title: Isocitrate dehydrogenase 1 is downregulated during early skin tumorigenesis which can be inhibited by overexpression of manganese superoxide dismutase.
abstract: Isocitrate dehydrogenase 1 (IDH1), a cytosolic enzyme that converts isocitrate to alpha-ketoglutarate, has been shown to be dysregulated during tumorigenesis. However, at what stage of cancer development IDH1 is dysregulated and how IDH1 may affect cell transformation and tumor promotion during early stages of cancer development are unclear. We used a skin cell transformation model and mouse skin epidermal tissues to study the role of IDH1 in early skin tumorigenesis. Our studies demonstrate that both the tumor promoter TPA and UVC irradiation decreased expression and activity levels of IDH1, not IDH2, in the tumor promotable JB6 P+ cell model. Skin epidermal tissues treated with dimethylbenz[α]anthracene/TPA also showed decreases in IDH1 expression and activity. In non-promotable JB6 P-cells, IDH1 was upregulated upon TPA treatment, whereas IDH2 was maintained at similar levels with TPA treatment. Interestingly, IDH1 knockdown enhanced, whereas IDH1 overexpression suppressed, TPA-induced cell transformation. Finally, manganese superoxide dismutase overexpression suppressed tumor promoter induced decreases in IDH1 expression and mitochondrial respiration, while intracellular alpha-ketoglutarate levels were unchanged. These results suggest that decreased IDH1 expression in early stage skin tumorigenesis is highly correlated with tumor promotion. In addition, oxidative stress might contribute to IDH1 inactivation, because manganese superoxide dismutase, a mitochondrial antioxidant enzyme, blocked decreases in IDH1 expression and activity.
authors.affiliation: Department of Pharmacology, LSU Health Sciences Center, Shreveport, Louisiana, USA.
authors.forename: Delira
authors.initials: D
authors.lastname: Robbins
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Wittwer
authors.forename: Sarah
authors.initials: S
authors.lastname: Codarin
authors.forename: Magdalena L
authors.initials: ML
authors.lastname: Circu
authors.forename: Tak Yee
authors.initials: TY
authors.lastname: Aw
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Huang
authors.forename: Holly
authors.initials: H
authors.lastname: Van Remmen
authors.forename: Arlan
authors.initials: A
authors.lastname: Richardson
authors.forename: David B
authors.initials: DB
authors.lastname: Wang
authors.forename: Stephan N
authors.initials: SN
authors.lastname: Witt
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Klein
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D015153:Blotting, Western; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D015536:Down-Regulation; D005455:Fluorescent Antibody Technique; D007521:Isocitrate Dehydrogenase / Q000378:metabolism*; D015603:Keratinocytes / Q000378:metabolism*; D051379:Mice; D008811:Mice, Inbred DBA; D018384:Oxidative Stress; D010101:Oxygen Consumption; D010212:Papilloma / Q000378:metabolism*; D034741:RNA, Small Interfering; D012867:Skin / Q000378:metabolism* / Q000473:pathology; D012878:Skin Neoplasms / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism*; D014162:Transfection; D000099156:Superoxide Dismutase 2
chemical_list: D000975:Antioxidants; D007521:Isocitrate Dehydrogenase; D034741:RNA, Small Interfering; D013482:Superoxide Dismutase; D000099156:Superoxide Dismutase 2