Optimizing and Validating Systemic DNA Damage Response Profiling to Predict Neoadjuvant Chemoradiation Response in...

Area of Science:

• Oncology
• Molecular Biology
• Clinical Diagnostics

Background:

• Locally advanced rectal cancer (LARC) treatment involves neoadjuvant chemoradiation therapy (nCRT), but patient response varies significantly.
• Identifying non-responders to nCRT is crucial to avoid ineffective treatment and associated toxicities.
• Personalized medicine approaches are needed to optimize treatment selection for LARC patients.

Purpose of the Study:

• To develop and validate a predictive assay for nCRT response in LARC patients.
• To stratify LARC patients based on DNA damage response (DDR) proteins in peripheral blood monocytes (PBMCs).
• To establish a framework for predicting nCRT response using a novel blood assay.

Main Methods:

• Collected PBMCs from LARC patients before and after nCRT, categorized by neoadjuvant rectal (NAR) score.
• Assessed DDR using immunofluorescence (γH2AX foci) and Luminex xMAP assay for multiple DDR proteins (Chk1, Chk2, γH2AX, p53, ATR, MDM2, p21).
• Validated assay performance and analyzed clinical associations between DDR protein levels and treatment response.

Main Results:

• PBMCs from poor responders showed significantly lower γH2AX foci compared to complete responders (p<0.0001).
• The xMAP assay demonstrated high precision, reproducibility, and linearity.
• Six DDR proteins (ATR, MDM2, Chk1, Chk2, γH2AX, p53) significantly differentiated complete responders from poor responders (p ≤ 1e-5).

Conclusions:

• An optimized assay can assess DDR proteins in PBMCs to predict nCRT response in LARC patients.
• Specific protein thresholds identified accurately segregate responders from non-responders.
• This predictive assay supports personalized oncology by optimizing treatment efficacy and minimizing toxicity.