HLA class I antigen downregulation has been used as a prognostic biomarker in esophageal cancer (Hosch et al., 1997), melanoma (Kageshita et al., 1999), lung cancer (Kikuchi et al., 2007), ovarian cancer (Vitale et al., 2005), renal cell carcinoma (Kitamura et al., 2007), bladder cancer (Homma et al., 2009), and oral squamous cell carcinoma (Koike et al., 2020) and has improved the survival of patients. The gene discussed is MICA; the disease is oral cavity squamous cell carcinoma.