The development of AML in mice transplanted with Egr1 and Apc haploinsufficient BM transduced with Tp53 shRNA. C57BL/6 recipient mice were transplanted with Egr1^+/−, Apc^del/+ BM transduced with Tp53 shRNA, or Luc shRNA, as a control. Two of 12 recipient mice harboring Tp53 knockdown (green fluorescent protein-positive [GFP⁺]) cells, 1586 and 4525, developed AML. (A) Representative peripheral blood smears (×400), BM smears (×400), and liver section (×100) stained with hematoxylin and eosin, and spleen section (×500) immunostained with myeloperoxidase-specific antibodies are shown. Leukemic cells stain positive (pink) and lymphocytes and megakaryocytes are devoid of stain and are myeloperoxidase-negative. Images were obtained using a Zeiss Axioskop (Jena, Germany), equipped with a Zeiss Axiocam digital camera. Myeloperoxidase immunostained spleen images were obtained using an Olympus microscope (Model BX51, Tokyo, Japan) equipped with an Optromics 3CCD digital camera (Goleta, CA). Images were processed with Adobe Photoshop (San Jose, CA). (B) Flow cytometric analysis of GFP-gated spleen cells from mouse 1586 and 4525. Histograms show the expression of KIT, Gr-1, CD11b, and F4/80 in GFP-gated spleen cells from experimental leukemic (blue) and control (red) mice. (C) The percent of GFP-positive cells in the blood of mouse 1586 and 4525. The final time point is the day of euthansia. (D) The percentages of GFP-positive cells in the BM and spleen of mouse were 1586 and 4525, respectively, at the time of euthanasia. (E) Real-time polymerase chain reaction (PCR), done in triplicate, was used to assess Tp53 expression in GFP-gated BM cells before transplantation and in spleen cells from mouse 1586 and 4525, respectively. Expression was normalized to glyceraldehyde-3-phosphate dehydrogenase and expressed relative to the control, with the standard error of the mean.