AIM: 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 3β (GSK-3β), at different concentrations (2-30mmol/L) and time points (0,2,4,6 and 24h). Cell proliferative ability was evaluated by 3-(4,5-Dlmethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and cell cycle distribution was examined by flow cytometry. Expressions of p-GSK-3β,15-catenin, cyclin B1, cdc2 and cyclin D1 protein were detected by West blotting, and the subcellular localization of β-catenin was determined by immunofluorescence. The a level of cylin 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 20mmol/L lithium for 24h produced obvious changes in the distribution of cell cycle, and increased the number of cells in G2/M phase (P<0.05 vs control group). West blotting showed that lithium inhibited GSK-313 by Ser-9 phosphorylation and stabilized free β-catenin in the cytoplasm. Immunofluorescence further confirmed that free β-catenin actively translocated to the nucleus. Moreover, lithium slightly elevated cyclin D1 protein expression, whereas lowered the cyclin B1 expression after 24h lithium exposure and no obvious change was observed for cdc2 protein.CONCLUSION: Lithium can inhibit the proliferation of human esophageal cancer cell line Eca-109 by inducing a G2/M cell cycle arrest, which is mainly mediated through the inhibition of lithium-sensitive molecule, GSK-3β, and reduction of cyclin B1 expression.