Wnt/β-catenin signaling is activated in over 90% of human colorectal cancer. In particular, loss-of-function mutations of the tumor suppressor adenomatous polyposis coli (APC), a key negative regulator of Wnt/β-catenin signaling, occur in 90% of patients. The secreted Frizzled-related proteins (sFRPs) and Wnt inhibitory protein (WIF) regulate Wnt/b-catenin signaling. Both...