A photodynamically sensitized dendritic cell vaccine that promotes the anti-tumor effects of anti-PD-L1 monoclonal antibody in a murine model of head and neck squamous cell carcinoma

Abstract

Abstract Background Immune checkpoint inhibitors are promising tools in combating several cancers, including head and neck squamous cell carcinoma (HNSCC). However, a substantial portion of HNSCC patients do not respond to PD-L1 antibody. Here we describe a photodynamic therapeutic (PDT) approach to enhance anti-tumor effects of the anti-PD-L1 antibody. Methods Phototoxicity of PDT was confirmed using fluorescence microscopy, Cell Counting Kit-8 (CCK-8), Enzyme Linked Immunosorbent Assay (ELISA) and flow cytometry analyses. Phenotypic and functional maturation of immature DCs (imDCs) induced by PDT were measured using flow cytometry and ELISA. A mouse model was established using the HNSCC line, SCC7, and was used to evaluate therapeutic effects of PDT-DC vaccine in facilitating anti-tumor immunity of PD-L1 antibody. Results Immunogenic cell death (ICD) of SCC7 cells was induced by PDT with 0.5 µM of m-THPC and the 5 J/cm2 of light dose. ICD of SCC7 cells stimulated imDCs maturation. In vivo assays suggested that PDT-DC vaccine and anti-PD-L1 mAb synergistically induced anti-tumor immunity and suppressed tumor progression. Conclusion PDT-DC vaccine enhances therapeutic effects of PD-L1 antibody, which might provide a novel approach for HNSCC immunotherapy. Graphic abstract

Keywords

• Head and neck squamous cell carcinoma
• PD-L1
• Immunotherapy
• Immune checkpoint
• DC vaccine
• Photodynamic therapy