title: Gambogic acid inhibits angiogenesis through inhibiting PHD2-VHL-HIF-1α pathway.
abstract: Our previous studies revealed that gambogic acid (GA), the major active ingredient of gamboge, possessed antiangiogenic activities. In this study, we further explored the mechanism of inhibition effects of GA in tumor angiogenesis. The results of luciferase, RT-PCR, and ELISA assays indicated that GA significantly decreased transcription activation, mRNA expression, and secretion of VEGF in hypoxia. We detected that GA had no effect on mRNA level of HIF-1α which targets VEGF gene, but the increase of HIF-1α protein expression in hypoxia was repressed by GA, which can be reversed by proteasomal inhibitor MG132 and siRNA of VHL. But GA exhibited no effect on expression of VHL both in normoxia and hypoxia. HIF prolyl hydroxylases (PHD enzymes) act as oxygen sensors regulating HIF, and hence angiogenesis. Our results showed that GA potentially enhanced level of PHD2, the most important HIF hydroxylase, and showed no effect on PHD1 and PHD3. Transient transfection of siRNA of PHD2 could eliminate GA-induced VEGF secretion increase. Growth of HepG2 xenografts in BALB/cA nude mice was inhibited by GA and angiogenesis was repressed significantly in tumor xenografts by immunohistochemical staining of CD-31, a vascular endothelial marker, accompanied with decrease of HIF-1α and increase of PHD2 expression in tissue extracts. This work provides the demonstration that GA shows anti-angiogenic effects via inhibiting PHD2-VHL-HIF-1α pathway.
authors.affiliation: State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Carcinogenesis and Intervention, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, People's Republic of China.
authors.forename: Na
authors.initials: N
authors.lastname: Lu
authors.forename: Hui
authors.initials: H
authors.lastname: Hui
authors.forename: Hao
authors.initials: H
authors.lastname: Yang
authors.forename: Kai
authors.initials: K
authors.lastname: Zhao
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.forename: Qi-Dong
authors.initials: QD
authors.lastname: You
authors.forename: Qing-Long
authors.initials: QL
authors.lastname: Guo
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D056945:Hep G2 Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D047368:Tumor Burden / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism; D044004:Xanthones / Q000494:pharmacology* / Q000627:therapeutic use; D023041:Xenograft Model Antitumor Assays
chemical_list: D020533:Angiogenesis Inhibitors; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D044004:Xanthones; C052659:gambogic acid; C490189:Egln1 protein, mouse; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D051794:Von Hippel-Lindau Tumor Suppressor Protein; C494469:VHL protein, mouse