Soon after, the APC gene product would be found to be an essential regulator of the intracellular Wnt cascade, leading to the establishment of constitutive Wnt activation as a key oncogenic driver in APC−/− colon carcinomas (Kinzler et al., 1991; Nishisho et al., 1991; Rubinfeld et al., 1993; Su et al., 1993; Korinek et al., 1997). This evidence concerns the gene APC and colon carcinoma.