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Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2013.

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68Ga-1,4,7-Triazacyclononane-1,4,7-triacetic acid-p-isothiocyanatobenzyl-vascular endothelial growth factor-121

, PhD
National Center for Biotechnology Information, NLM, NIH
Corresponding author.

Created: ; Last Update: June 6, 2013.

Chemical name:68Ga-1,4,7-Triazacyclononane-1,4,7-triacetic acid-p-isothiocyanatobenzyl- vascular endothelial growth factor-121
Abbreviated name:68Ga-NOTA-VEGF121, 68Ga-NOTA-p-Bn-SCN-VEGF121
Agent category:Polypeptide
Target:Vascular endothelial growth factor receptor (VEGFR)
Target category:Receptor
Method of detection:Positron emission tomography (PET)
Source of signal:68Ga
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Click on protein, nucleotide (RefSeq), and gene for more information about VEGF-A.



The vascular endothelial growth factor (VEGF) family is composed of five VEGF glycoproteins (VEGF-A, VEGF-B, VEGF-C, VEGF-D, and VEGF-E) and includes at least six isoforms of various numbers of amino acids (121, 145, 165, 183, 189, and 206 amino acids) produced through alternative splicing (1). VEGF-A is composed of VEGF121, VEGF165, and VEGF189 isoforms, which are secreted by most cell types and are active as homodimers linked by disulfide bonds. VEGF121 does not bind to heparin as other VEGF polypeptides do (2). VEGF is a potent angiogenic factor that induces proliferation, sprouting, migration, and tube formation of endothelial cells. There are three high-affinity tyrosine kinase VEGF receptors (VEGFR-1, Flt-1; VEGFR-2, KDR/Flt-1; and VEGFR-3, Flt-4) on endothelial cells. Several types of non-endothelial cells, such as hematopoietic stem cells, melanoma cells, monocytes, osteoblasts, and pancreatic β cells, also express VEGFRs (1).

VEGF is overexpressed in various tumor cells and tumor-associated endothelial cells (3). Among the isoforms of VEGF-A, VEGF121 is freely soluble while all VEGF189 is bound to the cell membrane or extracellular matrix (ECM). VEGF165 exhibits an intermediary behavior (i.e., partly diffusible and partly bound). Inhibition of VEGFR function has been shown to inhibit pathological angiogenesis as well as tumor growth and metastasis (4, 5). Radiolabeled VEGF has been developed as a single-photon emission computed tomography tracer for imaging solid tumors and angiogenesis in humans (6-8). VEGFR-2 has been shown to mediate most of the VEGF-A activation in tumor endothelial cells (9, 10). Kang et al. (11) prepared 68Ga-1,4,7-triazacyclononane-1,4,7-triacetic acid-p-isothiocyanatobenzyl-VEGF121 (68Ga-NOTA-VEGF121) for use with positron emission tomography (PET) imaging of VEGFR expression in nude mice bearing U87MG human glioblastoma xenografts.



NOTA-VEGF121 was prepared by conjugation of p-SCN-Bn-NOTA to VEGF121 (4.9 nmol) in a 100:1 molar ratio at pH 9.5 for 18 h at room temperature (11). NOTA-VEGF121 was purified with column chromatography. There were 2.7 NOTA moieties per conjugate as determined with mass spectroscopy. NOTA-VEGF121 (0.35 nmol) was radiolabeled using ~185 MBq (5 mCi) 68GaCl3 in phosphate buffer (pH 6.0) for 30 min at room temperature. 68Ga-NOTA-VEGF121 was purified with a PD-10 column. Total preparation time of the tracer was ~60 min. The radiochemical yield was 40 ± 5%. The radiochemical purity was >98%. The specific activity of 68Ga-NOTA-VEGF121 was reported to be 243.1 ± 104.6 MBq/µmol (6.6 ± 2.8 mCi/µmol). 68Ga-NOTA-VEGF121 remained >95% intact in 50% bovine serum medium for 6 h at 37°C.

In Vitro Studies: Testing in Cells and Tissues


Binding affinities of VEGF121 and NOTA-VEGF121 for mouse recombinant VEGFR-2 were determined with 125I-VEGF121 (11). VEGF121 and NOTA-VEGF121 exhibited IC50 values of 1.40 ± 0.36 nM and 8.24 ± 3.35 nM, respectively. Cellular uptake of 68Ga-NOTA-VEGF121 (0.56 pM) was determined using human arterial endothelial cells (HAECs), with uptake values of 6.4% and 11.0% incubation dose at 1 h and 4 h after incubation at 37°C, respectively. Excess VEGF121 (100 nM) and anti-VEGFR-2 antibody (45.5 nM) inhibited the radioactivity in HAECs at 4 h by 32% and 49%, respectively.

Animal Studies



Kang et al. (11) studied the whole-body distribution of 68Ga-NOTA-VEGF121 in nude mice (n = 3) bearing human U87MG xenografts with the use of PET imaging at 1, 2, and 4 h after intravenous injection of 5.12 MBq (0.14 mCi) 64Cu-NOTA-VEGF121 (~25 pmol). The U87MG tumors were clearly visualized at 1–4 h after injection. The tumor accumulation of radioactivity levels were 2.43 ± 0.15% injected dose per gram (ID/g) at 1 h, 2.73 ± 0.32% ID/g at 2 h, and 2.97 ± 0.06% ID/g at 4 h. Tumor/muscle ratios were 2.58 and 2.95 at 1 h and 4 h, respectively. Co-injection with VEGF121 (3.5 nmol/mouse) inhibited accumulation of radioactivity in the U87MG tumors by 40% at 2 h (P < 0.01). The tumor/muscle ratios of the blocked mice were 1.78 and 1.95 at 1 h and 4 h, respectively.

Ex vivo biodistribution studies were performed in nude mice (n = 3/group) bearing human U87MG xenografts at 1, 2, and 4 h after injection of 4.8 MBq (0.13 mCi) 68Ga-NOTA-VEGF121 (~25 pmol) (11). The tumor accumulation of radioactivity levels were 1.46 ± 0.20% ID/g at 1 h, 1.84 ± 0.14% ID/g at 2 h, and 1.90 ± 0.02% ID/g at 4 h. Tumor/muscle ratios were 2.9, 3.2, and 3.1 at 1, 2, and 4 h, respectively. High radioactivity levels were observed in the liver (40.9% ID/g) and spleen (21.2% ID/g) at 2 h. The radioactivity levels in the blood (3.5% ID/g at 2 h) and kidney (3.2% ID/g at 2 h) were higher than that in the tumor but markedly lower than that in the liver and spleen. Co-injection with VEGF121 (3.5 nmol/mouse) inhibited accumulation of radioactivity in the U87MG tumors by 52% at 2 h (P < 0.01). The tumor/muscle ratio of the blocked mice was ~1 at 2 h. The ex vivo tumor biodistribution data are consistent with the in vivo PET tumor radioactivity levels. Immunohistostaining of tumor sections confirmed the co-localization of radioactivity to tumor endothelial cells expressing VEFGR-2 at 1–4 h.

Other Non-Primate Mammals


No publication is currently available.

Non-Human Primates


No publication is currently available.

Human Studies


No publication is currently available.


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