TGFβ-SMAD2/3 signaling inhibits IRF2 to drive metastasis in KRAS-mutant colorectal cancer.

KRAS-mutant colorectal cancer (CRC) exhibits an aggressive metastatic phenotype, largely driven by TGFβ-induced epithelial-mesenchymal transition (EMT). However, the downstream effectors mediating TGFβ-driven metastasis in this context remain incompletely defined. This study identifies interferon regulatory factor 2 (IRF2) as a key metastasis suppressor and direct transcriptional repression target of TGFβ-SMAD2/3 signaling. IRF2 expression is markedly downregulated at invasive tumor fronts, showing a significant inverse correlation with p-SMAD2 levels and advanced metastatic stage. Single-cell trajectory analysis reveals temporal IRF2 suppression precisely coinciding with TGFβ/EMT program activation during metastatic progression. Mechanistically, SMAD2/3 complexes directly bind the IRF2 promoter to mediate repression, and IRF2 overexpression effectively reverses TGFβ1-induced invasive phenotypes in vitro. Pharmacological TGFβR1 inhibition restores IRF2 expression, slowing tumor progression and extending survival in the KRAS-driven iKAP mouse model. Furthermore, IRF2 reconstitution potently inhibits CRC cell invasion and metastasis by transcriptionally repressing EMT-related genes and enhancing anti-tumor immunity, characterized by increased CD8+ T-cell infiltration and reduced regulatory T cells (Tregs). While active in various CRC contexts, the TGFβ-SMAD2/3-IRF2 axis is particularly critical in KRAS-mutant CRC, where IRF2 loss acts as a functional second hit to accelerate dissemination. These findings uncover a TGFβ-SMAD2/3-IRF2 axis governing EMT and metastatic dissemination, positioning IRF2 restoration as a promising therapeutic strategy for aggressive KRAS-mutant CRC.