title: (-)-Xanthatin up-regulation of the GADD45γ tumor suppressor gene in MDA-MB-231 breast cancer cells: role of topoisomerase IIα inhibition and reactive oxygen species.
abstract: Previously, we reported that (-)-xanthatin, a naturally occurring xanthanolide present in the Cocklebur plant, exhibits potent anti-proliferative effects on human breast cancer cells, accompanied by an induction of the growth arrest and DNA damage-inducible gene 45γ (GADD45γ), recognized recently as a novel tumor suppressor gene. However, the mechanisms mediating this activation were unknown. Topoisomerase IIα (Topo IIα) inhibition has been reported to produce a cell death response accompanied by an atypical DNA laddering fragmentation profile, similar to that noted previously for (-)-xanthatin. Therefore we hypothesized that (-)-xanthatin's GADD45γ activation was mediated through the Topo IIα pathway. Here, we identify that (-)-xanthatin does function as a catalytic inhibitor of Topo IIα, promoting DNA damage. In addition, reactive oxygen species (ROS) were elevated in cells treated with this agent. Mechanistically, it was determined that the induced levels of GADD45γ mRNA resulting from (-)-xanthatin exposures were stabilized by coordinately produced ROS, and that the consequent induction of GADD45γ mRNA, GADD45γ protein and ROS generation were abrogated by co-treatment with N-acetyl-l-cysteine. Taken together, the data support the concept that Topo IIα inhibition by (-)-xanthatin is a trigger that stimulates expression of DNA damage-inducible GADD45γ mRNA and that concomitantly produced ROS act downstream to further enhance the GADD45γ mRNA/GADD45γ protein induction process, resulting in breast cancer cell death.
authors: Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan.
authors: Shuso
authors: S
authors: Takeda
authors: Momoko
authors: M
authors: Noguchi
authors: Kazumasa
authors: K
authors: Matsuo
authors: Yasuhiro
authors: Y
authors: Yamaguchi
authors: Taichi
authors: T
authors: Kudo
authors: Hajime
authors: H
authors: Nishimura
authors: Yoshiko
authors: Y
authors: Okamoto
authors: Toshiaki
authors: T
authors: Amamoto
authors: Mitsuru
authors: M
authors: Shindo
authors: Curtis J
authors: CJ
authors: Omiecinski
authors: Hironori
authors: H
authors: Aramaki
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000951:Antigens, Neoplasm / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004249:DNA Damage; D004250:DNA Topoisomerases, Type II / Q000187:drug effects / Q000502:physiology*; D004273:DNA, Neoplasm / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000502:physiology*; D005260:Female; D016166:Free Radical Scavengers / Q000494:pharmacology; D005663:Furans / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D006207:Half-Life; D006801:Humans; D007306:Insecticides / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism*; D059005:Topoisomerase II Inhibitors; D015854:Up-Regulation / Q000187:drug effects; D000097642:GADD45 Proteins
chemical_list: D000111:Acetylcysteine; D000951:Antigens, Neoplasm; D004250:DNA Topoisomerases, Type II; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D016166:Free Radical Scavengers; D005663:Furans; D005978:Glutathione; D007306:Insecticides; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D059005:Topoisomerase II Inhibitors; D000097642:GADD45 Proteins; C022186:xanthatin