Pomolic acid suppresses HIF1α/VEGF-mediated angiogenesis by targeting p38-MAPK and mTOR signaling cascades

Background: Pomolic acid (PA), an active triterpenoid from Euscaphis japonica, inhibits the proliferation of a variety of cancer cells, but the molecular mechanisms of the anti-angiogenic potential of PA have not been fully elucidated in breast cancer cells. Hypothesis/Purpose: We investigated the molecular mechanisms underlying the anti-angiogenic effect of PA in epidermal growth factor (EGF)-responsive human breast cancer cells, MCF-7 and MDA-MB-231, and human umbilical vascular endothelial cells (HUVEC). Study design/Methods: Effects of PA on EGF-induced HIF1 alpha/VEGF expression in MCF-7, MDA-MB-231 and HUVEC were assayed. As to the mechanisms, EGF-mediated MAPKs, PI3K/Akt, and mTOR signaling pathway were performed. Wound healing and invasion assay, tube formation assay, immunoblot assay, realtime PCR, luciferase gene assay, electrophoretic mobility shift assay and immunofluorescence staining were used for assessment. Results: PA significantly and selectively suppressed EGF-induced HIF1 alpha/VEGF expression, whereas it did not affect the expression of HIF1 beta MCF-7 and MDA-MB-231. Furthermore, PA inhibited EGF-induced angiogenesis in vitro and downregulated HIF1 alpha/VEGF expression in HUVEC. Mechanistically, we found that the inhibitory effects of PA on HIF1 alpha/VEGF expression are associated with inhibition of HIF1 alpha/VEGF expression through an EGF-dependent mechanism. In addition, PA suppressed the EGF-induced phosphorylation of p38-MAPK and mTOR. Conclusion: PA suppresses EGF-induced HIF1 alpha protein translation by inhibiting the p38-MAPK and mTOR kinase signaling pathways and plays a novel anti-angiogenic role. (C) 2016 Elsevier GmbH. All rights reserved.