title: Inhibition of STAT3 by Anticancer Drug Bendamustine.
abstract: Bendamustine (BENDA), which bears the bis(2-chloroethyl)amino moiety, is an alkylating agent that stops the growth of cancer cells by binding to DNA and interfering with its replication. However, the mechanism of action underlying its excellent clinical efficacy remains unclear. In this work, we report that BENDA inhibits signal transducer and activator of transcription 3 (STAT3). In an AlphaScreen-based biochemical assay using recombinant human STAT3, binding of STAT3-Src homology 2 (SH2) to the phosphotyrosine (pTyr, pY) peptide was inhibited by BENDA but not by the inactive metabolite dihydroxy bendamustine (HP2). When a single point mutation of C550A or C712A was introduced into recombinant human STAT3, its sensitivity to BENDA was substantially reduced, suggesting that these cysteine residues are important for BENDA to inhibit STAT3. Furthermore, BENDA suppressed the function of cellular STAT3 as a transcriptional activator in a human breast cancer cell line, MDA-MB-468, with constitutively activated STAT3. A competitive pull-down assay using biotinylated BENDA (Bio-BENDA) revealed that BENDA bound tightly to cellular STAT3, presumably through covalent bonds. Therefore, our results suggest that the anticancer effects of BENDA may be associated, at least in part, with its inhibitory effect on the SH2 domain of STAT3.
authors.affiliation: Center for Drug Discovery, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Iwamoto
authors.affiliation: Center for Drug Discovery, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Uehara
authors.affiliation: Center for Drug Discovery, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
authors.forename: Yukie
authors.initials: Y
authors.lastname: Inoue
authors.affiliation: Center for Drug Discovery, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Taguchi
authors.affiliation: Center for Drug Discovery, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Muraoka
authors.affiliation: Center for Drug Discovery, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
authors.forename: Naohisa
authors.initials: N
authors.lastname: Ogo
authors.affiliation: Center for Drug Discovery, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Matsuno
authors.affiliation: Center for Drug Discovery, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Asai
mesh_terms: D000409:Alanine / Q000737:chemistry / Q000378:metabolism; D018906:Antineoplastic Agents, Alkylating / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D000069461:Bendamustine Hydrochloride / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D001665:Binding Sites; D045744:Cell Line, Tumor; D003545:Cysteine / Q000737:chemistry* / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor; D015870:Gene Expression; D006801:Humans; D010455:Peptides / Q000037:antagonists & inhibitors / Q000138:chemical synthesis / Q000378:metabolism; D019000:Phosphotyrosine / Q000737:chemistry* / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D018909:src Homology Domains
chemical_list: D018906:Antineoplastic Agents, Alkylating; D010455:Peptides; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D019000:Phosphotyrosine; D000069461:Bendamustine Hydrochloride; D003545:Cysteine; D000409:Alanine