Imaging tumor endothelial marker 8 using an 18F-labeled peptide

Area of Science:

• Oncology
• Molecular Imaging
• Biochemistry

Background:

• Tumor Endothelial Marker 8 (TEM8) is upregulated in various cancers, making it a target for cancer therapeutics.
• TEM8-targeted therapies and imaging agents are under development.
• Visualizing TEM8 expression is crucial for assessing the efficacy of TEM8-targeted cancer treatments.

Purpose of the Study:

• To evaluate a peptide identified from anthrax toxin for its ability to bind TEM8.
• To develop and assess a radiolabeled version of this peptide for small-animal Positron Emission Tomography (PET) imaging of TEM8 expression.

Main Methods:

• A 13-meric peptide (QQM) was tested for TEM8 binding using ELISA.
• The QQM peptide was labeled with Fluorine-18 (18F) to create the tracer 18F-FP-QQM.
• PET imaging was performed in head-and-neck cancer (UM-SCC1) and melanoma (MDA-MB-435) models with varying TEM8 expression levels.

Main Results:

• The QQM peptide demonstrated specific binding to the extracellular domain of TEM8.
• The synthesized 18F-FP-QQM tracer exhibited high specific activity and predominantly renal clearance.
• Higher accumulation of 18F-FP-QQM was observed in TEM8-positive UM-SCC1 tumors compared to TEM8-low MDA-MB-435 tumors.

Conclusions:

• The QQM peptide specifically binds to TEM8.
• The 18F-FP-QQM tracer is a promising candidate for measuring TEM8 expression in vivo.
• Further optimization of the tracer's affinity, specificity, and metabolic stability is recommended.