中文摘要：

目的研究RNA干扰DNA聚合酶β（polβ）基因对人胃癌BGC-823细胞生物学行为的影响。方法针对DNApolβ基因序列构建小干扰RNA（siRNA）真核表达载体，用脂质体介导转染人胃癌BGC-823细胞，G418筛选出稳定细胞株；采用荧光定量PCR和Western blot测定各组细胞的DNApolβ mRNA和蛋白表达水平；用流式细胞术和裸鼠体内成瘤检测各组细胞的增殖情况。结果成功构建了针对polβ基因的siRNA表达载体。转染polβ靶向siRNA的BGC-823细胞，其polβ mRNA和蛋白表达水平均明显降低，且载体pRNAT—U6．1-sipolβ2（抑制程度83％）的沉默抑制作用强于载体pRNAT—U6．1-sipolβ1（抑制程度56％）；与无关siRNA对照组、空载体对照组和空白对照组相比，转染pRNAT—U6．1-sipolβ1的细胞G0／G1期比例显著升高，S期比例及细胞增殖速度显著下降（P〈0．05）；转染pRNAT—U6．1-sipolβ2的细胞G0／G1期比例显著降低，S期比例及细胞增殖率显著升高（P〈0．05）。结论靶向DNApolβ的siRNA可以显著抑制polβ的表达；polβ的高表达和近乎完全抑制的超低水平表达都不利于维持细胞的生理状态；通过siRNA将BGC-823细胞中polβ表达沉默到合适的低水平，可能对肿瘤的生长起到抑制作用。

英文摘要：

Objective To study the influence of DNA polymerase β （polβ） gene silencing by small interfering RNA on biological behavior of human gastric cancer cell line BGC-823. Methods The siRNA eukaryotic expression vectors targeting polβ gene were constructed and transfected into BGC-823 cells by liposome. Stable cell lines were screened with G418. The expression levels of polβ mRNA and protein were detected by real time PCR and Western blot in the cells of each group. The proliferation of each group was detected by flow cytometry and tumorigenicity was determined in nude mice. Results The siRNA expression vector targeting polβ gene was successfully constructed. The expression levels of polβ mRNA and protein were significantly reduced in the experimental group transfected with siRNA expression vectors targeting po113, and the silencing effect of pRNAT-U6. 1-sipolβ2 （suppression degree was 83% ） was stronger than that of pRNAT-U6.1-sipolβ1 （depression degree is 56% ）. Compared with irrelevant siRNA control group, empty vector control group and untransfected group, the ratio of G0/G1 cells was increased, proportion of S phase cells and cell proliferation were decreased in the experimental group 1 cells transfected with pRNAT-U6.1-sipolβ1 （P 〈0.05）. On the contrary, the ratio of G1/G0 was decreased, proportion of S phase ceils and cell proliferation was increased in the experimental group 2 cells transfeeted with pRNAT- U6.1-sipolβ2 （P 〈 0.05）. Conclusion The siRNA expression vectors targeting DNA polymerase β gene can significantly inhibit the expression of polβ mRNA. Neither high nor extremely low expression of polβ is beneficial to maintain the cellular physiological functions. The expression of polβ silenced to a proper level by siRNA may play an important role in inhibiting tumorigenesis.