^177Lu-EB-RGD分子探针的构建及其在非小细胞肺癌PDX模型中的显像与治疗研究

目的 构建靶向整合素αvβ3诊疗一体化放射性分子177 Lu-伊文思蓝(EB)-精氨酸-甘氨酸-天冬氨酸(RGD)并探讨其用于非小细胞肺癌(NSCLC)-患者来源异种移植瘤(PDX)模型显像及治疗的效果.方法 将RGD肽与白蛋白结合基团EB相连接,构建特异性靶向整合素αvβ3的EB-RGD,并经螯合剂1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸(DOTA)偶联完成靶向分子177 Lu标记.构建68只NSCLC-PDX模型鼠,取28只注射177 Lu-EB-RGD或177 Lu-RGD行microSPECT显像和生物分布研究;另行177 Lu-EB-RGD放射靶向治疗实验:取PDX模型鼠40只,分为生理盐水组(A组)、18.5 MBq ^177Lu-RGD组(B组)、18.5 MBq ^177Lu-EB-RGD组(C组)、29.6 MBq ^177Lu-EB-RGD组(D组),每组10只,观察治疗后50 d内模型鼠肿瘤体积变化情况.2组间比较采用两独立样本t检验.结果 ^177Lu-EB-RGD的标记率在95%以上,比活度为(55±14) GBq/μmol,其体外稳定性好,放化纯大于95%.注射^177Lu-EB-RGD后4~96 h,NSCLC-PDX模型鼠肿瘤清晰可见,注射后4、24、72、96 h的肿瘤/肌肉摄取比值(T/M)分别为7.34±0.67、14.63±3.82、15.69±3.58及15.99±5.42;生物分布结果示177 Lu-EB-RGD摄取[每克组织百分注射剂量率(%ID/g)]与SPECT显像结果一致,且4h时的^177Lu-EB-RGD在肿瘤中的摄取明显高于^177Lu-RGD[(10.15±1.17)与(3.30±1.47) %ID/g;t=18.60,P<0.05].^177Lu-EB-RGD治疗后,A组与B组模型鼠的肿瘤体积均快速增加;而C组与D组肿瘤体积呈持续降低趋势,在第28天时C组与D组肿瘤均已肉眼不可见,且在随后的监测时间内未见复发.结论 ^177Lu-EB-RGD能靶向αvβ3阳性的NSCLC-PDX模型,显像效果好,对肿瘤生长有明显抑制作用,有望为晚期靶向治疗耐药或无效的肺癌患者提供新的治疗策略.

Development of ^177Lu-EB-RGD molecular probe and its imaging and therapy in the patient-derived xenografts of non-small cell lung cancer

Objective To develop a novelαvβ3-targeted theranostic agent ^177Lu-Evans blue(EB)-Arg-Gly-Asp(RGD)and evaluate its value for SPECT imaging and targeted radionuclide therapy in the non-small cell lung cancer(NSCLC)-patient-derived xenografts(PDX).Methods Theαvβ3-targeted molecule RGD was conjugated with the albumin binding moiety EB to obtain EB-RGD,and EB-RGD was further conjugated with the chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid(DOTA)for ^177Lu radiolabeling.NSCLC-PDX mice models(n=68)were established.^177Lu-EB-RGD SPECT imaging,biodistribution study were performed in 28 PDX mice models after being injected with ^177Lu-EB-RGD or ^177Lu-RGD.Targeted radionuclide therapy were subsequently performed in NSCLC-PDX mice models,saline group(group A),18.5 MBq ^177Lu-RGD group(group B),18.5 MBq ^177Lu-EB-RGD group(group C),29.6 MBq ^177Lu-EB-RGD group(group D),n=10 in each group;tumor volumes of PDX mice models in each group were observed within 50 d.Differences between 2 groups were compared using independent-sample t test.Results ^177Lu-EB-RGD was radiolabeled at a specific activity of(55±14)GBq/μmol,with a radiochemical yield of more than 95%and a radiochemical purity of more than 95%.Regarding the SPECT imaging,tumors in NSCLC-PDX mice were clearly observed from 4 to 96 h post-injection and the tumor to muscle ratio(T/M)reached 7.34±0.67,14.63±3.82,15.69±3.58 and 15.99±5.42 at 4,24,72,96 h post-injection,respectively.Biodistribution study further confirmed the findings from SPECT imaging,and the tumor uptake of ^177Lu-EB-RGD were markedly increased compared to ^177Lu-RGD 4 h post-injection((10.15±1.17)vs(3.30±1.47)percent injection dose per gram(%ID/g);t=18.60,P<0.05).Regarding targeted radiotherapy,the tumor volumes were quickly increased within 50 d after treatment in group A and B,while the tumor volumes were decreased in group C and D,until the tumors in group C and D disappeared at the 28th day after initial treatment with no sign of recurrence during the observation period.Conclusions ^177Lu-EB-RGD can targetαvβ3-positive NSCLC-PDX with intense tumor to background ratio and strong tumor inhibition efficacy.The preclinical data suggests that ^177Lu-EB-RGD may be an effective new treatment option for advanced NSCLC patients with resistance or ineffective results for targeted therapy.