Enhancing the Efficacy of Cancer Therapy: Use of Small Molecule Inhibitors of DNA Glycosylases as Potential Drugs

Published

March 12, 2017

Author(s)

Erdem Coskun, Aaron C. Jacobs, Nathan Donley, Marcus J. Calkins, Dorjbal Dorjsuren, David Maloney, Anton Simeonov, Pawel Jaruga, Amanda K. McCullough, M Miral Dizdar, R. S. Lloyd

Abstract

Chemotherapy aims to destroy cancer cells by damaging their DNA. However, the overexpression of DNA repair proteins in cancer cells causes the removal of DNA lesions before they become toxic and thus leads to an increased DNA repair capacity resulting in resistance to therapy. The DNA base excision repair (BER) pathway, which utilizes DNA glycosylases to initiate repair of specific DNA lesions, is the major pathway for the repair of DNA damage induced by oxidation, alkylation, and deamination. Growing body of evidence with early results from clinical trials suggest that inhibiting certain enzymes in the BER pathway is a promising approach to enhance the efficacy of cancer therapy as a mono or combination therapy. The aim of this study was to discover small molecule inhibitors of the major human DNA glycosylases; NEIL1, NTH1 and OGG1. First, we developed a fluorescencebased assay using double stranded oligodeoxynucleotides containing one substrate lesion to detect both glycosylase and apyrimidinic/apurinic lyase activities of DNA glycosylases. From a screen of ∼400,000 compounds, a number of inhibitors were identified. Subsequently, we applied gas chromatography/isotope dilution tandem mass spectrometry to measure the glycosylase activities of NEIL1, NTH1 and OGG1 using damaged DNA containing multiple lesions, which provide structural elucidation of products and ascertain accurate quantification. We identified four purine analogs as potent inhibitors of excision of the main substrates of NEIL1. Three of NEIL1 inhibitors also inhibited the excision of NTH1 substrates, but did not affect OGG1 activity. From a screen of ∼50,000 molecules, five hydrazydes were identified as potent inhibitors of OGG1. These compounds exhibited no inhibition of NEIL1 and NTH1 activities for all their substrates analyzed by two different methodologies used in this work. Overall, this work forms the foundation for future drug discovery for the entire family of DNA glycosylases.

Proceedings Title

The Toxicologist

Conference Dates

March 12-16, 2017

Conference Location

Baltimore, MD

Conference Title

Society of Toxicology 56th Annual Meeting

Pub Type

Conferences

Keywords

DNA glycosylases, Mass Spectroscopy, Cancer Drug Development

Citation

Coskun, E. , Jacobs, A. , Donley, N. , Calkins, M. , Dorjsuren, D. , Maloney, D. , Simeonov, A. , Jaruga, P. , McCullough, A. , , M. and Lloyd, R. (2017), Enhancing the Efficacy of Cancer Therapy: Use of Small Molecule Inhibitors of DNA Glycosylases as Potential Drugs, The Toxicologist, Baltimore, MD (Accessed April 26, 2024)