The observations that various Wnt antagonists like members of the Dickkopf (Dkk) family are highly expressed in osteotropic prostate cancer cells [33], upregulated in prostate cancer patients [34] and that stable expression of Dkk-1 stimulates prostate cancer growth [35] all suggest that decreased Wnt signaling may also be beneficial for metastatic outgrowth. This evidence concerns the gene DKK1 and prostate carcinoma.