抗ProGRP（31-98）单克隆抗体E-B5的^131I标记及体内生物分布研究

The in vivo pharmacokinetics study of anti-ProGRP（31-98） monocional antibody E-B5

目的研究抗胃泌素释放肽前体（ProGRP）片段ProGRP（31-98）单克隆抗体E—B5的^131I标记方法以及标记抗体在正常小鼠体内的生物分布特点。方法利用流式细胞仪检测人小细胞肺癌NCI—H446细胞株和肺腺癌A549细胞株（对照）ProGRP表达，对人小细胞肺癌组织切片进行免疫组织化学染色分析。采用氯胺T法进行^131I-E—B5标记，利用纸层析法测定其标记率、放化纯和稳定性，细胞结合分析法测定标记抗体的免疫活性。将^131I—E—B5注入正常昆明小鼠体内，对药物体内分布及药物代谢动力学进行研究。对荷小细胞肺癌裸鼠模型进行^131I—E—B5放射免疫显像，观察移植瘤的显影情况。采用SPSS13．0软件处理数据。结果流式细胞仪测得处于对数生长期的NCI—H446、A549细胞ProGRP表达率分别为89％和12％，人小细胞肺癌组织切片免疫组织化学染色见明显的E—B5阳性细胞分布，并显示ProGRP表达在肿瘤细胞的细胞质内。^131I—E—B5标记率为90．8％，放化纯为99．28％，在37℃水浴箱中放置24h后放化纯仍〉70％，和健康人血清充分混合后放置24h放化纯为68．1％，对NCI-H446和A549的免疫结合率分别为71．6％和33．2％。^131I—E—B5在小鼠体内过程符合一级血药动力学二室模型，t1/2α=0．2h，t1／2β=8．35h，在体内主要通过肝和肾代谢。注射^131I—E—B5后72和96h小细胞肺癌裸鼠移植瘤体显影最清晰。结论NCI—H446细胞株及人小细胞肺癌组织高表达ProGRP，E-B5对小细胞肺癌有较好的靶向作用。^131I—E—B5标记率及放化纯高，在体内外有很好的稳定性，标记后的E—B5仍然保持着良好的免疫活性，对小细胞肺癌放免显像和治疗有潜在的应用前景。

Objective Progastrin-releasing peptide（31-98） （ ProGRP（31-98） ） is a specific tumor marker in patients with small cell lung cancer （SCLC）. E-B5 antibody against ProGRP（31-98） was produced by China Institute for Radiation Protection. The aim of this study was to explore the ^131I labeling methods, stability, immunological activity and biological distribution pattern of E-B5 antibody against ProGRP（31-98）. Methods Chloramine-T method was used for ^131I labeling E-B5 antibody. Labeling efficiency, radiochemical purity and stability were estimated by using paper chromatography method. Immunological activity of ^131I-E-B5 was detected with cell conjugation assay. After healthy Kunming mice were injected with ^131I-E-B5 antibody through tail veil, the biodistribution and pharmaeokinetics of ^131I-E-B5 antibody in healthy Kunming mice were studied. Continuous images of the nude mice bearing SCLC were carried out at different time points after injection of ^131I-E-B5 antibody. Continuous variables were expressed as x^ -＋ s and compared by t-test with SPSS 13.0 software. Results The labeling efficiency and radiochemical purity of ^131 I-E-B5 were 90.8% , 99.28%, respectively. The radiochemical purity still maintained above 70% after incubation in water bath at 37 ℃ for 24 h. After incubation with healthy serum for 24 h, the radiochemical purity still reached 68. 1%. The immunobinding ratios were 71.6% and 33.2% for NCI-H446 cells and A549 cells respectively. The in vivo distribution and elimination of ^131I-E-B5 antibody were consistent with a first-order and two- compartment model, t1/2α = 0. 2 h, t1/2β = 8.35 h. The metabolism of ^131I-E-B5 antibody mainly depended on liver and kidney and with rapid elimination in blood. Conclusions ^131I-E-B5 antibody not only has high labeling efficiency and radiochemical purity, but also has good stability and keeps good immunological activity. ^131I-E-B5 is a promising agent of radioimmunoimaging and radioimmunotherapy of SCLC.