KRAS and colorectal carcinoma: According to Fearon [24], the first step of CRC tumorigenesis is the constitutive activation of the Wnt/ß-catenin oncogenic pathway induced by the mutation of the Adenomatous Polyposis Coli gene (APC), the most frequent, or ß-catenin, followed by the mutational activation of the oncogene KRAS and the inactivation of the tumor suppressor gene TP53.