Targeted Transport of 125I-Labeled Antibody to GFAP and AMVB1 in an Experimental Rat Model of C6 Glioma

Glioblastoma is the most common high-grade glioma characterized by strikingly poor therapeutic outcome with survival time of about a year. This makes a search for new therapeutic approaches to glioblastoma treatment an area of great clinical importance. The present study aims to explore the potential of targeted delivery of I-125-radiolabeled antibodies, specific to glial fibrillary acidic protein (GFAP) and AMVB1 (antigen of abluminal membrane of endotheliocytes predominantly expressed in glioblastoma microvessels) as a strategy for in vivo tumor targeting. Rat C6 glioma model was used to test this hypothesis. Tumor bearing animals, injected with radiolabeled monoclonal antibodies to GFAP or AMVB1, were compared to control group, which received nonspecific mouse IgG. Radioactivity of blood, brain hemispheres, and some other tissues was measured 6, 24, 48, 72, and 96 h posttreatment. Our results demonstrate accumulation of both types of antibodies in tumors. Concentrations of both antibodies were significantly increased in tumor-bearing hemisphere compared to intact hemisphere. Antibodies to GFAP specifically accumulated in brain and bound tumor tissue with the high affinity. In contrast, increased accumulation of anti-AMVB1 antibody was detected in antigen-expressing organs, such as spleen and kidney. Based on results presented, we propose that the monoclonal antibodies to GFAP can be used as vectors for the delivery of diagnostic and pharmacological agents to high-grade gliomas. Development of this strategy would open new clinical perspectives for glioblastoma diagnostics and therapy.