JS08.5.A VEGFR2-SPECIFIC CAR T CELLS WITH ANTI-GLIOMA AND ANTI-ANGIOGENIC ACTIVITY AGAINST GLIOBLASTOMA

Abstract

Abstract BACKGROUND Chimeric antigen receptor (CAR) T cell therapy has emerged as a potent immunotherapy against hematological malignancies. In glioblastoma, however, limited infiltration of the tumor by CAR T cells, tumor heterogeneity, antigen escape and an immunosuppressive tumor microenvironment remain significant obstacles. Vessel-targeting CAR T cells have been shown to infiltrate solid tumors more efficiently and have the additional benefit of co-targeting the tumor vasculature with genomic stability. Therefore, vascular endothelial growth factor receptor 2 (VEGFR2)-CAR T cells may represent a promising strategy by targeting the tumor vasculature as well as VEGFR2-expressing tumor cells. Here, we explored the efficacy of VEGFR2-specific CAR T cells against experimental gliomas as well as the contribution of anti-tumor and anti-vasculature-dependent effects of this strategy. METHODS Tissue microarrays of glioblastoma patients (n=113) were stained for VEGFR2 expression. Human CAR T cells were generated by lentiviral transduction to express a second generation CAR construct against either mouse or human VEGFR2 (mVEGFR2 or hVEGFR2). Their activity was assessed in co-culture assays in vitro against murine endothelial and human glioma cells, respectively. Several orthotopic xenograft mouse glioma models were used to test the in vivo activity of the newly generated CAR T cells. RESULTS We confirmed high VEGFR2 expression on endothelial cells in glioblastoma tissue of stained tissue microarrays as well as in 20.3% of tissue samples also on tumor cells. In co-culture assays, hVEGFR2-CAR T cells were exclusively active against human glioma cells and mVEGFR2-CAR T cells against mouse endothelial cells, respectively. The specificity of hVEGFR2-CAR T cells was confirmed by a CRISPR/Cas9-mediated knockout of hVEGFR2 in a human glioma cell line. In all three in vivo glioma models, intratumoral treatment of hVEGFR2-CAR T cells significantly prolonged the survival of glioma-bearing mice and cured a substantial fraction of these animals in one model. Additionally, we found that survival was prolonged after mVEGFR2-CAR T cell treatment in one glioma model, which correlated with high vascularization of these tumors. CONCLUSION Our dataset demonstrates that VEGFR2-CAR T cells prolong the survival of glioma-bearing mice through anti-glioma and anti-glioma vasculature activity. The results suggest that the magnitude of the vasculature-targeting activity depends on vessel-density within the tumor. VEGFR2 might be a relevant target that could be exploited for a novel CAR T cell-based immunotherapeutic approach against glioblastoma.