ESR1 and breast neoplasm: Hypermethylation of numerous genes, whose biological functions include hormone regulation (ERα, ERβ and PR); DNA repair (BRCA1, MGMT, MLH1, and GST3); cell cycle regulation (p16Ink4a, cyclin D2, p14ARF, p57KIP2); apoptosis (DAPK1, HOXA5, TMS1, TWIST, FHIT, GPC3); cell-growth inhibition (RARβ, TGFβRII, SOCS1, RASSF1A, HIN1, NES1, SYK, WIF1); angiogenesis (maspin and THBS1); invasion (TIMP3, E-cadherin); and metastasis (APC, TIMP3), has been identified in breast tumors [65].