99Tcm—NGR—IFN-α2a在荷瘤小鼠体内分布及SPECT／CT显像

目的制备99Tcm标记天冬酰胺-甘氨酸-精氨酸（NGR）-干扰素-α2α（NGR—IFN—α2a），并研究其在荷瘤小鼠体内的动态分布及显像。方法（1）双半胱氨酸（EC）作为双功能螯合剂合成EC—NGR—IFN-α2a，用MDP作为转移螯合剂，采用二步法对EC—NGR—IFN-α2a进行99Tcm标记，制备99Tcm-NGR-IFN-α2a，同时进行生物学活性测定，采用最小显著差异法t检验比较99Tcm-NGR-IFN-α2a与EC—NGR—IFN—α2a，NGR—IFN—α2a的生物活性；（2）建立肝癌MHCC97-H细胞严重联合免疫缺陷病（SCID）小鼠皮下移植瘤模型，采用随机数字表法分组，尾静脉注射99Tcm-NGR-IFN-α2a7．4MBq，分别于注射后0．5，1，2，4，6，8，12和24h处死小鼠。取血、肝、肾、心、脾、肺、胃、肠、骨骼、肌肉及肿瘤组织，测质量及测放射性计数，经物理衰变校正后计算％ID／g，以肿瘤组织为靶组织，以肌肉组织为非靶组织，计算不同时间点T／NT放射性比值；（3）荷瘤小鼠经尾静脉注射7．4MBq99Tcm-NGR-IFN-α2a，分别于注射后0．5，1，2，4，6，8，12和24h行静态平面及SPECT／CT显像，采用ROI技术，同上计算不同时间点的T／NT比值。结果99Tcm-NGR-IFN-α2a的标记率及放化纯均〉90％99Tcm-NGR-IFN-α2a在生理盐水中放置24h后放化纯为71％；标记后生物学活性未发生改变（t=0．416，0．120和1．300，P均〉0．05）；99Tcm-NGR-IFN-α2a经小鼠尾静脉注射后24h内，由泌尿和消化系统排泄，肾、肝、脾、肠道肿瘤的％ID／g值达到高峰的时间分别为8h，6h，6h，4h，高峰值分别为41．5±8．0，31．3±5．0，36．0±7．8，43．0±4．8；其在血液内清除迅速，其他组织器官的放射性随时间延长逐渐降低，rr／NT比值最高可达16．5，最佳显像时间为注射后4～8h。结论99Tcm-NGR-IFN-α2a易于制备，具有良好的靶向性和显像效果。放射性核素标记的NGR—IFN—α2a有望成为-种新的肿瘤血管靶向性诊断与治疗药物。

The distribution and scintigraphy of 99Tcm labeled NGR-interferon-alpha2a in tumor bearing mice

Objective To sythesize 99Tcm labeled asparagine-glycine-arginine (NGR)- interferon (INF)-α2a and investigate its biodistribution by scintigraphy in tumor bearing mice. Methods NGR-INFα2a was labeled with 99Tcm by a two-step method. Ethylenedicysteine (EC) and MDP were used as bifunctional and transferring chelating agents. The bioactivities of 99Tcm-NGR-IFN-EC-NGR-IFN-α2a, EC-NGRIFN-α2a and NGR-IFN-α2a were compared using least significant difference t-test. The hepatoma bearing mice models were established by subcutaneous injection of MHCC97-H cells. The mice were randomly divided into eight groups and 7.4 MBq 99Tcm-NGR-IFN-α2a was injected via the tail vein. The tissue uptake of the radiolabeled compound was measured as % ID/g. The scintigraphy was performed at 0.5, 1, 2, 4,6, 8, 12 and 24 h after injection. ROI were drawn around tumor and non-tumor tissue and the radioactivity ratio of T/NT was calculated. Results Both the labeling efficiency and radiochemical purity of 99Tcm-EC-NGR-IFN-α2a were more than 90%. The radiochemical purity was 71% after 24 h in saline. The bioactivity showed no significant difference among three compounds (t = 0.416, 0. 120 and 1. 300, all P >0.05). The tracer was mainly excreted through alimentary and urinary tract within 24 h after injection. The peak values of % ID/g in kidney, liver, interstinal tract and tumor were 41.5 ± 8.0_ (at 8 h), 31.3 ± 5.0(at 6 h), 36.0 ± 7.8 (at 6 h), 43.0 ± 4.8 (at 4 h), respectively. The tracer was cleared quickly from the blood and the highest T/NT ratio was 16.5. The optimal imaging time ranged from 4 to 8 h after injection. Conclusions The sythesis of 99Tcm-NGR-IFN-α2a is applicable and it may be used as a potential tumor imaging agent.