Localization of experimental glioma grafts by means of iodinated monoclonal antibodies and radionuclide imaging.

Purified McAbs (14AC1) of IgG2a isotype raised against an experimental rat glioma (79FR-G-41) were labeled with Na131I and used for in vivo imaging of glioma grafts by external body scintigraphy. Normal mouse 131I-IgG was applied as control for non-specific uptake of proteins in the tumor. Nude mice bearing glioma grafts were injected i.v. with 15 micrograms of the 131I-McAb or 131I-IgG with an activity of approximately 150 microCi. Scans obtained 30 min, 24, 48, 72, and 96 h after injecting the intact 131I-14AC1 antibody demonstrated enrichment of radioactivity in the tumors. The tumors were clearly visible 48 h after injection of 131I-labeled antibody. The time course experiments showed that the uptake of 131I-14AC1 antibody in the glioma grafts was the result of specific antigen binding. Intact antibody provided adequate tumor visualization in the scintigrams without background subtraction. Therefore, this technique appears promising for in vivo tumor detection and may offer the possibility of improvement in the evaluation of diagnostic and therapeutic approaches to human gliomas.