CDK4 and hepatocellular carcinoma: An oleanane-type saponin oleiferasaponin C6 from Camellia oleifera seeds was found to induce cell cycle arrest at the G0/G1 phases through regulating p21, cyclin-dependent kinase 4 (CDK4) and cyclin D1 in human promyelocytic leukemia HL-60 cells and hepatocellular carcinoma BEL-7402 cells.