Figure 4.
Effect of single chain IL-12-producing NXS2 cells on established neuroblastoma metastases. Syngeneic A/J mice (n = 8) injected i.v. with 5 × 104 NXS2 cells received s.c. injections with intermediate and high scIL-12-producing NXS2 cell clones 5 days later. Developing s.c. tumors were surgically removed 14 days after s.c. inoculation. Twenty-six days after i.v. inoculation, mice were sacrificed and analyzed for liver (A) and bone marrow metastases (B). Horizontal lines represent the median for each experimental group. (A) Liver metastases were scored after s.c. injection with 4 × 106 intermediate (▾) and 10 × 106 high (▴) scIL-12-producing NXS2 cells according to the percent liver surface covered with metastatic lesions. 4 = >75%; 3 = 50–75%; 2 = 25–50%; 1= >0–25%; 0 = 0%. Results were compared with those of mice receiving either no s.c. injection (▪) or injection with 10 × 106 NXS2 cells carrying only the empty vector (•). Differences between all experimental and control groups were statistically significant (P < 0.001). (B) Bone marrow metastases were analyzed by tyrosine hydroxylase RT-PCR and scored, as described in Materials and Methods, after s.c. injection of 4 × 106 intermediate (▾) or 10 × 106 high (▴) scIL-12-producing NXS2 cells and compared with control animals receiving either no s.c. injection (▪) or injection with 10 × 106 NXS2 cells carrying only the empty vector (•). Differences between results with 10 × 106 high scIL-12-producing NXS2 cells and all control groups were statistically significant (P < 0.05).