title: Novel acridine-triazenes as prototype combilexins: synthesis, DNA binding, and biological activity.
abstract: A series of bifunctional ligands has been developed as prototype DNA-binding combilexins using a DNA template-directed approach. These novel agents contain a 1,3-diaryltriazene linker moiety, present in the established DNA minor groove-binder berenil [1,3-bis(4'-amidinophenyl)-triazene], which is attached to an intercalating acridine chromophore by a functionalized thiazole residue. This 9-arylacridine is predicted to confer rotational freedom to the hybrid molecule and thus facilitate bifunctional interaction with double-stranded DNA through a combination of 'classical' intercalation and minor groove-binding processes. The noncovalent DNA-binding properties of these acridine-triazene combilexins, together with the component molecular fragments, have been examined by fluorescence quenching and thermal denaturation studies with calf thymus DNA and two oligonucleotides, [poly(dA-dT)]2 and [poly(dG-dC)]2. In addition, the binding behaviors of these acridine compounds are compared to those of proflavine (3,6-diaminoacridine) and its 9-phenyl derivative. The results indicate that the hybrid agents (i) are more DNA-affinic than either molecular component, (ii) retain the AT-preferential binding properties of the parent difunctionalized 1,3-diaryltriazene residues, despite weak GC-preferential behavior associated with the acridine chromophore, and (iii) have a reduced binding affinity at pH 7 that reflects the protonation status of the acridine. In contrast, the more basic proflavines show much greater binding affinity and a marked preference for GC-rich DNA sequences. In vitro cytotoxicity data with L1210 mouse leukemia and A2780 human colon cancer cell lines show that the conjugate molecules are approximately 10-40-fold more potent than the acridine or triazene subunits and have activities that compare favorably with those of other reported synthetic combilexins. Intercalative binding modes with a model d(GATACGATAC).d(GTATCGTATC) target duplex have been investigated using molecular modeling techniques. These studies provide a rational basis for the binding properties and suggest that the prototype combilexins can bind in a bimodal manner that induces little distortion of the host DNA duplex. Energy-minimized models for the possible dual interactions are discussed.
authors.affiliation: Cancer Research Campaign Biomolecular Structure Unit, Institute of Cancer Research, Sutton, Surrey, UK.
authors.forename: A W
authors.initials: AW
authors.lastname: McConnaughie
authors.forename: T C
authors.initials: TC
authors.lastname: Jenkins
mesh_terms: D000166:Acridines / Q000138:chemical synthesis / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D002417:Cattle; D004247:DNA / Q000378:metabolism*; D004133:Diminazene / Q000031:analogs & derivatives / Q000737:chemistry; D015195:Drug Design; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D013950:Thymus Gland / Q000166:cytology; D014226:Triazenes / Q000138:chemical synthesis / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000166:Acridines; D000970:Antineoplastic Agents; D014226:Triazenes; D004247:DNA; C003915:diminazene aceturate; D004133:Diminazene