title: Bcl-2 overexpression sensitizes MCF-7 cells to genistein by multiple mechanisms.
abstract: Genistein is a soy isoflavone with anti-tumor properties. Genistein-induced apoptosis involves Bcl-2 downregulation. However, overexpression of Bcl-2 in breast cancer has been associated with better prognosis and response to hormonal therapy. To examine genistein's effect on breast cancer cells with different Bcl-2 levels, we established control (MCF-7/PV) and Bcl-2 overexpressing MCF-7 (MCF-7/Bcl-2) cell lines and characterized genistein regulated apoptosis and cell cycle progression in these cells. Our results demonstrate that overexpression of Bcl-2 rendered MCF-7 cells more sensitive, rather than resistant, to genistein. We found that genistein induces enhanced cytochrome c release and mitochondrial membrane depolarization in MCF-7/Bcl-2 cells, as compared to control. We also found that genistein increases Bcl-2 levels and Bcl-2/Bax ratio in the mitochondrial fractions of MCF-7/Bcl-2 cells, suggesting that disturbed Bcl-2/Bax distribution may cause cytochrome c release and apoptosis in these cells. Cell cycle analysis indicated that genistein induces G0/G1 arrest in MCF-7/PV cells but increases in G2/M arrest in MCF-7/Bcl-2 cells. This was accompanied by modified responses of several cell cycle regulators, such as p21 and cyclin B1. Taken together, our results indicate that genistein-Bcl-2 interaction switches Bcl-2 from an anti-apoptotic protein into a proapoptotic protein, which involves disturbed Bcl-2/Bax distribution in mitochondria, increased cytochrome c release and modified cell cycle regulation.
authors.affiliation: Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
authors.forename: Chaitali
authors.initials: C
authors.lastname: Tophkhane
authors.forename: Shihe
authors.initials: S
authors.lastname: Yang
authors.forename: Wesley
authors.initials: W
authors.lastname: Bales
authors.forename: Linda
authors.initials: L
authors.lastname: Archer
authors.forename: Adeboye
authors.initials: A
authors.lastname: Osunkoya
authors.forename: Ann D
authors.initials: AD
authors.lastname: Thor
authors.forename: Xiaohe
authors.initials: X
authors.lastname: Yang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D051028:bcl-2-Associated X Protein / Q000378:metabolism