Moreover, we recently showed that pharmacological reduction of Wnt signalling reduced intestinal stem cell (ISC) number, ISC competition and increased proximal small intestinal tumour formation in mice where Apc was deleted in the ISCs17 These studies suggest that colon tumours select for APC mutations providing the optimal level of Wnt signalling and that Wnt signalling influences the size of the ISC pool as well as ISC competition. This evidence concerns the gene APC and colonic neoplasm.