title: Activation of camptothecin derivatives by conjugation to triple helix-forming oligonucleotides.
abstract: Topoisomerase I (topo I) is a ubiquitous DNA-cleaving enzyme and an important therapeutic target in cancer chemotherapy. Camptothecins (CPTs) reversibly trap topo I in covalent complex with DNA but exhibit limited sequence preference. The utilization of conjugates such as triplex-forming oligonucleotides (TFOs) to target a medicinal agent (like CPT) to a specific genetic sequence and orientation within the DNA has been accomplished successfully. In this study, different attachment points of the TFO to CPT (including positions 7, 9, 10, and 12) were investigated and our findings confirmed and extended previous conclusions. Interestingly, the conjugates induced specific DNA cleavage by topo I at the triplex site even when poorly active or inactive CPT derivatives were used. This suggests that the positioning of the drug in the cleavage complex by the sequence-specific DNA ligand is able to stabilize the ternary complex, even when important interactions between topo I and CPT are disrupted. Finally, certain TFO-CPT conjugates were able to induce sequence-specific DNA cleavage with the topo I mutants R364H and N722S that are resistant to camptothecin. The TFO-CPT conjugates are thus valuable tools to study the interactions involved in the formation of the ternary complex and also to enlarge the family of compounds that poison topo I. The fact that an inactive CPT analogue can act as a topo I poison when appropriately coupled to a TFO provides a new perspective at the level of drug design.
authors.affiliation: Laboratoire de Biophysique, CNRS UMR 5153, Muséum National d'Histoire Naturelle, USM0503, INSERM UR565, 43 rue Cuvier, 75231 Paris Cedex 05, France. arimondo@mnhn.fr
authors.forename: Paola B
authors.initials: PB
authors.lastname: Arimondo
authors.forename: Gary S
authors.initials: GS
authors.lastname: Laco
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Thomas
authors.forename: Ludovic
authors.initials: L
authors.lastname: Halby
authors.forename: Didier
authors.initials: D
authors.lastname: Pez
authors.forename: Philippe
authors.initials: P
authors.lastname: Schmitt
authors.forename: Alexandre
authors.initials: A
authors.lastname: Boutorine
authors.forename: Thérèse
authors.initials: T
authors.lastname: Garestier
authors.forename: Yves
authors.initials: Y
authors.lastname: Pommier
authors.forename: Sidney M
authors.initials: SM
authors.lastname: Hecht
authors.forename: Jian-Sheng
authors.initials: JS
authors.lastname: Sun
authors.forename: Christian
authors.initials: C
authors.lastname: Bailly
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D001483:Base Sequence; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000378:metabolism*; D004249:DNA Damage; D004264:DNA Topoisomerases, Type I / Q000737:chemistry / Q000235:genetics / Q000633:toxicity; D004789:Enzyme Activation; D004795:Enzyme Stability / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000138:chemical synthesis* / Q000378:metabolism; D009841:Oligonucleotides / Q000138:chemical synthesis* / Q000378:metabolism; D017354:Point Mutation; D013329:Structure-Activity Relationship
chemical_list: D009692:Nucleic Acid Heteroduplexes; D009841:Oligonucleotides; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin