title: Inhibition of STAT3 activation by KT-18618 via the disruption of the interaction between JAK3 and STAT3.
abstract: The constitutive activation of STAT3 in human cancers causes the abnormal proliferation and survival of cancer cells, and thus, STAT3 is a therapeutic target of antitumor drugs. We screened a small-molecule library of 8600 synthetic compounds from the "Korea Chemical Bank" to identify inhibit STAT3 activity using a cell-based luciferase assay system. KT-18618 ((Z)-N-(4-chlorophenyl)-N-methyl-2-[1,3,3,3,-tetrafluoro-2-(thiophen-2-yl)prop-1-enyloxy]-acetamide) was selected as a novel inhibitor of the JAK/STAT3 pathway. KT-18618 inhibited STAT3 phosphorylation and the expression of STAT3-regulated genes. The inhibition of STAT3 phosphorylation led to the apoptosis of MDA-MB-468 cells. We postulated that the inhibition of the JAK family of proteins or c-Src inhibited STAT3 phosphorylation. Interestingly, the phosphorylation of these kinases was only mildly inhibited, but the phosphorylation of STAT3 was completely inhibited. This result implies that the inhibition of STAT3 phosphorylation by KT-18618 is an independent event that occurs through the phosphorylation of upstream kinases. Co-immunoprecipitation experiments revealed that KT-18618 inhibited the JAK3-STAT3 interaction. Moreover, JAK3 molecules were captured by biotinylated KT-18618, implying that KT-18618 bound to JAK3 molecules. Additionally, 1μM KT-18618 inhibited JAK3 kinase activity by approximately 28% in an in vitro kinase assay. From these results, we suggest that KT-18618 binds to JAK3 molecules and disrupts the JAK3-STAT3 interaction, which leads to the inhibition of STAT3 phosphorylation. KT-18618 is the first inhibitor of the JAK3-STAT3 interaction.
authors.affiliation: Laboratory of Biology and Genomics, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahakro, Daejeon 305-806, Republic of Korea; University of Science and Technology in Korea, 125 Gwahakro, Daejeon 305-806, Republic of Korea.
authors.forename: Dae-Seop
authors.initials: DS
authors.lastname: Shin
authors.affiliation: Laboratory of Biology and Genomics, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahakro, Daejeon 305-806, Republic of Korea.
authors.forename: Seung Nam
authors.initials: SN
authors.lastname: Jung
authors.affiliation: Bio-Evaluation Center, Korea Research Institute of Bioscience and Biotechnology, Ochang, Cheongwon, Chungbuk 363-883, Republic of Korea; University of Science and Technology in Korea, 125 Gwahakro, Daejeon 305-806, Republic of Korea.
authors.forename: Jieun
authors.initials: J
authors.lastname: Yun
authors.affiliation: Bio-Evaluation Center, Korea Research Institute of Bioscience and Biotechnology, Ochang, Cheongwon, Chungbuk 363-883, Republic of Korea.
authors.forename: Chang Woo
authors.initials: CW
authors.lastname: Lee
authors.affiliation: Laboratory of Biology and Genomics, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahakro, Daejeon 305-806, Republic of Korea; University of Science and Technology in Korea, 125 Gwahakro, Daejeon 305-806, Republic of Korea.
authors.forename: Dong Cho
authors.initials: DC
authors.lastname: Han
authors.affiliation: Laboratory of Chemical Genomics, Korea Research Institute of Chemical Technology, Daejeon 305-600, Republic of Korea.
authors.forename: Bumtae
authors.initials: B
authors.lastname: Kim
authors.affiliation: Laboratory of Chemical Genomics, Korea Research Institute of Chemical Technology, Daejeon 305-600, Republic of Korea.
authors.forename: Yong Ki
authors.initials: YK
authors.lastname: Min
authors.affiliation: Graduate School of New Drug Discovery and Development, Chungnam National University, Daejeon 305-764, Republic of Korea.
authors.forename: Nam Sook
authors.initials: NS
authors.lastname: Kang
authors.affiliation: Laboratory of Biology and Genomics, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahakro, Daejeon 305-806, Republic of Korea; University of Science and Technology in Korea, 125 Gwahakro, Daejeon 305-806, Republic of Korea. Electronic address: kwonbm@kribb.re.kr.
authors.forename: Byoung-Mog
authors.initials: BM
authors.lastname: Kwon
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D064593:Heterografts; D006801:Humans; D053616:Janus Kinase 3 / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D010766:Phosphorylation; D011485:Protein Binding; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013876:Thiophenes / Q000494:pharmacology*
chemical_list: C000588597:KT-18618; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D013876:Thiophenes; C507933:JAK3 protein, human; D053616:Janus Kinase 3
keywords: Apoptosis; Breast cancer; JAK3; STAT3