Radioimaging of malignant melanoma xenografts in nude mice using 111In-labeled monoclonal antibody against human malignant melanoma

By using ¹¹¹In-labeled monoclonal antibody (ZME-018) against human malignant melanoma, we examined its usefulness in radioimmunodetection of human melanoma xenografts in nude mice. Two human malignant melanoma cell lines were used in this study, KHm-1/4; and KHm-3/ps. KHm-1/4 cells express melanoma-associated antigen which is reactive with ZME-018, whereas KHm-3/ps cells do not. ZME-018 was conjugated with DTPA (diethylene triamine pentaacetic acid) first; then the conjugate was labeled with ¹¹¹In. After these procedures, labeled ZME-018 retained its binding activity against KHm-1/4 cells in vitro. Nude mice, bearing melenoma xenografts started from injections into the right hind legs, were i.p. or i.v. injected with ∽300 μCi (60 μg) of labeled ZME-018. Tumor images were taken with gamma camera at 24 hr intervals. Clear tumor images were obtained by 24 hrs after injection. The best imaging was obtained at 72 hrs with no background of internal organs. Specific localization was confirmed by the absence of imaging in the mice which received free ¹¹¹In only and also by using control mice bearing antigen-negative melanoma cells (KHm-3/PS). An example of tissue distribution of the labeled antibody in terms of tumor to tissue ratio at day 3 is as follows: tumor/intestine; 20/1, tumor/liver; 10/1, tumor/blood; 8/1, tumor/muscle; 8/1, tumor/heart; 3/1, tumor/kidney; 2/1. This study demonstrates the future applicability of ¹¹¹In-labeled monoclonal anti-melanoma antibody for radioimmunodetection of metastatic lesions in melanoma patients.