HNSCC. Conclusion: P16 expression may predict PD-L1 expression, and p16 expression may also be associated with the immune evasion of HNSCC.