Runx1 is required for Cbfb-MYH11–induced leukemia. (A) Mice of the indicated genotype were treated with pIpC to induce the expression of Cbfb-MYH11 and/or Runx1 deficiency, and leukemia development in these mice was monitored for 1 year. Kaplan-Meier survival curves of these mice are shown. (B-D) Mice of the indicated genotypes were treated with pIpC and then killed 4 months after the last dose of pIpC for analysis. (B) Representative fluorescence-activated cell sorting (FACS) plots of c-Kit⁺ and Mac1⁺ cells in the peripheral blood of these mice. (C) Representative Wright-Giemsa–stained peripheral blood smears from these mice. (D) Representative hematoxylin and eosin–stained spleen sections (i, 50×; ii, 400×) from these mice. (E) Kaplan-Meier survival curves of recipient mice (3-5 per donor mouse) after noncompetitive transplantation assay. *P < .05 and **P < .01, each comparing the Runx1^f/fMx1-CreCbfb^+/56M group with the Mx1-CreCbfb^+/56M group.