RNAi技术抑制乳腺癌细胞表皮生长因子受体表达的在体实验研究

Effects of RNA interference on epidermal growth factor receptor expression in breast cancer cells:a study in tumor-bearing nude mice

目的探讨采用体外化学合成的小干扰RNA(siRNA)结合阳离子脂质体是否能有效在体转染乳腺癌细胞,以期为RNAi的在体实验研究提供实验数据和理论依据。方法(1)建立裸鼠肿瘤动物模型,计算成瘤率。(2)体外转染乳腺癌细胞,常规动物接种,测量肿瘤体积和动物重量,计算肿瘤抑制率。(3)采用免疫组化和Western blotting技术测定肿瘤组织的表皮生长因子受体蛋白水平,采用Real-time PCR检测表皮生长因子受体基因水平,采用ELISA检测动物血清及肿瘤抽提蛋白中EGF含量。结果MDA-MB-231、ZR-75细胞成瘤率依次为30.00%、88.89%,MDA-MB-231细胞的成瘤能力明显弱于ZR-75细胞。ELISA检测结果证实dsRNA-表皮生长因子受体可将血清及肿瘤组织抽提蛋白中的EGF含量分别降低16.77%、12.59%。Real-time PCR结果表明dsRNA-表皮生长因子受体可将表皮生长因子受体基因表达下调21.05%。结论(1)采用体外化学合成的siRNA结合阳离子脂质体可有效在体转染乳腺癌细胞。(2)在体实验中RNAi效应持续的时间明显长于体外实验。(3)针对表皮生长因子受体基因序列设计的siRNA可作为极具开发前途的抗肿瘤新药,其在体实验中触发RNAi可能的作用机制尚需进一步深入探讨。

Objective To investigate the effect of cationic liposome-mediated RNA interference （RNAi） in silencing epidermal growth factor （EGF） receptor （EGFR） gene in breast cancer cells in vivo. Methods A small interfering RNA （siRNA） targeting EGFR gene was constructed and transfected into human breast cancer cell in vitro via cationic liposome. The transfected cells were inoculated into nude mice, and the tumor growth inhibition rate was calculated, The tumors were then removed for immunohistochemistry and Western blotting to examine the expression of EGFR protein. Quantitative RT-PCR was used to detect the mRNA expression of the EGF receptor gene, and enzyme-linked immunosorbent assay （ELISA） performed to assess the EGF level in both the serum and tumor extraction. Results In athymic nude mice, MDA-MB-231 cells had obviously lower tumor formation rate than ZR-75 cells （30,00% and 88.89%）, Transfection of the cells with EGFR siRNA significantly inhibited tumor formation capacity of the cells in vivo as compared with the cells transfected with empty vector or irrelevant siRNA. The results of ELISA demonstrated that in mice bearing the tumors grown from EGFR siRNA-transfected cells, the EGF levels in the serum and tumor extraction were lowered by 16.77% and 12,59%, respectively, Real-time RT-PCR showed that EGFR siRNA transfection caused a specific downregulation of EGFR mRNA expression by 21.05% in the tumor. Conclusion Chemically synthesized 21-nucleotide siRNA duplexes can be effectively delivered via lipofectarnine 2000 into breast cancer cells in vivo to induce a longer-lasting gene silencing effect than in vitro transfection. RNAi ofEGFR gene may indicate a promising approach for management of lung cancers, especially those nodular ones with easy access.