ERBB2 and breast cancer: Alterations in DNA methylation are paralleled by changes in expression of DNMTs [72,73], which are themselves strongly implicated in establishing the epigenetic phenotype of certain BC subtypes [74]: DNMT1 is more overexpressed in TNBC and ER− tumors, DNMT3A is highly expressed in luminal B, HER2+, and TNBC subtypes, and DNMT3B is broadly overexpressed across all subtypes [73].