Multiple Wnt antagonists frequently methylated in breast cancer have been identified, including SFRP1 [33], SFRP2 [34], SFRP5 [35], WIF1 [36], DKK1 [37] and DKK3. The DKK3 gene, located at 11p15.1, is a key gene in Wnt signalling pathway. The gene discussed is DKK1; the disease is breast cancer.