Localization of pulmonary human sarcoma xenografts in athymic nude mice with indium-111-labeled monoclonal antibodies.

In order to study localization of metastatic tumors with a radiolabeled monoclonal antibody, a pulmonary metastases model was devised in athymic mice. Metastatic pulmonary sarcoma colonies were verified by histological examination. A murine monoclonal antibody (MAb 19-24) directed against a human sarcoma antigen was labeled with indium-111 (111In) by use of the linker 1-(p-isothiocyanatobenzyl)-diethylenetriaminepentaacetic acid (SCN-Bz-DTPA). MAb P3 was similarly labeled as a negative control. In the group given MAb 19-24, the percent injected dose per gram lung tissue bearing tumor colonies (30.1%, 29.6%, and 27.7% on Days 1, 2, and 3, respectively) was significantly (p less than 0.05) higher than in those receiving MAb P3. Hepatic activities of both 111In-MAb 19-24 and 111In-MAb P3 were low. The lungs with tumor colonies demonstrated clearest images on Day 3. The specific binding of 111In-SCN-Bz-DTPA-labeled MAb 19-24 to pulmonary xenografts without appreciable liver uptake indicates that it may be useful in the clinical localization of pulmonic metastatic lesions.