RB1 and glioma: In addition, a 24 h exposure to CAPE (50 μg/ml) inhibited the growth of C6 glioma cells, inducing cell cycle arrest at the G1 subphase after a 24 h incubation, decreasing the CDK2/cyclin E and CDK4/cyclin D activity and inhibiting Rb phosphorylation by increasing p21, p27 and p16 expression [31].