Distribution of ¹¹¹In and ¹²⁵I Labeled Monoclonal Antibody 17-1A in Human Pancreatic Carcinoma HuP-T 4 Bearing Mice

Abstract

The potential of monoclonal antibody 17-1A (MoAb 17-1A) , which binds preferentially to a tumor cell surface glycoprotein moiety, was investigated for the detection and therapy of pancreatic carcinomas. Immunoreactivity of MoAb 17-1A with human pancreatic carcinoma cell line HuP-T4 was confirmed histochemically by the avidin-biotinylated enzyme complex method. The biodistribution of¹¹¹In-and ¹²⁵I-labeled MoAb 17-1A was examined at 24, 48, and 72 h in nude mice bearing HuP-T4 xenografts. MoAb 17-1A was labeled with ¹²⁵I using the Iodogen method, giving a labeling efficiency of 92.5% and a specific activity of 6.0 MBq/mg. MoAb 17-1A was also labeled with ¹¹¹In using a chelating agent of either diethylene-triaminepentaacetic anhydride (DTPA anhy) or 1- (p-benzyldiazonium) DTPA (DTPA azo) . The labeling efficiencies were 77.6% for DTPA anhy and 82.3% for DTPA azo, and specific activities were 2.9 MBq/mg and 3.0 MBq/mg, respectively. Significant higher tumor uptake was observed at 72 h after I. V. injection of ¹²⁵I-labeled MoAb 17-1A compared with that of¹²⁵I-labeled nonspecific mouse IgG.¹²⁵I-Labeled MoAb 17-IA showed a higher localization in the tumor than in any other tissues except the blood and the lung. Furthermore in the experiment of¹¹¹In-labeled MoAb 17-1A, a much higher accumulation in the tumor and a lower blood level were achieved as compared with those of¹²⁵I-labeled MoAb 17-1A, resulting in a better tumor to blood ratio. These results suggest that MoAb 17-1A may be applicable to the radioimmunodetection and radioimmunotherapy of pancreatic carcinomas.