CDK2 and glioblastoma: At 24 h, both p21 alone (Fig. 6c) and the p21/Cdk2 ratio (Fig. 6d) significantly correlated with the percent of SA-β-gal positive cells at 5 days in female human GBM lines (r = 0.85 for both), but only moderately correlated in male human GBM lines (r = 0.23 and r = 0.54, respectively) (Supplementary Table 3).