BMI1 and cancer: PcG proteins form large complexes, including PRC1 (Polycomb repressive complex 1) and PRC2 (Polycomb repressive complex 2), which silence target genes by modifying chromatin organization.24, 25 Bmi1 also can bind to the Runx1/CBFβ transcription factor complex to silence target gene in a PRC2-independent manner.26 Although many researchers focus on the role of Bmi1 in self-renewal of embryonic, adult and cancer stem cell,27, 28, 29, 30, 31, 32, 33, 34, 35, 36 several evidences suggest that Bmi1 also regulate cell survival by controlling mitochondrial function and ROS level.