CDKN1A and glioblastoma: To assess whether the p21/Cdk2 ratio may similarly influence the induction of senescence in our mouse GBM model cells, we measured levels of Cdk2 mRNA 24 h after irradiation and correlated the Cdkn1a/Cdk2 ratio with the percent of SA-β-gal positive cells at 5 days (Fig. 4c, Supplementary Table 3).