Abstract
Napabucasin, undergoing multiple clinical trials, was reported to inhibit the signal transducer and transcription factor 3 (STAT3). To better elucidate its mechanism of action, we designed a napabucasin-based proteolysis targeting chimera (PROTAC), XD2-149 that resulted in inhibition of STAT3 signaling in pancreatic cancer cell lines without inducing proteasome-dependent degradation of STAT3. Proteomics analysis of XD2-149 revealed the downregulation of the E3 ubiquitin-protein ligase ZFP91. XD2-149 degrades ZFP91 with DC50 values in the nanomolar range. The cytotoxicity of XD2-149 was significantly, but not fully, reduced with ZFP91 knockdown providing evidence for its multi-targeted mechanism of action. The NQO1 inhibitor, dicoumarol, rescued the cytotoxicity of XD2-149 but not ZFP91 degradation, suggesting that the NQO1-induced cell death is independent of ZFP91. ZFP91 plays a role in tumorigenesis and is involved in multiple oncogenic pathways including NF-κB and HIF-1α.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Benzofurans / chemical synthesis*
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Benzofurans / pharmacology*
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Cell Line, Tumor
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Drug Design
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Drug Screening Assays, Antitumor
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Gene Knockdown Techniques
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Humans
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Hypoxia-Inducible Factor 1, alpha Subunit / drug effects
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Mutant Chimeric Proteins / chemistry*
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NAD(P)H Dehydrogenase (Quinone) / antagonists & inhibitors
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Naphthoquinones / chemical synthesis*
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Naphthoquinones / pharmacology*
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Pancreatic Neoplasms / drug therapy
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Pancreatic Neoplasms / physiopathology
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Proteolysis
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STAT3 Transcription Factor / antagonists & inhibitors
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Signal Transduction / drug effects
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Structure-Activity Relationship
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Ubiquitin-Protein Ligases / chemistry
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Ubiquitin-Protein Ligases / genetics*
Substances
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Benzofurans
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Hypoxia-Inducible Factor 1, alpha Subunit
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Mutant Chimeric Proteins
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Naphthoquinones
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STAT3 Transcription Factor
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STAT3 protein, human
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napabucasin
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NAD(P)H Dehydrogenase (Quinone)
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NQO1 protein, human
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Ubiquitin-Protein Ligases
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ZFP91 protein, human