EZH2 promotes breast cancer tumorigenesis in vivo. (A) EZH2 was stably knocked down via shRNA in MDA-MB-231 cells. Knockdown efficiency was assessed via quantitative RT-PCR. (B) Control or EZH2-KD MDA-MB-231 cells were xenografted into mammary fat pads of nude mice and tumor burden was quantified over time via weekly bioluminescent imagine (BLI). BLI signals are normalized to the Day 1 signal for each mouse. (C) Images of mice injected with control or EZH2-KD cells are displayed (24 days post-injection). Data are shown as the mean + SD (RT-PCR) or mean + SEM (xenografts). *P <0.05; **P <0.01.