TIGIT and esophageal squamous cell carcinoma: Overexpression and the presence of a soluble form of CD155 in the blood serum of patients are associated with a poor clinical prognosis [102,106,107]. The association of the co-expression of TIGIT and CD155 with an unfavorable disease course in lung adenocarcinoma and primary SCC of the esophagus has been shown [106,108].