Targeting mutant p53: Evaluation of novel anti-p53^R175H monoclonal antibodies as diagnostic tools

Area of Science:

• Oncology
• Immunology
• Molecular Imaging

Background:

• Approximately 50% of cancers harbor p53 mutations, impairing its tumor suppressor function.
• The p53^R175H missense mutation is a frequent hotspot mutation across various cancer types.
• Targeting mutant p53 with specific monoclonal antibodies offers potential for improved cancer diagnostics and therapeutics.

Purpose of the Study:

• To evaluate the in vitro and in vivo binding properties of two novel anti-p53^R175H monoclonal antibodies.
• To assess the performance of these antibodies as agents for molecular imaging of mutant p53 tumors.
• To compare the diagnostic potential of anti-p53^R175H antibodies in a preclinical cancer model.

Main Methods:

• In vitro characterization of ¹²⁵I-labeled anti-p53^R175H antibodies (4H5 and 7B9) for binding affinity and stability.
• In vivo SPECT/CT imaging in a double tumor model to compare antibody performance.
• Biodistribution studies and ex vivo autoradiography to quantify tumor uptake and assess specificity.

Main Results:

• Both ¹²⁵I-4H5 and ¹²⁵I-7B9 demonstrated antigen-specific binding and suitable shelf life in vitro.
• In vivo imaging revealed comparable performance for both antibodies, with ¹²⁵I-7B9 showing slightly faster blood clearance.
• Optimal imaging contrast was achieved at 48 hours post-injection, with significantly higher tracer uptake in tumors expressing mutant p53.
• Ex vivo autoradiography confirmed specific accumulation of the tracers in mut-p53-expressing tumors.

Conclusions:

• Molecular imaging using anti-p53^R175H tracers is a promising approach for cancer diagnostics.
• These novel antibodies can effectively detect tumors with p53^R175H mutations.
• Potential applications include patient stratification and monitoring treatment response for therapies targeting mutant p53.