Radioimmunodetection of human melanoma tumor xenografts with human monoclonal antibodies.

We established a human IgM monoclonal antibody that defines a tumor-associated membrane antigen expressed on human melanoma cells. The antigen has been identified as the ganglioside GD2. In this paper, we describe the potential usefulness of the human monoclonal antibody for radioimaging. Nude mice bearing tumors derived from a human melanoma cell line were used as a model. Antibody activity was degradated significantly after labeling with 131I by the use of a modified chloramine-T method. After testing various concentrations, labeled antibody of a specific activity of 2.8 microCi/micrograms produced the best results. Balb/c nude mice bearing a GD2-positive M14 melanoma cell line were injected with 10-30 micrograms of labeled antibody, and its radiolocalization in different organs and in the whole body were evaluated. The best tumor image was obtained on Day 6. The labeled antibody uptake ratio between tumor and muscle was 9.2:1; the ratio between tumor and liver was 1.4:1. These studies represent the first report of experimental tumor imaging with human monoclonal antibody. Human monoclonals with probably prove to be superior reagents for tumor imaging in melanoma patients if the problem of antibody radiolysis is resolved.