RBMS3 promotes ferroptosis in colorectal cancer and is suppressed by M2 tumor-associated macrophages via STAT3 activation.

BACKGROUNDColon adenocarcinoma (COAD) shows marked clinical heterogeneity, and robust biomarkers with mechanistic relevance are still needed for prognostic stratification. RBMS3 has been implicated in tumor biology, but its pan-cancer significance, prognostic value in COAD, and regulatory mechanisms remain insufficiently defined.

METHODSWe performed integrated analyses of The Cancer Genome Atlas pan-cancer and COAD cohorts, followed by external validation in GEO datasets. Prognostic associations were evaluated by Cox and Kaplan-Meier analyses, and clinicopathological relevance was assessed in TCGA-COAD. A prognostic nomogram combining RBMS3 and clinical variables was constructed. Single-cell RNA-seq analysis was used to characterize RBMS3-associated functional programs. In vitro experiments in HCT116 cell and THP-1-derived M2 macrophage co-culture systems were conducted to validate ferroptosis-related effects and upstream STAT3-dependent regulation.

RESULTSRBMS3 was significantly dysregulated across multiple tumor types and showed prognostic relevance in pan-cancer analysis, with a prominent adverse survival association in COAD. GEO cohorts confirmed decreased RBMS3 expression in tumor samples relative to normal controls, and low RBMS3 expression was associated with unfavorable prognosis, supporting its tumor-suppressive prognostic role. In TCGA-COAD, RBMS3 expression correlated with T stage and pathological stage, and integration of RBMS3 with staging factors improved prognostic stratification in a nomogram model. Single-cell analysis showed enrichment of ferroptosis-related pathways in RBMS3-positive tumor cells. Functionally, RBMS3 overexpression in HCT116 cells reduced viability, decreased GPX4, increased ACSL4, and elevated intracellular Fe ion levels, indicating molecular features consistent with enhanced ferroptotic sensitivity. Mechanistically, M2 macrophages suppressed RBMS3 expression in tumor cells with concomitant STAT3 activation, while pharmacological STAT3 inhibition partially restored RBMS3 expression.

CONCLUSIONRBMS3 is a clinically relevant prognostic biomarker in COAD and is linked to ferroptosis-associated tumor-cell programs. The M2 macrophage-STAT3-RBMS3 axis provides a mechanistic connection between the immune microenvironment and tumor intrinsic regulation, highlighting RBMS3 as a potential target for prognostic modeling and translational intervention in COAD.