S9pep is a short sequence of the transcription factor SOX-9, located at the hinge between the high mobility group (HMG) - DNA-binding domain and the SOX-E central conserved domain, that can mimic SOX9 tumour suppressive properties. Like full length SOX9, S9pep inhibits Wnt/beta-catenin signaling and the expression of c-Myc, its oncogenic target gene, by relocating beta-catenin from the chromatin to the cytosol. S9pep disrupts colorectal cancer cell morphology, reduces the growth of colorectal cancer cells and stem cells, and inhibits tumour development in vivo.