肿瘤血管内皮特异性靶向肽 GX1 与 NGR 在胃癌中显像差异分析

目的：分析肿瘤血管内皮特异性靶向肽GXl与NGR在胃癌中显像差异。方法：构建人胃癌移植瘤裸鼠模型，99Tcm直接法制,99Tcm-GXI、99Tcm-NGR，由尾静脉分别注入荷瘤小鼠体内，SPECT显像连续追踪24h，观察两组小肽在胃癌中显像差异，计算机勾划肿瘤及心脏感兴趣区，比较两组T／NT比值差异。结果：99Tcm直接法标记NGR，所得标记率在90％以上，无需纯化，比活度大于200Ci／mmol，具有良好的体内外稳定性。两组荷瘤小鼠自8h起右后肢背侧肿瘤部位均可见放射性浓聚，T／NT比值随时间延长总体呈递增趋势。99Tcm-GX1组自8h起，肿瘤部位放射性浓聚即高于心血池本底，T／NT比值〉199Tcm-NGR组8h-18h肿瘤部位放射性分布均低于心血池本底，T／NT比值〈1，至24h其肿瘤部位放射性明显浓聚，并超过心血池本底，T／NT比值增高至1．34。比较两组T／NT比值，自8h至18h，99Tcm-GXl组其比值持续高于99Tcm-NGR组，但至24h小时，99Tcm-NGR组比值迅速升高并高于99Tcm-GXl组。结论：99Tcm-直接法标记NGR，标记率大于90％，比活度高，体内外稳定性好，具有良好的生物学活性，完全可以满足SPECT显像的要求。”99Tcm-GX1、99Tcm-NGR均能够靶向到荷瘤小鼠的肿瘤组织，具有肿瘤标志物的影像学特征，与99Tcm-NGR相比，99Tcm-GX1灵敏度更高，适合早期实时探测，而99Tcm-NGR在晚期实时探测方面具有更多优势。

Imaging variation analysis of tumor vasculature homing peptides GX1 and NGR in gastric cancer

Objective：To analyze the imaging variation of tumor vasculature homing peptides GX1 and NGR in gastric cancer. Methods：99Tcm -GX1 and 99Tcm -NGR were prepared by labeling GX1 and NGR peptides acquired by chemosynthesis with 99TcmO4 - using direct labeling methods. ECT imaging of nude mice bearing tumor xenografts of human gastric carcinoma injected with 99TcTM -- GX1 or 99Tcm - NGR was performed to analyze the imaging variation of these two peptides in gastric cancer. T/NT ratios were calculated by comparing the radioactivity in tumor and heart. Result~：99Tcm -NGR was acquired with high label radiolabeling efficiency exceeding 90% ,high specific activity be- yond 200Ci/mmol, and perfect in vitro and in vivo stability. The tumors on the fight flank can be visualized from 8h in two groups with a increasing trend on the whole. In 99Tern - GX1 group, the radioactivity of the tumor on the right flank can be visualized higher than that of heart from 8h with T/NT ratio greater than 1. On the contrary,in 99Tern - NGR group, the radioactivity in tumor was lower than that of heart from 8h to 18h with T/NT ratio lower than 1. How- ever it increased obviously at 24h so that the T/NT ratio reached to 1.34. Continuous higher T/NT ratios between tumor and heart were observed in 99Tcm - GX1 group compared to that of 99Tcm - NGR group from 8h to 18h. But there was a sharp increase of T/NT ratio in 99Tcm - NGR group at 24h beyond that of 99Tcm - GX1 group. Conclu- sion ：NGR peptide was labeled successfully with 99TcmO4 - at high labeling efficiency（ 〉 90% ） ,favorable specific ac- tivity,perfect in vitro and in vivo stability, which confirmed the qualification of 99Tcm - NGR for ECT imaging. Both GX1 and NGR owned the imaging feature of tumor marker by specific targeting to gastric cancer tissue in tumor - bearing nude mice. Different from NGR peptide which is fit for late detection, GX1 peptide possess the superiority for early detection due to its higher sensitivity than that of NGR peptide.