Depletion of tyrosyl DNA phosphodiesterase 2 activity enhances etoposide-mediated double-strand break formation and cell killing

Yasemin Saygideger Kont, Arijit Dutta, Apurva Mallisetty, Jeena Mathew, Tsion Minas, Christina Kraus, Priyanka Dhopeshwarkar, Bhaskar Kallakury, Sankar Mitra, Aykut Üren, Sanjay Adhikari

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)38-47
Number of pages10
JournalDNA Repair
StatePublished - Jul 1 2016


  • DNA repair
  • Enzyme assay
  • High throughput screening
  • Inhibitor
  • Molecular probe
  • NSC111041
  • TDP2

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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