Identification of Natural Products That Inhibit the Catalytic Function of Human Tyrosyl-DNA Phosphodiesterase (TDP1)

Author:

Bermingham, Alun

Price, Edmund

Marchand, Christophe

Chergui, Adel

Naumova, Alena

Whitson, Emily L

Haugh Krumpe, Lauren

Goncharova, Katya

Evans, Jason

McKee, Tawnya

Henrich, Curtis

Pommier, Yves

O'Keefe, Barry
Author Address

1 Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD, USA., 2 Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA., 3 Basic Science Program, Leidos Biomedical Research, Inc., Frederick National Laboratory, Frederick, MD, USA., 4 Data Management Services, Inc., Frederick, MD, USA., 5 Natural Products Branch, Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute, National Institutes of Health, Frederick, MD, USA.,

Abstract:

Tyrosyl-DNA phosphodiesterase 1 (TDP1) is an enzyme crucial for cleavage of the covalent topoisomerase 1-DNA complex, an intermediate in DNA repair. TDP1 plays a role in reversing inhibition of topoisomerase I by camptothecins, a series of potent and effective inhibitors used in the treatment of colorectal, ovarian, and small-cell lung cancers. It is hypothesized that inhibition of TDP1 activity may enhance camptothecin sensitivity in tumors. Here, we describe the design, development, and execution of a novel assay to identify inhibitors of TDP1 present in natural product extracts. The assay was designed to address issues with fluorescent "nuisance" molecules and to minimize the detection of false-positives caused by polyphenolic molecules known to nonspecifically inhibit enzyme activity. A total of 227,905 purified molecules, prefractionated extracts, and crude natural product extracts were screened. This yielded 534 initial positives (0.23%). Secondary prioritization reduced this number to 117 (0.05% final hit rate). Several novel inhibitors have been identified showing micromolar affinity for human TDP1, including halenaquinol sulfate, a pentacyclic hydroquinone from the sponge Xestospongia sp.

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