title: Desferrioxamine, an iron chelator, enhances HIF-1alpha accumulation via cyclooxygenase-2 signaling pathway.
abstract: Cyclooxygenase-2 (COX-2) is an important inducible enzyme in inflammation and is overexpressed in a variety of cancers. Evidence is rapidly accumulating that chronic inflammation may contribute to carcinogenesis through increase of cell proliferation, angiogenesis, and metastasis in a number of neoplasms, including colorectal carcinoma. In the present study, we investigated some mechanistic aspects of DFX-induced hypoxia-driven COX-2 expression. Desferrioxamine (DFX), an iron chelator, is known to upregulate inflammatory mediators. DFX induced the expression of COX-2 and accumulation of HIF-1alpha protein in dose-dependent manners, but hypoxia mimetic agent cobalt chloride (CoCl2) induced accumulation of HIF-1alpha protein but not increase of COX-2 expression. DFX-induced increase of COX-2 expression and HIF-1alpha protein level was attenuated by addition of ferric citrate. This result suggested that the iron chelating function of DFX was important to induce the increase of COX-2 and HIF-1alpha protein. PD98059 significantly inhibited the induction of COX-2 protein and accumulation of HIF-1alpha, suggesting that DFX-induced increase of HIF-1alpha and COX-2 protein was mediated, at least in part, through the ERK signaling pathway. In addition, pretreatment with NS-398 to inhibit COX-2 activity also effectively suppressed DFX-induced HIF-1alpha accumulation in human colon cancer cells, providing the evidence that COX-2 plays as a regulator of HIF-1alpha accumulation in DFX-treated colon cancer cells. Together, our findings suggest that iron metabolism may regulate stabilization of HIF-1alpha protein by modulating cyclooxygenase-2 signaling pathway.
authors.affiliation: Department of Immunology and Chronic Disease Research Center and Institute for Medical Science, School of Medicine, Keimyung University, 194 DongSan-Dong Jung-Gu, Taegu 700-712, South Korea.
authors.forename: Kyung Jin
authors.initials: KJ
authors.lastname: Woo
authors.forename: Tae-Jin
authors.initials: TJ
authors.lastname: Lee
authors.forename: Jong-Wook
authors.initials: JW
authors.lastname: Park
authors.forename: Taeg Kyu
authors.initials: TK
authors.lastname: Kwon
mesh_terms: D003110:Colonic Neoplasms / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000187:drug effects / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology*; D005290:Ferric Compounds / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D000860:Hypoxia / Q000139:chemically induced* / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D052246:Cyclooxygenase 2 Inhibitors; D005290:Ferric Compounds; D005419:Flavonoids; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007502:Iron Chelating Agents; D016159:Tumor Suppressor Protein p53; C025314:ferric citrate; D051546:Cyclooxygenase 2; D020928:Mitogen-Activated Protein Kinases; D003676:Deferoxamine; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one