Angiogenesis is the development of new blood vessels to provide oxygen and nutrients and is indispensable for solid tumor growth. Therefore, the inhibition of angiogenesis is an important modality for cancer chemotherapy. Here we report the antiangiogenic mechanism and antitumor effects of epoxyquinol B (EPQB), which was isolated from fungal metabolites. Short-term treatment of EPQB resulted in the reduction of tumor growth and the number of blood vessels directed to the tumor in a murine xenografts model. Furthermore, EPQB inhibited vascular endothelial growth factor (VEGF)-induced migration and tube formation in human umbilical vein endothelial cells (HUVECs) without cytotoxicity. VEGF-stimulated phosphorylation of VEGF receptor 2 (VEGFR2), phospholipase Cγ-1 (PLCy1), and p44/42 MAP kinases (ERK) was inhibited by EPQB in a dose-dependent manner, and in vitro assay using kinase domain of VEGFR2 showed that EPQB covalently bound and inhibited the VEGFR2 kinase. Its binding site on VEGFR2 was different from SU5614, a well-known VEGFR2 kinase inhibitor. Interestingly, EPQB inhibited growth factor-induced activation of not only VEGFR2 but also epidermal growth factor receptor (EGFR), fibroblast growth factor receptor (FGFR), and platelet-derived growth factor receptor (PDGFR), suggesting that EPQB is a novel multiple kinase inhibitor. These findings suggest that EPQB would be a good lead compound for the development of potent antiangiogenic and antitumor drugs.
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