Predictive value of serum immunosuppressive acidic protein for lung metastasis after amputation of murine osteosarcoma of the lower limb

A spontaneously occurring murine osteosarcoma cell line (POS-1) was inoculated into the footpads of 88 mice. In 59 mice, the tumor-bearing leg was amputated at 1, 3, 5, or 7 weeks after inoculation and the mice sacrificed at 9 weeks. Lung metastasis was observed in 82.6–100% of the mice undergoing leg amputation at 5 or 7 weeks after inoculation. There were no lung metastasis in the mice amputated at 1 or 3 weeks. The serum immunosuppressive acidic protein (IAP) concentration showed a significant increase at 5 or 7 weeks after inoculation (P<0.005 and P<0.0005, respectively). When amputation was done 5 weeks after inoculation, the serum IAP concentration increased further to 5.9 times the pre-amputation level 1 week after the amputation. The IAP concentration increased only 1.3-fold in the control group without inoculation. Thus, a high serum IAP concentration before amputation and a further increase after amputation were indicators of lung metastasis in this mouse model of osteosarcoma.