Epithelial Wnt secretion drives the progression of inflammation-induced colon carcinoma

Colon cancer is initiated by stem cells that escape the strict control. In most colon tumors this process is driven through aberrant activation of Wnt signaling by mutations that occur in components acting downstream of the receptor complex and that unfetter tumor cells from the need for Wnt ligands. Here we describe a special type of colon cancer that does not depend on mutated core components of the Wnt pathway. Genetically blocking Wnt secretion from epithelial cells of such tumors results in apoptosis, reduced expression of colon cancer markers, followed by enhanced tumor differentiation. In contrast to the normal colonic epithelium, such tumor cells auto-secrete Wnt ligands to maintain their uncontrolled proliferative behavior. In humans, we determined certain cases of colon cancers in which the Wnt pathway is hyperactive, but not through mutations in its core components. Our findings illuminate the path in therapy to find further subtypes of Wnt- dependent colon cancer, that might be responsive to Wnt secretion inhibitors. Overall design: Examination of gene expression of wild type (WT) and Villin-Wls cKO tumors.