SFRP1 and colorectal carcinoma: In CRC, epigenetic silencing has been observed not only for negative regulators of Wnt signaling upstream in the pathway, such as the extracellular Wnt inhibitors SFRP1, SFRP2, SFRP3, SFRP4, SFRP5, WIF1, DKK1 and DKK3[12–19] and DACT3 [20] but also for negative regulators acting further downstream in the pathway, including APC[21], AXIN2[22], CDH1[23] and SOX17[24].