PVR and malignant colon neoplasm: The TIGIT/CD155 inhibitory axis is an attractive target as CD155 (PVR, necl-5) is overexpressed in multiple cancer types including colon cancer, lung adenocarcinoma, melanoma, ovarian, breast, pancreatic cancer and glioblastoma and its expression is correlated with poor prognosis and tumor proliferation [13, 17].