Human IgM monoclonal anti-GD2 antibody: reactivity to a human melanoma xenograft

The cell membranes of human melanoma express a tumor-associated ganglioside, GD2. We previously established a human melanoma cell line, M14-A, that metastasizes to the lung, liver, skin, lymph nodes, and abdominal organs of nude mice in addition to forming ascites and pleural effusions. We also reported the successful in vitro production of human IgM monoclonal antibody to GD2. In the present study, we evaluated the GD2 expression of human melanoma cells at the primary and metastatic sites and their reactivity to human monoclonal anti-GD2 antibody in vivo. GD2 was expressed strongly on the melanoma cells from both primary and metastatic sites, except for cells from pleural effusions and ascites. When M14-A-bearing nude mice received systemic injections of the human monoclonal antibody, the anti-GD2 titer in the sera was reduced markedly at 2 hours, whereas the reduction was minimal in sera from tumor-free mice and mice bearing GD2-negative human M24 cells. The immune adherence test confirmed that antibody was fixed on cells of primary subcutaneous M14-A tumors and on their metastases to liver, lung, abdominal organs and skin. These results suggest that this large molecule protein can penetrate the blood-tumor barrier and bind immunologically to antigen-positive melanoma cells in vivo.