EZH2 and breast cancer: Furthermore, EZH2 has been reported to be overexpressed and to function as an oncogene in various cancers by mediating the expression of target genes involved in tumorigenesis [9, 10], including prostate cancer [11], breast cancer [12, 13], hepatocellular carcinoma [14], colorectal cancer [15, 16], gastric cancer [17], ovarian cancer [18], melanoma [19] and cervical cancer [20–23], suggesting the potential role of EZH2 in tumor.