title: p53-dependent inhibition of TrxR1 contributes to the tumor-specific induction of apoptosis by RITA.
abstract: Thioredoxin reductase 1 (TrxR1) is a key regulator in many redox-dependent cellular pathways, and is often overexpressed in cancer. Several studies have identified TrxR1 as a potentially important target for anticancer therapy. The low molecular weight compound RITA (NSC 652287) binds p53 and induces p53-dependent apoptosis. Here we found that RITA also targets TrxR1 by non-covalent binding, followed by inhibition of its activity in vitro and by inhibition of TrxR activity in cancer cells. Interestingly, a novel approximately 130 kDa form of TrxR1, presumably representing a stable covalently linked dimer, and an increased generation of reactive oxygen species (ROS) were induced by RITA in cancer cells in a p53-dependent manner. Similarly, the gold-based TrxR inhibitor auranofin induced apoptosis related to oxidative stress, but independently of p53 and without apparent induction of the approximately 130 kDa form of TrxR1. In contrast to the effects observed in cancer cells, RITA did not inhibit TrxR or ROS formation in normal fibroblasts (NHDF). The inhibition of TrxR1 can sensitize tumor cells to agents that induce oxidative stress and may directly trigger cell death. Thus, our results suggest that a unique p53-dependent effect of RITA on TrxR1 in cancer cells might synergize with p53-dependent induction of pro-apoptotic genes and oxidative stress, thereby leading to a robust induction of cancer cell death, without affecting non-transformed cells.
authors.affiliation: Department for Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Hedström
authors.forename: Sofi
authors.initials: S
authors.lastname: Eriksson
authors.forename: Joanna
authors.initials: J
authors.lastname: Zawacka-Pankau
authors.forename: Elias S J
authors.initials: ES
authors.lastname: Arnér
authors.forename: Galina
authors.initials: G
authors.lastname: Selivanova
mesh_terms: D017209:Apoptosis; D001310:Auranofin / Q000494:pharmacology; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000235:genetics / Q000502:physiology; D005663:Furans / Q000494:pharmacology*; D006801:Humans; D009369:Neoplasms / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000819:agonists / Q000378:metabolism; D054481:Thioredoxin Reductase 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000235:genetics / Q000502:physiology
chemical_list: D005663:Furans; C118989:NSC 652287; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D001310:Auranofin; D054481:Thioredoxin Reductase 1