HSV-tk基因治疗靶向载体的构建及特异性表达分析

Construction and Identification of Recombinant Vectors Carrying Herpes Simplex Virus Thymidine Kinase Genes Expressed in Vascular Endothelial Cells

背景与目的:阻断肿瘤组织内血管生成和血管化是一个很有发展前景的灭瘤途径之一。胸苷激酶自杀基因系统(herpessimplexvirus-thymidinekinase,HSV-tk/GCV)能有效杀伤血管内皮细胞,目前多采用巨细胞病毒(cytomegalovirus,CMV)作为启动子,但其杀伤缺乏特异性。KDR(kinasedomaininsertcontainingreceptor)是血管内皮生长因子的两种受体之一,它在肿瘤血管内皮细胞中高表达,而在正常组织中呈低表达。本研究是构建KDR启动子介导的HSV-tk重组腺病毒、并对其内皮细胞特异性表达作用进行分析。方法:采用pAdeasy系统,按定向克隆方法将KDR-tk片段正向插入表达载体的多克隆位点间,构建受KDR启动子调控并可表达HSV-tk基因的AdKDR-tk,在293细胞中包装、扩增后,体外感染人脐静脉血管内皮细胞系(humanumbilicalvenousendothelialcells,HUVEC)和不表达KDR的肝癌细胞系HepG2。用更昔洛韦(ganciclovir,GCV)处理受染细胞,并以MTT法检测其细胞增殖情况。结果:经限制性酶切分析,RT-PCR及PCR方法鉴定,插入基因大小、位置、方向正确。病毒滴度为1×1010pfu/ml。在感染复数(multiplicityofinfection,MOI)为100的条件下,GCV浓度由0增至50μg/ml时,感染含AdKDR-tk的HUVEC细胞和HepG2细胞存活率由100%分别下降至(28.94±5.67)%和(75.45±2.91)%(P<0.01)。结论:构建的含KDR-tk重组腺病毒可在血管内皮细胞中特异性地表达HSV-tk。

BACKGROUND ＆ OBJECTIVE. Blocking tumor angiogenesis is a promising tumoricidal approach. Herpes simplex virus-thymidine kinase （HSV-tk） suicide gene could effectively damage neoplastic vascular endothelial cells. However, the killing effect of currently used HSV-tk system is non-specific clue to employing cytomegalovirus （CMV） as its promoter. Kinase domain insert containing receptor （KDR）, a kind of vascular endothelial growth factor receptor, is highly expressed on tumor vascular endothelial cells, but lowly expressed on normal tissues. This study was to construct a recombinant adenovirus containing KDR promoter-mediated HSV- tk suicide gene, and analyze its specific expression on vascular endothelial cells. MEAHODS. KDR-tk fragment was subcloned into corresponding restriction sites of vector with directional cloning method using pAdeasy system to construct recombinant adenoviral plasmid containing KDR promoter-controlled HSV-tk gene （AdKDR-tk）. After packaged and amplified in 293 cells, the virus was used to infect KDR-expressed human umbilical venous endothelial cells （HUVECs） and KDR-unexpressed liver cancer cell line HepG2. After administration of ganciclovir （GCV）, proliferation of gene- transfected HUVECs and HepG2 cells was evaluated by MTT assay. RESULTS. According to the results of restriction digestion, reverse transcription-polymerase chain reaction （RT-PCR） and PCR, the length, position and orientation of inserted genes were correct. The titer of the recombinant adenovirus was 1×10^10 pfu/ml. Under infection index of 100, with the concentration of GCV increased from 0 to 50μg/ml, the survival rates of AdKDR-tk-transfected HUVECs and HepG2 cells decreased from 100% to （28.94±5.67）% and （75.45±2.91）%, respectively （P〈0.01）. CONCLUSION： Adenovirus-mediated transfection of KDR promoter-HSV-tk gene could direct endothelial specific gene expression.