Colorectal cancer (CRC) is one of the leading causes of cancer morbidity and mortality in the United States. The multistep progression from normal intestinal epithelial tissue to metastatic neoplasm results from impairment of multiple regulatory mechanisms involving critical signaling pathways that regulate normal patterns of proliferation, differentiation, migration, and apoptosis. Among these, the Wnt and RAS signaling pathways play crucial roles in governing intestinal cell proliferation and are the most frequently perturbed in colorectal cancer. Despite this knowledge, few therapeutic strategies have been developed to specifically target components of these particular pathways, and none have gained FDA approval. Our group has identified Kr?ppel-like factor 5 (KLF5) as an important regulator of intestinal epithelial cell proliferation that is frequently overexpressed during intestinal tumorigenesis. Recently, we have linked KLF5 to both the RAS and Wnt signaling pathways in colorectal carcinogenesis. Our group has also observed that reduction in KLF5 expression leads to reduced intestinal tumor formation in mice harboring a germline mutation in the tumor suppressor gene, APC, a crucial component of the Wnt pathway, or combined APC and KRAS mutations. Using an ultrahigh-throughput screening (uHTS) approach to identify novel lead compounds with potential therapeutic benefits by targeting KLF5 expression, followed by structure-activity studies on the resultant hits, we identified a novel small molecule, ML264, which potently and selectively blocks KLF5 expression in and decreases proliferation of colorectal cancer cell lines. We propose to further characterize the mechanisms by which ML264 inhibits KLF5 expression and evaluate its efficacy as a therapeutic agent for colorectal cancer. The Long-Term Goal of this research proposal is to develop and characterize novel therapeutic agents for the prevention and/or treatment of colorectal cancer. Based on our results we propose the Central Hypothesis that the compound ML264 prevents colorectal cancer development and progression by decreasing KLF5 expression in vivo. To test this hypothesis we propose three Specific Aims: 1) To investigate the mechanism by which ML264 regulates KLF5 expression in CRC cells; 2) To evaluate the preclinical efficacy of compound ML264 in preventing colon cancer formation in mouse models of colorectal cancer; and 3) To generate optimized analogs of ML264 with fully appropriate pharmacokinetic properties for anticancer therapy. The experiments proposed in this application will provide a definitive refinement of the structure and function of ML264 and its optimized analogs. The intent of this effort is to obtain well-tolerated, long-lived bioavailable compounds suitable for therapeutic use in colorectal cancer.