BMI1 and hepatocellular carcinoma: Western blot analysis demonstrated a positive correlation between CTSB and BMI1 expression in a panel of HCC cell lines (Supplementary Fig. 4a), while its expression was up-regulated at the translational level, but not at the mRNA level, in WBBMI1/PLCBMI1 cells as compared to their control cells (Fig. 4c, d).