Abstract 6: A triple-helix forming oligonucleotide targeting a genomic locus is capable of sequence specific mutagenesis in human lymphoblastoid TK6 cells

Abstract

Abstract It has been reported that DNA triplex formation induces mutagenesis as determined using plasmid-based reporter constructs (Wang et al 1996, Science, 271, p802). Triplex mediated mutagenesis has been shown to include point mutations, deletions, small insertions and homologous recombination. To the best of our knowledge, no study has successfully examined the mutagenic potential of a non-conjugated triplex-forming oligonucleotide (TFO) targeting a genomic sequence. In this study, we have designed a TFO that targets the hemizygous hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus, in the human lymphoblastoid TK6 cell line, and assessed mutagenicity through resistance to 6-thioguanine. Our TFO, TFO27, has been designed to form a triplex with a purine tract in exon 3 of the HPRT gene. Triplex formation at the target motif was shown to occur at nanomolar concentrations, confirmed by Electrophoretic Mobility Shift Assays. A scrambled oligonucleotide, SCR27, failed to form a triplex at the target motif. A range of transfection reagents were evaluated for facilitated delivery of TFO27, and resulted in variable cellular toxicity. Transfection of high concentrations of oligonucleotide, with acceptable levels of cytotoxicity, resulted in HPRT mutation with TFO27 but not SCR27. Similar experiments failed to result in mutation at the non-targeted thymidine kinase (TK) locus, suggesting locus specificity for the mode of action of TFO27. The target specificity and sequence context of these mutagenic events is being determined to establish the mechanism of mutation. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 6.