Production of a monoclonal antibody against a human osteosarcoma xenograft.

Monoclonal antibodies (MAbs) against a human sarcoma xenograft carried in BALB/c nu/nu mice were produced by immunizing BALB/c mice with tumor cells and fusing their spleens with the SP2/O-Ag 14 mouse myeloma cell line. Hybridoma supernatants were screened using cryostat tissue sections and an immunoperoxidase reaction for ability to stain osteosarcoma xenograft tumor cells but not tonsil lymphocytes. Of 73 supernatants tested, 19 reacted with both osteosarcoma tumor cells and lymphocytes, while three reacted only with osteosarcoma. One of the latter hybridomas was cloned by limiting dilution to establish a line producing an IgG1 MAb (OS-1). By immunoperoxidase, this MAb stained tumor cells in surgical biopsies of primary (6 of 7) and metastatic (1) osteosarcomas and showed limited cross-reactivity with other tumors. It also cross-reacted with some basement membranes, endothelium and muscular media of blood vessels, and smooth muscle, but not with parenchymal cells of various normal tissues. This MAb may prove useful for the immunohistochemical confirmation of a diagnosis of osteosarcoma in surgical pathology.