Abstract 3252: Eriocalyxin B (EriB), a natural diterpenoid, inhibits VEGF-induced angiogenesis by suppressing VEGFR2 signaling

Abstract

Abstract Introduction: Angiogenesis, the formation of new capillaries from existing blood vessels, is an essential requirement for tumor growth and metastasis. Vascular endothelial growth factor (VEGF), one of the most potent angiogenic factors, is crucial for the promotion of new vascular sprout formation in vessel stabilization. Previous studies showed that the inhibition of angiogenesis via targeting on VEGF is a promising strategy for the suppression of tumor growth as well as metastasis. Eriocalyxin B (EriB), a natural diterpenoid isolated from Isodon eriocalyx Dunn, exerts anti-tumor activities1,2. Here, the aim of the present study was to determine the effect of EriB on angiogenesis both in vitro and in vivo. Methods: Human umbilical vein endothelial cells (HUVECs) were used to demonstrate the anti-angiogenic activities of EriB and its underlying mechanisms. The transgenic zebrafish Tg(fli1:EGFP)y1, in which the endothelial cells express enhanced Green Fluorescent Proteins (eGFP), was also applied to evaluate the effect of EriB on angiogenesis in vivo. Results: Our results in HUVECs showed that EriB exerted no inhibitory effect on cell viability and cell proliferation. However, it could significantly inhibit VEGF-induced cell viability and cell proliferation. In addition, the decreased tube formation, cell migration and cell invasion were also observed. Flow cytometry analysis demonstrated that EriB could induce cell cycle arrest at G1 phase by interference with cyclinD1/CDK4/pRb pathway. Investigation of the signal transduction revealed that EriB was involved in the suppression of VEGFR2 signaling. Results from the zebrafish model demonstrated that EriB treatment could inhibit the formation of sub-intestinal vessels. Besides, genome wide mRNA expression profiling of zebrafish after EriB treatment revealed the alteration of various angiogenic genes. The expressions of several genes such as kdr, pcdh15b, cdkn1a, loxl1, etc. were evaluated by quantitative real-time PCR. Conclusions: The present study reported the activities of EriB as a novel anti-angiogenic agent. Thus, EriB has the potential of modulating tumor angiogenesis, which may be useful in the treatment of human cancers.