A, BMI-1 protein levels in various cells were measured by western blotting analysis, including human breast cancer cells MDA-MB-231, lung cancer cells A549, ovarian cancer cells ES2, liver cancer cells HepG2, prostate cancer cells PC3 and DU145, colorectal cancer cells HT29 and HCT116, as well as human normal liver cell L02, human skin fibroblast cell HAF, human normal colon epithelium cell NCM460 and human umbilical vein endothelial cell HUVEC. Here, BMI1 is linked to ovarian cancer.