A metagene of NRF2 expression is a prognostic biomarker in all stage colorectal cancer

Objective: Nrf2 overexpression confers poor prognosis in some cancers but its role in colorectal cancer (CRC) is unknown. Due to its role as a transcription factor we hypothesise a metagene of NRF2 regulated genes could act as a prognostic biomarker in CRC. Design: Using known NRF2 regulated genes, we defined an NRF2 metagene to represent the pathway expression using principal component analysis and Cox proportional hazard models. The NRF2 metagene was validated in four independent datasets, including the recently profiled MRC FOCUS randomised controlled trial. Results: 36 genes comprised the final prognostic metagene in the training set. 1,360 patients were included in the validation analyses. High NRF2 metagene expression is associated with worse disease free survival (DFS) and overall survival (OS) outcomes in stage I/II/III disease and worse OS in stage IV disease. In multivariate analyses, NRF2 expression remained significant when adjusted for known prognostic factors of adjuvant chemotherapy and stage in stage I/II/III disease, as well as BRAF V600E mutation and sidedness in stage IV disease. NRF2 metagene expression exhibits variation within each of the Consensus Molecular Subtypes (CMS) but high expression is particularly enriched in CMS 4. Conclusion: We demonstrate in a large scale analysis that NRF2 expression is a novel biomarker of poor prognosis across all stages of colorectal cancer. Higher expression observed in CMS 4 further refines the molecular taxonomy of colorectal cancer.