In vivo leukemogenic potential of TEL-FGFR3–transfected Ba/F3 cells. (A) Kaplan-Meier survival curves of BALB/c mice that had been injected with clonal populations of TF-V5– (▪), mock- (□), or ΔHLH-TF-V5–transfected Ba/F3 cells (▴). (Bi) Macroscopic view of the abdominal organs of a mouse that had been injected with TF-V5–transfected Ba/F3 cells. The terminally sick mouse was humanely killed 8 weeks after injection; Li indicates liver; Sp, spleen. (ii) Whole spleen specimens isolated from a mouse that had been injected with TF-V5–transfected Ba/F3 cells (right) and a mouse that had been injected with mock-transfected Ba/F3 cells (left). The mice were humanely killed 8 weeks after injection. Scale is in centimeters. (C) RT-PCR for TEL-FGFR3 using RNA that had been extracted from the spleens of mice injected with TF-V5–transfected Ba/F3 cells or mock-transfected Ba/F3 cells. RT-PCR for β-actin was performed as a positive control. (D) Histopathology of the spleen of a mouse that had been injected with TF-V5–transfected Ba/F3 cells. The same paraffin sections are shown. Photographs are taken on a light microscope (BHT-321; Olympus, Tokyo, Japan) with an Olympus NC SPlan 100×/1.40 dry objective lens (Olympus). (i) Hematoxylin and eosin staining. Infiltration of a massive number of leukemia cells is observed. (ii) Staining with anti-V5 antibody. Infiltration of leukemia cells is observed. Normal residual lesions in the spleen were not stained. Similar results were obtained in 3 experiments using 3 independent monoclonal transfectants.