For example, Bmi1 was found to be necessary for the self-renewal of normal hematopoietic stem cells as well as leukemic stem and progenitor cells.20, 21, 22Bmi1 has also been shown to regulate the self-renewal and proliferation of CSCs from other tumor types, such as prostate cancer and pancreatic cancer.9, 23 Chiba et al.16 reported that knockdown of Bmi1 markedly decreased side population fractions in HCC cell lines. This evidence concerns the gene BMI1 and hepatocellular carcinoma.