Genistein-induced G2/M arrest is associated with the inhibition of cyclin B1 and the induction of p21 in human breast carcinoma cells.
Genistein is an isoflavone known to inhibit both tyrosine protein kinase and DNA topoisomerase II. We have investigated the mechanism of genistein-induced growth inhibition in MCF-7 and MDA-MB-231 breast carcinoma cell lines. DNA flow cytometric analysis indicated that genistein induced a G2/M arrest in both cell lines. Therefore, we examined the effect of genistein on cell cycle-related proteins. Western blot analysis using whole cell lysates from MCF-7 and MDA-MB-231 treated with genistein demonstrated that genistein treatment did not change the steady-state level of cdks, cyclin A, D-type cyclins and cyclin E protein, but inhibited expression of cyclin B1 protein in a time-dependent manner. The reduction in the protein level of cyclin B1 correlated with a decrease in the level of cyclin B1 mRNA. Genistein induced expression of p21, and the increased levels of p21 were associated with increased binding of p21 with cdc2 and cdk2. These observations suggest that genistein induces a G2/M arrest in human breast cancer cells, the mechanism of which is in part due to inhibition of kinase activities of cdc2 and cdk2, and decrease in cyclin B1 expression.
Medicine Branch, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
Y H
YH
Choi
L
L
Zhang
W H
WH
Lee
K Y
KY
Park
D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors; D042846:CDC2-CDC28 Kinases; D019926:Cyclin B / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D056744:Cyclin B1; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016213:Cyclins / Q000096:biosynthesis* / Q000378:metabolism; D016195:G2 Phase / Q000187:drug effects*; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D008938:Mitosis / Q000187:drug effects*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000970:Antineoplastic Agents; C534699:CCNB1 protein, human; C493956:CDKN1A protein, human; D019926:Cyclin B; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D012333:RNA, Messenger; D019833:Genistein; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases