title: Involvement of Ras in survival responsiveness to nitric oxide toxicity in pheochromocytoma cells.
abstract: Nitric oxide (NO) plays a key role in attenuation of tumor growth by activated macrophages that generate large amount of cytotoxic/cytostatic free radicals. However, some tumor cells may survive from NO cytotoxicity and continue to proliferate to malignant tumors. Since a protooncogene product Ras was shown to be activated by NO, this study investigated the involvement of Ras in the cell survival in response to NO cytotoxicity in pheochromocytoma (PC12) cells. Treatment with Ras inhibitor or constitutive expression of dominant negative Ras markedly increased NO-induced cell death. NO-resistant PC12 cells (PC12-NO-R) exhibited higher steady state Ras activity than the parental PC12 cells. Inducible expression using tetracycline-on (Tet-on) system of Ras mutants (dominant negative Ras or dominant active Ras) demonstrated that blockade of Ras activity increased NO-induced cell death whereas enhancement of Ras activity attenuated NO-induced cell death. Furthermore, inducible expression of NO-insensitive mutant Ras selectively increased cellular vulnerability to NO but not to ROS. NO, Ras inhibitor and extracellular signal-regulated kinase (Erk) blocker synergistically increased cell death. These observations suggest that Ras activity may be a critical factor for survival response of tumor cells to NO toxicity and pharmacological agents affecting Ras activity may enhance efficacy of NO-mediated tumor therapies.
authors.affiliation: Department of Biochemistry, College of Medicine, Chung-Ang University, Seoul, Korea.
authors.forename: Hyun Sik
authors.initials: HS
authors.lastname: Jeong
authors.forename: Seong Won
authors.initials: SW
authors.lastname: Kim
authors.forename: Kwang Jin
authors.initials: KJ
authors.lastname: Baek
authors.forename: Hee Sung
authors.initials: HS
authors.lastname: Lee
authors.forename: Nyoun Soo
authors.initials: NS
authors.lastname: Kwon
authors.forename: Young-Myeong
authors.initials: YM
authors.lastname: Kim
authors.forename: Hye-Young
authors.initials: HY
authors.lastname: Yun
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D015870:Gene Expression / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D016296:Mutagenesis / Q000502:physiology; D009569:Nitric Oxide / Q000633:toxicity*; D020030:Nitric Oxide Donors / Q000633:toxicity; D018384:Oxidative Stress / Q000502:physiology; D016716:PC12 Cells; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000633:toxicity; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics* / Q000378:metabolism*; D051381:Rats; D014162:Transfection
chemical_list: D004791:Enzyme Inhibitors; D005419:Flavonoids; D020030:Nitric Oxide Donors; C110881:S-nitro-N-acetylpenicillamine; D009569:Nitric Oxide; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D016283:Proto-Oncogene Proteins p21(ras); D010396:Penicillamine; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one