The incidence of colorectal cancer (CRC) is higher in African Americans (AAs) compared with US whites(NHWs) overall but the disparity is more extreme in persons with earlier age of onset. The median age ofonset is 65 in AAs compared to 72 in NHWs and early-onset CRC is more than twice as frequent in AAs thanin NHWs. In addition epidemiologic evidence suggests that younger age CRCs may have a more rapidprogression through the steps of carcinogenesis. Yet younger age CRC is not well characterized in anypopulation and we have no explanation for its higher incidence in AAs. In a recent genomic analysis of aseries of Chicago African American CRC cases we found an excess of CRCs lacking mutation in the tumorsuppressor gene APC (APC mutation-negative CRCs). Microsatellite stable APC mutation-negative CRCswere associated with younger age of diagnosis fewer numbers of somatic mutations and microsatellite andchromosome stability. Importantly we discovered that APC mutation-negative CRCs exhibited a novelmethylation profile characterized by increased levels of methylation in key cancer driver genes including thosein stem-cell maintenance and the WNT signaling pathway. Based on our preliminary data we hypothesize thatepigenetic dysregulation in APC mutation-negative CRCs drives specific DNA methylation changes and generegulatory networks that maintain a stem-like cancer phenotype. The overall goal of the project is tocharacterize the molecular mechanisms that drive this novel subtype of CRCs. We have three aims. Aim 1.Identify and characterize significant differentially methylated regions in AA CRC. Hypothesis: Tumor-specific differentially methylated regions are associated with carcinogenesis in APC mutation-negative CRCs.APC mutation-negative CRCs will be associated with earlier age of onset and with distinct molecular andclinicopathological features. Aim 2. Identify and characterize differentially expressed genes andregulatory networks in AA CRCs. Hypothesis: Specific regulatory networks that maintain a stem-like cancerphenotype are associated with APC mutation-negative CRCs. Aim 3. Determine driver gene dependenciesof AA CRCs in organoid cancer models. Hypothesis: Suppression of specific WNT signaling factors andepigenetic modulators will induce increased epithelial differentiation in APC mutation-negative organoids incomparison to APC mutation-positive organoids. The proposed studies will provide essential knowledge of theDNA methylation and gene expression changes underlying AA CRCs and will characterize cancer cellresponses to chemical challenge. The new knowledge will provide translatable information includingdiagnostic and predictive biomarkers and precision-medicine approaches that could be used to treat a novelsubtype of CRC that occurs in excess in AAs and is associated with earlier age of onset.