鸡tie-2受体胞外片段重组蛋白的制备及其抗血管生成作用的研究

目的　设法调控血管的生长发育 ,从而达到治疗疾病的目的。方法　用 PCR方法从既往构建含鸡 tie- 2受体胞外段基因的表达质粒中扩增目的片段 ,构建 p QE质粒原核表达载体并诱导目的蛋白的表达 ;将目的蛋白进一步纯化、复性并免疫小鼠 ,获得抗血清 ,用 EL ISA和 Western印迹检测抗血清中抗体的存在 ;分离纯化抗体 ,用流式细胞仪体外观察其对血管内皮细胞生长情况的影响用体内藻酸盐包裹肿瘤细胞实验和肿瘤内微血管 CD31免疫组化观察其对血管生成情况的影响。结果　经酶切分析及测序鉴定表明获得了鸡 tie- 2受体胞外目的片段的p QE原核表达载体 ,且高效表达目的蛋白 ,其免疫小鼠可产生抗重组蛋白的抗体 ;体外细胞培养结果显示免疫后产生的抗体明显的诱导血管内皮细胞凋亡 ;藻酸盐包裹实验表明此抗体能显著降低肿瘤新生血管的形成 ;CD31微血管计数显示此抗体能明显减少肿瘤内微血管数。结论　用原核表达的方法成功制备了鸡 tie- 2受体胞外片段 (配体结构域 )的蛋白疫苗 ,且此疫苗能明显产生抗血管生成作用。

Prokaryotic expression of extracellular ligand binding domains of chick tie-2 and its anti-angiogenesis effect

OBJECTIVE: To study the prokaryotic expression of extracellular ligand binding domains of chick tie-2, the purification, refolding conditions of the recombinant protein, and its anti-angiogeneic effect. METHODS: A DNA fragment encoding extracellular ligand binding domains of chick tie-2 was obtained by PCR amplification using a previous constructed plasmid as a template. The amplified fragment was then inserted into prokaryotic expression vector pQE30, and was expressed in E.Coli XL-1 blue by adding isopropyl-beta-D-thiogalactoside(IPTG). The recombinant protein in inclusion bodies was purified by nickel-nitrilotriacetic acid (Ni-NTA) affinity chromatography under denatured conditions. Then the refolding of the purified protein was performed with gradient dialysis. The target protein was injected s.c. into mouse, and the antibody was detected by ELISA and Western blot analysis. The antibody was purified from the antiserum and then incubated with human umbilical endothelial vein cell (HUEVC) to find its anti-angiogenesis in vitro by using propidium iodide(PI) dying through FACS. Alginate encapsulated tumor cell assays were performed and micro-vessel density was determined by counting per high power field in the sections stained with an antibody reactive to CD31 to test its inhibition of angiogenesis. RESULTS: The recombinant protein was highly expressed in E.Coli XL-1 blue, and the antibody produced in mouse could specifically recognize the recombinant protein. The purified antibody could induce apoptosis of HUEVC in vitro. The anti-angiogenic effect of the antibody could also be found in alginate-encapsulate tumor cell assay and by counting micro-vessel density. CONCLUSION: The protein of extracellular ligand binding domains of chick tie-2 can be expressed at high level in the prokaryotic expression system, and the expressed protein can induce immune response in mouse. Furthermore, the antibody can induce the anti-angiogenic effect.