In contrast, depletion of CTSB by siRNA or an CTSB inhibitor CA-074 reduced the invasion ability of WBBMI1 and PLCBMI1 cells as compared to non-silencing control siRNA (siNSC) transfected/placebo treated cells (Fig. 5a–d), while overexpression of CTSB in BMI1 depleted MHCC97H cells enhanced cancer cell invasion when compared with control cells (Supplementary Fig. 5j). Here, BMI1 is linked to cancer.