Distinct Chk2 activation pathways are triggered by genistein and DNA-damaging agents in human melanoma cells.
Genistein, a natural isoflavone found in soybeans, exerts a number of biological actions suggesting that it may have a role in cancer prevention. We have previously shown that it potently inhibits OCM-1 melanoma cell proliferation by inducing a G(2) cell cycle arrest. Here we show that genistein exerts this effect by impairing the Cdc25C-dependent Tyr-15 dephosphorylation of Cdk1, as the overexpression of this phosphatase allows the cells to escape G(2) arrest and enter an abnormal chromatin condensation stage. Caffeine totally overrides the genistein-induced G(2) arrest, whereas the block caused by etoposide is not bypassed and that caused by adriamycin is only partially abolished. We also report that genistein activates the checkpoint kinase Chk2 as efficiently as the two genotoxic agents and that caffeine may counteract the activation of Chk2 by genistein but not by etoposide. In contrast, caffeine abolishes the accumulation of p53 caused by all the compounds. Wortmannin does not suppress the Chk2 activation in any situation, suggesting that the ataxia telangiectasia-mutated kinase is not involved in this regulation. Finally, unlike etoposide and adriamycin, genistein induces only a weak response in terms of DNA damage in OCM-1 cells. Taken together, these results suggest that the G(2) checkpoints activated by genistein and the two genotoxic agents involve different pathways.
Darbon
J M
JM
Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération Cellulaire, UMR 5088 CNRS, Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Cedex, France. darbon@cict.fr
Penary
M
M
Escalas
N
N
Casagrande
F
F
Goubin-Gramatica
F
F
Baudouin
C
C
Ducommun
B
B
D002110:Caffeine / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects*; D064447:Checkpoint Kinase 2; D002830:Choroid Neoplasms; D004249:DNA Damage; D004317:Doxorubicin / Q000494:pharmacology*; D004789:Enzyme Activation; D005047:Etoposide / Q000494:pharmacology*; D016195:G2 Phase; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D008545:Melanoma; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D014407:Tumor Cells, Cultured; D020687:cdc25 Phosphatases / Q000378:metabolism
D018797:Cell Cycle Proteins; D002110:Caffeine; D005047:Etoposide; D004317:Doxorubicin; D019833:Genistein; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases