中文摘要：

目的研究5-氮杂-2＇-脱氧胞苷（5-aza-CdR）在肝癌细胞株SMMC7721中对程序性细胞死亡因子4（PDCD4）表达的影响及可能机制。方法培养肝癌细胞株SMMC7721，用5-aza-CdR处理肝癌细胞株SMMC7721，Western-blotting检测DNMT3b、PDCD4蛋白在处理前后的变化，甲基化特异性PCR即MSP检测PDCD4基因启动子区域甲基化水平。结果1×10mol／L、5×10^-6 mol／L的5-azaCdR作用于SMMC7721细胞后，DNMT3b表达水平降低，而PDCD4表达水平升高，且浓度之间有差异；MSP示药物处理前PDCD4启动子区域处于高甲基化水平，在用5×10^-6mol／L药物处理后，其启动子发生了去甲基化。结论5-aza-CdR可以抑制DNMT3b在SMMC7721中的表达，且可能通过改变抑癌基因PDCD4启动子甲基化状态影响PDCD4表达。

英文摘要：

Objective To investigate the effects of 5-aza CdR on expression of programmed cell death factor 4 （PDCD4） in SMMC7721and explore its possible mechanism. Methods Hepatocellular carcinoma cell line SMMC7721 was cultivated with 5-aza-CdR inhibiting the expression of DNMT3b. Western blotting was used to determine the changes of DNMT3b and PDCD4 proteins and the methyl- ation level of PDCD4＇s promoter was tested by methylation specific polymerase chain reaction（MSP）. Results Using the 5-aza-CdR on concentration of 1×10-6mol/L and 5×10^-6mol/L to cultivate SMMC7721, the expression of DNMT3b protein was decreased while the PDCD4 protein was increased. The methylation level of PDCD4＇s promoter was high in SMMC7721. However, after the treatment of 5-aza-CdR on concentration of 5×10^-6mol/L, the promoter of PDCD4 had demethylation. Conclusion The expression of DNMT3b can be inhibited by 5-aza-CdR and DNMT3b may control the expression of PDCD4 in SMMC7721 by influencing the methylation status of its promoter.