The functional role of this phenomenon, however, has rarely been investigated: Claudin 1 has been shown to induce epithelial–mesenchymal transdifferentiation in cultured human colon cancer cell lines, to promote the growth of xenograft tumours and the formation of metastases in athymic mice (Dhawan et al, 2005). The gene discussed is CLDN1; the disease is colonic neoplasm.