Abstract 3847: Dual targeting of EGFL6 and VEGF-A to overcome immune suppression in ovarian cancer

Abstract Background: Ovarian carcinomas are known to have a high degree of immune suppression, which may be related, in part, to high levels of vascular endothelial growth factor-A (VEGF-A). Bevacizumab (anti-VEGF antibody) has been shown to increase infiltration of T-cells in the tumor microenvironment (TME). We have also identified EGFL6 as an important angiogenic protein. Here, we examined the biological effects of blocking EGFL6 and VEGF-A in ovarian cancer models. Methods: We studied the in vitro (endothelial tube formation and migration assays) and in vivo (ID8KO-Trp53;Brca2 and SKOV3-ip1 models) biological effects of EGFL6 and VEGF-A blockade. Tumor-infiltrating immune cells were studied by flow cytometry and immunohistochemistry staining. Results: Blocking EGFL6 and VEGF-A simultaneously with monoclonal antibodies in RF24 endothelial cells decreased tube formation and migration significantly, in comparison to VEGF-A blockade alone (p0. 001). EGFL6 monotherapy in ID8KO-Trp53;Brca2 tumor bearing syngeneic mice decreased tumor burden (~2. 5 fold, p0. 0001) and increased the infiltration of IFNγ+ (~2. 75 fold, p0. 0001) and GzmB+ (~1. 75 fold, p0. 01) CD8+ T-cells and IFNγ+ (~2 fold, p0. 0001) and GzmB+ (~2 fold, p0. 01) CD4+ T-cells while decreasing PD-L1+ cells (~1. 8 fold, p=0. 01). Dual blockade of EGFL6 and VEGF-A in SKOV3-ip1 tumor bearing nude mice significantly decreased tumor burden (~3. 72 fold, p0. 01) and angiogenesis (~2. 36 fold, p0. 05) compared to controls and single-agent blockade. Similar blockade in ID8KO-Trp53;Brca2 tumor bearing mice significantly decreased tumor burden (~4. 2 fold, p=0. 0004), improved CD8+ (~3. 32 fold, p=0. 0004) and CD4+ (~2. 81 fold, p0. 0001) T-cell infiltration, NK cell infiltration (~2. 3 fold, p=0. 0005) and decreased myeloid-derived suppressor cells (MDSCs) (~1. 92 fold, p=0. 0278) compared to EGFL6 and VEGF-A blockade alone. Conclusions: Our results demonstrate that simultaneously targeting the angiogenesis drivers EGFL6 and VEGF-A in ovarian cancer significantly decreased tumor burden in vivo and increased the infiltration of T lymphocytes compared to single-agent blockade. AACR Category: Tumor Microenvironment and Immune Oncology Key words: ovarian cancer, immune suppression, angiogenesis, VEGF-A, EGFL6 Citation Format: Sujanitha Umamaheswaran, Lingegowda S. Mangala, Robiya Joseph, Nicholas B. Jennings, Mark S. Kim, Yunfei Wen, Emine Bayraktar, Ningyan Zhang, Zhiqiang An, Anil K. Sood. Dual targeting of EGFL6 and VEGF-A to overcome immune suppression in ovarian cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3847.