Myeloid Cell Adhesion Molecule 1 (CADM1) promotes pro-inflammatory signaling in human Inflammatory Bowel Diseases

Cytotoxic T cells have been postulated to facilitate the destruction of intestinal epithelium in inflammatory bowel diseases (IBDs). CADM1, which encodes a membrane adhesion protein that can bind the T cell receptor CRTAM, was markedly up regulated in colon of IBD patients compared to non-IBD (NIBD) patients. We then identified CADM1 enrichment in multiple immune cell clusters including macrophages and dendritic cells in the colons of IBD patients. Increased numbers of CADM1+ myeloid cells were measured adjacent to CD8+ T cells within colons of ulcerative colitis patients compared to NIBD patients. Conditional deletion of Cadm1 in myeloid cells resulted in reduced numbers of activated T cell populations and protected mice from chemical-induced colitis. Similarly, administration of a Cadm1 ‘neutralizing’ antibody which binds its extracellular domain reduced tissue inflammation and breakdown of the intestinal epithelium and crypts after induction of colitis in mice. Lastly, serum levels of sCADM1 were elevated in IBD patients compared to NIBD controls and treatment of LPMCs with recombinant sCADM1 enhanced inflammatory STAT3 phosphorylation. Therefore, we concluded that CADM1 is a mediator of pro-inflammatory signaling cascades in the colon and a potential therapeutic target for the IBDs.