Down-regulation of BMI1 expression in CB or AML CD34⁺ cells results in derepression of p14ARF and p16INK4a. CB or AML CD34⁺ cells were transduced with scrambled RNAi or BMI1-RNAi lentiviral vectors and sorted, and RNA was isolated. Quantitative RT-PCRs were performed to determine the expression levels of BMI1, p14ARF, and p16INK4a. As a control, BMI1 was overexpressed in CB CD34⁺ cells, and quantitative RT-PCR analysis was performed (right panels).