ESR1 and breast cancer: Other studies have reported promoter hypermethylation in different breast cancer genes that are implicated in DNA repair (e.g., BRCA1), apoptosis (e.g., BCL2), metastasis (e.g., TWIST), regulation of cell transcription (e.g., HOXA5), cell adhesion (e.g., CDH1), and hormone-mediated cell signaling (e.g., ERα/β) [40].