MEIS1 and acute lymphoblastic leukemia: We observed high levels of MEIS1 mRNA in leukemia-derived cell lines and also in the blood samples of patients with ALL; our results are in agreement with observations that lower levels of MEIS1 are unfavorable for cell life, because MEIS1 down-regulation has been related with decreased proliferation and poor survival of neuroblastoma and leukemia cell lines [24,25].