CD274 and glioblastoma: Recent research has identified costimulatory (Signal 2) receptors such as 4‐1BBL and cytokine IL‐12 (Signal 3) to preferentially recruit natural killer and cytotoxic CD8+ cells and increase affinity to MHC I complexes on tAPCs.[20, 21] Furthermore, PD‐L1 expression is increased in resistant/recurrent GBM and meningioma patient tumors and represents a possible adjuvant target to sustain the immune response.