BMI1 and cancer: Cancer stem cells have been shown to produce cytokines, chemokines, angiogenic factors (Levina et al. 2008; Hermann et al. 2007), and possess up-regulated signaling cascades essential for cancer metastasis, including hedgehog, epidermal growth factor receptor, NOTCH, and Bmi-1 (Mimeault and Batra 2010; Simeone 2008).