A number of signalling pathways discovered in Drosophila flies and other model organisms have subsequently turned out to be important in cancer and specifically in cancer stem cell function. Prof Mariann Bienz talks about the role of the Wnt signalling pathway in cancer growth and cancer metastases but warns of difficulties developing therapies to target this pathway. Prof Bienz explains what progress has been made by academic labs working to develop therapies to target signalling pathways and explains the mechanisms through which the pathways can be affected.