title: Structure-function relationship of thiazolide-induced apoptosis in colorectal tumor cells.
abstract: Thiazolides are a novel class of anti-infectious agents against intestinal intracellular and extracellular protozoan parasites, bacteria, and viruses. While the parent compound nitazoxanide (NTZ; 2-(acetolyloxy)-N-(5-nitro-2-thiazolyl)benzamide) has potent antimicrobial activity, the bromo-thiazolide RM4819 (N-(5-bromothiazol-2-yl)-2-hydroxy-3-methylbenzamide) shows only reduced activity. Interestingly, both molecules are able to induce cell death in colon carcinoma cell lines, indicating that the molecular target in intestinal pathogens and in colon cancer cells is different. The detoxification enzyme glutathione S-transferase of class Pi 1 (GSTP1) is frequently overexpressed in various tumors, including colon carcinomas, and limits the efficacy of antitumor chemotherapeutic drugs due to its detoxifying activities. In colorectal tumor cells RM4819 has been shown to interact with GSTP1, and GSTP1 enzymatic activity is required for thiazolide-induced apoptosis. At present it is unclear which molecular structures of RM4819 are required to interact with GSTP1 and to induce cell death in colon carcinoma cell lines. Here, we demonstrate that novel thiazolide derivatives with variation in their substituents of the benzene ring do not significantly affect apoptosis induction in Caco-2 cells, whereas removal of the bromide atom on the thiazole ring leads to a strong reduction of cell death induction in colon cancer cells. We further show that active thiazolides require caspase activation and GSTP1 expression in order to induce apoptosis. We demonstrate that increased glutathione (GSH) levels sensitize colon cancer cells to thiazolides, indicating that both GSTP1 enzymatic activity as well as GSH levels are critical factors in thiazolide-induced cell death.
authors.affiliation: Biochemical Pharmacology, Department of Biology, ‡Organic Chemistry/Cellular Chemistry, Department of Chemistry, and §Konstanz Research School Chemical Biology, University of Konstanz , Universitätsstr. 10, 78457 Konstanz, Germany.
authors.forename: Anette
authors.initials: A
authors.lastname: Brockmann
authors.forename: Tobias
authors.initials: T
authors.lastname: Strittmatter
authors.forename: Sarah
authors.initials: S
authors.lastname: May
authors.forename: Kerstin
authors.initials: K
authors.lastname: Stemmer
authors.forename: Andreas
authors.initials: A
authors.lastname: Marx
authors.forename: Thomas
authors.initials: T
authors.lastname: Brunner
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry* / Q000494:pharmacology*; D000977:Antiparasitic Agents / Q000737:chemistry / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001549:Benzamides / Q000737:chemistry* / Q000494:pharmacology*; D018938:Caco-2 Cells; D020169:Caspases / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D051549:Glutathione S-Transferase pi / Q000378:metabolism; D054879:Halogenation; D006801:Humans; D008958:Models, Molecular; D009574:Nitro Compounds; D013329:Structure-Activity Relationship; D013844:Thiazoles / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D000977:Antiparasitic Agents; D001549:Benzamides; D009574:Nitro Compounds; C531315:RM 4819; D013844:Thiazoles; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi; D020169:Caspases; C041747:nitazoxanide