PD-1 and its ligands, programmed death-ligand 1 (PD-L1) (Dong et al., 1999) and PD-L2 (Latchman et al., 2001), were shown to be part of an important family of molecules involved in tumor immunosuppression (Freeman et al., 2000; Brahmer et al., 2012). Here, CD274 is linked to neoplasm.