小发夹RNA对白血病K562细胞血管内皮生长因子受体Fit-1基因表达的抑制作用

本研究观察小发夹RNA对白血病细胞血管内皮生长N子受体flt-1基因表达的抑制作用并探讨其对白血病细胞侵袭能力的影响及作用机制。采用脂质体介导的方法将构建的人flt-1基N特异性shRNA真核表达载体转染入K562细胞，用（3418抗性筛选获得阳性克隆；抽提基因组DNA，用PCR方法验证shRNA基因对K562细胞的转染；以RT—PCR和免疫印迹反应检测flt-1mRNA和蛋白表达量的变化；用Boyden小室体外侵袭实验检测白血病细胞的侵袭能力；RT～PCR方法检测白血病细胞MMP-2和MMP-9的表达。结果表明，flt-1基因特异性shRNA真核表达载体转染入白血病细胞株K562，G418筛选2周获得阳性克隆；PCR检测证实shRNA基因整合入白血病细胞基因DNA；携有shRNA的flt-1基因能明显下调白血病细胞内flt-1基因mRNA表达水平；设计的2种不同flt-1shRNA序列能不同程度干扰flt—1基因和蛋白在细胞中的表达，两纽阳性细胞中flt-1基因表达抑制率分别为46．1％和65．4％；flt—1 shRNA转染白血病细胞系K562细胞后，MMP-2和MMP-9mRNA表达水平均较转染前明显下降；阳性细胞穿透人工重组基底膜的能力（4．3±1．2）％较对照组（12．7±1．9）％及（9．6±1．7）％明显降低（P〈0．01）。结论：VEGF受体flt-1特异性shRNA的真核表达载体能够高效转染入白血病细胞株K562，有效抑制flt-1基因的表达，并使白血病细胞体外侵袭能力减弱，MMP-2和MMP-9mRNA表达水平下降。这提示VEGF可能通过与其受体结合调控MMP-2和MMP-9的方式，参与白血病细胞的转移。

Inhibition Effect of Short Hairpin RNA on VEGF Receptor Fit-1 Gene Expression in Leukemia Cell Line K562

This study was purposed to investigate the inhibitory effect of short hairpin RNA （shRNA） on expression of vascular endothelial growth factor （VEGF） receptor flt-1 gene in leukemia cells line K562, and to explore the influence of shRNA invasive ability on leukemia cells and its mechanism. The recombinant eukaryotic expression plasmid containing flt-1 shRNA gene was transfected into K562 cells by lipofectamine mediation and positive clones were screened by G418. shRNA gene in K562 cells was confirmed by PCR. RT-PCR and Western blot were employed to detect the expression of flt-1 mRNA and protein in leukemia cells. The invasive ability of K562 cells was studied by Boyden chamber invasion assay before and after flt-1 shRNA transfection. MMP-2 and MMP-9 mRNA expressions were detected by RT-PCR after transfection of the recombinant plasmid C1/U6/FltS2 into K562 cells through liposome. The results showed that the recombinant eukaryotic expression plasrnid had been transfected into the human leukemia cell line K562 and positive clones had been screened by G418 for 2 weeks. PCR detection revealed the stable expression of the shRNA gene in K562 cells. Flt-1 gene and protein expressions were inhibited by plasmid-expressed shRNA after transfection of recombinant vetors C1/U6/FltS into K562 cells. The inhibitory efficiency of two different shRNA sequences targeting Fit-1 gene were 46. 1% and 65.4% respectively. The expression of MMP-2 and MMP-9 rnRNA decreased, and the mean invasion rate in C1/U6/fltS2-transfected K562 cells was lower than that in nontransfected cells. It is coucluded that shRNA eukaryotic expression vector specific to VEGF receptor flt-1 gene can high efficiantly be transfected into leukemia cell line K562, effectively inhibites the expression of flt-1 gene, weakens the in vitro invasive ability of leukemia cells and the expression levels of MMP-2 and MMP-9 mRNA, which suggests that the VEGF involves in the migration of leukemia cells by regulating the MMP-2 and MMP-9 through joints with the receptor.