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99mTc-labeled vasoactive intestinal peptide receptor agonist: functional studies.
V R Pallela1, M L Thakur, S Chakder
1Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania 19107, USA.
Summary
Technetium-99m-labeled vasoactive intestinal peptide (99mTc-VIP) was developed for tumor imaging. This radiotracer demonstrated specific tumor uptake and retained biological activity, showing promise for detecting experimental tumors.
Area of Science:
- Nuclear medicine
- Radiopharmaceutical chemistry
- Oncology
Background:
- Vasoactive intestinal peptide (VIP) receptors are upregulated on various malignant tumors.
- VIP is a naturally occurring peptide with diverse biological functions.
- Current imaging techniques may not optimally detect VIP receptor-expressing tumors.
Purpose of the Study:
- To label VIP with technetium-99m (99mTc) for scintigraphic imaging.
- To evaluate the bioactivity and tumor-detection capability of 99mTc-VIP.
Main Methods:
- Modified VIP28 (TP3654) with an N4 configuration for 99mTc chelation and an Aba spacer.
- Labeled TP3654 with 99mTc and VIP28 with 125I as a control.
- Assessed in vitro biological activity (cell-binding, smooth muscle relaxivity) and in vivo tumor targeting in mice.
Main Results:
- Quantitative yield for 99mTc-TP3654 labeling; >90% yield for 125I-labeled compounds.
- 99mTc-TP3654 exhibited biological activity equivalent to native VIP28.
- Tumor uptake of 99mTc-TP3654 was significantly higher than 125I-VIP and showed receptor-specific binding.
Conclusions:
- Modified VIP28 (TP3654) was successfully labeled with 99mTc.
- The resulting radiotracer, 99mTc-TP3654, retains biological activity and demonstrates specific tumor targeting.
- This 99mTc-labeled VIP analog shows potential as a diagnostic imaging agent for VIP receptor-positive tumors.