CTSB and cancer: To determine the role of CTSB in BMI1 mediated cancer cell properties, we genetically modified CTSB expression in WBBMI1/PLCBMI and BMI1 depleted MHCC97H cells (Supplementary Fig. 5a–c), indicating that neither CTSB depletion/overexpression affected the proliferation and colony formation in these cells (Supplementary Fig. 5d–i).