HHLA2 and head and neck squamous cell carcinoma: As shown in Figure 1(d), the outcomes of HHLA2 expression from the TIMER database, in most cancers of cholangiocarcinoma (CHOL), colon adenocarcinoma (COAD), head and neck squamous cell carcinoma (HNSC), kidney chromophobe (KICH), kidney renal clear cell carcinoma (KIRC), kidney renal papillary cell carcinoma (KIRP), lung squamous cell carcinoma (LUSC), prostate adenocarcinoma (PRAD), rectum adenocarcinoma (READ), and uterine corpus endometrial carcinoma (UCEC) is higher than their adjacent normal tissues (p < 0.05).