A virally induced osteosarcoma in rats. A model for immunological studies of human osteosarcoma.

Inoculation of Moloney sarcoma virus into the medullary canal of the tibia in newborn Wistar-Lewis rats resulted in an initially localized osteosarcoma which usually metastasized to the lung and resulted in the death of the animal within four to five weeks. Tumor cells were grown in tissue culture and used as target cells in the assay of lymphocyte-mediated cytotoxicity using a microcytotoxicity and a radioisotope labeling method. Lymphocyte-mediated cytotoxicity was demonstrated throughout the course of the clinical disease as well as in a small number of animals which showed spontaneous regression of their tumors. Serum factors which could "block" or augment the cellular response were also identified. This model resembles the spontaneous osteosarcoma of humans in many respects and may be useful for studies of the human disease.