title: Small-molecule inhibitors targeting the DNA-binding domain of STAT3 suppress tumor growth, metastasis and STAT3 target gene expression in vivo.
abstract: Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in malignant tumors and has important roles in multiple aspects of cancer aggressiveness. Thus targeting STAT3 promises to be an attractive strategy for treatment of advanced metastatic tumors. Although many STAT3 inhibitors targeting the SH2 domain have been reported, few have moved into clinical trials. Targeting the DNA-binding domain (DBD) of STAT3, however, has been avoided due to its 'undruggable' nature and potentially limited selectivity. In a previous study, we reported an improved in silico approach targeting the DBD of STAT3 that resulted in a small-molecule STAT3 inhibitor (inS3-54). Further studies, however, showed that inS3-54 has off-target effect although it is selective to STAT3 over STAT1. In this study, we describe an extensive structure and activity-guided hit optimization and mechanistic characterization effort, which led to identification of an improved lead compound (inS3-54A18) with increased specificity and pharmacological properties. InS3-54A18 not only binds directly to the DBD and inhibits the DNA-binding activity of STAT3 both in vitro and in situ but also effectively inhibits the constitutive and interleukin-6-stimulated expression of STAT3 downstream target genes. InS3-54A18 is completely soluble in an oral formulation and effectively inhibits lung xenograft tumor growth and metastasis with little adverse effect on animals. Thus inS3-54A18 may serve as a potential candidate for further development as anticancer therapeutics targeting the DBD of human STAT3 and DBD of transcription factors may not be 'undruggable' as previously thought.
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: W
authors.initials: W
authors.lastname: Huang
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Dong
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: F
authors.initials: F
authors.lastname: Wang
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Wang
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: H
authors.initials: H
authors.lastname: Peng
authors.affiliation: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: He
authors.affiliation: Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: G
authors.initials: G
authors.lastname: Hangoc
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.|Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA.|IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: K
authors.initials: K
authors.lastname: Pollok
authors.affiliation: IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA.|Department of Pathology and Molecular Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: G
authors.initials: G
authors.lastname: Sandusky
authors.affiliation: Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA.|IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: X-Y
authors.initials: XY
authors.lastname: Fu
authors.affiliation: Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA.|IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: H E
authors.initials: HE
authors.lastname: Broxmeyer
authors.affiliation: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA.|IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: Z-Y
authors.initials: ZY
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.|Department of Computer and Information Science, Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA.
authors.forename: J-Y
authors.initials: JY
authors.lastname: Liu
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.|IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: J-T
authors.initials: JT
authors.lastname: Zhang
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD; D018345:Mice, Knockout; D016513:Mice, SCID; D058990:Molecular Targeted Therapy; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000235:genetics / Q000473:pathology*; D054730:Protein Interaction Domains and Motifs / Q000187:drug effects*; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D004247:DNA