title: Sequence-specific targeting of IGF-I and IGF-IR genes by camptothecins.
abstract: We and others have clearly demonstrated that a topoisomerase I (Top1) inhibitor, such as camptothecin (CPT), coupled to a triplex-forming oligonucleotide (TFO) through a suitable linker can be used to cause site-specific cleavage of the targeted DNA sequence in in vitro models. Here we evaluated whether these molecular tools induce sequence-specific DNA damage in a genome context. We targeted the insulin-like growth factor (IGF)-I axis and in particular promoter 1 of IGF-I and intron 2 of type 1 insulin-like growth factor receptor (IGF-IR) in cancer cells. The IGF axis molecules represent important targets for anticancer strategies, because of their central role in oncogenic maintenance and metastasis processes. We chemically attached 2 CPT derivatives to 2 TFOs. Both conjugates efficiently blocked gene expression in cells, reducing the quantity of mRNA transcribed by 70-80%, as measured by quantitative RT-PCR. We confirmed that the inhibitory mechanism of these TFO conjugates was mediated by Top1-induced cleavage through the use of RNA interference experiments and a camptothecin-resistant cell line. In addition, induction of phospho-H2AX foci supports the DNA-damaging activity of TFO-CPT conjugates at specific sites. The evaluated conjugates induce a specific DNA damage at the target gene mediated by Top1.
authors.affiliation: Centre National de la Recherche, Scientifique, Unité Mixte de Recherche 7196, Muséum National d'Histoire Naturelle, Paris, France.
authors.forename: Kahina
authors.initials: K
authors.lastname: Oussedik
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: François
authors.forename: Ludovic
authors.initials: L
authors.lastname: Halby
authors.forename: Catherine
authors.initials: C
authors.lastname: Senamaud-Beaufort
authors.forename: Géraldine
authors.initials: G
authors.lastname: Toutirais
authors.forename: Sabrina
authors.initials: S
authors.lastname: Dallavalle
authors.forename: Yves
authors.initials: Y
authors.lastname: Pommier
authors.forename: Claudio
authors.initials: C
authors.lastname: Pisano
authors.forename: Paola B
authors.initials: PB
authors.lastname: Arimondo
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic; D001483:Base Sequence; D001665:Binding Sites; D002166:Camptothecin / Q000494:pharmacology*; D002460:Cell Line; D004249:DNA Damage / Q000187:drug effects*; D004791:Enzyme Inhibitors; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors* / Q000235:genetics; D011401:Promoter Regions, Genetic; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors* / Q000235:genetics; D059004:Topoisomerase I Inhibitors
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D059004:Topoisomerase I Inhibitors; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D002166:Camptothecin