Defining the Function of Age-Related Epimutation in Intestinal Tumorigenesis

PROJECT SUMMARY The accumulation of aberrant DNA methylation is a shared molecular phenomenon in both biological aging and cancer development. Indeed, epimutation — mitotically stable gene silencing associated with epigenetic alterations in DNA methylation — is now recognized as a common feature of human cancer. However, our understanding of how age-related epigenetic changes contribute to tumor progression and response to therapy is surprisingly limited. The proposed research builds upon our previous work revealing aberrant promoter DNA methylation in both human and mouse colons. Notably, we identified age-dependent epimutation of the tumor suppressor p16 as a driver in the adenoma-adenocarcinoma sequence of intestinal tumorigenesis. We also identified two additional candidate tumor suppressor epimutations that likely contribute to colorectal cancer (CRC). We hypothesize that age-related epimutations allow for subsequent accumulation of both genetic and epigenetic alterations that promote CRC development and progression. We will test this hypothesis by 1) Employing epigenetic engineering in mice to model advanced human colon cancers; 2) Investigating the functional implications of combined epimutations in intestinal stem cells; and 3) Testing combinatorial epigenetic immunotherapy in mouse colon tumors carrying a driver epimutation. We will elucidate the epigenetic mechanisms driving metastasis in CRCs with BRAF mutations. Our preclinical studies will provide key insights into optimally integrating epigenetic therapy into clinical trials. Leveraging organoids and CRISPR epigenome editing will allow us to test new, uncharacterized epigenetic drivers that regulate intestinal stem cell function and promote tumorigenesis. These studies will establish more faithful mouse models of human CRC development, advancing our understanding of fundamental epigenetic mechanisms that underlie susceptibility to colon cancer. Furthermore, the successful completion of this project will provide a mechanistic rationale to pursue combination epigenetic immunotherapy as a more effective strategy for treating CRC.