Induction of Immunological Antitumor Effects by the Combination of Adenovirus-Mediated Gene Transfer of B7-1 and Anti-Programmed Cell Death-1 Antibody in a Murine Squamous Cell Carcinoma Model

Simple Summary Head and neck cancer is the seventh most common cancer and most cases of head and neck cancer are squamous cell carcinoma (SCC). Recently, immune checkpoint inhibitors (ICPIs) such as anti-programmed cell death-1 (PD-1) have been developed. The aim of our study was to evaluate the antitumor effect of adenoviral vector carrying B7-1 (AdB7) in a murine SCC model in order to further explore the potential of the B7-1 gene in immunotherapy for head and neck cancers. Results indicated that tumor size was significantly reduced in the mice treated with both AdB7 and anti-mouse PD-1 antibody. Additionally, treatment resulted in significantly increased cell densities of total immune cells and Ki-67+ CD8+ T cells and decreased the number of regulatory T cells. Our findings indicate that adenovirus-mediated B7-1 gene expression may enhance the antitumor effect of antiPD1 against SCC.Abstract Background: The goal of this study was to evaluate the antitumor immune effects of B7-1 gene expression in addition to immune checkpoint inhibitor against squamous cell carcinoma. Methods: A murine SCC cell line, KLN205, was infected with adenoviral vector carrying B7-1 (AdB7). Infected cells were injected subcutaneously in the flanks of DBA/2 mice. Three weeks after implantation, anti-mouse PD-1 antibody (antiPD1) was intraperitonially administrated twice a week for a total of six times. Results: CD80 was significantly overexpressed in the AdB7-infected tumors. IFN-gamma in the T cells in the spleen was significantly increased and tumor size was significantly reduced in the mice treated with both AdB7 and antiPD1. Targeted tumors treated with both AdB7 and antiPD1 exhibited significantly increased cell densities of total immune cells as well as Ki-67+ CD8+ T cells and decreased regulatory T cells. Conclusions: These results suggest that the B7-1 gene transfer may enhance the antitumor effect of anti-PD1 antibody against SCC.