title: Gallic acid induces G2/M phase arrest of breast cancer cell MCF-7 through stabilization of p27(Kip1) attributed to disruption of p27(Kip1)/Skp2 complex.
abstract: Gallic acid (GA), 3,4,5-trihydroxybenzoic acid, is a natural polyphenolic acid and widely found in gallnuts, tea leaves and various fruits. Previous studies have shown that GA possesses anti-inflammatory, antiallergic and anticarcinogenic activity. In the present study, we aim to investigate the antitumor effects of GA on breast cancer cell. Our results revealed that GA treatment significantly reduced the cell growth of human breast cancer cell MCF-7 in a dose-dependent manner. Further flow cytometric analysis showed that GA induced significant G2/M phase arrest but slightly affected the population of sub-G1MCF-7 cells. Therefore, levels of cyclins, cyclin-dependent kinases (CDKs), and their regulatory proteins involved in S-G2/M transition were investigated. Our findings revealed that levels of cyclin A, CDK2, cyclin B1 and cdc2/CDK1 were diminished; in contrast, levels of the negative regulators p27(Kip1) and p21(Cip1) were increased by GA treatment. Additionally, Skp2, a specific ubiquitin E3 ligase for polyubiquitination of p27(Kip1) was reduced by GA treatment. Further investigation showed that GA attenuated Skp2-p27(Kip1) association and diminished polyubiquitination of p27(Kip1) in MCF-7 cells. Moreover, knockdown of p27(Kip1) but not p21(Cip1) significantly alleviated GA-induced accumulation of G2/M phase. These findings indicate that GA may upregulate p27(Kip1) level via disruption of p27(Kip1)/Skp2 association and the consequent degradation of p27(Kip1) by proteosome, leading to G2/M phase arrest of MCF-7 cell. It is suggested that GA should be beneficial to treatment of breast cancer and p27(Kip1)-deficient carcinomas.
authors.affiliation: Department of Pathology, Chung Shan Medical University Hospital , Taichung, Taiwan.
authors.forename: Jeng-Dong
authors.initials: JD
authors.lastname: Hsu
authors.forename: Shao-Hsuan
authors.initials: SH
authors.lastname: Kao
authors.forename: Ting-Tsz
authors.initials: TT
authors.lastname: Ou
authors.forename: Yu-Jen
authors.initials: YJ
authors.lastname: Chen
authors.forename: Yi-Ju
authors.initials: YJ
authors.lastname: Li
authors.forename: Chau-Jong
authors.initials: CJ
authors.lastname: Wang
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000032:analysis / Q000378:metabolism*; D018844:Cyclin-Dependent Kinases / Q000032:analysis; D016213:Cyclins / Q000032:analysis; D016195:G2 Phase / Q000187:drug effects*; D005707:Gallic Acid / Q000494:pharmacology*; D006801:Humans; D044786:S-Phase Kinase-Associated Proteins / Q000032:analysis / Q000378:metabolism*
chemical_list: C436291:CDKN1B protein, human; D016213:Cyclins; D044786:S-Phase Kinase-Associated Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D005707:Gallic Acid; D018844:Cyclin-Dependent Kinases