Susan R. Sturgeon, et al. evaluated whether the degree of methylation would lead to a useful serum-based marker of breast cancer by pyrosequencing promoter DNA in a panel of 12 breast cancer-related genes (APC, BRCA1, CCND2, CDH1, ESR1, GSTP1, HIN1, P16, RARβ, RASSF1, SFRP1 and TWIST). Here, SFRP1 is linked to breast cancer.