99Tcm标记RGD环肽四聚体在神经胶质瘤裸鼠模型中的显像研究

目的 制备99Tcm标记的含有精氨酸-甘氨酸-天冬氨酸(Arg-Gly-Asp,RGD)序列的环肽四聚体99Tcm-联肼尼克酰胺(HYNIC)-E{Ec(RGDfK)]2}2,评价其在整合素αvβ3表达阳性的荷人神经胶质瘤裸鼠模型的生物分布和显像.方法 以HYNIC为双功能螫合剂,以三羟甲基甘氨酸(tricine)和三苯基膦三磺酸钠(TPfffS)为协同配体,采用两步法制备99Tcm-HYNIC-E{Ec(RGDfK)2}2.通过体外受体竞争结合实验比较e(RGDyK)单体、HYNIC-Ec(RGDfK)2二聚体和HYNIC-E{Ec(RGDfK)]2}2四聚体与整合素αvβ3亲和力.生物分布实验数据显示,99Tcm-HYNIC-E{Ec(RGDtK)]2}2主要经肾排泄;注射后1h,肿瘤对99Tcm-HYNIC-E{Ec(RGDfK)]2}2的摄取为99Tcm-HYNIC-Ec(RG-DfK)]2的2倍,分别为(10.32±0．07)％ID／g和(5.15±O.52)％ID／g,与体外受体竞争结合实验数据相一致;注射后4h,肿瘤对99Tcm-HYNIC-E{Ec(RGDfK)]2}2的摄取仍达(9.35.4±1.35)％ID／g,表明标记物在肿瘤中的滞留时间足够长.r显像结果显示,注射后1h肿瘤清晰可见.注射后4h显像效果更佳.结论 99Tcm-HYNIC-E{Ec(RGDfK)]2}2具有较高的肿瘤摄取和较长的肿瘤滞留时间,可以用于整合素αvβ3表达阳性肿瘤的显像;放射性核素(如90Y)标记的RGD环肽四聚体可用于整合素(αvβ3表达阳性肿瘤的治疗.

Imaging of 99Tcm-cycllc RGD tetramer in nude mice bearing U87MG human glioma xenografts

Objective Multimeric cyclic RGD (Arg-Gly-Asp) peptides are capable of improving the integrin αvβ3-binding affinity due to the polyvalence effect.In this study,the authors prepare 99Tcm-la-bearing cyclic RGD tetramer E{Ec(RGDfK)]2}2,and evaluate its biodistribution and imaging in nude mice beating U87 MG human glioma xenografts with integrinαvβ3-positive.Methods 99Tcm-hydrazino-nictinamide (HYNIC)-E{Ec(RGDfK)]2}2 was prepared by two-step method,while HYNIC wag chosen as bifunctional chelator,and tricine and trisodium triphenylphosphine-3,3,3-trisuifonate (TPPTS) as coligands.The af-finity of c (RGDyK) monomer,HYNIC-Ec(RGDfK)]2 dimer and HYNIC-E{Ec(RGDfK)]2}2 tetramer to integrin αvβ3 was compared by in vitro competitive assay against binding of 125I-c(RGDyK)to integrin αvβ3.positive U87 MG human glioma cells.The biodistribution the percentage of injection dose per gram of tissue(%ID/g)] and imaging were performed in nude mice bearing UB7MG human glioma xenografts.Re-suits The labeling yield of 99Tcm-HYNIC-E{Ec(RGDfK)2}2 was over 95%,and the radiochemical purity was more than 99%after purification with Sop-Pak C18 cartridge.The 50%inhibiting concentration (IC30) val-ues of c(RGDyk),HYNIC-Ec(RGDfK)]2 and HYNIC-E{Ec(RGDfK)]2}2 were 85.9,9.5 and 4.5 nmol/L, respectively.The result indicated that RGD tetramer possessed a significantly higher affinity to in-tegrinαvβ3.The biodistribution data showed that 99Tcm-HYNIC-E{Ec(RGDfK)]2}2 was excreted mainly through kidneys.The tumor uptake of 99Tcm-HYNIC-E{Ec(RGDfK)]2}2 was two times higher than 99Tcm- HYNIC-Ec(RGDfK)]2,at 1h postinjection,with the uptake of(10.32±0.07)%ID/g and(5.15±0.52)%ID/g,respectively,which was consistent with the in vitro competitive binding data.The tumor up-tale of 99Tcm-HYNIC.E{Ec(RGDfK)]2}2 was still as higher as(9.35±1.35)%ID/g at 4 h postinjec-tion, which demonstrated that the retention time of radiotracer in tumor was long enough.The imaging showed that tumor was clearly visualized at 1h postinjection,and the image at 4 h postinjection Was better.Conclusion The higher tumor uptake and longer retention time in tumor make 99Tem-HYNIC-E{Ec(RG-DfK)J 2}2 a promising radiotracer for integrinαvβ3-positive tumors imaging,furthermore,suggest that radi-onuelides(such as 90Y).1abeled RGD tetramer is more suitable for the therapy of integrin αvβ3-positive tumors.