CCND1 and cancer: It has been found that Apigenin treatment of human malignant neuroblastoma combined with silencing of hTERT expression (via siRNA technique) reduced the expression of cell cycle regulatory molecules (CDK2, CDK4, and cyclin D1) and dramatically increased the expression of the cell cycle inhibitor p21Waf1, leading to cell cycle arrest at the G1 phase and thereby blocking cell cycle progression from G1 to S phase and inhibiting cancer cell growth [105].