CD80 and cancer: Notably, programmed death ligand 1 (PD-L1, i.e., B7-H1) is noted to be expressed on many cancer and immune cells and by binding to programmed death-1 (PD-1) and CD80, negative regulators of T-lymphocyte activation, it suppresses T-cell migration, proliferation, and secretion of cytotoxic mediators, thereby restricting tumor cell killing and blocking the cancer immunity cycle [40].