Inhibition of lung metastasis of osteosarcoma cell line POS-1 transplanted into mice by thigh ligation

Using a model with external ligation of the thigh, the effect of ischemia-reperfusion injury on tumor growth and the activity of lung metastasis was investigated in mice inoculated a spontaneous murine osteosarcoma cell line (POS-1) in vivo. POS-1 cell suspension was inoculated into the right hind footpad of 70 mice. Four weeks after inoculation, the ipsilateral thigh was ligated for 3 h in 15 mice and the contralateral thigh in 15 mice. Another ten mice were inoculated with POS-1 without ligating the thigh. The number of metastatic foci on the lung surface 6 weeks after inoculation was 2.29±0.98 (mean±SE) foci/lungs in mice with ipsilateral ligation and 6.25±2.41 in mice with contralateral ligation, which were significantly lower than control (13.40±1.42 in mice no ligation) (P<0.01). The number of metastatic foci on the lung surface in mice with intraperitoneal injection of superoxide dismutase (SOD) and catalase was 3.25±0.65 (mean±SE) foci/lungs in mice with ligation which was significantly greater than that in mice without SOD and catalase injection 1.29±0.97 (P=0.04). iability was 9.12±4.07% with 100 μM H2O2 in 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. It revealed that at concentrations of 100 μM H2O2 or higher was cytotoxic to POS-1. In cell invasion assay, the number of invading cells with 10 μM H2O2 was 2.80±0.53 cells/field, which was significantly lower than control (5.93±0.18) (mean±SE), indicating that low-dose H2O2 suppressed invasion of POS-1. These results suggested that reperfusion injury had selective cytotoxicity to POS-1 through producing reactive oxygen species. Activated oxygen was considered to inhibit the regional growth and the ability of lung metastasis of POS-1 cells.