Interestingly, hypermethylation-mediated inactivation of HoxA4 and HoxA5 was found in 34% of CD34+ cells from patients with chronic phase CML whereas it was observed in up to 90% of patients with CD34+ CML in blast crisis (Strathdee et al., 2007). This evidence concerns the gene HOXA4 and chronic myelogenous leukemia, BCR-ABL1 positive.