Tumor localization of human brain malignant glioma xenograft in nude mice with a radiolabeled monoclonal antibody

A murine monoclonal antibody designated as Mab 3H9 (IgG1 subclass immunoglobulin, k light chain) expressed specific antibody binding activity to a human brain malignant glioma cell line (GBM8401/TSGH,NDMC) and many formalin-fixed and paraffin-embedded malignant gliomas that have been produced in our laboratory by hybridoma technology. The immunohistochemical indirect immunofluorescence, peroxidase-antiperoxidase assays, and specific electron microscopic immunogold staining revealed that 3H9 probably recognized a distinct glioma-associated surface antigen on the GBM8401 cultured cells. In vivo radioimmunolocalization of GBM8401 xenografts in nude mice by external scintigraphy with radiolabeled 3H9 has been performed to evaluate potential clinical application as diagnostic or therapeutic reagents. On the 3rd day after an intravenous injection of 15 μCi, the ¹²⁵I- or ¹³¹I-radiolabeled 3H9 was successful in immunolocalization of a human brain GBM8401 xenograft in the nude mouse. In large xenografts, the radioactivity ratios of tumor to brain and tumor to blood were 11.0 and 2.4, respectively. In small xenografts, the tumor to brain and tumor to blood ratios were 14.0 and 2.9, respectively. The clearance of radiolabeled 3H9 in the bloodstream of the nude mouse was not affected by the presence of a GBM8401 xenograft. This preliminary experiment reveals that human brain GBM8401 xenografts in nude mice can be detected in vivo by radiolabeled 3H9.