Regarding previous reports on the influence of altered expression of PU.1 on erythroleukemia    10  and myeloid leukemia   11 , we aimed to clarify whether the PU.1 gene expression modification affects B-and T-cell lymphopoiesis and involves in acute lymphoblastic leukemia (ALL) malignancy. The gene discussed is SPI1; the disease is myeloid leukemia.