For instance, Yao et al.'s model consisted of four immune-related genes (IRGs), including PVR, TNFRSF12A, IL21R, and SOCS1 [16]; Chen et al. constructed predictive model based on three IRGs (SFRP4, CPXM1, and COL5A1) [17]; and Zhang et al. established a model based on six IRGs (PLAU, STC2, TNFRSF4, PDGFA, DKK1, and CHGB) for the prognostic prediction of HNSCC [18]. The gene discussed is DKK1; the disease is head and neck squamous cell carcinoma.