Swarm rat chondrosarcoma cells as an in vivo model: lung colonization and effects of tissue environment on tumor growth.

Swarm rat chondrosarcoma cells have been used extensively for biochemical studies of extra-cellular matrix metabolism in cartilage. However, these cells also possess tumor-like behavior in vivo and are useful in investigation of chondrosarcoma biology. the current study was designed to develop a metastatic model using swarm rat chondrosarcoma cells, and to assess the effect of tissue-environment on tumor behavior in vivo. Tumors were implanted subcutaneously or into bone, and animals were assessed radiographically and microscopically for tumor growth and metastasis. The subcutaneous tumor grew to an average mass of 35 g, while tumor implanted into bone grew 75 mg. Transplantation of the cells into the bone led to extensive bone remodeling with invasion of the medullary cavity and destruction of the bone cortex. Light microscopy demonstrated no significant differences in the number of mitoses, cellular atypia or extracellular matrix staining between the two sites of tumor implantation. Interestingly, lung colonization was observed in none of the animals in the subcutaneous tumor injection group, while tumors colonized the lungs in 95% of the rats with tumor injected into bone. Analysis of cDNA libraries from subcutaneous and bone-transplanted tumors demonstrated a complex and diverse array of expressed transcripts, and there were significant differences in gene expression between tumors at different sites. The results of this study suggest swarm rat chondrosarcoma is a model that resembles human chondrosarcoma mimicking its ability to infiltrate and remodel local bone and to colonize the lungs. Furthermore, the interaction between host-tissue and tumor cells plays a major role in the tumor behavior in this model. Identifying these interactions will lead to further understanding of chondrosarcoma and contribute to therapeutic targets in the future.