Targeting of MMP2 activity in malignant tumors with a 68Ga-labeled gelatinase inhibitor cyclic peptide.
BACKGROUND
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.


METHODS
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).


RESULTS
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.


CONCLUSIONS
(68)Ga-NOTA-C6 is a potential radiopharmaceutical for the imaging of in vivo MMP2 activity in tumors.
Department of Nuclear Medicine, Changhai Hospital, the Second Military Medical University, Shanghai, China, 200433. Electronic address: shlqh@126.com.
Qinghua
Q
Liu
Jiangsu Institute of Nuclear Medicine, Key Laboratory of Nuclear Medicine, Ministry of Health, Wuxi, Jiangsu, China, 214063.
Donghui
D
Pan
Department of Nuclear Medicine, Changhai Hospital, the Second Military Medical University, Shanghai, China, 200433.
Chao
C
Cheng
Department of Nuclear Medicine, Changhai Hospital, the Second Military Medical University, Shanghai, China, 200433.
Anyu
A
Zhang
Department of Nuclear Medicine, Zhongshan Hospital, Xiamen University, Xiamen, Fujian, China, 361004.
Chao
C
Ma
Jiangsu Institute of Nuclear Medicine, Key Laboratory of Nuclear Medicine, Ministry of Health, Wuxi, Jiangsu, China, 214063.
Lizhen
L
Wang
Department of Organic Chemistry, School of Pharmacy, the Second Military Medical University, Shanghai, China, 200433.
Dazhi
D
Zhang
Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai, China, 201203.
Hongrui
H
Liu
Department of Nuclear Medicine, Changhai Hospital, the Second Military Medical University, Shanghai, China, 200433.
Hongdie
H
Jiang
Department of Nuclear Medicine, Changhai Hospital, the Second Military Medical University, Shanghai, China, 200433.
Tao
T
Wang
Jiangsu Institute of Nuclear Medicine, Key Laboratory of Nuclear Medicine, Ministry of Health, Wuxi, Jiangsu, China, 214063.
Yuping
Y
Xu
Jiangsu Institute of Nuclear Medicine, Key Laboratory of Nuclear Medicine, Ministry of Health, Wuxi, Jiangsu, China, 214063.
Runlin
R
Yang
Jiangsu Institute of Nuclear Medicine, Key Laboratory of Nuclear Medicine, Ministry of Health, Wuxi, Jiangsu, China, 214063.
Fei
F
Chen
Jiangsu Institute of Nuclear Medicine, Key Laboratory of Nuclear Medicine, Ministry of Health, Wuxi, Jiangsu, China, 214063. Electronic address: ymzfk@163.com.
Min
M
Yang
Department of Nuclear Medicine, Changhai Hospital, the Second Military Medical University, Shanghai, China, 200433. Electronic address: changjing.zuo@qq.com.
Changjing
C
Zuo
D000818:Animals; D005260:Female; D005710:Gallium Radioisotopes / Q000493:pharmacokinetics*; D018093:Gelatinases / Q000037:antagonists & inhibitors*; D006571:Heterocyclic Compounds / Q000008:administration & dosage / Q000737:chemistry; D006573:Heterocyclic Compounds, 1-Ring; D006801:Humans; D007124:Immunoenzyme Techniques; D020778:Matrix Metalloproteinase 2 / Q000737:chemistry* / Q000378:metabolism; D061965:Matrix Metalloproteinase Inhibitors / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D010051:Ovarian Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000201:enzymology; D010456:Peptides, Cyclic / Q000494:pharmacology*; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
D005710:Gallium Radioisotopes; D006571:Heterocyclic Compounds; D006573:Heterocyclic Compounds, 1-Ring; D061965:Matrix Metalloproteinase Inhibitors; D010456:Peptides, Cyclic; D019275:Radiopharmaceuticals; C048993:1,4,7-triazacyclononane-N,N',N''-triacetic acid; D018093:Gelatinases; D020778:Matrix Metalloproteinase 2
Gallium-68; Gelatinase inhibitor; MMP2; Positron emission tomography (PET); Tumor