The phenotype of HOX-induced leukemia is governed by the homeodomain. (A) Surface immunophenotype of cells cotransduced with Meis1 and HOX or a HOX swap as indicated. Staining was done for the stem cell and precursor cell marker c-Kit (CD117-PE) and for Gr-1 (Gr1-FITC) a protein associated with myeloid differentiation. (B) Kaplan-Meier survival blot of recipient animals transplanted with the cells characterized in panel A. Irradiated recipients received the graft at day 0. Animals were killed according to institutional regulations at first signs of overt disease. The experiment was terminated after 120 days, with 1 animal of the HOXA1 and HOXA9/1 cohorts still surviving. n = number of animals per group. (C) Spleen weight of leukemic animals. Individual data points and average values are given. P values were calculated for a Student t distribution. (D) Representative example of leukemia cell immunophenotypes. Transformed cells were regrown from the spleen of diseased animals and analyzed by FACS for c-Kit and Gr-1 markers. (E) Quantitative RT-PCR of HOX-sentinel genes in leukemia samples. RNA was isolated from the explanted cell lines, and HOX-specific gene expression was examined by quantitative RT-PCR. Each bar represents an individual cell line. Data are mean ± SD of triplicate PCR experiments.