Although APC mutation is believed to activate Wnt signaling constitutively, histopathological studies show that only about 50% colon carcinoma cells display homogeneous nuclear β-catenin staining (Chung et al., 2001), a surrogate for Wnt signaling activity, indicating that APC mutation alone is not sufficient to cause persistent or full activation of the Wnt pathway in CRC cells, therefore Wnt signaling is regulatable in APC-mutated CRCs. This evidence concerns the gene APC and colorectal carcinoma.