An isolated Shoca polypeptide comprising: (i) the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 4; or (ii) a variant thereof which is capable of interacting with a polypeptide of the wnt signalling pathway; or (iii) a fragment of (i) or (ii) which is capable of interacting with a polypeptide of the wnt signalling pathway, a polypeptide encoding said polypeptide, a method for identifying a modulator of the wnt signalling pathway utilising said polypeptide or polynucleotide and methods of diagnosing and treating cancer.