Objective:To investigate the inhibitory effect and its possible molecular mechanisms of MicroRNA-34a(miR-34a) on the human nasopharyngeal carcinoma CNE-2 cell line subcutaneous xenograft tumor in nude mice.Methods: The human nasopharyngeal carcinoma CNE-2 cell line was cultured in vitro.miR-34a and Scrambled miRNA recombinant plasmids were successfully established and stably transfected into CNE-2 cells.Fifteen six-week-old male nude mice were divided randomly into three groups:miR-34a group(5 mice) ,Scrambled miRNA group(5 mice) ,Blank control group(5 mice).Different CNE-2 cells were subcuta-neously injected on the back near right lower limb.Tumor volumes were examined every 7 days.Mice were executed on the 35 days,and the eventual average tumor volumes and weights were examined.Total RNA and protein were isolated from tumors,and the expression of miR-34a,CDK6,and Bcl-2 mRNA and protein were determined by qRT-PCR and western blot,respectively.Results: The relative expressions of miR-34a was significantly up-regulated in miR-34a transfected group compared to Scrambled miRNA transfected group (P<0.05).Eight subcutaneous xenograft tumor models were successfully established.The nude mice of miR-34a transfected group appeared a smaller tumor volume compared to the other two groups at the beginning of 21th day( P<0.05).The eventual average tumor volumes in miR-34a group,Scrambled miRNA group and blank control group were(351.37±98.19)mm3,(798.75±91.04)mm3 and (849.62±101.32) mm3 ,respectively,and the eventual average tumor weights in miR-34a group,Scrambled miRNA group and blank control group were(0.81±0.13)g,(1.47±0.21)g and(1.58±0.37)g,respectively.Both the eventual average tumor volumes and weights in miR-34a group were lower compared to the other two groups(P<0.05).qRT-PCR results revealed that the expression of miR-34a in miR-34a transfected group was significantly higher than in the other two groups,while the mRNA and protein expression of CDK6 and Bcl-2 were lower than the other two groups ( P<0.05 ) .Conclusion: miR-34a may inhibit the growth of human nasopharyngeal carcinoma CNE-2 cell line subcutaneous xenograft tumor in nude mice by down-regulating CDK6 and Bcl-2.%目的：探讨MicroRNA-34a(miR-34a）对鼻咽癌裸鼠皮下移植瘤的生长抑制作用及其可能的分子机制。方法：体外培养人鼻咽癌CNE-2细胞系，利用miR-34a重组质粒及Scrambled miRNA重组质粒分别构建miR-34a及阴性对照miRNA稳定转染细胞株，qRT-PCR检测细胞内miR-34a表达。选取6周龄雄性BLAB／c裸鼠15只，随机分为3组：miR-34a组(5只），Scrambled miRNA组(5只）及空白对照组(5只）。于裸鼠背部近右后肢皮下注射重组CNE-2细胞悬液，建立移植瘤模型，每7 d测定实验组与对照组肿瘤体积变化，饲养35 d后处死，完整取出肿瘤，测定肿瘤重量及终体积。提取肿瘤组织RNA及蛋白，采用qRT-PCR检测肿瘤组织中miR-34a的表达；分别采用qRT-PCR及免疫组化法检测细胞周期调控基因CDK6及抗凋亡基因Bcl-2 mRNA及蛋白的表达。结果：miR-34a稳定转染CNE-2细胞后可显著提高细胞内miR-34a表达量( P＜0.05）。15只裸鼠均成功构建皮下移植瘤模型，饲养21 d后，与Scrambled miRNA组及空白对照组相比，miR-34a组肿瘤体积显著减小(P＜0.05）。饲养35 d后，miR-34a组、Scrambled miRNA组及空白对照组肿瘤平均重量分别为(0.81±0.13）g、(1.47±0.21）g、(1.58±0.37）g，肿瘤平均终体积分别为(351.37±98.19）mm3、(798.75±91.04）mm3、(849.62±101.32）mm3，miR-34a组肿瘤平均重量及肿瘤平均终体积均显著小于其余两组(P＜0.05）。 miR-34a组中miR-34a的表达量显著高于其余两组(P＜0.05）；miR-34a组中CDK6及Bcl-2 mRNA及蛋白表达量显著低于其余两组( P＜0.05）。结论：miR-34a可能通过下调CNE-2细胞内CDK6及Bcl-2的表达水平从而抑制CNE-2细胞裸鼠皮下移植瘤的生长，发挥其抗肿瘤作用。
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