Gene mutations in well-known components of the Wnt-signaling pathways, such as β-catenin and APC, and repression of Wnt inhibitor genes by DNA methylation or histone modification of their promoters (SFRP-1, Axin-2, DKK-1, DKK-3, and WIF-1) are frequently observed in NET cell lines and human NET tumor samples [10]. Here, DKK1 is linked to neoplasm.