CDK4 and pilocytic astrocytoma: Rickman et al. found 360 distinct genes in GBM from pilocytic astrocytomas, including MDM2, IGFBP2 (Insulin-like growth factor-binding protein 2), CD44 (CD44 antigen), and CDK4 (Cyclin-dependent Kinase 4) (Rickman et al., 2001).