KRAS oncogene expression in various settings with additional mutations, including deletion or inactivation of p53 or TGF-β signaling molecule SMAD4, is significant in tumor development and, in some instances, acquisition of metastatic properties (Aguirre et al, 2003; Tuveson & Hingorani, 2005; Bardeesy et al, 2006). The gene discussed is SMAD4; the disease is neoplasm.