Unveiling MAGEA3: a novel predictive biomarker for bevacizumab resistance in colorectal cancer

<b>Aim:</b> Bevacizumab has long been a cornerstone in the treatment of colorectal cancer (CRC), serving as a fundamental antiangiogenic therapeutic option. However, a significant proportion of patients exhibit insensitivity to bevacizumab, and no reliable biomarker has been established to predict treatment efficacy. Notably, while many angiogenic factors in tumors have been extensively studied, they have failed to consistently demonstrate reliable predictive value for patient survival outcomes in CRC. This study is designed to screen tumor biomarkers with predictive value for bevacizumab resistance in CRC. <b>Methods:</b> Online CRC databases with bevacizumab treatment were downloaded from the GEO datasets along with the TCGA database, which were then analyzed to generate genes overexpressed in bevacizumab non-responders. In vitro experiments using colorectal cancer cell lines were then performed to explore the underlying mechanism of the candidate gene that impacts bevacizumab efficacy. Finally, clinical samples of CRC were collected to validate the predictive effect of the candidate gene on bevacizumab efficacy. <b>Results:</b> We conducted comprehensive analyses of CRC patient datasets, identifying MAGEA3 as a pivotal gene that is not only highly upregulated in bevacizumab-resistant primary CRC but also strongly associated with poor overall survival prognosis. Our in vitro experiments revealed a novel mechanistic insight: MAGEA3 specifically inhibits the expression and secretion of VEGF through the mTOR signaling pathway in colorectal cancer cells, while exhibiting minimal impact on other key angiogenic factors such as PDGF, FGF, and ANGPT2. This selective regulation of VEGF provides a molecular basis for MAGEA3's role in bevacizumab resistance. Furthermore, we discovered that MAGEA3 significantly impairs mitochondrial function in cancer cells, suggesting an additional layer of complexity in its oncogenic role. Clinically, our findings demonstrated that high baseline levels of MAGEA3 in CRC patients were strongly associated with worse progression-free survival (PFS) following bevacizumab treatment. <b>Conclusion:</b> Collectively, these findings position MAGEA3 as a promising predictive biomarker for bevacizumab resistance in CRC, offering a potential solution to the longstanding challenge of treatment stratification.