EpCAM-Targeting Aptamer Radiotracer for Tumor-Specific PET Imaging

Area of Science:

• Biomedical Imaging
• Molecular Biology
• Radiochemistry

Background:

• Epithelial cell adhesion molecule (EpCAM) is a biomarker overexpressed in many carcinomas, making it a target for noninvasive tumor imaging.
• Accurate tumor staging and therapy evaluation require reliable methods to measure EpCAM expression in vivo.
• Current imaging techniques may lack the specificity or sensitivity needed for precise EpCAM detection.

Purpose of the Study:

• To develop and evaluate an aptamer radiotracer for targeted positron emission tomography (PET) imaging of EpCAM.
• To assess the specificity and efficacy of the aptamer radiotracer in vitro and in vivo.
• To demonstrate the potential of aptamer-based radiotracers for cancer diagnostics.

Main Methods:

• Formulation of an aptamer radiotracer by chelating 64Cu isotope with DOTA-PEGylated aptamer targeting EpCAM.
• In vitro cell uptake assays using EpCAM-positive (MDA-MB-231) and EpCAM-negative (lymphoma 937) cell lines.
• In vivo microPET/CT imaging in xenograft mouse models bearing EpCAM-positive or EpCAM-negative tumors.

Main Results:

• In vitro assays confirmed specific binding of the aptamer radiotracer to EpCAM-expressing cells.
• In vivo imaging demonstrated rapid and specific tumor highlighting of EpCAM-positive xenografts as early as 2 hours post-injection.
• Tumor uptake peaked at 24 hours, with minimal uptake in EpCAM-negative tumors and rapid clearance from background organs like the liver and kidneys.

Conclusions:

• Aptamer radiotracers can achieve tumor-specific PET imaging by targeting biomarkers like EpCAM.
• This approach offers a promising noninvasive tool for cancer staging and treatment monitoring.
• Further development of aptamer radiotracers could enhance precision in cancer diagnostics.