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DNA Repair (Amst). 2016 Jul;43:38-47. doi: 10.1016/j.dnarep.2016.04.009. Epub 2016 May 7.

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

Author information

1
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, United States; Department of Molecular Medicine, Institute of Health Sciences, Dokuz Eylul University, Inciralti, Izmir 35340, Turkey. Electronic address: ys452@georgetown.edu.
2
Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX-77030, United States; Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX-77555, United States. Electronic address: ardutta@utmb.edu.
3
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, United States. Electronic address: apurva.mallisetty@gmail.com.
4
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, United States. Electronic address: jm722@georgetown.edu.
5
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, United States. Electronic address: tm484@georgetown.edu.
6
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, United States. Electronic address: cnk10@georgetown.edu.
7
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, United States. Electronic address: priyanka.dhopeshwarkar@ablinc.com.
8
Department of Pathology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, United States. Electronic address: kallakub@georgetown.edu.
9
Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX-77030, United States. Electronic address: smitra2@houstonmethodist.org.
10
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, United States. Electronic address: au26@georgetown.edu.
11
Compass Laboratory Services, 1910 Nonconnah Rd, Memphis, United States. Electronic address: sadhikari@houstonmethodist.org.

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

PMID:
27235629
DOI:
10.1016/j.dnarep.2016.04.009
[Indexed for MEDLINE]

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