OBJECTIVETo investigate the effect of bufalin on nucleus-mitochondria localization of human telomerase reverse transcriptase(hTERT) by exploring its effect on proliferation and apoptosis in human esophageal squamous carcinoma EC9706 cells.

METHODSEC9706 cells were treated with bufalin at various concentrations, and then the cell growth inhibition of EC9706 cells was examined by CCK-8 assay and the 50% inhibitory concentration (IC(50)) was calculated.Cell cycle analysis was performed by flow cytometry with PI staining, and nucleus morphology of apoptosis were observed by fluorescence microscopy with Hoechst 33342 staining. The apoptotic index was measured by flow cytometry with Annexin V-FITC/PI double staining. hTERT subcellular localization and protein expression were determined by Western blotting and multiple immunofluorescence labling combined with laser confocal scanning microscopy.

RESULTSThe proliferation of EC 9706 cells was significantly inhibited by bufalin along with the increase of processing time and concentrations (p<0.01). After the EC9706 cells were exposed to 100 nmol/L bufalin,the number of cells gradually decreased in G(1) phase and increased in S and G(2)/M phases(p<0.05). The typical nucleus morphological changes of apoptosis were observed and the apoptotic index was increased(p<0.01). The expression of hTERT decreased in nucleus but increased in mitochondria(p<0.05).

CONCLUSIONSBufalin can inhibit the proliferation of human esophageal squamous carcinoma EC9706 cells in a time- and dose-dependent manner. It can arrest cell cycle in S and G(2)/M phases and induce the apoptosis of EC 9706 cells. hTERT is localized in both nucleus and mitochondria,and can be partially translocated from nucleus to mitochondria during the bufalin-induced apoptosis.