Specific Inhibition of HER-2/Neu Transcription Initiation
Annual rept. 1 Jul 2004-30 Jun 2005
ARIZONA UNIV TUCSON
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A polypurine tract PPT containing multiple GGA repeats in the HER-2neu promoter is important to control HER-2neu transcription. We investigated the ability of the PPT to form a G-quadruplex-related secondary structure using biochemical techniques and screened a small family of potential G-quadruplex ligands that could stabilize PPT secondary structure formation in solution. We evaluated several potential lead compounds for their ability to suppress HER-2neu expression in breast cancer cells. Circular dichroism studies with the distal half of the PPT were similar to findings previously reported for tetradheptad DNA. DNA polymerase arrest assays demonstrated potassium induced arrest, and several G-quadruplex interactive compounds that stabilize the HER-2neu PPT secondary structure were identified from this assay. Telomestatin and a lead compound in the fluoroquinolone class stabilize the HER-2neu PPT secondary structure in solution and reduce HER-2neu expression in breast cancer cells. We conclude the HER-2neu promoter can form a stable secondary structure known as a tetradheptad in solution. Compounds that stabilize the tetradheptad were identified and some of them reduced HER-2neu expression in breast cancer cells. Further studies are needed to fully characterize the secondary structure and link the effects of compounds on HER-2neu expression to their direct interaction with the HER-2neu promoter.
- Medicine and Medical Research