PD-L1 in squamous cell carcinoma of the oral tongue shows gender-specific association with prognosis.

OBJECTIVE: To use alternative quantitation approaches to clarify the clinical implication of programmed cell death ligand 1 (PD-L1) in squamous cell carcinoma of the oral tongue (SCCOT). MATERIALS AND METHODS: Ventana SP263 immunohistochemistry assay and a multiplicative QuickScore method were applied to quantify PD-L1 in tumor and surrounding immune cells from 101 patients with SCCOT. Tumor-infiltrating immune cells were estimated from bulk tissue transcriptional profiles of 25 patients. Circulating PD-L1 levels were measured in serum from 30 patients using an electrochemiluminescence assay platform. RESULTS: We found higher tumor cell PD-L1 levels in females than males (P = 0.019). For patients with low PD-L1 in tumor cells, better survival was seen in males than females (overall survival P = 0.021, disease-free survival P = 0.020). Tumor-infiltrating natural killer T cells, immature dendritic cells and M1 macrophages were positively associated with tumor cell PD-L1 (P < 0.05). CONCLUSIONS: Our data confirmed the significance of gender on tumor cell PD-L1 expression and demonstrated combined effects of gender and PD-L1 levels on clinical outcome in patients with SCCOT. The data also indicated the involvement of specific immune cell types in PD-L1 regulated immune evasion.