Postmortem immunohistochemical examination of mouse tissues confirms eradication of MV4-11 cells in mice cotreated with Gem and VX-970. (A) Bone marrow (from injected femur), liver, and other tumors (as indicated) were stained with hematoxylin and eosin (large images), human CD33 (insets), human CD45 (not shown), and human Ki67 (not shown). Images are from a representative mouse in each treatment arm (for vehicle treated, VX-970 monotherapy, and Gem monotherapy) using tissues taken at the point of death (specified humane end point) to confirm the presence of human AML cells. For the VX-970 and Gem cotreatment arm (including localized and disseminated [delayed treatment] AML), disease-free mice are shown, confirming normal morphology and eradication of leukemic cells. (B) Hematoxylin and eosin staining of bone marrow from a nonengrafted mouse after treatment with 60 mg/kg VX-970 for 5 consecutive days. Scale bars represent 10 µm.