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.