@article{17f980eb35c4439aa2e80f672c421ea9,
title = "Depletion of tyrosyl DNA phosphodiesterase 2 activity enhances etoposide-mediated double-strand break formation and cell killing",
abstract = "DNA topoisomerase 2 (Top2) poisons, including common anticancer drugs etoposide and doxorubicin kill cancer cells by stabilizing covalent Top2-tyrosyl-DNA 5'-phosphodiester adducts and DNA double-strand breaks (DSBs). Proteolytic degradation of the covalently attached Top2 leaves a 5'-tyrosylated blocked termini which is removed by tyrosyl DNA phosphodiesterase 2 (TDP2), prior to DSB repair through non-homologous end joining (NHEJ). Thus, TDP2 confers resistance of tumor cells to Top2-poisons by repairing such covalent DNA-protein adducts, and its pharmacological inhibition could enhance the efficacy of Top2-poisons. We discovered NSC111041, a selective inhibitor of TDP2, by optimizing a high throughput screening (HTS) assay for TDP2's 5'-tyrosyl phosphodiesterase activity and subsequent validation studies. We found that NSC111041 inhibits TDP2's binding to DNA without getting intercalated into DNA and enhanced etoposide's cytotoxicity synergistically in TDP2-expressing cells but not in TDP2 depleted cells. Furthermore, NSC111041 enhanced formation of etoposide-induced γ-H2AX foci presumably by affecting DSB repair. Immuno-histochemical analysis showed higher TDP2 expression in a sub-set of different type of tumor tissues. These findings underscore the feasibility of clinical use of suitable TDP2 inhibitors in adjuvant therapy with Top2-poisons for a sub-set of cancer patients with high TDP2 expression.",
keywords = "DNA repair, Enzyme assay, High throughput screening, Inhibitor, Molecular probe, NSC111041, TDP2",
author = "Kont, {Yasemin Saygideger} and Arijit Dutta and Apurva Mallisetty and Jeena Mathew and Tsion Minas and Christina Kraus and Priyanka Dhopeshwarkar and Bhaskar Kallakury and Sankar Mitra and Aykut {\"U}ren and Sanjay Adhikari",
note = "Funding Information: We thank Dr. Rabindra Roy, Georgetown University Medical Center, for allowing his radio-active working facility and space for some of the experiments. We thank Dr. Venkata Yenugonda for helping us to contact Toronto research chemical, Canada for resynthesizing NSC111041. This project has been supported partly by pilots awards IRG-92-152-17 American Cancer Society, “American Cancer Society Institutional Research Grant” (SA), Nina Hyde Mechanism (SA) and NIH R03DA035193 (SA), and Federal funds (UL1TR000101) from the National Center for Advancing Translational Sciences (NCATS), National Institutes of Health, through the Clinical and Translational Science Awards Program (CTSA), a trademark of DHHS, part of the Roadmap Initiative, “Re-Engineering the Clinical Research Enterprise (SA), R01CA158910 (SM), P01CA92584 (SM). We thank LCCC{\textquoteright}s Genomics & Epigenomics Shared Resource for High-throughput screening, surface plasmon resonance and biostatistics experiments. We also thank LCCC{\textquoteright}s Histopathology & Tissue Shared Resource for human tissue samples, Proteomics & Metabolomics Shared Resource for high resolution mass spectrometry experiment, Tissue Culture Shared Resources for different cell lines (P30 CA51008). We thank Prof. Jeffrey Toretsky, Georgetown University for A4573, SKES, TC32 and TC71 cell lines. We thank Microscopy & Imaging Shared Resource of Houston Methodist Research Institutes. Finally, we thank Prof. Louis Weiner, Director, Lombardi Comprehensive Cancer Center for supporting this work. Publisher Copyright: {\textcopyright} 2016 Elsevier B.V.",
year = "2016",
month = jul,
day = "1",
doi = "10.1016/j.dnarep.2016.04.009",
language = "English (US)",
volume = "43",
pages = "38--47",
journal = "DNA Repair",
issn = "1568-7864",
publisher = "Elsevier B.V.",
}