CCNA2 and hepatocellular carcinoma: Bufotalin, a cardiac glycoside secreted by a number of toad species, also induced G2/M arrest through down-regulation of several cell cycle regulators including aurora A, Cdc25, cyclin-dependent kinase 1 and cyclin A, and up-regulation of p53 and p21 in hepatocellular carcinoma HepG2 cells [4].