Abstract IA022: Uracil DNA glycosylase activity limits deoxyuridine contamination in genomic DNA and is essential for the type-1 interferon response in cells treated with ATR kinase inhibitors

Abstract

Abstract Most chemotherapies target DNA replication, and their efficacy depends on the DNA damage response that integrates DNA repair with the cell cycle. Widely used standard-of-care antimetabolites inhibit thymidylate synthase and increase the incorporation of deoxyuridine (dU) into DNA by polymerases. Contamination of dU in DNA is limited by the DNA damage response kinase ATR that induces cell cycle checkpoints and reduces the rate of DNA replication. ATR inhibitors (ATRi) induce origin firing across active replicons and cause ribonuclease reductase degradation in otherwise unperturbed cells. This increases both the amount of DNA replication and the amount of free dUTP in cells. Thus, ATRi increase the incorporation of dU into DNA by polymerases. Since ATRi also inhibit cell cycle checkpoints, ATRi induce more dU contamination than antimetabolites. ATRi-induced dU contamination in DNA is associated with an innate immune response. We showed this with the simple observation that ATRi-induced dU contamination and IFN-α/β expression is reversed by low doses of thymidine. Here we show that ATRi-induced IFN-α/β response is dependent on uracil DNA glycosylase (UNG) which removes dU from DNA. Our data are consistent with a model in which UNG-dependent base excision repair (BER) removes dU from DNA, ultimately generating cytoplasmic dsDNA that induces IFN-α/β. We propose that ATRi-induced dU contamination contributes to dose-limiting leukocytopenia and inflammation in the clinic and CD8+ T cell dependent anti-tumor responses in mouse models of cancer treated with radiation therapy. Citation Format: Pinakin Pandya, Frank P. Vendetti, Joseph A. Ghoubaira, Sudipta Pathak, Joshua J. Deppas, Reyna E. Jones, Yunqi Zhang, Daniel Ivanov, Raquel Buj, Katherine M. Aird, Jan H. Beumer, Robert W. Sobol, Christopher J. Bakkenist. Uracil DNA glycosylase activity limits deoxyuridine contamination in genomic DNA and is essential for the type-1 interferon response in cells treated with ATR kinase inhibitors [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Damage Repair: From Basic Science to Future Clinical Application; 2024 Jan 9-11; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2024;84(1 Suppl):Abstract nr IA022.