VSIR and digestive system neoplasm: Two VISTA binding partners under investigation: one being a known receptor on T cells, P-selectin glycoprotein ligand 1 (PSGL-1), and a second being V-set and Ig domain-containing 3 (VSIG-3), a known cell surface adhesion molecule with increased expression in GI tumors, might indicate dual roles of VISTA as both a ligand for PSGL-1 on T cells and as a receptor for VSIG-3 on tumor cells or myeloid cells (Figure 1) (14, 21).