From paradox to target: IFN-β hijacks MEK signaling to drive a cell death-evading dormant phenotype in colorectal cancer

BACKGROUND: The high clinical recurrence rate of colorectal cancer (CRC) is driven by the survival of residual tumor cells that evade therapy-induced death by entering a dormant state. While dormancy is a recognized mechanism of treatment resistance, the molecular drivers governing this "quiescent reservoir" and its associated vulnerabilities remain poorly characterized, limiting the development of strategies to eradicate these dormant seeds. METHODS: We developed a COAD-specific Dormancy Score (CADS) derived from NMF analysis of ~ 69,000 single cells to quantify and identify a dormant subpopulation at single-cell resolution. Mechanistically, the IFN-β/cDC1 axis and its downstream MEK/ERK dependency were validated using a GFP-p27K- dormancy reporter system, spatial transcriptomics, and CRISPR/Cas9-mediated Ifnar1 knockdown. Finally, the synergistic efficacy of anti-PD-1 combined with MEK inhibition (Trametinib) was evaluated in orthotopic CRC mouse models. RESULTS: The CADS effectively identified a distinct dormant subpopulation in CRC characterized by profound G0/G1 arrest, enhanced stemness, and multi-drug resistance. We uncovered a novel evasion mechanism mediated by the hijacking of IFN-β signaling. Conventionally recognized for its anti-proliferative roles, IFN-β signaling is exploited by surviving tumor cells to enter a deep quiescent state. This phenotype acts as a biological reservoir that fuels intratumoral heterogeneity and underpins the relapse of colorectal tumors by conferring resistance to conventional cytotoxic regimens. Effective anti-PD-1 therapy paradoxically enriches this dormant population via an enhanced IFN-β-conventional type 1 dendritic cell (cDC1) axis. Mechanistically, IFN-β-induced dormancy depends on MEK/ERK pathway activity, which sustains survival while suppressing apoptosis. This creates a synthetic lethal vulnerability: MEK inhibition (e.g., Trametinib) synergizes with IFN-β to re-sensitize dormant cells to apoptosis. Consequently, combining Trametinib with anti-PD-1 therapy overcomes this evasion mechanism, eliminates the dormant subpopulation, remodels the immune microenvironment, and shows strong synergistic efficacy in preclinical models. CONCLUSION: Our work redefines an immune-cell death paradox, revealing how tumors exploit IFN-β to evade therapy. We propose CADS as a translational biomarker for identifying tumors reliant on this pathway and validate a mechanism-based combination therapy that selectively targets dormancy-associated death resistance, offering a promising strategy to improve CRC outcomes.