SOX7 expression reduced the repopulating potential of K562 and THP-1 cells and primary CD33⁺CD34⁺ AML samples in immunodeficient NOD/SCID mice. (A) A representative of the myeloid sarcomas detected in 3 of 7 mice transplanted with K562 cells (left). The excised tumor shows GFP positivity (middle). The GFP intensity in the sarcoma was detected by flow cytometry (right). (B) K562 cells engrafted in mouse BM were enumerated by flow cytometry as mouse CD45.1⁻/ GFP⁺ population (left, circled) and completely abolished by SOX7 expression (right; n = 3 separate experiments based on a total of 7 and 8 mice transplanted with GFP and GFP-SOX7 transduced cells, respectively). (C) A summary of GFP⁺ population in 3 sets of the experiment in panel B. SOX7 expression completely abolished the repopulating potential of K562 in mice. (D) SOX7 overexpression in THP-1 cells completely abolished engraftment in mouse BM, whereas SOX7Δ expression had no significant effect. (E) (i) Mice transplanted with untransduced, GFP-expressing, and SOX7Δ-expressing THP-1 cells resulted in leukemic deposits in liver, whereas in those with SOX7 overexpression, leukemia deposition was significantly less. (ii) Individual data on liver weights are shown. Mice were euthanized at 6 to 8 weeks. (F) Six CD33⁺CD34⁺ AML samples from 4 patients were lentivirally transduced with GFP or GFP-SOX7 and transplanted into irradiated NOD/SCID mice with equal cell doses. BM was aspirated at 6 and 9 weeks and harvested 12 weeks after transplantation. SOX7 expression nearly abolished leukemia engraftment. (G) Mouse BM cells stained by PC5-conjugated human CD45 antibody and subjected to flow cytometry show correlation between GFP and CD45 expression. In all xenotransplantation studies, successful leukemia engraftment was defined by the presence of GFP⁺, human CD45⁺, and murine CD45.1⁻ cells in the recipient BM enumerated by flow cytometry. h, human.