中文摘要：

目的研究亚硒酸钠对结直肠癌HCT116和SW480细胞中β-catenin及下游靶基因cyclin D1表达的影响。方法采用10μmol/L亚硒酸钠处理HCT116和SW480细胞,Western blot及RT-PCR检测亚硒酸钠处理后不同时间HCT116和SW480细胞中β-catenin和cyclin D1的表达情况,并观察蛋白酶体抑制剂MG132预处理后对HCT116和SW480细胞中β-catenin和cyclin D1表达的影响。采用免疫共沉淀方法检测亚硒酸钠对HCT116和SW480细胞中β-catenin与T细胞因子4（TCF4）相互作用的影响。结果亚硒酸钠可降低HCT116和SW480细胞中β-catenin和cyclin D1的表达水平,用蛋白酶体抑制剂MG132预处理可增加亚硒酸钠处理后HCT116和SW480细胞中β-catenin和cyclin D1的表达水平。免疫共沉淀实验结果显示,亚硒酸钠能破坏β-catenin与TCF4间的相互作用。结论亚硒酸钠可降低结直肠癌HCT116和SW480细胞中β-catenin及cyclin D1的表达水平,蛋白酶体介导的降解途径可能在这一过程中发挥了重要作用。亚硒酸钠引起的β-catenin与TCF4相互作用减少可能对β-catenin靶基因的转录也起到了一定的调控作用。

英文摘要：

Objective To explore the effects of sodium selenite on the expressions of β-catenin and cyclin D1 in colorectal cancer cells HCT 116 and SW480.Methods HCT 116 and SW480 cells were treated by 10μmol/L sodium selenite at different time points.The expressions and transcription of β-catenin and cyclin D1 were detected by Western blot analysis and reverse transcriptase polymerase chain reaction（RT-PCR）,respectively.Meanwhile,the impact of MG132（a proteasome inhibitor） pretreatment on the expressions of β-catenin and cyclin D1 was observed through Western blot analysis.The interaction between β-catenin and T cell factor 4（TCF4） after selenite treatment was evaluated using co-immunoprecipitation assay.Results Sodium selenite inhibited the expression of β-catenin and transcription of its target such as cylcin D1.MG132 pretreatment prevented the inhibition of β-catenin signaling triggered by selenite in HCT 116 and SW480 cells.Furthermore,selenite treatment disrupted the interaction between β-catenin and TCF4 in HCT 116 and SW480 cells.Conclusions Sodium selenite can lower the expression levels of β-catenin and its target cyclin D1,during which the proteasome-mediated degradative pathway may be involved.The decreased interaction between β-catenin and TCF4 due to sodium selenite may be also involved in the regulation of β-catenin signaling.