ARID2 Loss Reprograms the Kynurenine-AhR Pathway to Restore Antitumor Immunity in CTNNB1-Mutant Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) driven by gain-of-function mutations in CTNNB1 (CTNNB1GOF) that stabilize β-catenin exhibits a profoundly immunosuppressive tumor microenvironment (TME), rendering it resistant to immune checkpoint blockade (ICB). Metabolic reprogramming is increasingly recognized as a crucial mediator of immune activity, highlighting the need to elucidate the specific metabolic mechanisms underlying immune exclusion in CTNNB1GOF HCC. Here, we identified a critical metabolic-immune network orchestrated by co-mutations of CTNNB1 and ARID2. Integrative analysis of HCC patient cohorts and a de novo MYC/CTNNB1GOF HCC mouse model revealed that tumors harboring concurrent CTNNB1 and ARID2 mutations exhibited a more immune-active TME and improved survival compared to tumors with CTNNB1 mutations alone. Mechanistically, β-catenin and ARID2 cooperatively enhanced the transcription of tryptophan 2,3-dioxygenase (TDO2), leading to accelerated kynurenine production and activation of the aryl hydrocarbon receptor (AhR) in myeloid-derived suppressor cells (MDSCs). This metabolic axis established an immunosuppressive milieu characterized by MDSC accumulation and impaired T cell function. Genetic ablation of Arid2 in CTNNB1GOF HCC attenuated TDO2-dependent kynurenine synthesis, reduced MDSC infiltration, and enhanced CD8⁺ T cell cytotoxicity, thereby sensitizing tumors to anti-PD-1 therapy. Clinically, co-mutations of CTNNB1 and ARID2 correlated with elevated immune infiltration and favorable ICB responses across multiple human cancers, including HCC. Importantly, pharmacological inhibition of AhR phenocopied the immunomodulatory effect of ARID2 loss and, when combined with anti-PD-1, robustly reversed the immune-cold phenotype of CTNNB1GOF HCC. These findings reveal TDO2-kynurenine-AhR signaling as a pivotal metabolic pathway enforcing immune evasion in CTNNB1-mutant HCC.