新型肿瘤新生血管靶向分子探针（99m）~Tc-RRL的合成及初步研究

A Novel （99m）~Tc-Labeled Molecular Probe for Tumor Angiogenesis Imaging in Hepatoma Xenografts Model：A Preliminary Study

[目的]探讨新型肿瘤新生血管显像剂99mTc-RRL的合成与标记及其在不同肿瘤动物模型中的初步显像效果,评价99mTc-RRL用于肝癌裸鼠模型体内的生物分布特点。[方法]固相合成法合成RRL,与99mTc进行标记。制备不同类型肿瘤动物模型,并进行单光子计算机断层(SPECT)显像。荷瘤HepG2肝癌裸鼠尾静脉注射99mTc-RRL后,于不同时刻处死动物,取感兴趣器官和组织称重并测量其放射性计数,计算各器官或组织的%ID/g值。同时,高锝酸钠阴性对照组、非标记RRL竞争阻断组采用同样方法,计算其6h时刻各脏器或组织的%ID/g值。HE染色和CD34免疫组化方法用于评价瘤体新生血管状态及分子探针检测阈值的相关性分析。[结果]99mTc-RRL标记率达80%,放射化学纯度高,体外稳定性好。SPECT显像示肿瘤部位见显影,轮廓清晰,放射性明显高于其他器官,随时间延长,肿瘤部位有持续放射性聚集。生物分布数据显示99mTc-RRL血液清除快,肿瘤部位显示放射性持续滞留,提供良好靶/非靶组织比值。HE染色和免疫组化结果显示了瘤体旺盛的血管生成;瘤体大小与探针摄取量呈明显正相关关系。[结论]99mTc-RRL能够特异性地聚集于不同类型肿瘤组织。体内生物分布好,可提供良好的靶/非靶组织比值,是具有应用价值的肿瘤新生血管靶向示踪剂。

[Purpose] To evaluate 99mTc-radiolabeled RRL to be used for imaging of malignant tumors in vivo,and act as a new molecular probe targeting tumor angiogenesis.[Methods] The RRL peptide was designed and radiosynthesized with 99mTc by a one-step method.The radiolabeling efficiency and radiochemical purity were then characterized in vitro.99mTc-RRL was injected intravenously in HepG2xenograft-bearing BALB/c nude mice.Biodistribution and in vivo imaging were performed periodically.The relationship between tumor size and %ID uptake of 99mTc-RRL was also explored.[Results] The labeling efficiencies of 99mTc-RRL reached 76.9%±4.5%（n=6） within 30~60min at room temperature,and the radiochemical purity exceeded 96% after purification.In vitro stability experiment revealed the radiolabeled peptide was stable.Biodistribution data showed that 99mTc-RRL rapidly cleared from the blood and predominantly accumulated in the kidney and tumor.The specific uptake of 99mTc-RRL in tumor was significantly higher than that of unlabeled RRL blocking and free pertechnetate control test after injection（P0.05）.The ratio of the tumor-to-muscle exceeded 6.5,tumor-to-liver reached 1.98 and tumor-to-blood reached 1.95.In planar gamma imaging study,the tumors were imaged clearly at 2~6h after injection of 99mTc-RRL,whereas the tumor was not imaged clearly in blocking group.Immunohistochemical analysis verified the excessive vasculature of tumor.There was a linear relationship between the tumor size and uptake of 99mTc-RRL.[Conclusion] 99mTc-RRL can be used as a potential candidate for visualization of tumor angiogenesis in malignancies.