Effect of interferon administration on pulmonary osteogenic sarcomas in an experimental murine model.

The iv inoculation of a suspension of osteogenic sarcoma cells induced metastatic tumor nodules in the lungs of C57BL/6 mice. The administration of 50,000-100,000 U of interferon daily for 7 days strikingly reduced the tumor mass in the lung and the number of tumor nodules present in histopathologic sections when the interferon treatment was initiated immediately after tumor cell inoculation. In some animals the development of any detectable metastatic lesion was completely prevented. Extending the therapy form 7 days to 21 days failed to improve the protective effect. Interferon therapy delayed until 7 days after tumor cell inoculation had no effect. These findings indicate the effectiveness of exogenous interferon in this murine osteogenic sarcoma model when interferon treatment is initiated within 1 hour of tumor cell inoculation, but not when it is delayed until tumor nodules are established in the lungs.