Fast progression to AML in mice transplanted with Smad4^−/− primitive hematopoietic cells. (A) Twenty-two weeks after the transplantation with HOXA9-transduced HSPCs, a total reconstitution of LK (c-Kit⁺ Sca-1⁻) progenitors, which largely consists of granulocyte-monocyte progenitors (GMP; CD34⁺ FcγR⁺) indicates transformation of myeloid progenitors in the BM of 75% of mice in the Smad4^−/− group (n = 8 mice each). The transformation is moreover accompanied by a dominant reconstitution of donor Ly5.1⁻ cells in the BM. (B) Kaplan-Meier plot of recipient survival more than time (Mig, n = 6 mice; HOXA9, n = 10 mice; and NUP98-HOXA9, n = 10 mice; P value measured by Mantel Haenszel logrank test). (C) Development of the WBC count more than time in peripheral blood after transplantation with Wt (blue) or Smad4^−/− (red) HSPCs, transduced with NUP98-HOXA9 (n = 10 mice). During the chronic phase, only the total WBC level is affected, whereas other constituents of peripheral blood, red blood cells (RBCs), hematocrit (HCT), and hemoglobin (HGB) remain constant more than time (n = 10 mice). (D) Loss of Smad4 increases the LIC frequency in mice. The Kaplan-Meier plot displays survival over time of secondary recipient mice transplanted with HOXA9- or NUP98-HOXA9–leukemic Smad4^−/− and Wt cells (n = 12 mice for each group; P value measured by Mantel Haenszel logrank test; leukemic cells were isolated from moribund mice to analyze LIC frequencies at the same stage of the disease). (E) Quantification of transplanted leukemic cells needed to generate leukemia in 50% of the secondary recipients. The percentage of LICs in the population of leukemic cells is calculated as 1 LIC per total number of cells injected to induce lethality in 50% of the recipients (n = 7 mice for each group; full and empty circles represent 2 independent clones tested).