TNFR1 Promotes Tumor Necrosis Factor-mediated Mouse Colon Epithelial Cell Survival through RAF Activation of NF-κB

Tumor necrosis factor (TNF) is a therapeutic target in the treatment of inflammatory bowel disease; however, the exact role of TNF signaling in the colon epithelium remains unclear. We demonstrate that TNF activation of TNF receptor (R) 1 stimulates both pro- and anti-apoptotic signaling pathways in the colon epithelium; however, TNFR1 protects against colon epithelial cell apoptosis following TNF exposure. To investigate anti-apoptotic signaling pathways downstream of TNFR1, we generated an intestinal epithelium-specific Raf knock-out mouse and identified Raf kinase as a key regulator of colon epithelial cell survival in response to TNF. Surprisingly, Raf promotes NF-kappa Bp65 phosphorylation, independent of MEK signaling, to support cell survival. Taken together, these data demonstrate a novel pathway in which Raf promotes colon epithelial cell survival through NF-kappa B downstream of TNFR1 activation. Thus, further understanding of colon epithelial cell-specific TNFR signaling may result in the identification of new targets for inflammatory bowel disease treatment and define novel mediators of colitis-associated cancer.