Objective To explore the biodistribution and radioimmunoimaging of 99Tcm-labeled anti-ProGRP monoclonal antibody D-D3 in nude mice bearing human small cell lung cancer (SCLC) xenografts.Methods (1) D-D3 antibody was labeled with 99Tcm via the 2-mercaptoethanol reduction method.99Tcm-D-D3 was purified by the gel column separation method.The labeling efficiency,radiochemical purity,specific radioactivity and stability of 99Tcm-D-D3 were measured by thin-layer chromatography.Antigen-binding ability was determined by cell binding assay.(2)After tail vein injection of 99Tcm-D-D3,nude mice bearing SCLC NCI-H446 xenografts were sacrificed at designated time points.The blood and major organs were removed and weighed,and counted in a gamma scintillation counter.Radioactive uptake in each organ (％ID/g),tumor/muscle and tumor/blood ratios at each time point were calculated.(3)After injection of 99Tcm-D-D3,continuous imaging of the nude mice bearing NCI-H446 and lung adenocarcinoma A549 xenografts were carried out respectively,and the T/NT ratios were calculated.Two-sample t test was used to analyze the data.Results (1) The labeling rate of 99Tcm-D-D3 was (73.87±2.89)％.The radiochemical purity was (94.13±4.49) ％.The specific radioactivity was (1.64±0.06) MBq/μg.Being fully mixed with either saline or healthy human serum and incubated at 37 ℃ for 4 h,the radiochemical purities of 99Tcm-D-D3 were (82.17± 1.00) ％ and (74.13±1.67) ％ respectively,and (55.73± 1.07) ％ and (54.07± 1.88) ％ respectively after being incubated for 12 h.The immunobinding rates of 99Tcm-D-D3 to NCI-H446 and A549 cells were (81.20± 2.37) ％ and (24.30± 1.46) ％,respectively.(2) The ％ID/g of 99Tcm-D-D3 in NCI-H446 tumor was 2.13± 0.06,which was significantly higher than those of other organs except liver,kidneys,stomach and blood at 8 h after injection (t =2.52-24.53,all P＜0.05).The uptake in the tumors was higher than those of all other organs at 12 h (t=1.98-20.88,all P＜0.05),and reached the peak level (4.16±0.45) ％ID/g at 24 h.The tmor/muscle and tumor/blood ratios gradually increased with time.(3) At 2 h after injection of 99Tcm-D-D3,the tumor in NCI-H446 bearing nude mice could be visualized and definitely delineated at 4 h.The tumor uptake of 99Tcm-D-D3 gradually increased.No significant accumulation of 99Tcm-D-D3 was found in the A549 tumor mass from 1 to 24 h after injection.Conclusion 99Tcm-D-D3 can selectively accumulate in the tumor site of NCI-H446 xenografts and has a potential targeting property to SCLC.%目的 研究99Tcm标记的抗胃泌素释放肽前体[ProGRP(31-98)]单克隆抗体D-D3在荷人小细胞肺癌(SC LC)裸鼠体内的生物分布及放射免疫显像情况.方法 (1)采用2-巯基乙醇还原法制备99Tcm-D-D3,凝胶柱分离法纯化标记产物,纸层析法检测标记率、放化纯、比活度及稳定性,细胞结合分析法测定标记抗体的抗原结合能力.(2)建立SCLC NCI-H446及肺腺癌A549荷瘤裸鼠模型.(3)自NCl-H446荷瘤裸鼠尾静脉注射99Tcm-D-D3后,于不同时间点处死裸鼠并取血液及各主要脏器组织标本,计算各时间点的放射性摄取值(％ID/g)和肿瘤/肌肉、肿瘤/血液的放射性计数比值.(4)对荷瘤裸鼠模型进行放射免疫显像,计算T/NT比值.采用SPSS 17.0软件处理数据,两样本均数比较采用两样本t检验.结果 (1) 99Tcm-D-D3标记率为(73.87±2.89)％,放化纯为(94.13±4.49)％,比活度为(1.64±0.06) MBq/μg.与生理盐水及健康人血清充分混合,37℃放置4h后的放化纯分别为(82.17±1.00)％和(74.13±1.67)％,12 h后的放化纯分别为(55.73±1.07)％和(54.07±1.88)％.99 Tcm-D-D3与NCI-H446和A549细胞结合率分别为(81.20±2.37)％和(24.30± 1.46)％.(2) NCI-H446荷瘤裸鼠体内生物分布研究显示:注射99Tcm-D-D3后8h,瘤体的放射性摄取值[(2.13±0.06) ％ID/g]已明显高于除肝、肾、胃及血液外的其他脏器及组织(t=2.52～ 24.53,均P＜0.05),12h时显著高于其他脏器及组织(t=1.98～20.88,均P＜0.05),24 h时达最高值[(4.16±0.45) ％ID/g];肿瘤/肌肉、肿瘤/血液的放射性比值随时间延长而逐渐升高.(3)放射免疫显像结果显示:注射后4h,NCI-H446荷瘤裸鼠的瘤体已较清晰,随时间延长移植瘤部位的放射性逐渐增多.A549荷瘤裸鼠注射99Tcm-D-D3后24 h内,移植瘤局部仅见少量放射性聚集,隐约可见移植瘤轮廓,其放射性聚集程度与周围组织的差异甚小.结论 99Tcm-D-D3能选择性聚集在NCI-H446移植瘤部位,具有潜在的SCLC靶向功能.
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