CDK4 and central nervous system cancer: In a study by Qi et al., it was shown that over-expression of ZEB2 in glioma samples and cell lines (U251 and U87) has an unfavorable effect on cancer condition, so that ZEB2 knocking down by decreasing antiapoptotic proteins (like cyclinD1, CDK6, CDK4, P-Rb) and E2F1 and increasing pro-apoptotic proteins (such as P15 and P21) leads to apoptosis induction and suppresses cell proliferation and invasion/migration of glioma cells [33].