Henry Ford Hospital Medical Journal


A radiolabeled anticalcitonin monoclonal antibody (MoAb) was testedfor tumor-localizing capability in WAG/Rij rats allografted with cultured medullary thyroid carcinoma cells (line 44-2). 131I-labeled anticalcitonin IgG was taken up by the tumors in a time-dependent and dose-dependent manner. Tumor tissue uptake of the injected MoAb was 0.7 to 1.3%/g of tumor tissue when tested with a dose range of 40 lo 250 μg/kg of body weight. Distribution ratios of the radiolabeled MoAb were 1.2:1 for tumor-to-blood and 2-20:1 for tumor-to-organs. In rats injected with control IgG, disiribution ratios of radioactivity were 0.4:1 for tumor-to-blood, and 0.6-2:1 for tumor-to-organs. These results suggested a specific uptake of MoAb by the tumor. Some nonspecific uptake was seen by the visceral organs. This may represent the metabolic clearance of MoAb. presence of cross-reacting antigens, or metastasis of tumor to these organs.