ESR1 and breast cancer: Our results are in slight contradiction with what was observed in an immunohistochemistry study of the global Ezh2 and H3K27me3 levels in breast cancer tumors and cell lines [39], where Mda-MB231 (claudin-low subtype, ER-negative) was reported to have moderate expression of both EZH2 and H3K27me3, but MCF-7 (luminal subtype, ER-positive) was reported to have low expression of both EZH2 and H3K27me3.