中文摘要：

目的：探讨中期因子（Midkine，MK）基因表达对人乳腺癌MDA－MB－231细胞株裸鼠体内成瘤性的影响。方法将转染pSilencer－3．1－H1－MK（MK KD组）和pSilencer－3．1－H1－NC（NC组）质粒的乳腺癌细胞分别接种于雌性BALB／c裸鼠右侧前肢腋部皮下，然后于接种第7、14、21、28和35天观察测量肿瘤大小。结果与NC组相比，MK KD组裸鼠肿瘤形成时间长，并且肿瘤生长速度慢，瘤体重量轻、体积小（P＜0．05）。结论抑制MDA－MB－231乳腺癌细胞MK基因的表达，可以抑制裸鼠体内成瘤能力。

英文摘要：

Objective To investigate the effects of Midkine （ MK） expression on the tumorigenic ability of MDA -MB-231 cells in nude mice.Methods Plasmids pSilencer -3.1-H1-MK （Group MK KD） and pSilencer-3.1-H1-NC （ Group NC） were transfected into MDA 231 cells which were then inoculated in the right side of female BALB /c nude mice.The tumor size was measured on Days 7, 14, 21, 28 and 35.Results Compared with Group NC, nude mice in Group MK KD showed longer time to develop tumor , with a slower rate of tumor growth , lower tumor volume and weight （P〈0.05）.Conclusion The inhibition of MK gene expression in MDA -MB-231 cells can inhibit the growth of tumor in nude mice .