Gallic acid induces G2/M phase cell cycle arrest via regulating 14-3-3β release from Cdc25C and Chk2 activation in human bladder transitional carcinoma cells.
METHODS
Cell cycle regulation is a critical issue in cancer treatment. Previously, gallic acid (GA) has been reported to possess anticancer ability. Here, we have evaluated the molecular mechanism of GA on cell cycle modulation in a human bladder transitional carcinoma cell line (TSGH-8301 cell).


RESULTS
Using flow cytometer analysis, exposure of the cells to 40 μM GA resulted in a statistically significant increase in G2/M phase cells, which was accompanied by a decrease in G0/G1 phase cells. GA-treated cells resulted in significant growth inhibition in a dose-dependent manner accompanied by a decrease in cyclin-dependent kinases (Cdk1), Cyclin B1, and Cdc25C, but significant increases in p-cdc2 (Tyr-15) and Cip1/p21 by western blotting. Additional mechanistic studies showed that GA induces phosphorylation of Cdc25C at Ser-216. This mechanism leads to its translocation from the nucleus to the cytoplasm resulting in an increased binding with 14-3-3β. When treated with GA, phosphorylated Cdc25C can be activated by ataxia telangiectasia-mutated checkpoint kinase 2 (Chk2). This might be a DNA damage response as indicated by Ser-139 phosphorylation of histine H2A.X. Furthermore, treatment of the cells with a Chk2 inhibitor significantly attenuated GA-induced G2/M phase arrest.


CONCLUSIONS
These results indicate that GA can induce cell cycle arrest at G2/M phase via Chk2-mediated phosphorylation of Cdc25C in a bladder transitional carcinoma cell line.
Ou
Ting-Tsz
TT
Institute of Biochemistry and Biotechnology, College of Medicine, Chung Shan Medical University, Taichung, Taiwan.
Wang
Chau-Jong
CJ
Lee
Yung-Shu
YS
Wu
Cheng-Hsun
CH
Lee
Huei-Jane
HJ
D048948:14-3-3 Proteins / Q000378:metabolism*; D000704:Analysis of Variance; D002453:Cell Cycle; D002455:Cell Division; D045744:Cell Line, Tumor; D064447:Checkpoint Kinase 2; D056744:Cyclin B1 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016195:G2 Phase; D005707:Gallic Acid / Q000494:pharmacology*; D006801:Humans; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D001749:Urinary Bladder Neoplasms / Q000378:metabolism; D020687:cdc25 Phosphatases / Q000378:metabolism*
D048948:14-3-3 Proteins; D056744:Cyclin B1; D005707:Gallic Acid; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases