EZH2 and breast cancer: EZH2 overexpression or gain-of-function mutation is associated with cancer progression and poor prognoses in many solid cancers and hematologic malignancies, such as prostate cancer, breast cancer, lymphoma, and AML.685–687 Inhibition of EZH2 or other PRC2 components diminishes the H3K27me3 level and derepresses the expression of tumor-suppressive genes, impairing cell proliferation and tumor growth in vivo.