TIGIT and cancer: reported TIGIT as an effective tumor biomarker in human hepatocellular carcinoma (HCC) that the expression levels of TIGIT were upregulated in the cancerous tissues with the degree of cancerous differentiation from high to low from patients with HCC, and TIGIT showed positive correlation with the level of α-fetoprotein (AFP), which reveals the potential of TIGIT as a cancer biomarker in HCC (39).