Quantitative radioimmunoPET imaging of EphA2 in tumor-bearing mice
Quantitative radioimmunoPET imaging of EphA2 in tumor-bearing mice
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DOI：
10.1007/s00259-007-0503-5
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发表时间：
2007-12-01
影响因子：
9.1
通讯作者：
Chen, Xiaoyuan
中科院分区：
文献类型：
--
作者：
Cai, Weibo;Ebrahimnejad, Alireza;Chen, Xiaoyuan
目的
EphA2受体酪氨酸激酶在多种癌症类型中显著过度表达。EphA2的高表达与转移潜能增加和患者生存率低相关。尽管最近许多报道都集中在阻断癌症中的EphA2信号通路，但EphA2的体内成像尚未得到研究。
方法
我们通过螯合剂1,4,7,10 - 四氮杂环十二烷 - N,N',N",N'''-四乙酸（DOTA）用Cu - 64标记1C1（一种针对人和鼠EphA2的人源化单克隆抗体），并对8种具有不同EphA2表达水平的肿瘤模型进行正电子发射断层扫描（PET）成像。对肿瘤组织裂解物进行蛋白质印迹分析，以将EphA2表达水平与肿瘤中Cu - 64 - DOTA - 1C1的摄取相关联。还进行了免疫荧光染色和生物分布研究以验证体内结果。
结果
放射性标记产率为88.9 ± 9.5%（n = 7），Cu - 64 - DOTA - 1C1的比活度为1.32 ± 0.14 GBq/mg的1C1单克隆抗体。通过流式细胞术分析测量，抗体在DOTA偶联后保留了抗原结合亲和力/特异性。在注射后18小时，CT - 26肿瘤中Cu - 64 - DOTA - 1C1的摄取高达25.1 ± 2.5 %ID/g（n = 3）。Cu - 64 - DOTA - IgG（一种同型匹配的对照）在所有8种肿瘤模型中表现出极小的非特异性摄取。通过未标记的1C1成功阻断CT - 26肿瘤摄取，证实了Cu - 64 - DOTA - 1C1在体内对EphA2的特异性。最重要的是，从PET成像获得的肿瘤摄取值与通过蛋白质印迹测量的相对肿瘤组织EphA2表达水平具有极好的线性相关性，在注射后18小时和42小时，r²分别等于0.90和0.92。
结论
通过微型PET成像测量的Cu - 64 - DOTA - 1C1的肿瘤摄取反映了体内肿瘤EphA2的表达水平。据我们所知，这是在活体中对EphA2进行定量放射免疫PET成像的首次报道。未来对Cu - 64 - DOTA - 1C1进行临床研究是有必要的。
Purpose EphA2 receptor tyrosine kinase is significantly overexpressed in a wide variety of cancer types. High EphA2 expression has been correlated with increased metastatic potential and poor patient survival. Although many recent reports have focused on blocking the EphA2 signaling pathway in cancer, the in vivo imaging of EphA2 has not yet been investigated.Methods We labeled 1C1, a humanized monoclonal antibody against both human and murine EphA2, with Cu-64 through the chelating agent 1,4,7,10-tetraazacyclododecane N,N',N",N'''-tetraacetic acid (DOTA) and carried out positron emission tomography (PET) imaging of eight tumor models with different EphA2 expression levels. Western blotting of tumor tissue lysate was performed to correlate the EphA2 expression level with Cu-64-DOTA-1C1 uptake in the tumors. Immunofluorescence staining and biodistribution studies were also carried out to validate the in vivo results.Results The radiolabeling yield was 88.9 +/- 9.5% (n = 7) and the specific activity of Cu-64-DOTA-1C1 was 1.32 +/- 0.14 GBq/mg of 1C1 mAb. The antibody retained antigen-binding affinity/specificity after DOTA conjugation as measured by FACS analysis. The uptake of Cu-64-DOTA-1C1 in CT-26 tumors was as high as 25.1 +/- 2.5 %ID/g (n = 3) at 18 h post injection. Cu-64-DOTA-IgG, an isotype-matched control, exhibited minimal non-specific uptake in all eight tumor models. In vivo EphA2 specificity of Cu-64-DOTA-1C1 was confirmed by successful blocking of CT-26 tumor uptake by unlabeled 1C1. Most importantly, the tumor uptake value obtained from PET imaging had excellent linear correlation with the relative tumor tissue EphA2 expression level measured by Western blot, where r(2) equals 0.90 and 0.92 at 18 h and 42 h post injection, respectively.Conclusion The tumor uptake of Cu-64-DOTA-1C1 measured by microPET imaging reflects tumor EphA2 expression level in vivo. This is, to our knowledge, the first report of quantitative radioimmunoPET imaging of EphA2 in living subjects. Future clinical investigation of Cu-64-DOTA-1C1 is warranted.