An orthotopic model of human osteosarcoma using two isogenic cell lines differing in their ability to form spontaneous pulmonary metastasis

3891 Osteosarcoma (OSA) is the second leading cause of cancer-related death in children. The five year survival is 50-65%. Greater than 30% of patients develop lung metastases despite aggressive chemotherapy and surgery. In order to develop more effective therapies, an OSA model is needed that closely follows the biology of metastasis and clinical progression of this disease in humans. Ideally, this should be done without mutagenizing the tumor cells to ensure the relevance of the model to the disease in vivo. Here we describe a model that utilizes orthotopic injection of two isogenic human OSA cell lines differing in their ability to form spontaneous pulmonary metastasis, the parental OS187-luc and derivative 82L. OS187-luc was engineered to express luciferase to allow bioluminescent imaging to follow the progression of primary tumor growth and development of pulmonary metastases. Five hundred thousand OS187-luc cells were injected into the tibias of nude mice. Pulmonary nodules were isolated approximately two months later, disassociated into cell suspensions, then re-injected into nude mice intratibially. This was repeated for four cycles, and finally the pulmonary metastases were established and expanded in culture to produce the 82L cell line. Visible pulmonary nodules were present when using 82L at 3-4 weeks compared to 8-10 weeks using OS187-luc. Significantly more pulmonary nodules were present in lungs from mice injected with 82L compared to OS187. We have developed a more aggressive OSA cell line that mimics the clinical biology of human OS. This model has application in preclinical studies to determine the effectiveness of new therapeutic strategies against both primary and metastatic OSA.