CDK4 and central nervous system cancer: In DBRTG glioma cells, curcumin increased p53 protein levels and also inhibited the RB signaling pathway, B1/CDK4/p16INK4, involved in cell cycle activation in the G1/S phase via upregulation of CDKN2A/p16 and downregulation of phosphorylated RB, arresting cells in the G1 phase/S (Trotta et al., 2019).