Anti-tumor effects of radiolabeled syngeneic monoclonal anti-melanoma antibodies.

The effect of 131I-labeled syngeneic mouse monoclonal anti-melanoma antibodies on tumor growth in vivo were investigated. The injection of unlabeled antibody had little effect on tumor growth, whereas the anti-tumor activity was considerably increased when the antibody was conjugated with 131I and also when a mixture of two different radiolabeled monoclonal antibodies with distinct specificities was used. The anti-tumor effects of the radiolabeled antibody were transient but significant under the present experimental conditions: melanoma growth was completely inhibited for about 10 days or more after the antibody treatment, but resumed thereafter. Possible mechanisms of escape of the tumor from the therapy with radiolabeled monoclonal anti-tumor antibody are discussed.