A laboratory model for the study of the immunobiology of osteosarcoma.

Inoculation of Moloney sarcoma virus into the marrow cavity of the tibia of newborn Wistar-Lewis rats resulted in the appearance of an initially localized osteosarcoma in 97.7% of these animals. At least 77.9% of the rats developed lung metastases and died, usually within 6 weeks of inoculation. The remaining 22.1% showed regression of disease after initial growth of the tumor. Tumor cells were maintained in tissue culture and used as target cells for a visual and isotopic (3H-thymidine or 125IUdR) microcytotoxicity assay. Cell-mediated immunity could be measured by these methods throughout the course of the illness in animals with progressive disease as well as in those whose tumors eventually regressed. The presence of serum factors capable of modifying the level of CMI was documented. This Moloney-sarcoma-virus-induced rat osteosarcoma and human osteosarcoma thus appear to have several basic pathologic and immunologic similarities. The model may be useful for studying the effects of a variety of treatment protocols upon the clinical course and immune response to osteosarcoma.