In a study of 96 breast cancer samples, promoter methylation of the Dickkopf (DKK) family member DKK3 was found to be significantly enriched in tumors from patients with advanced disease, lymph node metastasis, and positive Estrogen Receptor alpha (ERα) status (42 of 47 samples were ER+) (99). This evidence concerns the gene ESR1 and breast cancer.