title: Genistein arrests hepatoma cells at G2/M phase: involvement of ATM activation and upregulation of p21waf1/cip1 and Wee1.
abstract: Genistein, a soy isoflavone, has a wide range of biological actions that suggest it may be of use in cancer prevention. We have recently reported that it arrests hepatoma cells at G2/M phase and inhibits Cdc2 kinase activity. In the present study, we examined the signaling pathway by which genistein modulates Cdc2 kinase activity in HepG2 cells and leads to G2/M arrest, and found that it caused an increase in both Cdc2 phosphorylation and expression of the Cdc2-active kinase, Wee1. Genistein also enhanced the expression of the cell cycle inhibitor, p21waf1/cip1, which interacts with Cdc2. Furthermore, phosphorylation/inactivation of Cdc25C phosphatase, which dephosphorylates/activates Cdc2, was increased. Genistein enhanced the activity of the checkpoint kinase, Chk2, which phosphorylates/inactivates Cdc25C, induced accumulation of p53, and activated the ataxia-telangiectasia-mutated (ATM) gene. Caffeine, an ATM kinase inhibitor, inhibited these effects of genistein on Chk2, p53, and p21waf1/cip1. These findings suggest that the effect of genistein on G2/M arrest in HepG2 cells is partly due to ATM-dependent Chk2 activation, an increase in Cdc2 phosphorylation/inactivation as a result of induction of Wee1 expression, and a decrease in Cdc2 activity as a result of induction of p21waf1/cip1 expression.
authors.affiliation: Department of Biochemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan, ROC.
authors.forename: Kee-Lung
authors.initials: KL
authors.lastname: Chang
authors.forename: Mei-Lang
authors.initials: ML
authors.lastname: Kung
authors.forename: Nan-Haw
authors.initials: NH
authors.lastname: Chow
authors.forename: Shu-Jem
authors.initials: SJ
authors.lastname: Su
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D042863:Cyclin-Dependent Kinase 9 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism*; D004268:DNA-Binding Proteins; D016195:G2 Phase / Q000187:drug effects*; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D008938:Mitosis / Q000187:drug effects*; D009687:Nuclear Proteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D015854:Up-Regulation / Q000187:drug effects; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; C534699:CCNB1 protein, human; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D019926:Cyclin B; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; D019833:Genistein; D011505:Protein-Tyrosine Kinases; C499349:WEE1 protein, human; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D042863:Cyclin-Dependent Kinase 9; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases