ABCB1 and ductal breast carcinoma in situ: Muggerud identified ABCB1, FOXC1, GSTP1, MGMT, MCH1, PPP2R2B, PTEN and RASSF1A as potential biomarkers for early breast cancer detection in DCIS as these genes already show altered methylation in DCIS compared to normal breast tissue, at the same level as in IDCs [230].