口服DNA疫苗pcDNA3.1+/flk-1_((n1-7))抗小鼠结肠癌肝转移

Inhibition of liver metastasis of colon cancer in mice by oral DNA vaccine pcDNA3.1(+)/flk-1_((n1-7))

背景与目的:血管内皮生长因子(vascular endothelial growth factor,VEGF)及其主要受体血管内皮生长因子受体-2(vascular endothelial growth factor receptor-2,VEGFR-2)在肿瘤血管生成过程中起着重要作用。VEG-FR-2在鼠中为flk-1,本研究以减毒沙门氏菌SL3261为载体制备了抗肿瘤血管生成口服DNA疫苗pcDNA3.1+/flk-1(n1-7),研究该疫苗抗小鼠结肠癌肝转移的作用,并探讨其可能的作用机制。方法:RT-PCR法扩增鼠VEGFR-2胞外cDNA全长序列flk-1(n1-7),构建重组质粒pcDNA3.1+/flk-1(n1-7)。将重组质粒转化减毒沙门氏菌SL3261,制备成以SL3261为载体的口服DNA疫苗。将18只小鼠随机分组,口服接种疫苗两周后,用CT-26细胞建立结肠癌肝转移动物模型,15d后处死小鼠,体视学方法计数肝脏的肿瘤结节数目。流式细胞仪检测小鼠外周血CD4+细胞和CD8+细胞变化。结果:构建成重组质粒pcDNA3.1(+)/flk-1(n1-7),制备成以SL3261为载体的口服DNA疫苗pcD-NA3.1(+)/flk-1(n1-7)。疫苗组小鼠肝脏内的肿瘤转移病灶明显低于对照组,P<0.05。结论:成功构建了重组质粒pcDNA3.1(+)/flk-1(n1-7),制备成以SL3261为载体的口服DNA疫苗pcDNA3.1(+)/flk-1(n1-7)。这种疫苗能抑制小鼠结肠癌的肝脏转移。

Background and purpose： Vascular endothelial growth factor （VEGF） and vascular endothelial growth factor receptor-2（ VEGFR-2, mouse flk-1）play an important role in tumor-associated angiogenesis in both tumor growth and metastasis, This study was done to test the impacts of oral DNA vaccine pcDNA3.1 （ ＋ ）/flk-1（n1-7）on tumor metastasis by inhibiting angiogenesis and investigate its mechanism in vivo. Methods： ① Extracellular domain of flk-1 was amplified by RT-PCR, and then the flk-1（n1-7） cDNA was inserted into eucaryotic expression vector pcDNA3.1（ ＋ ） so that the recombinant plasmids pcDNA3. 1 （ ＋ ）flk-1（n1-7） was constructed. ② The recombinant plasmid pcDNA3. 1 （ ＋ ）flk-1（n1-7） was transformed into attenuated Salmonella typhimurium SL3261 in order to develop an oral DNA vaccine against the extracellular domain of flk-1. ③ Mice were divided into 3 groups randomly（ vaccine group, empty-vector group and saline group） and were respectively orally immunized with either SL3261 transformed with the recombinant plasmid, pcDNA3. 1 ＋ or saline for 3 times with 2-wk intervals apart from each other Mice were inoculated with colonic adenocarcinoma cells （CT-26） by intrasplenic injection 2 weeks after the last immunization. Mice were sacrificed and liver metastasis were analyzed fifteen days after tumor cell inoculation. Results： ① We successfully constructed a recombinant plasmid DNA encoding extracellular domain of flk-1. ② We developed an oral DNA vaccine against the extracellular domain of flk-1 carried by attenuated Salmonella typhimurium SL3261. ③ There were much more liver metastasises in the vector group and saline group than in the vaccine group （ P 〈 0.05）. Conclusions： We successfully constructed the recombinant plasmid pcDNA3. 1 （ ＋ ）/flk-1（n1-7） and developed an oral DNA vaccine against the extracellular domain of flk-1 carried by attenuated Salmonella typhimurium SL3261. The oral DNA vaccine can reduce the possibility of liver metastasises of colon cancer.