A genome-wide histone modification study has revealed distinct binding patterns of H3K27me3 and H3K4me3 between human mammary epithelial cells and three breast cancer cell lines representing the luminal, HER2-enriched, and basal subtypes; while H3K27me3 and H3K4me3 genomic distribution is generally similar among subtypes, each cancer subtype exhibited thousands of unique, locus-specific binding events for the single modification [122]. Here, ERBB2 is linked to breast cancer.