Our study further highlights that the final outcome and the cellular fate following PRIMA-1MET treatment depend on MGMT protein levels and additional cell type-specific factors irrespective of p53 status: i) apoptosis in mutp53 GBM cells expressing very low levels of MGMT potentially mediated through abrogation of the G2 checkpoint control, activation of GADD45A and sustained expression of cytoplasmic phosphorylated Erk1/2 kinases (T98G-based model with MGMT silencing) and ii) senescence in MGMT-negative GBM cells harboring wtp53 (U87MG). Here, MGMT is linked to glioblastoma.