靶向整合素αvβ3的新型isoDGR多肽用于脑胶质瘤SP ECT/CT显像

A novel integrinαvβ3-targeted isoDGR probe for SPECT/CT imaging of glioma

目的 制备用于整合素αvβ3靶向的新型分子探针99 Tcm-HYNIC-c（isoDGRKy）,评价其在荷U87MG人脑胶质瘤裸鼠体内的生物分布,探究其用于整合素αvβ3阳性肿瘤SPECT/CT显像的可行性.方法 将双功能螯合剂HYNIC与c（isoDGRKy）偶联,再以三羟甲基甘氨酸和TPPTS为协同配体,进行99 Tcm标记,制备99 Tcm-HYNIC-c（isoDGRKy）,测定其放化纯和稳定性.细胞实验检测U87MG细胞整合素αvβ3表达情况及与c（isoDGRKy）的亲和力[以半数抑制浓度（IC50）表示].在荷U87MG肿瘤裸鼠体内进行生物分布、SPECT/CT显像及封闭实验.结果 99 Tcm-HYNIC-c（isoDGRKy）的放化纯大于99%,室温放置4 h后放化纯仍大于99%.细胞实验表明U87MG细胞为整合素αvβ3阳性（表达率70%）,其与c（isoDGRKy）的亲和力检测结果：IC50为6.67×10-8 mol/L.99Tcm-HYNIC-c（isoDGRKy）血液清除快,主要经肾脏排泄;肿瘤有明显摄取,注射后15和45 min摄取值分别为（7.31±1.42）和（1.09±0.11）%ID/g,15 min时肿瘤/肌肉比值为5.01±1.47.荷瘤鼠注射99Tcm-HYNIC-c（isoDGRKy）后0.5和1 h显像肿瘤均清晰可见,本底较低.封闭实验同时注射过量c（RGDfK）冷肽阻断整合素αvβ3后,肿瘤几乎不显像.结论 99 Tcm-HYNIC-c（isoDGRKy）制备简单,稳定性好,能特异性靶向整合素αvβ3,有望用于整合素αvβ3阳性肿瘤的SPECT/CT诊断显像.

Objective To prepare 99 Tcm-HYNIC-c（ isoDGRKy） as a SPECT/CT imaging molecu-lar probe targeting integrin αvβ3 , and evaluate its biodistribution and feasibility on SPECT/CT imaging for integrinαvβ3-positive tumor in U87MG human glioma xenograft mouse models. Methods The bifunctional chelator HYNIC was conjugated to c（ isoDGRKy） , and tricine and TPPTS were used as coligands for 99 Tcm labeling to prepare 99 Tcm-HYNIC-c（ isoDGRKy） . The radiochemical purity and stability of the product were measured. The expression of integrin αvβ3 and binding affinity （ half maximal inhibitory concentration, IC50 ） of c （ isoDGRKy ） was detected in U87MG cells by cell experiments in vitro. Biodistribution and SPECT/CT imaging of 99 Tcm-HYNIC-c（ isoDGRKy） including blocking experiments were performed respec-tively in nude mice bearing U87MG human glioma xenografts. Results The radiochemical purity of 99 Tcm-HYNIC-c（ isoDGRKy） was over 99%, and was still over 99% after 4 h incubation in saline at room temper-ature. Flow cytometry assay showed that U87MG cells were integrinαvβ3-positive （ expressive rate：70%） . The IC50 of c（isoDGRKy） was 6.67×10-8 mol/L. Biodistribution results showed 99Tcm-HYNIC-c（isoDGRKy） with a rapid clearance from blood was excreted mainly via the kidneys. The 99 Tcm-HYNIC-c（ isoDGRKy） uptake values in U87MG tumors were （7.31±1.42） and （1.09±0.11） %ID/g at 15 and 45 min post-injection re-spectively, and tumor-to-muscle ratio reached 5.01±1.47 at 15 min post-injection. The tumors were clearlyvisualized with low background from 0.5 to 1 h post-injection in tumor bearing mice. In the blocking experi-ment, the tumor was barely visualized after co-injection of excess cold c（RGDfK） peptide with 99Tcm-HYNIC-c（isoDGRKy）. Conclusions 99Tcm-HYNIC-c（isoDGRKy） may be easily and steadily prepared. It may be a RGD-like promising SPECT/CT imaging probe for integrinαvβ3-positive tumor.