Abstract 4591: Mechanisms of tumor-mediated endothelial cell proliferation independent of VEGF

Abstract

Abstract A hallmark of cancer is dysregulated angiogenesis and blood vessel co-option, which are often driven by vascular endothelial growth factor (VEGF). Despite the key role of VEGF signaling in promoting endothelial cell (EC) proliferation, survival, and migration, the clinical use of VEGF inhibitors has modest success and faces many challenges. In particular, patients demonstrate variable initial responses to anti-VEGF therapy, and many of those who respond to treatment subsequently develop resistance. These challenges suggest that there may be VEGF-independent mechanisms driving EC proliferation in the tumor microenvironment. To study these mechanisms, we established an in vitro model using a dual-reporter system in a co-culture model of ECs and tumor cells. Specifically, we used an immortalized endothelial cell line (SVEC4-10) expressing GFP and Renilla luciferase and a mouse renal carcinoma cell line (RENCA) expressing Tomato and Firefly luciferase. This model allowed us to independently evaluate the growth rates and cell viabilities of both ECs and tumor cells in direct co-culture. Our preliminary data revealed that ECs exhibit increased growth rates when directly co-cultured with tumor cells. Interestingly, this EC proliferation is VEGF-independent and not impacted by VEGF-A knockout in tumor cells or with treatment of a pan-VEGFR small molecule inhibitor (axitinib). To further characterize if our phenotype was due to other tumor secreted factors, we used a transwell setup to eliminate direct contact between ECs and tumor cells and found that EC growth rates were substantially mitigated. These results revealed that tumor cells induced EC proliferation through a physical cell-to-cell interaction that is independent of VEGF. Further characterizing this unknown mechanism may inform therapeutic interventions to overcome the clinical challenges of anti-VEGF therapies for cancer. To expand our understanding of this VEGF-independent EC proliferation, we aim to characterize the cell surface proteome from tumor-conditioned ECs using cell surface mass spectrometry. We will validate hits from this study using our in vitro model and translate these findings to in vivo mouse models. We expect that our current and future research will reveal new insights into tumor co-option of the vascular system and identify novel targets for developing therapies to effectively treat cancer. Citation Format: Kevin L. Sheng, Jude Raj, Kris C. Wood. Mechanisms of tumor-mediated endothelial cell proliferation independent of VEGF. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4591.