MKI67 and breast neoplasm: As EZH2 also regulates cell cycle in addition to its histone H3 methyltransferase function [23], and EZH2 overexpression contributes to uncontrolled mammary cell proliferation [24], the significant association between EZH2 overexpression and Ki67 proliferative index further provides evidence of EZH2 in the regulation of breast tumor cell proliferation.