EDIL3 as an angiogenic target of immune exclusion following checkpoint blockade.

Immune checkpoint blockade (ICB) has become the standard of care for several solid tumors. Multiple combinatorial approaches have been studied to improve therapeutic efficacy. The combination of anti-angiogenesis agents and ICB has demonstrated efficacy in several cancers. To improve the mechanistic understanding of synergies with these treatment modalities, we performed serologic screens of human protein array using sera from long-term responding patients treated with ipilimumab and bevacizumab. We discovered a high-titer antibody response against EDIL3 that correlated with favorable clinical outcomes. EDIL3 is an extracellular protein, identified as a marker of poor prognosis in various malignancies. Our Tumor Immune Dysfunction and Exclusion analysis predicted that EDIL3 is associated with immune exclusion signatures for cytotoxic immune cell infiltration and non-response to ICB. In our study, cancer-associated fibroblasts (CAFs) were predicted as source of EDIL3 in immune exclusion-related cells. Furthermore, TCGA-SKCM and CheckMate 064 data analyses correlated high levels of EDIL3 with increased pan-fibroblast TGF-β response, enrichment of angiogenic signatures, and induction of epithelial-to-mesenchymal transition. Our in vitro studies validated EDIL3 overexpression and TGF-β regulation in patient-derived CAFs. In pre-treatment serum samples from patients, circulating levels of EDIL3 were associated with circulating levels of VEGF, and like VEGF, EDIL3 increased the angiogenic abilities of patient-derived tumor endothelial cells (TEC). Mechanistically, 3-D microfluidic cultures and 2D transmigration assays with TEC endorsed EDIL3-mediated disruption of LFA-1/ICAM-1 interaction as possible means of T cell exclusion. We propose EDIL3 as a potential target for improving the transendothelial migration of immune cells and efficacy of ICB therapy.