The etiology of colorectal cancer (CRC) is complex and multifactorial, however Inflammatory Bowel Disease (IBD) is demonstrated to be a strong risk factor for CRC. Autophagy, the process of degrading and recycling cellular parts, is strongly associated with IBD. Autophagy is likely to be of importance in both IBD and CRC. Unfortunately, the role of autophagy in IBD and CRC remains understudied due to insufficient availability of genetic tools. Dap1 may provide a link between CRC, IBD, and autophagy. An intronic SNP within DAP1 is associated with UC, and Dap1 is highly over-expressed in many tumors, including CRC. Dap1 negatively regulates autophagy in starvation conditions in transformed cell lines. Furthermore, Dap1 is phosphorylated by mTOR, an important molecule in colitis and tumorigenesis. Therefore, we hypothesize that by regulating autophagy, Dap1 expression contributes to ulcerative colitis susceptibility, then in conjunction with IBD, accelerates tumorigenesis resulting in colorectal cancer. Our long-term goals are to delineate the role of Dap1 in IBD, then to test its role in IBD-initiated CRC. We believe this approach will allow us to better understand the spatio-temporal role of autophagy and mTOR in these diseases, and provide a targeted approach to therapies modulating these pathways in IBD and CRC. The focus of this proposal will be to test the following aims:
Aim 1. Confirm that Dap1 negatively regulates autophagy, and is regulated by mTOR in primary cells. We will approach this by culturing Dap1 deficient primary cells and analyze autophagy after starvation and/or treatment with mTOR inhibitors.
Aim 2. Define Dap1 contributions to colonic inflammation in primary cells. We will culture primary colonic epithelium and macrophages that lack Dap1 expression, analyze inflammatory cytokines after stimulating with bacteria and virus.
Aim 3. Define contribution of Dap1 to colitis in vivo. We will test if Dap1 deficiency protects mice from gastrointestinal pathologies occurring in mice hypomorphic for Atg16L1 after virus infection, determine if Dap1-/- mice are resistant to colitis induced by IL10 deficiencies, and analyze inflammatory responses to colonic wounding in Dap1-/- mice.
Inflammatory bowel disease (IBD) impacts the quality of life of millions of individuals and can lead to colorectal cancer, yet because the causes of IBD are unknown, prevention, treatment, and cures are hampered or non-existent. Several genes have been linked with the tendency to develop IBD, but it is not known how they contribute to IBD. This project seeks to discover how the gene Dap1 contributes to IBD.