DKK3 (dickkopf related protein 3) is a member of the dickkopf-related family consisting of DKK1, DKK2, DKK3 and DKK4. It is a secreted protein, and also known as REIC (Reduced Expansion in Immortalized Cells). The DKK3 protein is proposed to function as a secreted tumor suppressor since it is downregulated in a number of cancer cells and prostate cancer tissue and may be a promising candidate molecule for therapeutic interference. DKK3 protein is also a negative regulator of beta-catenin and its downregulation contribute to an activation of the beta-catenin signaling pathway.