PDCD1 and head and neck squamous cell carcinoma: At present, treatment approaches for HNSCC are mainly comprehensive modalities with surgery, radiotherapy, chemotherapy, targeted therapy, immunotherapies, et al. However, the overall responses rates of patients with HNSCC to targeted therapeutic drugs, such as epidermal growth factor receptor (EGFR) inhibitors (cetuximab) and programmed cell death protein 1 inhibitors (pembrolizumab and nivolumab), were moderate (Zhang et al., 2021).