10059- IM-3 IDENTIFICATION OF THERAPEUTIC TARGET ANTIGENS USING PATIENT DERIVED GLIOBLASTOMA AND THEIR APPLICATION TO CAR-T THERAP

Abstract INTRODUCTION Recently, CAR-T cell (chimertic antigen receptor T-cell) therapy has been attracting and has shown high therapeutic efficacy, especially in the hematological tumors. In the brain, EGFRv3 or HER2 have been used as antigens, but have yet to show positive results. It is necessary to find antibodies that are more specific and have a therapeutic effect. METHODS A primary culture line was prepared from glioblastoma surgical specimens, and immunized to Balb/c mice with it. The B cells from the mice were fused with myeloma cells, immortalized, and cultured nonclonally to obtain a number of monoclonal antibodies reacted glioblastoma cells. The obtained antibodies were reacted with glioblastoma cells and normal brain cells, and those that specifically react to glioblastoma were selected by flowcytometry to obtain antibody candidates that could be specifically expressed on the surface of glioblastoma cells. Then, we generated CAR-T cells derived from the obtained antibody and confirmed anti-tumor effect of CAR-T cells in vitro and in vivo. RESULTS Approximately 25,000 antibody-producing strains were generated. From these, we selected the antibody, which reacted with several glioblastomas and did not react with several normal brain cells. Finally, we identified the antibody as Prostaglandin F2 receptor negative regulator (PTGFRN) by using expression cloning. CAR-T cells derived from PTGFRN produced cytokines and exerted cytotoxicity upon co-culture with tumor cells from patients with GBM. Furthermore, intracranial injection of 5E17-CAR-T cells demonstrated antitumor effects in an orthotopic xenograft murine model with patient-derived GBM cells. DISCUSSION In this study, we identified PTGFRN as a tumor-specific surface antigen and confirmed its antitumor effect in vitro and in vivo. PTGFRN is involved in the control of cell proliferation, migration, invasion, cell cycle, and apoptosis, and is expressed in multiple cancers. Cell surface PTGFRN is a candidate target for intracranial CAR-T-cell therapy for GBM.