In general, glioma cells have been shown to promote exhaustion directly by expressing the checkpoint receptor ligands PD-L1, Galectin-9, B7-H4, B7-H3, CD155, HVEM, PD-L2, CEACAM-1, but there are differences in which ligands are expressed depending which GBM cell line is considered (58). Here, CD274 is linked to glioblastoma.