Development of Triplex-Forming Oligonucleotides to Inhibit Expression of the c-myc Oncogene in Breast Cancer Cells
Annual Summary rept. 6 Mar 2000-5 Mar 2003
MEDICAL COLL OF SOUTH CAROLINA CHARLESTON
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Triple helix-forming oligonucleotides TFOs directed to regulatory sequences in gene promoters can selectively block transcription. We are investigating TFO-mediated reduction of c-myc oncogene expression as a means of decreasing breast tumor growth. We designed a novel parallelantiparallel TFO Myc-GTC that had high binding affinity in vitro, but required modifications for increased stability in cells. To further optimize TFO activity we investigated effects of conjugation with the anthracycline antibiotic daunomycin Dnm, which intercalates into double-stranded DNA. This modification increased stability of triple helix formed by parallel and antiparallel short TFOs targeted to each segment of the target sequence. The anti-parallel TFO inhibited expression in breast cancer cells of a luciferase gene under the control of the c-myc promoter. Gel shift assays showed that triple helix formed by this TFO was specifically bound by a protein or proteins in MCF-7, MDA-MB-231 and Hela nuclear extracts. These may be DNA repair-associated proteins, but do not appear to include XPA, a required protein in the nucleotide excision repair mechanism. Efforts to identify the triple helix-binding proteins are in progress.
- Anatomy and Physiology
- Medicine and Medical Research