microPET-CT显像监测叶酸受体靶向放射性药物药代动力学的实验研究

MicroPET-CT imaging for in vivo pharmacokinetics study of folate receptor targeting ^(68)Ga-DOTA-lys-FA

目的制备叶酸受体靶向的^(68)Ga-1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸-赖氨酸-叶酸(^(68)Ga-DOTA-lysFA),用小动物正电子发射计算机体层摄影术(microPET)-CT动态显像考察其间质给药后体内药代动力学。方法合成^(68)Ga-DOTA-lys-FA,考察其理化特性。用人卵巢癌细胞(SKOV3)和人肺癌细胞(A549)测定受体结合实验。荷人卵巢癌细胞裸鼠模型33只,雌性,体质量18~20 g,鼠龄8~10周;瘤体直径0.6~0.8 cm;荷人肺癌细胞裸鼠模型4只,雌性,体质量18~20 g,鼠龄8~10周。通过尾静脉注射^(68)Ga-DOTA-lys-FA后不同时间点处死荷瘤鼠,解剖分离重要脏器称质量和用γ计数仪进行放射性测定,分析其体内生物学分布。抽签法随机分为^(68)Ga-DOTA-lys-FA尾静脉注射组(Ⅳ组)、肿瘤间质注射组(IT组),荷人肺癌细胞模型(A549)作为阴性对照组(ITC组),在给药后不同时间点行microPET-CT显像,勾画肿瘤及脏器感兴趣区并计算其放射性摄取(%ID和%ID/cm^3),对比分析^(68)Ga-DOTA-lys-FA给药后不同时间体内生物学分布。结果 ^(68)Ga-DOTA-lys-FA标记率为(97.80±2.11)%。3 h内体外稳定性好,尾静脉注射后microPET-CT获得的60 min肿瘤/肺部放射性摄取比值为5.36±1.03,明显高于生物学分布结果 (4.13±1.25,t=4.97,P=0.001)。基于microPET-CT定量,IT组60 min、180 min肿瘤放射摄取量分别为(125.60±18.40)%ID/cm^3、(91.80±14.50)%ID/cm^3,明显高于ITC组[(42.30±11.46)%ID/cm^3、(12.82±3.86)%ID/cm^3](P<0.001、0.001),也明显高于IV组。结论 ^(68)Ga-DOTAlys-FA microPET-CT动态显像可更有效评价其体内生物学分布,瘤内注射可明显增加其瘤内生物半减期,为治疗性核素标记叶酸靶向治疗提供数据支持。

Objective To prepare the folate receptor（FR） targeted radiotracer 6SGallium-DOTA- lys-folic acid（^68Ga-DOTA-lys- FA）, and investigate its pharmacokinetics in vivo after passive targeted administration with mieroPET-CT imaging. Methods Characteristics of ^68Ga-DOTA-lys-FA was investigated after its preparation,and receptor experiments were performed using human ovarian cancer cell（SKOV3） cells and human lung cancer cells（A549）. There were 33 female nude mice models of ovarian cancer, body weight of 18 - 20 g, aged 8 - 10 weeks and tumor diameter of 0.6 - 0.8 cm; 4 female nude mice models of lung cancer, body weight of 18 - 20 g, aged 8 - 10 weeks. The mice were sacrificed at different time points after injection of ^68Ga- DOTA-lys-FA by tail vein, anatomical separation was conducted and mass of vital organs were weighed and radioactivity measurement was carried out with gamma counter, and the biological distribution in vivo was analyzed. The ovary cancer xenograghts （SKOV3： folate receptor positive） bearing nude mice were established and divided into tail vein injection group（IV group） and intratumor injection group（IT group） while prostated cancer（A549： folate receptor negative） bearing nude mice（ITC group） was served as control group. MicroPET-CT imaging was performed at different time points after tracer administration and volume of interest（VOI） of important organs was drawn for pharmacokineties（%ID and %ID/cm^3）. Comparative analysis was performed to study ^68Ga-DOTA-lys-FA distribution in different groups. Results 6SGa-DOTA-lys-FA was stable for 3 hours after its preparation with radiopurity of （97.80 ± 2.11） %. Uptake ratio of tumor to lung at 60 minutes after tail vein injection of ^68Ga-DOTA- lys-FA determined on mieroPET-CT was 5.36 ± 1.03, which was higher than that in biodistribution studies（4.13 ± 1.25, t = 4.97,P = 0.001）. Based on microPET-CT quantification, tumor uptake of IT group was （125.60 ± 18.40） %ID/cm^3 at 60-minute and （91.80 ± 14.50） % ID/cma at 180-minute, respectively, which was significantly higher than that of ITC group[（42.30 ± 11.46） % ID/cm^3 at 60-minute and （12.82 ± 3.86） %ID/cm^3]（P 〈 0.001, 0.001）, also significantly higher than that of IV group. Conclusion MieroPET-CT sequential imaging can better determine pharmaeokinetics of ^68Ga-DOTA-lys-FA in vivo. Intratumor injection of 68Ga-DOTA-lys-FA, combining active and passive targeting advantages, increase its intratumor effective half life and offer great support for folate receptor targeted therapy.