title: Covalent binding to glutathione of the DNA-alkylating antitumor agent, S23906-1.
abstract: The benzoacronycine derivative, S23906-1, was characterized recently as a novel potent antitumor agent through alkylation of the N2 position of guanines in DNA. We show here that its reactivity towards DNA can be modulated by glutathione (GSH). The formation of covalent adducts between GSH and S23906-1 was evidenced by EI-MS, and the use of different GSH derivatives, amino acids and dipeptides revealed that the cysteine thiol group is absolutely required for complex formation because glutathione disulfide (GSSG) and other S-blocked derivatives failed to react covalently with S23906-1. Gel shift assays and fluorescence measurements indicated that the binding of S23906-1 to DNA and to GSH are mutually exclusive. Binding of S23906-1 to an excess of GSH prevents DNA alkylation. Additional EI-MS measurements performed with the mixed diester, S28053-1, showed that the acetate leaving group at the C1 position is the main reactive site in the drug: a reaction scheme common to GSH and guanines is presented. At the cellular level, the presence of GSH slightly reduces the cytotoxic potential of S23906-1 towards KB-3-1 epidermoid carcinoma cells. The GSH-induced threefold reduction of the cytotoxicity of S23906-1 is attributed to the reduced formation of lethal drug-DNA covalent complexes in cells. Treatment of the cells with buthionine sulfoximine, an inhibitor of GSH biosynthesis, facilitates the formation of drug-DNA adducts and promotes the cytotoxic activity. This study identifies GSH as a reactant for the antitumor drug, S23906-1, and illustrates a pathway by which GSH may modulate the cellular sensitivity to this DNA alkylating agent. The results presented here, using GSH as a biological nucleophile, fully support our initial hypothesis that DNA alkylation is the major mechanism of action of the promising anticancer drug S23906-1.
authors.affiliation: INSERM U-524, IRCL, Lille, France.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: David-Cordonnier
authors.forename: William
authors.initials: W
authors.lastname: Laine
authors.forename: Alexandra
authors.initials: A
authors.lastname: Joubert
authors.forename: Christelle
authors.initials: C
authors.lastname: Tardy
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Goossens
authors.forename: Mostafa
authors.initials: M
authors.lastname: Kouach
authors.forename: Gilbert
authors.initials: G
authors.lastname: Briand
authors.forename: Huong Doan
authors.initials: HD
authors.lastname: Thi Mai
authors.forename: Sylvie
authors.initials: S
authors.lastname: Michel
authors.forename: Francois
authors.initials: F
authors.lastname: Tillequin
authors.forename: Michel
authors.initials: M
authors.lastname: Koch
authors.forename: Stéphane
authors.initials: S
authors.lastname: Leonce
authors.forename: Alain
authors.initials: A
authors.lastname: Pierre
authors.forename: Christian
authors.initials: C
authors.lastname: Bailly
mesh_terms: D000175:Acronine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D018906:Antineoplastic Agents, Alkylating / Q000737:chemistry / Q000378:metabolism*; D019328:Buthionine Sulfoximine / Q000378:metabolism; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization; D014407:Tumor Cells, Cultured
chemical_list: D018906:Antineoplastic Agents, Alkylating; D004791:Enzyme Inhibitors; D046911:Macromolecular Substances; C436732:S 23906-1; D019328:Buthionine Sulfoximine; D004247:DNA; D005978:Glutathione; D000175:Acronine