CDK4 and glioblastoma: First, GBM has a wide variety of chromosomal changes, including amplification in chromosome 4 (Chr.4, PDGFRA), Chr.7 (EGFR; MET, hepatocyte growth factor receptor; CDK6, Cyclin-dependent kinase 6), Chr.12 (CDK4, Cyclin-dependent kinase 6; MDM2, Mouse double minute 2 homolog), and deletion in Chr.10 (PTEN).