EXTH-53. VEGFR2-SPECIFIC CAR-T CELLS SHOW IMPROVED TUMOR INFILTRATION IN SYNGENEIC MOUSE GLIOMA MODELS

Abstract

Abstract BACKGROUND Chimeric antigen receptor (CAR-)T cell therapy, a powerful immunotherapy against hematological malignancies, has so far limited efficiency in solid tumors. Also in glioblastoma, a major obstacle remains limited infiltration of CAR-T cells into the tumor. Vessel-targeting CAR-T cells have been shown to infiltrate solid tumors more efficiently. Vascular endothelial growth factor receptor 2 (VEGFR2) is expressed in the glioma vasculature and VEGFR2-specific CAR-T cells prolong the survival of xenograft glioma-bearing mice. In this study, we investigated the efficacy of murine VEGFR2-specific CAR-T cells against syngeneic experimental gliomas and assessed the CAR-T cell infiltration of this approach. METHODS VEGFR2-CAR-T cells were generated by retroviral transduction to express a second generation CAR construct. Their activity was assessed in co-culture assays in vitro against murine endothelial and glioma cells, respectively. Syngeneic orthotopic mouse glioma models were used to explore the infiltration of intravenously administered CAR-T cells by in vivo fluorescence molecular tomography (FMT), ex vivo flow cytometry as well as ex vivo 3D light-sheet fluorescence microscopy (LSFM). RESULTS VEGFR2-CAR-T cells showed anti-endothelial and anti-glioma activity in vitro. Intravenous treatment with fluorescently labeled CAR-T or mock-transduced T cells of tumor-bearing mice resulted in a higher FMT signal at the tumor site. This was confirmed by ex vivo flow cytometry, wherein CAR-T cells represented a larger fraction of all T cells within the tumor (26.5% CAR versus 5.4% Mock, p = 0.0013) resulting in a higher donor T cell to tumor cell ratio. Similarly, significantly more VEGFR2-CAR-T cells were detected at the tumor site compared to tumor-targeting (but not vessel-targeting) control CAR-T cells. Currently, VEGFR2-CAR-T cell infiltration patterns as well as vasculature density are further investigated and visualized by LSFM. CONCLUSION VEGFR2-CAR-T cells show improved glioma infiltration in syngeneic mouse models. Therefore, VEGFR2 might be a relevant target that could improve CAR-T cell infiltration in glioblastoma.