CDK4 and hepatocellular carcinoma: Analysis of cell cycle checkpoint proteins in HCC cells in the co-culture system showed that the expression of CDK4, CDK2, and cyclin A2 was reduced, whereas the expression of the cyclin-dependent kinase inhibitor p27 Kip1 was increased, indicating that Sch B may inhibit the growth of liver cancer by regulating the cell cycle of HCC cells in the co-culture system.