Liu Qinghua, Pan Donghui, Cheng Chao, Zhang Anyu, Ma Chao, Wang Lizhen, Zhang Dazhi, Liu Hongrui, Jiang Hongdie, Wang Tao, Xu Yuping, Yang Runlin, Chen Fei, Yang Min, Zuo Changjing
Department of Nuclear Medicine, Changhai Hospital, the Second Military Medical University, Shanghai, China, 200433.
Jiangsu Institute of Nuclear Medicine, Key Laboratory of Nuclear Medicine, Ministry of Health, Wuxi, Jiangsu, China, 214063.
Nucl Med Biol. 2015 Dec;42(12):939-44. doi: 10.1016/j.nucmedbio.2015.07.013. Epub 2015 Aug 4.
Elevated levels of gelatinases (matrix metalloproteinases 2/9, i.e., MMP2 and MMP9) are associated with tumor progression, invasion and metastasis, so these enzymes are potential targets for tumor imaging. The peptide c(KAHWGFTLD)NH2 (herein, C6) is a selective gelatinase inhibitor. Cy5.5-C6 has been visualized in many tumor models in vivo. However, the sensitivity and penetrance of optical imaging are poor. It is well known that positron emission tomography (PET) has a high detection sensitivity and Gallium-68 ((68)Ga) is an optimal PET radioisotope. Thus, in the present study, we developed a novel ligand, (68)Ga-NOTA-C6, to image MMP2 activity in tumors.
C6 was conjugated with the bifunctional chelator NOTA (1,4,7-triazacyclononanetriacetic acid) and labeled with (68)Ga. In vitro uptake and binding analyses were performed by using SKOV3 cell lines, coincubating with or without the MMP inhibitor doxycycline. The biodistribution and PET imaging were conducted on SKOV3 ovarian tumor models. MMP2 expression in tumors was analyzed by immunohistochemistry (IHC).
The non-decay corrected yield of (68)Ga-NOTA-C6 was 61.8%-63.3%. (68)Ga-NOTA-C6 was stable in both physiological saline and human serum. The uptake of (68)Ga-NOTA-C6 in SKOV3 cells increased with time, and could be blocked by doxycycline in a dose dependent manner. The results of biodistribution and PET imaging showed that high radioactivity concentrations of (68)Ga-NOTA-C6 occurred in tumors. The ratios of tumor to blood, muscle and ovary and oviduct at 30, 60 and 120min p.i. were 2.78±0.54, 3.86±0.65, 0.48±0.14, and 1.73±0.36, 10.31±3.12, 1.22±0.10, and 2.50±0.78, 7.03±1.85, 0.97±0.25, respectively. The tracer was excreted mainly through the renal system, as evidenced by high levels of radioactivity in the kidneys. These data support the possibility of using (68)Ga-NOTA-C6 in PET to visualize tumors that overexpress MMP2.
(68)Ga-NOTA-C6 is a potential radiopharmaceutical for the imaging of in vivo MMP2 activity in tumors.
明胶酶（基质金属蛋白酶2/9，即MMP2和MMP9）水平升高与肿瘤进展、侵袭和转移相关，因此这些酶是肿瘤成像的潜在靶点。肽c(KAHWGFTLD)NH2（本文中称为C6）是一种选择性明胶酶抑制剂。Cy5.5-C6已在多种体内肿瘤模型中实现可视化。然而，光学成像的灵敏度和穿透性较差。众所周知，正电子发射断层扫描（PET）具有高检测灵敏度，且镓-68（68Ga）是一种理想的PET放射性同位素。因此，在本研究中，我们开发了一种新型配体68Ga-NOTA-C6，用于肿瘤中MMP2活性的成像。
将C6与双功能螯合剂NOTA（1,4,7-三氮杂环壬烷三乙酸）偶联并用68Ga标记。通过使用SKOV3细胞系进行体外摄取和结合分析，分别在加入或不加入MMP抑制剂强力霉素的情况下共同孵育。在SKOV3卵巢肿瘤模型上进行生物分布和PET成像。通过免疫组织化学（IHC）分析肿瘤中的MMP2表达。
68Ga-NOTA-C6的非衰变校正产率为61.8%-63.3%。68Ga-NOTA-C6在生理盐水和人血清中均稳定。68Ga-NOTA-C6在SKOV3细胞中的摄取随时间增加，并且可被强力霉素以剂量依赖方式阻断。生物分布和PET成像结果显示，68Ga-NOTA-C6在肿瘤中出现高放射性浓度。注射后30、60和120分钟时，肿瘤与血液、肌肉以及卵巢和输卵管的比值分别为2.78±0.54、3.86±0.65、0.48±0.14，以及1.73±0.36、10.31±3.12、1.22±0.10，和2.50±0.78、7.03±1.85、0.97±0.25。示踪剂主要通过肾脏系统排泄，肾脏中高放射性水平证明了这一点。这些数据支持在PET中使用68Ga-NOTA-C6来可视化过表达MMP2的肿瘤的可能性。
68Ga-NOTA-C6是一种潜在的放射性药物，可用于肿瘤中体内MMP2活性的成像。
