title: 4-Pregnen-21-ol-3,20-dione-21-(4-bromobenzenesulfonate) (NSC 88915) and related novel steroid derivatives as tyrosyl-DNA phosphodiesterase (Tdp1) inhibitors.
abstract: Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is an enzyme that catalyzes the hydrolysis of 3'-phosphotyrosyl bonds. Such linkages form in vivo when topoisomerase I (Top1) processes DNA. For this reason, Tdp1 has been implicated in the repair of irreversible Top1-DNA covalent complexes. Tdp1 inhibitors have been regarded as potential therapeutics in combination with Top1 inhibitors, such as the camptothecin derivatives, topotecan, and irinotecan, which are used to treat human cancers. Using a novel high-throughput screening assay, we have identified the C21-substituted progesterone derivative, NSC 88915 (1), as a potential Tdp1 inhibitor. Secondary screening and cross-reactivity studies with related DNA processing enzymes confirmed that compound 1 possesses specific Tdp1 inhibitory activity. Deconstruction of compound 1 into discrete functional groups reveals that both components are required for inhibition of Tdp1 activity. Moreover, the synthesis of analogues of compound 1 has provided insight into the structural requirements for the inhibition of Tdp1. Surface plasmon resonance shows that compound 1 binds to Tdp1, whereas an inactive analogue fails to interact with the enzyme. On the basis of molecular docking and mechanistic studies, we propose that these compounds are competitive inhibitors, which mimics the oligonucleotide-peptide Tdp1 substrate. These steroid derivatives represent a novel chemotype and provide a new scaffold for developing small molecule inhibitors of Tdp1.
authors.affiliation: Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Dexheimer
authors.forename: Lalji K
authors.initials: LK
authors.lastname: Gediya
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Stephen
authors.forename: Iwona
authors.initials: I
authors.lastname: Weidlich
authors.forename: Smitha
authors.initials: S
authors.lastname: Antony
authors.forename: Christophe
authors.initials: C
authors.lastname: Marchand
authors.forename: Heidrun
authors.initials: H
authors.lastname: Interthal
authors.forename: Marc
authors.initials: M
authors.lastname: Nicklaus
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Fisher
authors.forename: Vincent C
authors.initials: VC
authors.lastname: Njar
authors.forename: Yves
authors.initials: Y
authors.lastname: Pommier
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000473:pathology; D001557:Benzenesulfonates / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D020134:Catalytic Domain; D004277:DNA, Single-Stranded / Q000378:metabolism; D004952:Esters / Q000737:chemistry; D057166:High-Throughput Screening Assays; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D009154:Mutation; D010726:Phosphodiesterase Inhibitors / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry / Q000378:metabolism*; D011282:Pregnenediones / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D020754:Spinocerebellar Ataxias / Q000150:complications / Q000235:genetics / Q000473:pathology; D013256:Steroids / Q000737:chemistry*; D020349:Surface Plasmon Resonance; D013816:Thermodynamics
chemical_list: C545684:4-pregnen-21-ol-3,20-dione-21-(4-bromobenzenesufonate); D001557:Benzenesulfonates; D004277:DNA, Single-Stranded; D004952:Esters; D010726:Phosphodiesterase Inhibitors; D011282:Pregnenediones; D013256:Steroids; C032365:benzenesulfonic acid; D010727:Phosphoric Diester Hydrolases; C498508:TDP1 protein, human