AhR—MMP—NK Cell Crosstalk Regulates Colonic Inflammation and Colitis-Associated Colorectal Cancer Progression 2256044

Abstract Introduction Inflammatory bowel diseases (IBD), a group of chronic inflammatory disorders, constitute a major risk factor for colorectal cancer (CRC), accounting for 10—15% of IBD-related deaths. Aryl hydrocarbon receptor (AhR) regulates mucosal immunity, while nature killer (NK) cells detect stress ligands via NKG2D. Matrix metalloproteinases (MMPs)-mediated shedding of these ligands promotes tumor immune escape. In this study, we identified a novel AhR—MMP—NK axis in colonic epithelial cells (CECs) that regulates immune escape during colitis. Methods We employed AhR-deficient mice and indole-3-carbinol (I3C) treatment in a dextran sulfate sodium (DSS)-induced colitis model. To assess the severity of colitis, we analyzed body weight loss, colon length, and histological scores. Molecular assays included RNA sequencing, Western blotting, quantitative polymerase chain reaction (qPCR), and immunocytochemistry/histochemistry. Additionally, flow cytometry was performed to identify and quantify natural killer (NK) cells. Results Using proteomics, scRNA-seq, patient samples, and murine colitis models, we observed reduced AhR activity with decreased expression but increased shedding of murine NKG2D ligands such as RAE1, MULT1, and H60 in CECs, impairing NK cell activation. Colitis-inducing agents (Dextran sulfate sodium, B. acidifaciens, C. rodentium) triggered ligands shedding in CECs. We also found that MMPs mediate the shedding of NKG2D ligands. Importantly, AhR activation in mice with colitis, using dietary metabolite, indole-3-carbinol (I3C), restored ligand expression, reduced NKG2D ligands shedding, and enhanced NK responses in WT mice with colitis but not in intestinal epithelial cells-specific AhR knockout (AhRΔIEC) mice. Conclusion Our findings identify an AhR—MMP—NK cell axis as central to mucosal immunity, with AhR agonists offering a promising approach to limit colonic inflammation and block colitis-associated CRC. Funding Source P20GM103641; P30GM154631; R01ES030144; R01AI160896 Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)