Chen et al. [66] found that, without influencing the expression of the p53 mRNA and protein, HIF-1α knockdown dramatically reduced the expression of the p21 mRNA and protein in CML cells, indicating that HIF-1α can control the proliferation of CML cells by controlling the expression of p21. This evidence concerns the gene HIF1A and chronic myelogenous leukemia, BCR-ABL1 positive.