title: Role of oxidative stress in the induction of metallothionein-2A and heme oxygenase-1 gene expression by the antineoplastic agent gallium nitrate in human lymphoma cells.
abstract: The mechanisms of action of gallium nitrate, an antineoplastic drug, are only partly understood. Using a DNA microarray to examine genes induced by gallium nitrate in CCRF-CEM cells, we found that gallium increased metallothionein-2A (MT2A) and heme oxygenase-1 (HO-1) gene expression and altered the levels of other stress-related genes. MT2A and HO-1 were increased after 6 and 16 h of incubation with gallium nitrate. An increase in oxidative stress, evidenced by a decrease in cellular GSH and GSH/GSSG ratio, and an increase in dichlorodihydrofluorescein (DCF) fluorescence, was seen after 1-4 h of incubation of cells with gallium nitrate. DCF fluorescence was blocked by the mitochondria-targeted antioxidant mitoquinone. N-Acetyl-L-cysteine blocked gallium-induced MT2A and HO-1 expression and increased gallium's cytotoxicity. Studies with a zinc-specific fluoroprobe suggested that gallium produced an expansion of an intracellular labile zinc pool, suggesting an action of gallium on zinc homeostasis. Gallium nitrate increased the phosphorylation of p38 mitogen-activated protein kinase and activated Nrf-2, a regulator of HO-1 gene transcription. Gallium-induced Nrf-2 activation and HO-1 expression were diminished by a p38 MAP kinase inhibitor. We conclude that gallium nitrate induces cellular oxidative stress as an early event which then triggers the expression of HO-1 and MT2A through different pathways.
authors.affiliation: Division of Neoplastic Diseases, Medical College of Wisconsin, 9200 W. Wisconsin Avenue, Milwaukee, WI 53226, USA.
authors.forename: Meiying
authors.initials: M
authors.lastname: Yang
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Chitambar
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D005708:Gallium / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics*; D006801:Humans; D008223:Lymphoma / Q000235:genetics* / Q000473:pathology; D008668:Metallothionein / Q000235:genetics*; D018384:Oxidative Stress
chemical_list: D000970:Antineoplastic Agents; C491053:MT2A protein, human; D008668:Metallothionein; D005708:Gallium; D006419:Heme Oxygenase (Decyclizing); C027235:gallium nitrate