To further identify the role of Bmi-1 in the progression of cancer, a short hairpin RNA for Bmi-1 was generated to reduce Bmi-1 expression stably and efficiently in the MDA-MB-435S cell line (Figure 5A), a highly metastatic breast cancer cell line [48] with high Bmi-1 expression (Figure 5A). Here, BMI1 is linked to breast carcinoma.