The many ways of Wnt in cancer

More than 20 years ago, the oncogenicity of a Writ ligand was revealed in a series of experiments originating with random proviral integration in mice. The significance of Writ signaling in human cancer has since been buttressed by the identification of mutations in genes coding for the Writ pathway components Axin, APC, and beta-catenin. This review summarizes the reported genetic defects in the Writ pathway, with an emphasis on their functional contribution to human tumor progression.