MDM2 and central nervous system cancer: However, while incorporation of both MDM2 amplification and MGMT expression status improved on the classification of p53 WT gliomaspheres insensitive to the combination strategy (Fig. 4A), approximately 30% of the remaining intact p53 signaling glioma cells were nonresponsive to treatment (IR + BCL-XLi: n = 5/15; TMZ + BCL-XLi: n = 3/10).