Radioimmunoimaging with mixed monoclonal antibodies of nude mice bearing human lung adenocarcinoma xenografts.

The present study was conducted to evaluate radioimmunoimaging (RII) and in vivo distribution of mixed antibodies Tc-99m-EGFR-mAb and Tc-99m-CD44-mAb in nude mice bearing human lung adenocarcinoma xenografts. Single and mixed applications of the two radiolabeled monoclonal antibodies (mAbs) were compared. Direct labeling of Tc-99m was applied to radiolabel the EGFR and CD44 mAbs. The properties of the radiolabeled antibodies were then characterized. RII and assessment of the distribution of the antibodies in nude mice bearing lung adenocarcinoma xenografts were achieved by applying separate and combined doses of Tc-99m-EGFR-mAb and Tc-99m-CD44-mAb. The labeling rates of Tc-99m for EGFR-mAb and CD44-mAb were 91.5% +/- 3.8% and 92.3% +/- 4.1% respectively, with specific activities of 2.8 and 2.9 MBq/mu g, respectively, and radiochemical purities (RCP) of 96.5% and 96.2%. The radioactivity uptake of the combined application of both radiolabeled antibodies was clearly higher than with a single application of either alone. The relative values of target-to-nontarget (T/NT) measured through the regional interest (ROI) technique were 5.59 +/- 0.42 (mixed antibodies), 2.78 +/- 0.20 (Tc-99m-EGFR-mAb), and 2.28 +/- 0.16 (Tc-99m-CD44-mAb) in the RII. The body distribution of the radiolabeled antibodies and their imaging results were basically identical. Application of the mixed antibodies with Tc-99m-EGFR-mAb and Tc-99m-CD44-mAb can increase the radioactivity uptake of tumor tissue, leading to more ideal target-to-nontarget ratios, and therefore superior results.