Murine osteosarcoma cell line; derived by intra-osseous injection of the K7 murine osteosarcoma cell line to the proximal tibia of a BALB/c mouse. The resultant primary tumor spontaneously metastasized to the lungs. A pulmonary metastasis was removed from the lung and then surgically implanted to a paraosteal tibial muscle flap of a naïve mouse. This cycle of implantation of pulmonary metastasis to paraosteal tibial muscle flap sites was repeated, resulting in the K7M2 primary tumor. This tumor was dissociated to a single cell suspension to create the K7M2 wt cell line.