Abstract 4248: Antiangiogenic mechanisms of Aflibercept in mouse hepatoma model

Abstract

Abstract [Background/Aim] VEGF plays a critical role in vascular development in tumor tissues. A new angiogenic inhibitor, aflibercept is a soluble decoy VEGF receptor created by fusing the Ig domains of VEGF receptor1 and 2 and captures VEGF and PlGF in the blood stream. We have reported that aflibercept suppresses tumor growth by inhibiting vascular development in mouse hepatoma model. In the present study, we investigated the precise antiangiogenic mechanisms of aflibercept in mouse hepatoma model. [Materials and methods] in vitro study: The inhibitory effects of aflibercept on cell proliferation of HUVEC and on phosphorylation of VEGF receptor 1 and 2 were evaluated. Influence of VEGF, PlGF and aflibercept on the phosphorylation of VEGF receptor 1 and 2, PI3K, AKT, and mTOR and the expression of VEGF by murine hepatoma cell line (Hepa1-6) were evaluated. The inhibitory effect of aflibercept on endothelial progenitor cells (EPC) differentiation was evaluated by colony-forming units (CFU) of EPC. I n vivo study: Aflibercept was injected intraperitoneally twice a week into tumor bearing nude mice of hepatoma cells (HuH-7, HAK1-B, KYN-2, Hepa1-6). Microvessel density in tumor tissue was counted. Hepa1-6 was implanted to GFP-bone marrow transplanted (BMT) mice to investigate the inhibitory effect of aflibercept on homing of EPC to tumor tissues. The expression of PlGF, VEGF in tumor tissue and Hepa1-6 cells was evaluated. [Results] in vitro study: Although VEGF stimulated the cell proliferation of HUVEC, PlGF did not upregulate the cell proliferation. Aflibercept suppressed the phosphorylation of VEGF receptor-1 and 2 and also inhibited the cell proliferation of HUVEC. In Hepa1-6 cells, VEGF phosphorylated VEGF receptor-1 and 2. PlGF phosphorylated VEGF receptor-1. VEGF and PlGF phosphorylated PI3K, AKT and mTOR. Aflibercept suppressed the phosphorylation of VEGF receptor-1, 2, PI3K, AKT and mTOR. Aflibercept suppressed the upregulated VEGF production by PlGF in Hepa1-6 cells. in vivo study: Aflibercept suppressed the homing of bone marrow cells to tumor tissues, the differentiation of bone marrow cell to EPC and also reduced microvessel density. The expression of VEGF in tumor tissue was suppressed by aflibercept administration. [Conclusion] Aflibercept suppresses the vascular development in hepatoma by inhibiting endothelial cells proliferation, VEGFavailability, homing of bone marrow cells to tumor tissue and EPC differentiation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4248. doi:10.1158/1538-7445.AM2011-4248