Combined blockade of VEGF, Angiopoietin-2, and PD1 reprograms glioblastoma endothelial cells into quasi-antigen-presenting cells

Glioblastoma (GBM) remains a highly aggressive and uniformly fatal tumor, with a 5-year survival of <10%. Moreover, all randomized clinical trials with immune-checkpoint blockers have failed to date. Here we report that tumor endothelial cell (EC) dysfunction confers resistance to immunotherapy in preclinical GBM models. Anti-VEGF-therapy-induced vascular normalization is insufficient to fully restore the EC function and alleviate inflammatory edema induced by blocking programmed cell death protein 1 (PD1). Strikingly, concomitant blockade of angiopoietin 2 (Ang2), vascular endothelial growth factor (VEGF), and programmed cell death protein 1 (PD1) reprograms dysfunctional ECs to quasi-antigen presenting cells and upregulates receptors required for cytotoxic T lymphocyte entry into the tumor. Blocking VEGF, Ang2, and PD1 induces durable anti-tumor response while controlling edema. Upregulation of the transcription factor T-bet is necessary for generating resident memory T cells elicited by this combination therapy. Moreover, a human GBM organoid model formed from human cancer cells, ECs, CD14 and CD8 cells recapitulated these findings. Our study reveals the role of Ang2 in resistance to VEGF and/or PD1-blockade and provides a compelling rationale for clinical evaluation of this combination in GBM patients.