title: Disruption of the mitochondrial thioredoxin system as a cell death mechanism of cationic triphenylmethanes.
abstract: Alterations in mitochondrial structure and function are a hallmark of cancer cells compared to normal cells and thus targeting mitochondria has emerged as an novel approach to cancer therapy. The mitochondrial thioredoxin 2 (Trx2) system is critical for cell viability, but its role in cancer biology is not well understood. Recently some cationic triphenylmethanes such as brilliant green (BG) and gentian violet were shown to have antitumor and antiangiogenic activity with unknown mechanisms. Here we demonstrate that BG killed cells at nanomolar concentrations and targeted mitochondrial Trx2, which was oxidized and degraded. HeLa cells were more sensitive to BG than fibroblasts. In HeLa cells, Trx2 down-regulation by siRNA resulted in increased sensitivity to BG, whereas for fibroblasts, the same treatments had no effect. BG was observed to accumulate in mitochondria and cause a rapid and dramatic decrease in mitochondrial Trx2 protein. With a redox Western blot method, we found that treatment with BG caused oxidation of both Trx1 and Trx2, followed by release of cytochrome c and apoptosis-inducing factor from the mitochondria into the cytosol. Moreover, this treatment resulted in an elevation of the mRNA level of Lon protease, a protein quality control enzyme in the mitochondrial matrix, suggesting that the oxidized Trx2 may be degraded by Lon protease.
authors.affiliation: Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
authors.forename: Xu
authors.initials: X
authors.lastname: Zhang
authors.forename: Yujuan
authors.initials: Y
authors.lastname: Zheng
authors.forename: Levi E
authors.initials: LE
authors.lastname: Fried
authors.forename: Yatao
authors.initials: Y
authors.lastname: Du
authors.forename: Sergio J
authors.initials: SJ
authors.lastname: Montano
authors.forename: Allie
authors.initials: A
authors.lastname: Sohn
authors.forename: Benjamin
authors.initials: B
authors.lastname: Lefkove
authors.forename: Lars
authors.initials: L
authors.lastname: Holmgren
authors.forename: Jack L
authors.initials: JL
authors.lastname: Arbiser
authors.forename: Arne
authors.initials: A
authors.lastname: Holmgren
authors.forename: Jun
authors.initials: J
authors.lastname: Lu
mesh_terms: D020533:Angiogenesis Inhibitors / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D051033:Apoptosis Inducing Factor / Q000032:analysis / Q000378:metabolism; D002412:Cations / Q000737:chemistry; D002470:Cell Survival / Q000187:drug effects; D045304:Cytochromes c / Q000032:analysis / Q000378:metabolism; D005347:Fibroblasts; D005840:Gentian Violet / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D009369:Neoplasms / Q000188:drug therapy; D010084:Oxidation-Reduction; D049070:Protease La / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D034741:RNA, Small Interfering / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013879:Thioredoxins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D014320:Triphenylmethyl Compounds / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D015854:Up-Regulation
chemical_list: D020533:Angiogenesis Inhibitors; D000970:Antineoplastic Agents; D051033:Apoptosis Inducing Factor; D002412:Cations; D000644:Quaternary Ammonium Compounds; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D014320:Triphenylmethyl Compounds; D013879:Thioredoxins; C046945:triphenylmethane; D045304:Cytochromes c; D049070:Protease La; C006798:brilliant green; D005840:Gentian Violet