靶向整合素αvβ3受体isoDGR-2CY的^(131)I标记与生物活性评价

^(131)I labeling and bioactivity evaluation for receptor isoDGR-CY of targeting integrin αvβ3

目的 131I标记αvβ3受体isoDGR-2CY模序,研究其在荷VX2肿瘤裸鼠体内的生物分布及显像。方法 (1)合成isoDGR-2CY模序并用131I标记。(2)20只荷VX2肿瘤裸鼠随机分成4组,每组5只,经尾静脉注射7.4 MBq(0.2 ml)131IisoDGR-2CY,分别于注射后2、5、12、24 h按组将裸鼠处死;另取5只荷瘤裸鼠作为竞争性抑制组,注射131I-isoDGR-2CY前1 h,先注射未标记的isoDGR-2CY,并于注射131I-isoDGR-2CY后12 h处死。各组取血及主要脏器,称取脏器质量并测量放射性计数,经衰减校正后计算每克组织百分注射剂量率(%ID/g)。(3)取6只荷VX2肿瘤裸鼠,实验前7 d在饮用水中加入0.1%碘化钾封闭甲状腺后,经尾静脉注射7.4 MBq的131I-isoDGR-2CY。4只作为显像组,另2只作为竞争性抑制组[注射131I-isoDGR-2CY前1 h,先注射未标记的isoDGR-2CY(isoDGR-2CY与131I-isoDGR-2CY摩尔比为10∶1)],分别于注射后2、4、8、12、24 h进行SPECT静态显像。结果合成的isoDGR-2CY模序纯度为97.06%,可以满足实验要求;131I-isoDGR-2CY标记率为(89.03±0.18)%,放化纯度(95.89±0.12)%,其在血清中具有良好的稳定性;131I-isoDGR-2CY主要通过肾脏排泄,肿瘤的靶向性明显,12 h靶/肌肉比值(T/M)为2.39;SPECT显示注射标记物1 h肿瘤即可见显影,12 h显影清晰,该显像可被未标记的isoDGR-2CY抑制。结论 isoDGR-2CY可被131I成功标记,肿瘤组织能特异性摄取131I-isoDGR-2CY,并通过SPECT清晰显像。

Objective To synthesize 131I labeled integrin αvβ3 receptor isoDGR-2CY motif, and to study its distribution and visualization in nude mice bearing VX2 tumor. Methods （ 1 ） The isoDRG-2CY motif was chemically synthetized and labeled with 131I. （ 2 ） Twenty nude mice bearing VX2 tumor were randomly divided to 4 groups with 5 ones in each group. The nude mice were sacrificed at the time of 2,5,12, and 24 hours after intravenous injection with 7.4 MBq（0.2 ml） 131I-isoDGR-2CY. Another 5 nude mice bearing VX2 tumor were selected as competitive inhibition group and received the injection with isoDGR-2CY one hour before the injection with 131I-isoDGR-2CY. Then those mice were sacrificed 12 hours later. Blood and main organs in each group were taken out. The weight of those organs was weighed, and the radiocounting was detected. After the attenuation correction, the percentage of injection dose rate for every gram of organs（ % ID/g）was calculated. （3）Six nude mice bearing VX2 tumor were administered with 1% potassium iodide in the drinking water in order to block thyroid 7 days before the test. Then they received the injection via caudal vein with 7.4 MBq 131I- isoDGR-2CY. Four mice were selected as visualization group, and another two were chosen as competitive inhibition group （injected with isoDGR-2CY one hour before the injection of 131I-isoDGR_2CY injection with the molar ratio of l0 to 1 ）. SPECT static imaging was carried out at 2,4,8,12, and 24 hours after the injection. Results The purity of synthetized isoDGR-2CY motif was 97.06%, which could meet the demand of the experiment. The labeling rate of 131I-isoDGR-2CY was （89.03 ＋ 0.18 ）% , and the radiochemical purity was （95.89 ＋ 0.12 ）%. It had good stability in blood serum. 1311-isoDGR-2CY was mainly eliminated through kidneys and targeted to tumor obviously. The 12 h target/muscle （T/M）ratio was 2.39. The tumors could be found at one hour and at 12 hours. The SPECT showed that the injection tumor marker could be visualized at 1 h and clearly visualized at 12 h. This visualization could be inhibited by isoDGR-2CY. Conclusion IsoDGR-2CY can be successfully labeled with 131I. 131I labeled isoDGR-2CY can be specifically absorbed by tumor tissues ,which can be clearly viewed through SPECT.