Lithium inhibits proliferation of human esophageal cancer cell line Eca-109 by inducing a G2/M cell cycle arrest.
OBJECTIVE
To investigate the effect of lithium on proliferation of esophageal cancer (EC) cells and its preliminary mechanisms.


METHODS
Eca-109 cells were treated with lithium chloride, a highly selective inhibitor of glycogen synthase kinase 3beta (GSK-3beta), at different concentrations (2-30 mmol/L) and time points (0, 2, 4, 6 and 24 h). Cell proliferative ability was evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, and cell cycle distribution was examined by flow cytometry. Expressions of p-GSK-3beta, beta-catenin, cyclin B1, cdc2 and cyclin D1 protein were detected by Western blotting, and the subcellular localization of beta-catenin was determined by immunofluorescence. The mRNA level of cyclin B1 was detected by reverse transcription polymerase chain reaction (RT-PCR).


RESULTS
Lithium could inhibit the proliferation of Eca-109 cells. Lithium at a concentration of 20 mmol/L lithium for 24 h produced obvious changes in the distribution of cell cycle, and increased the number of cells in G(2)/M phase (P<0.05 vs control group). Western blotting showed that lithium inhibited GSK-3beta by Ser-9 phosphorylation and stabilized free beta-catenin in the cytoplasm. Immunofluorescence further confirmed that free beta-catenin actively translocated to the nucleus. Moreover, lithium slightly elevated cyclin D1 protein expression, whereas lowered the cyclin B1 expression after 24 h lithium exposure and no obvious change was observed for cdc2 protein.


CONCLUSIONS
Lithium can inhibit the proliferation of human esophageal cancer cell line Eca-109 by inducing a G(2)/M cell cycle arrest, which is mainly mediated through the inhibition of lithium-sensitive molecule, GSK-3beta, and reduction of cyclin B1 expression.
Wang
Jin-Sheng
JS
Department of Pathology, Xiangya Medical College, Central South University, Changsha 410008, Hunan Province, China. jifangwen@hotmail.com
Wang
Cui-Lian
CL
Wen
Ji-Fang
JF
Wang
Yong-Jin
YJ
Hu
Yong-Bin
YB
Ren
Hong-Zheng
HZ
D021581:Active Transport, Cell Nucleus; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002455:Cell Division; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism; D056744:Cyclin B1; D056741:Cyclin D; D016213:Cyclins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004938:Esophageal Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D016195:G2 Phase; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D018021:Lithium Chloride / Q000494:pharmacology*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D051176:beta Catenin / Q000378:metabolism
D000970:Antineoplastic Agents; C534699:CCNB1 protein, human; C495270:CTNNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D056741:Cyclin D; D016213:Cyclins; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D051176:beta Catenin; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3; D018021:Lithium Chloride