Expression of immunoregulatory molecules PD-L1 and PD-1 in oral cancer and precancerous lesions: A cohort study of Japanese patients

Objective: An association of the programmed cell death-1 (PD-1) and its ligand PD-L1 with various types of malignant tumors has been established. This study aimed to investigate the role of the PD-L1/PD-1 pathway in oral squamous cell carcinoma (OSCC) and oral epithelial precursor lesions (OEPL). Materials and methods: We examined 106 OSCC and 79 OEPL specimens for PD-L1 and PD-1 expression by immunohistochemistry. The results were compared with clinicopathological features of OSCC patients. Results: In OSCC and OEPL specimens, PD-L1 expression was detected predominantly in epithelial or carcinoma cells, whereas PD-1 expression was found mainly in infiltrating or stromal lymphocytes. Seventy-two OSCC (67.9%) and 21 OEPL (26.6%) specimens were positive for PD-L1, and 73 OSCC (68.9%) and 23 OEPL (29.2%) specimens were positive for PD-1. PD-L1 and PD-1 expression levels were significantly different between OEPL and OSCC specimens (P < 0.001). There were significant positive correlations between PD-L1 and PD-1 expression in OEPL and OSCC specimens (P < 0.001). PD-L1 and PD-1 immunoreactivity was significantly associated with tumor size (P < 0.05). PD-L1 and PD-1 immunoreactivity in cases with advanced TNM staging was significantly higher than that in low staging cases (P < 0.01). There were significant correlations between PD-L1 and PD-1 expression in OSCC specimens and pathological variables such as stromal lymphocytic reaction (P < 0.05) and invasion depth (P < 0.01). Conclusion: PD-L1 and PD-1 immunohistochemical status may be related to carcinogenesis, tumor progression, and prognosis in oral epithelial lesions. Agents targeting PD-1 and PD-L1 might be useful for OSCC treatment.