title: Thioredoxin system inhibitors as mediators of apoptosis for cancer therapy.
abstract: The thioredoxin (Trx) system is a major antioxidant system integral to maintaining the intracellular redox state. It contains Trx, a redox active protein, which regulates the activity of various enzymes including those that function to counteract oxidative stress within the cell. Trx can also scavenge reactive oxygen species (ROS) and directly inhibits proapoptotic proteins such as apoptosis signal-regulating kinase 1 (ASK1). The oxidized form of Trx is reduced by thioredoxin reductase (TrxR). The cytoplasm and mitochondria contain equivalent Trx systems and inhibition of either system can lead to activation of apoptotic signaling pathways. There are a number of inhibitors with chemotherapy applications that target either Trx or TrxR to induce apoptosis in cancer cells. Suberoylanilide hydroxamic acid (SAHA) is effective against many cancer cells and functions by up-regulating an endogenous inhibitor of Trx. Other compounds target the selenocysteine-containing active site of TrxR. These include gold compounds, platinum compounds, arsenic trioxide, motexafin gadolinium, nitrous compounds, and various flavonoids. Inhibition of TrxR leads to an accumulation of oxidized Trx resulting in cellular conditions that promote apoptosis. In addition, some compounds also convert TrxR to a ROS generating enzyme. The role of Trx system inhibitors in cancer therapy is discussed in this review.
authors.affiliation: School of Biomolecular and Physical Sciences, Griffith University, Nathan, Qld, Australia. k.tonissen@griffith.edu.au
authors.forename: Kathryn F
authors.initials: KF
authors.lastname: Tonissen
authors.forename: Giovanna
authors.initials: G
authors.lastname: Di Trapani
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D016166:Free Radical Scavengers / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D009369:Neoplasms / Q000188:drug therapy* / Q000473:pathology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013880:Thioredoxin-Disulfide Reductase / Q000378:metabolism; D013879:Thioredoxins / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D013879:Thioredoxins; D013880:Thioredoxin-Disulfide Reductase