MDM2 and glioblastoma: To confirm that the accumulation of p53 was due to the decreased interaction of p53 with MDM2 rather than elevated p53 expression, we treated GBM cells with ISA27 and monitored the levels of p53 mRNA, p53 protein in the presence of the protein synthesis inhibitor, cycloheximide (CHX), and the MDM2-p53 complex.