TIGIT and malignant colon neoplasm: We therefore first established a T cell-engaging cancer cell line by transfecting the human colon cancer cell line RKO, which expresses endogenous PD-L1 (a PD-1 ligand) and CD155 (a TIGIT ligand) but not MHC-II (a LAG-3 ligand), with a transmembrane form of anti-human CD3 antibody (OKT3) scFv to engage and activate the TCR.