title: Increased susceptibility of H-Ras(G12V)-transformed human urothelial cells to the genotoxic effects of sodium arsenite.
abstract: Inorganic arsenite (iAs) is a human carcinogen. Numerous studies have shown that mutation-activated H-Ras is frequently observed in human urothelial carcinomas. The interaction between iAs, an environmental factor, and H-Ras, an oncogene, is not clear. In this study, we explored the genotoxic effects of iAs in human urothelial cells ectopically expressing H-Ras (G12V) an activated H-Ras oncogene. Our results showed that H-Ras(G12V)-transformed human urothelial cells (HUC-RAS) were more susceptible to arsenite-induced cell death, DNA damage, micronuclei formation and anchorage-independent growth than control cells (HUC-neo). Furthermore, iAs treatment induced higher intracellular levels of reactive oxygen species (ROS) in the HUC-RAS cells than in the HUC-neo cells. N-acetyl-L-cysteine could suppress the iAs-induced increases in ROS and genetic damage. We further demonstrated that the intracellular glutathione levels were significantly elevated by the iAs treatment of the HUC-neo cells, but that this effect was not observed in the HUC-RAS cells. The iAs treatment induced higher superoxide dismutase activity in the HUC-neo cells than in the HUC-RAS cells. Alternatively, catalase activity was higher in the HUC-RAS cells than in the HUC-neo cells, but this enzyme was significantly suppressed by iAs. Moreover, iAs activated the ERK and JNK signaling pathways, which are involved in iAs-induced ROS production and genetic damage. Taken together, our present results suggest that elevated catalase activity in H-Ras(G12V)-transformed cells is significantly suppressed by iAs via activation of ERK and JNK signaling pathways and hence attenuate the defense of the neoplastic transformed cells against iAs-induced oxidative injuries.
authors.affiliation: Institute of Pharmacology, National Yang-Ming University, Taipei, 112, Taiwan.
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Liao
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, 128, Sec. 2, Academia Road, Taipei, 11529, Taiwan.
authors.forename: Yi-Fan
authors.initials: YF
authors.lastname: Chen
authors.affiliation: Institute of Pharmacology, National Yang-Ming University, Taipei, 112, Taiwan. bmtcl@ibms.sinica.edu.tw.|Institute of Biomedical Sciences, Academia Sinica, 128, Sec. 2, Academia Road, Taipei, 11529, Taiwan. bmtcl@ibms.sinica.edu.tw.
authors.forename: Te-Chang
authors.initials: TC
authors.lastname: Lee
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D018053:Arsenites / Q000633:toxicity*; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D004249:DNA Damage / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects* / Q000473:pathology; D011905:Genes, ras / Q000235:genetics*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D009153:Mutagens / Q000633:toxicity; D017382:Reactive Oxygen Species / Q000378:metabolism; D017670:Sodium Compounds / Q000633:toxicity*; D013482:Superoxide Dismutase / Q000378:metabolism; D019459:Urothelium / Q000166:cytology / Q000187:drug effects* / Q000473:pathology
chemical_list: D018053:Arsenites; D009153:Mutagens; D017382:Reactive Oxygen Species; D017670:Sodium Compounds; C017947:sodium arsenite; D013482:Superoxide Dismutase; D005978:Glutathione; D000111:Acetylcysteine
keywords: Arsenic; Catalase; Genotoxicity; H-Ras oncogene; Reactive oxygen species; Stress signaling