Shivesh Punit

Epidermal growth factor receptor inhibits colitis-associated cancer in mice

Inflammatory bowel disease (IBD) is a chronic illness caused by complex interactions between genetic and environmental factors that propagate inflammation and damage to the gastrointestinal epithelium. This state of chronic inflammation increases the risk for development of colitis-associated cancer in IBD patients. Thus, the development of targeted therapeutics that can disrupt the cycle of inflammation and epithelial injury is highly attractive. However, such biological therapies, including those targeting epidermal growth factor receptor pathways, pose a risk of increasing cancer rates. Using two mouse models of colitis-associated cancer, we found that epidermal growth factor receptor inactivation accelerated the incidence and progression of colorectal tumors. By modulating inflammation and epithelial regeneration, epidermal growth factor receptor optimized the response to chronic inflammation and limited subsequent tumorigenesis. These findings provide important insights into the pathogenesis of colitis-associated cancer and suggest that epidermal growth factor-based therapies for IBD may reduce long-term cancer risk.

ErbB4 signaling stimulates pro-inflammatory macrophage apoptosis and limits colonic inflammation

Efficient clearance of pro-inflammatory macrophages from tissues after resolution of a challenge is critical to prevent prolonged inflammation. Defects in clearance can contribute to conditions such as inflammatory bowel disease, and thus may be therapeutically targetable. However, the signaling pathways that induce termination of pro-inflammatory macrophages are incompletely defined. We tested whether the ErbB4 receptor tyrosine kinase, previously not known to have role in macrophage biology, is involved in this process. In vitro, pro-inflammatory activation of cultured murine and human macrophages induced ErbB4 expression; in contrast, other ErbB family members were not induced in pro-inflammatory cells, and other innate immune lineages (dendritic cells, neutrophils) did not express detectable ErbB4 levels. Treatment of activated pro-inflammatory macrophages with the ErbB4 ligand neuregulin-4 (NRG4) induced apoptosis. ErbB4 localized to the mitochondria in these cells. Apoptosis was accompanied by loss of mitochondrial membrane potential, and was dependent upon the proteases that generate the cleaved ErbB4 intracellular domain fragment, suggesting a requirement for this fragment and mitochondrial pathway apoptosis. In vivo, ErbB4 was highly expressed on pro-inflammatory macrophages but not neutrophils during experimental DSS colitis in C57Bl/6 mice. Active inflammation in this model suppressed NRG4 expression, which may allow for macrophage persistence and ongoing inflammation. Consistent with this notion, NRG4 levels rebounded during the recovery phase, and administration of exogenous NRG4 during colitis reduced colonic macrophage numbers and ameliorated inflammation. These data define a novel role for ErbB4 in macrophage apoptosis, and outline a mechanism of feedback inhibition that may promote resolution of colitis.

Mo1733 Targeted Claudin-2 Overexpression Protects From Experimental Colitis and Colitis-Induced Colon Cancer

G A A b st ra ct s 2011). Although classical Th1 cells via IL-12 stimulation are thought to be pathogenic in colitic conditions, the exact developmental mechanism still remains unknown. We here clarify how classical Th1 cells participate in development of colitis. METHODS: RAG-2-/mice were transferred with CD4+CD45RBhigh T cells obtained from RORγtgfp/+ reporter (RORγt-R) or RORγt-/mice. 2) RAG-2-/mice were transferred with In Vitro-manipulated Th1 cells under Th1 polarized condition (in the presence of IL-12 and anti-IL-4 mAb) from CD4+CD45RBhigh T cells obtained from RORγt-R or RORγt-/mice. 3) RAG-2-/mice were transferred with LP RORγt (GFP)-expressing CD4+ T cells from colitic RAG-2-/mice previously transferred with RORγt-R CD4+CD45RBhigh T cells. RESULTS: 1) RAG-2-/mice transferred with RORγt-R CD4+CD45RBhigh T cells developed colitis with the accumulation of Th17, Th17/Th1, and Th1 cells in inflamed mucosa, while those with RORγt/CD4+CD45RBhigh T cells did not. 2) Surprisingly, both RAG-2-/mice transferred with In Vitro-manipulated RORγt-R Th1 cells and RAG-2-/mice with In Vitro-manipulated RORγt-/Th1 cells did similarly develop colitis with the accumulation of Th1 cells, but not Th17 and Th17/Th1 cells, in inflamed mucosa. 3) RAG-2-/mice were transferred with LP RORγtexpressing CD4+ T cells developed colitis with the marked accumulation of RORγt-losing Th1 cells in the inflamed mucosa. CONCLUSIONS: Our series of transfer experiments clearly explain why both Th1 and Th17 cells are mandatory for the development of colitis; 1) classical Th1 cells require the help of Th17 and/or Th17/Th1 cells for their developmental pathway In Vivo and 2) alternative Th1 cells are differentiated from Th17 and/or Th17/ Th1 cells.

Loss of TNFR2 Exacerbates Colitis in Interleukin-10 Knockout Mice

G A A b st ra ct s led to the significant reduction of both IL-17-producing LincKitThy1+ Sca1+ innate lymphoid cells and IL-17-producing CD4+ T cells in the colon of Muc1-deficient TCR alpha double KO mice. Since Muc1 was proposed previously to play an inflammatory role in a Th1-mediated colitis of IL-10 KO mice, we next examined the role of Muc1 in another Th1mediated colitis model, CD45RB model. As seen in TCR alpha KO mice, absence of Muc1 further enhanced Th17 responses and exacerbated the colitis in recipient Muc1-deficient RAG1 double KO mice (as compared to recipient RAG1 KO mice) after transfer of naïve CD4+ T cells from WT mice. Conclusion: A membrane-bound mucin functions as a key determinant of colitis-associated Th17 responses and seems to contribute to the suppression of both Th2and Th1-mediated colitis.