RPIA and malignant colon neoplasm: Transgenic zebrafish overexpressing RPIA under the control of a gut-specific promoter exhibited enhanced β-catenin expression and elevated mRNA levels of the colon cancer marker gene ccne1. Our work uncovers a new role of RPIA and provides a molecular mechanism of RPIA-mediated β-catenin stabilization and activation necessary for colon cancer formation.