Reportedly, PD-L1 is overexpressed in glioma cells [84] and MDSCs [29] in the glioma microenvironment, binding to PD-1 on the surface of activated T cells and leading to an immunosuppressive effect, which might have limited the immunotherapy efficacy of the miR-21 inhibitor-Dex complex. Here, CD274 is linked to central nervous system cancer.