Local Low-dose Anti-PD-L1 Antibodies Improve Antitumor Effects in Oral Squamous Cell Carcinoma

Background/Aim: Immune checkpoint inhibitors are highly effective for treating recurrent and metastatic head and neck cancers. However, they require systemic administration and are associated with immune-related adverse events (irAEs). Reducing therapeutic antibody doses to prevent irAEs is challenging. Materials and Methods: Mouse buccal mucosa squamous cell carcinoma cells (Sq-1979) were transplanted into the backs of mice to induce tumors. The antitumor efficacy and tumor immunohistological environment in tumor-bearing mice were compared after administering a standard dose of programmed death-ligand 1 (PD-L1) antibodies systemically (200 mg/body) or 1/10th of the standard dose (20 mg/body) directly to tumors. Mice received four doses of antibody administered in 3-day intervals. Tumor reduction rates and antitumor efficacies were evaluated 21 days after initiating treatment. CD8+T cell counts and PD-L1, PD-1, perforin, and granzyme B levels; CD25 and Foxp3 expression levels; and tumor Tregs were assessed in the resected subcutaneous tumors. Results: The antitumor efficacies in the local low-dose and systemic standard-dose groups were compared with that of the control group. The efficacies of the two treatment groups were similar, and both treatment groups revealed significant antitumor effects compared to the control group. Perforin and granzyme B levels were higher in the local low-dose group (p<0.05). Conclusion: Local low-dose administration of anti-PD-L1 antibodies exhibits antitumor efficacy similar to systemic standard-dose administration suggesting that local low-dose administration is useful for treating oral squamous cell carcinoma.