EZH2 and neoplasm: Murine Ezh2+/+ MLL-AF9 spleen tumor cells cultured in vitro demonstrated sensitivity to GSK343 with an IC50 (concentration where 50% maximal growth inhibition is observed) of ∼10 μM (Fig. 2 a) and showed a significant reduction in colony size and formation in its presence compared with vehicle control (Fig. 2 b).