WRN and Werner syndrome: Because WS patients are highly predisposed to tumorigenesis, showing a particularly higher incidence of non-epithelial tumors such as soft-tissue sarcoma and benign meningioma than epithelial carcinoma that are seen frequently in normal subjects (Goto et al., 1996), we hypothesized that WRN helicase could be a tumor suppressor in normal subjects that prevents tumorigenesis of non-epithelial cells and is required for the growth of carcinoma of epithelial origin (Futami et al., 2008b).