Tumorigenicity of vIL-6–expressing NIH3T3 cells in nude mice. Cells were injected subcutaneously into the right flanks of 6-week-old female BALB/c nu/nu mice (5 × 105 cells in 100 μL PBS per animal). Five mice were used in each group. (A) Representative mice 4 weeks after injections with v6O (upper), v6H (middle), or BN7 (lower) cells. (B) Tumor growth curves during 4 weeks observation: v6O (○), v6H (□), and BN7 (•). Values reflect the mean (±SD) of tumor size. Time to tumor formation was 5 to 7 days in v6O cells, 5 to 6 days in v6H cells, and 25 to 29 days in BN7 cells, respectively. Data are representative of two independent experiments. (C) Representative microscopic appearance of v6O- and v6H-derived tumor tissues. Abundance of blood vessels in a selected area of tumor tissue is shown (hematoxylin-eosin; original magnification × 100). (D) Immunohistochemical staining of vIL-6 in the tumor tissue from v6O cells (original magnification × 400). (E) vIL-6 detection in sera (0.1 μL) from mice injected with BN7 (lanes 2 and 3), v6O (lanes 4 and 5), and v6H (lanes 6 and 7) cells by Western blotting. Whole cell lysate of v6O cells was used as a positive control (lane 1).
