构建靶向杀伤白血病细胞的新型重组白细胞介素6D24-PE40KDEL融合蛋白

目的　构建能高度特异地靶向杀伤高表达白细胞介素 6受体 (IL 6R)白血病细胞的新型重组IL6 PE4 0KDEL(绿脓杆菌外毒素 )融合蛋白。方法　通过定点诱变将绿脓杆菌外毒素PE4 0基因羧基端最后 5个氨基酸REDLK替换成内质网蛋白滞留序列 (KDEL) ,采用重叠延伸的基因融合技术将N 末端缺失 2 4个氨基酸的人IL6 (IL6D2 4 )cDNA与PE4 0KDEL基因进行重组融合构建 ,利用HB10 1/pBV2 2 0表达系统实现该新型重组IL6D2 4 PE4 0KDEL外毒素融合蛋白在大肠杆菌中的高效表达 ,经MonoQ柱层析纯化后 ,以四甲基偶氮唑类似物 (MTS)法检测IL6D2 4 PE4 0KDEL的靶向杀伤活性。结果　构建的新型重组IL6D2 4 PE4 0KDEL融合蛋白在大肠杆菌中的表达水平达到 4 0 %左右 ;经包涵体分离、复性、变性及纯化所得该融合蛋白纯度 >95 % ;纯化的融合蛋白能与IL6抗体及绿脓杆菌外毒素A(PEA)抗体发生特异性结合 ;IL6D2 4 PE4 0KDEL融合蛋白能高度特异地选择性杀伤高表达IL6R的U937细胞 ,IC5 0约为 2 5 0ng/ml,而对不表达IL6R的人T淋巴白血病细胞系则无杀伤作用。结论　成功构建了具有靶向杀伤高表达IL6R白血病细胞的新型重组IL6D2 4 PE4 0KDEL融合蛋白 ,为深入地探索利用IL6 /IL6R系统介导靶向治疗高表达IL6R白血病奠定了坚实的基础。

Molecular design and construction of IL6D24-PE40KDEL,a novel recombinant interleukin6-pseudomonas exotoxin fusion protein,having targeted cytotoxicity for leukemias expressing interleukin6 receptors

OBJECTIVE: A novel recombinant interleukin6-Pseudomonas exotoxin fusion protein, having targeted cytotoxicity for leukemic cells highly expressing IL6R has been molecularly designed and constructed in this study. METHODS: Firstly, REDLK at C-terminus of Pseudomonas exotoxin PE40 was replaced with KDEL using point mutagenesis technology. Secondly, a cDNA encoding interleukin-6 devoid of N-terminal 24 amino acids IL6D24] was fused to 5' terminus of PE40KDEL DNA by the method of gene splicing by overlap extension, which could generate recombinant IL6D24-PE40KDEL and IL6D24-Linker-PE40KDEL fusion genes. Thirdly, recombinant fusion genes IL6D24-PE40KDEL and IL6D24-Linker-PE40KDEL were ligated into the EcoR I and Sma I cloning sites in the pBV220 plasmids respectively and then transformed into E.coli HB101 cells. The expressed recombinant exotoxin fusion proteins were purified to electrophoresis purity by Mono Q column chromatography. Its selectively killing was tested by the MTS colorimetric method using both U937 and CEM cells lines. RESULTS: Recombinant exotoxin fusion proteins IL6D24-PE40KDEL was expressed as a form of inclusion bodies at higher level of 40% approximately of total proteins in bacterial cells. Western blot showed that the purified products could react specifically with IL6 monoclonal antibody and PEA antiserum, respectively. IL6D24-PE40KDEL was selectively cytotoxic to U937 cells expressing IL6R-positive with ID50 of 250 ng/ml, and but not CEM cells expressing IL6R-negative. CONCLUSIONS: Two novel recombinant interleukin6-Pseudomonas exotoxin fusion proteins IL6D24-PE40KDEL and IL6D24-Linker-PE40KDEL have been successfully constructed and they can selectively kill the leukemic cells expressing highly IL6R.