KRAS and colorectal carcinoma: Braf-mutant genetically engineered mouse models (GEMMs) of CRC exhibit activated WNT signaling, indicated by nuclear accumulation of β-catenin, while KRAS-mutant tumors appear to develop independently of WNT pathway activation (Bennecke et al., 2010, Janssen et al., 2002, Trobridge et al., 2009).