^68Ga—DOTA—cNGR的制备及对荷肺腺癌裸鼠的显像研究

Preparation of ^68Ga-DOTA-cNGR and its application in imaging of the nude mice bearing human lung cancer

目的制备^68Ga-1，4，7，10-四氮杂环十二烷-1，4，7，10-四乙酸-环状NGR（DOTA-cNGR），并评价其在正常小鼠体内的生物分布及对荷肺腺癌裸鼠的靶向显像能力。方法以羟乙基哌嗪乙硫磺酸（HEPES）为缓冲体系（pH值5．0），水浴合成^68Ga—DOTA—cNGR，HPLC测定标记率及放化纯，观察其在人血清中的稳定性。进行^68Ga—DOTA—cNGR的正常小鼠体内生物分布和荷肺腺癌裸鼠活体microPET显像，对荷肺腺癌裸鼠的瘤组织进行病理及氨肽酶N（APN）的免疫组织化学分析。采用两样本t检验分析数据。结果^68Ga—DOTA—cNGR标记率为（99．8±0．1）％，性状稳定，在人血清中37℃保温2h后放化纯仍〉95％。正常小鼠体内生物分布结果表明，^68Ga—DOTA-cNGR主要经肾排泄，血液清除迅速，肝、胃肠道摄取较少；1h肾、血液、肝、胃、肠的放射性摄取分别为（1．61±0．22）、（0．19±0．07）、（0．25±0．24）、（0．16±0．04）、（0．12±0．05）％ID／g。荷肺腺癌裸鼠microPET显像可见肿瘤部位有放射性浓聚影，1h肿瘤与对侧正常肌肉T／NT高达7．61±0．47，经DOTA—cNGR特异性阻断后降至1．83±0．25，阻断前后差异有统计学意义（t=18．80，P〈0．05）。免疫组织化学检查证实APN特异性聚集于肿瘤新生血管表面。结论^68Ga-DOTA—cNGR易于制备，标记率和放化纯高，在人血清中的稳定性好，具有良好的代谢及肺腺瘤靶向特性，有望用于肺癌显像。

Objective To prepare ^68 Ga- 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetroaceticacid- cyclo NGD （DOTA-cNGR） and evaluate its biodistribution in normal mice and imaging efficacy in nude mice bearing human lung cancer. Methods ^68Ga-DOTA-cNGR was synthesized through water bath at pH= 5.0 with hydroxyl ethyl piperazine ethane sulfonic acid （HEPES） as the buffer system. The radiolabeling yield and radiochemistry purity were analyzed with HPLC. The stability of ^68Ga-DOTA-eNGR in serum was measured. The biodistribution of ^68g Ga-DOTA-cNGR was studied in the normal mice （expressed as %ID/g of tissues） and the nude mice bearing human lung cancer xenografts were imaged in vivo by microPET. Pathological and immunohistochemical analyses were performed on tumor tissues. Two-sample t test was used to analyze the data. Results The radiolabeling yield was （99.8±0.1）% and radiochemical purity after 2 h in serum was more than 95%. Biodistribution study showed rapid clearance of ^68Ga-DOTA-eNGR from the blood, and excretion was mainly via kidney with little uptake in the liver and gastrointestinal tract. The tracer uptake in kidneys, blood, liver, stomach, and intestine was （ 1.61 ± 0.22 ） , （ 0.19± 0.07 ） , （ 0.25 ± 0. 24）, （0.16±0.04）, （0.12±0.05） %ID/g respectively at 1 h post injection. The tumor uptake was significantly elevated on microPET with maximum T/NT of 7.61±0.47 at 1 h post injection. After specific blockage by DOTA-cNGR, the T/NT was significantly reduced to 1.83：1：0.25 （t= 18.80, P〈0.05）. The expression of aminopeptidase N was detected by immunohistochemistry. Conclusion ^68 Ga-DOTA-eNGR could be successfully prepared with high radiolabeling yield and radioehemical purity. Its good stability in serum, ideal biodistribution and imaging characteristics are factors favoring the potential for imaging human lung cancer with over-expression of NGR receptors.