let-7a对肺癌A549细胞裸鼠移植瘤生长的影响

Effect of let-7a on Growth of Lung Cancer A549 Cells Transplanted to Nude Mice

目的研究let-7a对肺癌A549细胞裸鼠移植瘤生长的影响及其可能的分子机制。方法将A549细胞、稳定转染let-7a重组质粒的A549-let-7a细胞及稳定转染对照质粒的A549-control细胞分别接种至BALB/c裸鼠背部皮下,观察各组细胞在裸鼠体内的生长情况,测量肿瘤体积并绘制生长曲线;30 d后处死裸鼠,取出瘤体,称重并计算抑瘤率;HE染色观察瘤组织的形态学改变;Western blot及免疫组化法检测各组瘤组织中k-Ras蛋白的表达情况。结果与A549细胞组相比,A549-let-7a细胞组裸鼠的瘤体生长速度明显减慢,瘤体重量显著降低(P<0.01),抑瘤率为27.51%,A549-control细胞组差异无统计学意义(P>0.05);HE染色显示,A549-let-7a细胞组癌细胞体积较其他两组减小,核浆比例明显缩小,核分裂相显著减少;Westernblot及免疫组化结果表明,与A549细胞组相比,A549-let-7a细胞组瘤组织中k-Ras蛋白的表达明显降低(P<0.01),而A549-control细胞组中k-Ras蛋白的表达差异无统计学意义(P>0.05)。结论 let-7a能显著抑制A549细胞在裸鼠体内的生长能力,其机制可能与下调k-Ras蛋白的表达有关。

Objective To investigate the effect of let-7a on growth of lung cancer A549 cells transplanted to nude mice as well as the relevant mechanism.Methods A549 cells,the A549 cells stably transfected with let-7a（A549-let07a cells） and those with control plasmid（A549-control cells） were inoculated s.c.to nude mice and observed for growth.The tumor sizes were measured,based on which the tumor growth curved was plotted.The nude mice were killed 30 d later,from which tumors were taken out and weigh to calculate the tumor inhibition rate.The morphology of tumor was observed by HE staining.The expressions of k-Ras protein in tumor tissues of various groups were determined by Western blot and immunohistochemical assay.Results As compared with those in A549 cell group,the tumors of nude mice in A549-let-7a cell group grew slowly,and the tumor weight decreased significantly（P〈0.01）,with a tumor inhibition rate of 27.51%.However,the sizes and weights of tumors in A549-control cell group showed no significant difference with those in A549 cell group（P〉0.05）.HE staining showed that,compared with those in the other two groups,the size of tumor cells,the ratio of nucleus to cytoplasm and mitosis figures in tumor xenografts in A549-let-7a cell group decreased significantly.Western blot and immunohistochemical assay proved that,compared with that in A549 cell group,the expression level of k-Ras protein in tumor tissue in A549-let-7a cell group decreased significantly（P〈0.01）,while that in A549-control cell group showed no significant difference（P 〉0.05）.Conclusion The let-7a inhibited the growth of A549 cells in nude mice significantly by a potential mechanism which might be associated with down-regulating the expression of k-Ras protein.