Disclosed is an isolated protein comprising a cancer-associated variant of Mammalian Scratch, wherein the cancer-associated variant of Mammalian Scratch comprises a transmembrane domain and is expressed on the surface of cancer cells, wherein the protein comprises an amino acid sequence as set forth in SEQ ID NO: 1 or SEQ ID NO:2 or an amino acid sequence having at least 70% identity to SEQ ID NO:1 or SEQ ID NO:2. Also disclosed is the use of the isolated proteins in the manufacture of a medicament to treat or prevent cancer.