CD274 and glioblastoma: Moreover, glioblastoma-derived stem cells secrete exosomes that enhance chemoresistance; indeed, these vesicles contain programmed death-ligand 1 (PD-L1), which activates the AMP-activated protein kinase (AMPK)/Unc-51-like kinase 1 (ULK1) pathway mediating autophagy activation that, in turn, results in the increased TMZ-resistance in glioblastoma cells (Table 2) [68].