Histopathology after CYT387 treatment of JAK2-dependent malignancy in vivo. Balb/c mice were subjected to bone marrow transplantation with bone marrow donor cells retrovirally transduced to express JAK2^V617F. Thirty-four days after transplantation, mice exhibited symptoms of MPN as measured by elevated white blood cell counts and hematocrit. Mice were divided into 3 groups and initiated on twice daily oral gavage administration of vehicle control, 25 mg/kg CYT387, or 50 mg/kg CYT387 (n = 12 per group). At day 83 after bone marrow transplantation, all mice were killed and representative histologic sections are shown from: (A) peripheral blood stained for reticulocytes, (B) spleen stained with H&E, (C) liver (H&E), (D) bone marrow (H&E), and (E) bone marrow (reticulin stain). The left column represents 0 mg/kg CYT387, the middle column represents 25 mg/kg CYT387, and the right column represents 50 mg/kg CYT387. Magnification is ×10 or ×40 for insets.