title: Replacement of a thiourea with an amidine group in a monofunctional platinum-acridine antitumor agent. Effect on DNA interactions, DNA adduct recognition and repair.
abstract: A combination of biophysical, biochemical, and computational techniques was used to delineate mechanistic differences between the platinum-acridine hybrid agent [PtCl(en)(L)](NO(3))(2) (complex 1, en = ethane-1,2-diamine, L = 1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea) and a considerably more potent second-generation analogue containing L' = N-[2-(acridin-9-ylamino)ethyl]-N-methylpropionamidine (complex 2). Calculations at the density functional theory level provide a rationale for the binding preference of both complexes for guanine-N7 and the relatively high level of adenine adducts observed for compound 1. A significant rate enhancement is observed for binding of the amidine-based complex 2 with DNA compared with the thiourea-based prototype 1. Studies conducted with chemical probes and on the bending and unwinding of model duplex DNA suggest that adducts of complex 2 perturb B-form DNA more severely than complex 1, however, without denaturing the double strand and significantly less than cisplatin. Circular and linear dichroism spectroscopies and viscosity measurements suggest that subtle differences exist between the intercalation modes and adduct geometries of the two complexes. The adducts formed by complex 2 most efficiently inhibit transcription of the damaged DNA by RNA polymerase II. Not only do complexes 1 and 2 cause less distortion to DNA than cisplatin, they also do not compromise the thermodynamic stability of the modified duplex. This leads to a decreased or negligible affinity of HMG domain proteins for the adducts formed by either Pt-acridine complex. In a DNA repair synthesis assay the lesions formed by complex 2 were repaired less efficiently than those formed by complex 1. These significant differences in DNA adduct formation, structure, and recognition between the two acridine complexes and cisplatin help to elucidate why compound 2 is highly active in cisplatin-resistant, repair proficient cancer cell lines.
authors.affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, vvi Kralovopolska 135, CZ-61265 Brno, Czech Republic.
authors.forename: Hana
authors.initials: H
authors.lastname: Kostrhunova
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Malina
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Pickard
authors.forename: Jana
authors.initials: J
authors.lastname: Stepankova
authors.forename: Marie
authors.initials: M
authors.lastname: Vojtiskova
authors.forename: Jana
authors.initials: J
authors.lastname: Kasparkova
authors.forename: Tereza
authors.initials: T
authors.lastname: Muchova
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Rohlfing
authors.forename: Ulrich
authors.initials: U
authors.lastname: Bierbach
authors.forename: Viktor
authors.initials: V
authors.lastname: Brabec
mesh_terms: D000166:Acridines / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D000578:Amidines / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D002945:Cisplatin / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D018736:DNA Adducts / Q000737:chemistry*; D004260:DNA Repair / Q000187:drug effects*; D059371:DNA, B-Form / Q000737:chemistry / Q000378:metabolism; D015195:Drug Design; D024243:HMGB1 Protein / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007364:Intercalating Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D009690:Nucleic Acid Conformation / Q000187:drug effects; D009944:Organoplatinum Compounds / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D020033:Protein Isoforms / Q000378:metabolism; D013329:Structure-Activity Relationship; D013890:Thiourea / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D000166:Acridines; D000578:Amidines; D000970:Antineoplastic Agents; D018736:DNA Adducts; D059371:DNA, B-Form; D024243:HMGB1 Protein; D007364:Intercalating Agents; D009944:Organoplatinum Compounds; D020033:Protein Isoforms; D004247:DNA; D013890:Thiourea; D002945:Cisplatin