EZH2 and cancer: We have chosen EZH2, which is a member of the polycomb gene (PcG) family, as it has been implicated in the pathogenesis of a number of other cancer types.13, 25, 26, 27 EZH2 is the catalytic subunit of the polycomb repressive complex 2 (PRC2), which is responsible for methylation of lysine 27 on histone H3.