title: JS-K, a nitric oxide prodrug, has enhanced cytotoxicity in colon cancer cells with knockdown of thioredoxin reductase 1.
abstract: BACKGROUND
  The selenoenzyme thioredoxin reductase 1 has a complex role relating to cell growth. It is induced as a component of the cellular response to potentially mutagenic oxidants, but also appears to provide growth advantages to transformed cells by inhibiting apoptosis. In addition, selenocysteine-deficient or alkylated forms of thioredoxin reductase 1 have also demonstrated oxidative, pro-apoptotic activity. Therefore, a greater understanding of the role of thioredoxin reductase in redox initiated apoptotic processes is warranted.
  
  
  METHODS
  The role of thioredoxin reductase 1 in RKO cells was evaluated by attenuating endogenous thioredoxin reductase 1 expression with siRNA and then either inducing a selenium-deficient thioredoxin reductase or treatment with distinct redox challenges including, hydrogen peroxide, an oxidized lipid, 4-hydroxy-2-nonenol, and a nitric oxide donating prodrug. Thioredoxin redox status, cellular viability, and effector caspase activity were measured.
  
  
  CONCLUSIONS
  In cells with attenuated endogenous thioredoxin reductase 1, a stably integrated selenocysteine-deficient form of the enzyme was induced but did not alter either the thioredoxin redox status or the cellular growth kinetics. The oxidized lipid and the nitric oxide donor demonstrated enhanced cytotoxicity when thioredoxin reductase 1 was knocked-down; however, the effect was more pronounced with the nitric oxide prodrug. These results are consistent with the hypothesis that attenuation of the thioredoxin-system can promote apoptosis in a nitric oxide-dependent manner.
authors.affiliation: Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah, United States of America.
authors.forename: Kornelia
authors.initials: K
authors.lastname: Edes
authors.forename: Pamela
authors.initials: P
authors.lastname: Cassidy
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Shami
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Moos
mesh_terms: D001391:Azo Compounds / Q000494:pharmacology*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000201:enzymology / Q000473:pathology*; D055785:Gene Knockdown Techniques; D006801:Humans; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011355:Prodrugs / Q000494:pharmacology*; D054481:Thioredoxin Reductase 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D001391:Azo Compounds; D020030:Nitric Oxide Donors; C474958:O(2)-(2,4-dinitrophenyl) 1-((4-ethoxycarbonyl)piperazin-1-yl)diazen-1-ium-1,2-diolate; D010879:Piperazines; D011355:Prodrugs; D054481:Thioredoxin Reductase 1