Direct detection and quantification of abasic sites for in vivo studies of DNA damage and repair

Area of Science:

• Molecular Biology
• Oncology
• Radiochemistry
• Medical Imaging

Background:

• Chemotherapeutic agents induce DNA damage for cancer treatment, but DNA repair mechanisms, like base excision repair (BER), can reduce their efficacy.
• The BER pathway generates abasic (AP) sites, and blocking these sites enhances drug sensitivity.
• Monitoring AP sites is crucial for developing effective DNA-targeted cancer therapies.

Purpose of the Study:

• To develop and validate a positron emission tomography (PET) imaging technique for in vivo quantification of abasic (AP) sites.
• To assess the potential of this technique as a clinical correlate for DNA-targeted chemotherapies.

Main Methods:

• Development of a novel radiotracer, carbon-11 methoxyamine ([(11)C]MX), which specifically binds to AP sites.
• In vivo validation of [(11)C]MX binding specificity using blocking experiments.
• Application of [(11)C]MX PET imaging in melanoma and glioma xenograft models to quantify AP sites after temozolomide treatment.

Main Results:

• [(11)C]MX demonstrated high specificity for binding to AP sites in vivo.
• PET studies showed a significant increase in [(11)C]MX uptake in tumors following temozolomide-induced AP site formation.
• The PET imaging results correlated well with conventional aldehyde reactive probe (ARP)-based bioassays for AP sites.

Conclusions:

• The developed [(11)C]MX PET imaging technique allows for direct and quantitative assessment of AP sites in vivo.
• This imaging approach can serve as a valuable tool for monitoring the efficacy of DNA-targeted chemotherapies and guiding treatment decisions.
• The technique holds promise for advancing the development of novel cancer treatments that target DNA repair pathways.