SP1 and central nervous system cancer: In our study, we found that modified Dex containing miR-21 inhibitor could disrupt the miR-21/SP1/DNMT1 positive feedback loop in GA-MSCs, leading to a decrease in MDSCs infiltration and CD73 expression on MDSCs, and synergizing with an anti-PD-1 monoclonal antibody (mAb) to prolong the survival of glioma-bearing mice.