MEIS1 and leukemia: Flow cytometric immunophenotyping of the leukemias arisen in two sets of mice transplanted with WT or Prep1i/i Meis1-HoxA9-transduced cells, demonstrated that they all were donor-derived as about 90% of the cells expressed GFP (Figure 2A) and displayed Mac-1 and Gr-1 myeloid cell surface antigens (Figure 2B).