Knockout of IGFBP2 delays leukemia development in the AML1-ETO AML model upon serial transplantation. (A) Mice transplanted with AML1-ETO-infected wild-type hematopoietic progenitors had significantly reduced survival upon secondary transplantation compared to that of mice transplanted with IGFBP2-null cells (n = 11; p < 0.01). (B) IGFBP2-null AML mice had significantly fewer leukemic GFP+ cells in peripheral blood compared to mice transplanted with wild-type cells at 3 weeks after secondary transplantation (n = 11; * p <0.05). (C) Percentages of progenitors and differentiated cells in the control and IGFBP2- null leukemic GFP+ compartments of peripheral blood at 3 weeks after secondary transplantation (n = 10). (D) Comparison of the sizes of spleens and livers of the mice transplanted with wild-type and IGFBP2-null AML1-ETO9a cells at 1 month after secondary transplantation (* p < 0.05). (E) Histological hematoxylin/eosin staining of AML infiltration in the livers and spleens of mice secondarily transplanted with control or IGFBP2-null AML1-ETO9a cells. (F) Representative Wright-Giemsa staining of peripheral blood and bone marrow AML cells from leukemic mice after secondary transplantation. (G) Phosphorylation of AKT and STAT3 decreased in IGFBP2-null AML BM cells compared with levels in the control cells. (H) IGFBP2-null AML1-ETO9a BM cells from secondarily transplanted mice had dramatically decreased CFU forming ability, including decreased colony number and size, relative to wild-type AML1-ETO9a BM cells (n = 6; * p < 0.05). (I) IGFBP2-null AML1-ETO9a BM cells showed increased apoptosis relative to control cells (n = 6; * p < 0.05). (J) AML cells from IGFBP2-null BM showed higher levels of PTEN expression than those from control mice both in primary and secondary transplantation. (K) A PTEN inhibitor increased the CFU activity of IGFBP2-null AML cells (n = 3; * p < 0.05).