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Hybrid PET/optical imaging of integrin αVβ3 receptor expression using a (64)Cu-labeled streptavidin/biotin-based
Choong Mo Kang1,2, Hyun-Jung Koo1, Gwang Il An3
1Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, 06351, Korea.
Insights
This study developed a novel hybrid PET/optical imaging probe, (64)Cu-DOTA-(AF)SAv/biotin-PEG-RGD2, for enhanced detection of tumors by targeting integrin αVβ3 expression.
Area of Science:
- Molecular Imaging
- Bioconjugate Chemistry
- Oncology
Background:
- Hybrid PET/optical imaging offers complementary data for tumor diagnosis.
- Integrin αVβ3 is a key target for cancer imaging.
- Development of targeted imaging probes is crucial for early cancer detection.
Purpose of the Study:
- To develop and evaluate a novel (64)Cu-labeled AlexaFluor 680-streptavidin ((AF)SAv)/biotin-based dimeric cyclic RGD peptide (RGD2) probe.
- To assess the probe's efficacy in hybrid PET/optical imaging of integrin αVβ3 expression in tumors.
- To investigate the probe's binding affinity, cellular uptake, and in vivo performance.
Main Methods:
- Synthesis and radiolabeling of the (64)Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 probe.
- In vitro receptor binding and cellular uptake studies using U87MG cells.
- In vivo microPET/optical imaging and ex vivo biodistribution studies in tumor-bearing mice.
- Immunofluorescence staining of tumor tissues.
Main Results:
- The probe was successfully synthesized with good radiochemical yield and specific activity.
- Enhanced binding affinity for integrin αVβ3 was observed, suggesting a polyvalency effect.
- High accumulation and specific uptake in tumors were demonstrated in vivo and ex vivo.
- Optical imaging revealed strong fluorescence in tumors, correlating with PET findings.
Conclusions:
- The developed (64)Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 probe enables quantitative hybrid PET/optical imaging.
- This probe shows significant potential for imaging integrin αVβ3 expression in tumors.
- The findings support the use of this hybrid probe for improved tumor diagnosis.
Background:
Hybrid PET/optical imaging provides quantitative and complementary information for diagnosis of tumors. Herein, we developed a (64)Cu-labeled AlexaFluor 680-streptavidin ((AF)SAv)/biotin-based dimeric cyclic RGD peptide (RGD2) for hybrid PET/optical imaging of integrin αVβ3 expression.
Methods:
(64)Cu-1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-(AF)SAv/biotin-PEG-RGD2 was prepared by formation of a complex comprising DOTA-(AF)SAv and biotin-PEG-RGD2, followed by radiolabeling with (64)Cu. Receptor binding studies of DOTA-(AF)SAv/biotin-PEG-RGD2 were performed using U87MG cells and (125)I-RGDyK as the radioligand, and cellular uptake studies of (64)Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 were also performed. MicroPET imaging followed by optical imaging of U87MG tumor-bearing mice was acquired after injection of the hybrid probe, and region of interest (ROI) analysis of tumors was performed. Ex vivo PET/optical imaging and biodistribution studies of the major tissues were performed after the in vivo imaging, and immunofluorescence staining of the tumor tissue sections was carried out.
Results:
(64)Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 was prepared in 52.1 ± 5.4 % radiochemical yield and with specific activity of 1.0 ± 0.1 GBq/mg. Receptor binding studies showed that DOTA-(AF)SAv/biotin-PEG-RGD2 had higher binding affinity for integrin αVβ3 than RGD2, reflecting a possible polyvalency effect. Moreover, the hybrid probe revealed time-dependent uptake by U87MG cells. In a microPET/optical imaging study, the hybrid probe demonstrated high accumulation in tumors; ROI analysis revealed 2.7 ± 0.2 % ID/g at 1 h and 4.7 ± 0.2 % ID/g at 21 h after injection, and subsequently acquired optical images showed tumors with strong fluorescence intensity. Ex vivo PET/optical images of the major tissues confirmed the in vivo imaging data, and biodistribution studies demonstrated high and specific uptake in tumors (4.8 ± 0.1 % ID/g). Immunofluorescence staining showed the formation of new blood vessels in tumor tissues, suggesting that the tumor uptake was due to specific binding of the hybrid probe to integrin αVβ3 expressed on tumor cells.
Conclusions:
These results indicate that a (64)Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 is able to provide quantitative information on hybrid PET/optical imaging of integrin αVβ3 expression.
