MGMT and glioblastoma: Thus, restoring wtp53 function and induction of p53 target genes p21, MDM2, and GADD45A through a mechanism involving activation of wtp53 seems to be restricted to CDKN2A (p14ARF)-competent GBM cells, while selective induction of GADD45A could be achieved in the context of MGMT silencing and decreased expression of mutp53.