Advances in T-cell checkpoint immunotherapy for head and neck squamous cell carcinoma

Xinmeng Qi,1,2,* Bo Jia,3,* Xue Zhao,1 Dan Yu1 1Department of Otolaryngology Head and Neck Surgery, The Second Hospital, Jilin University, Changchun, Jilin, 2Department of Otolaryngology Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, 3Department of Thoracic Medical Oncology, Peking University Cancer Hospital and Institute, Beijing People’s Republic of China *These authors contributed equally to this work Abstract: Head and neck squamous cell carcinoma (HNSCC) has been found to be a complex group of malignancies characterized by their profound immunosuppression and high aggressiveness. In most cases of advanced HNSCC, treatment fails to obtain total cancer cure. Efforts are needed to develop new therapeutic approaches to improve HNSCC outcomes. In this light, T-cells “immune checkpoint” has attracted much attention in cancer immunotherapy. It has been broadly accepted that inhibitory T-cell immune checkpoints contribute to tumor immune escape through negative immune regulatory signals (cytotoxic T-lymphocyte-associated antigen 4 [CTLA-4], programmed cell death 1 [PD-1], B7-H3, and B7-H4, etc). Current data suggest that PD-1 and CTLA-4 receptors can inhibit T-cell receptors and T-cell proliferation. Blockade of PD-1/PD-L1 and/or CTLA-4/CD28 pathways has shown promising tumor outcomes in clinical trials for advanced solid tumors like melanoma, renal cell cancer, and non-small cell lung cancer. The present review attempts to explore what is known about PD-1/PD-L1 and CTLA-4/CD28 pathways with a focus on HNSCC. We further discuss how these pathways can be manipulated with therapeutic intent. Keywords: immune checkpoint, PD-1/PD-L1, CTLA-4, HNSCC, immunotherap