CDK4 and glioblastoma: In contrast, enforced expression of p16INK4A or p18INK4C had no impact in LN-Z308 GBM cells with amplification and overexpression of Cyclin D1 and CDK4 and intact p16INK4A and p18INK4C genomic loci) (Table 2; Figure 3B; Figure S5C).