title: Definition of smad3 phosphorylation events that affect malignant and metastatic behaviors in breast cancer cells.
abstract: Smad3, a major intracellular mediator of TGFβ signaling, functions as both a positive and negative regulator in carcinogenesis. In response to TGFβ, the TGFβ receptor phosphorylates serine residues at the Smad3 C-tail. Cancer cells often contain high levels of the MAPK and CDK activities, which can lead to the Smad3 linker region becoming highly phosphorylated. Here, we report, for the first time, that mutation of the Smad3 linker phosphorylation sites markedly inhibited primary tumor growth, but significantly increased lung metastasis of breast cancer cell lines. In contrast, mutation of the Smad3 C-tail phosphorylation sites had the opposite effect. We show that mutation of the Smad3 linker phosphorylation sites greatly intensifies all TGFβ-induced responses, including growth arrest, apoptosis, reduction in the size of putative cancer stem cell population, epithelial-mesenchymal transition, and invasive activity. Moreover, all TGFβ responses were completely lost on mutation of the Smad3 C-tail phosphorylation sites. Our results demonstrate a critical role of the counterbalance between the Smad3 C-tail and linker phosphorylation in tumorigenesis and metastasis. Our findings have important implications for therapeutic intervention of breast cancer.
authors.affiliation: CHA Cancer Research Institute, CHA University, Seoul, Korea.
authors.forename: Eunjin
authors.initials: E
authors.lastname: Bae
authors.affiliation: Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland.
authors.forename: Misako
authors.initials: M
authors.lastname: Sato
authors.affiliation: CHA Cancer Research Institute, CHA University, Seoul, Korea.
authors.forename: Ran-Ju
authors.initials: RJ
authors.lastname: Kim
authors.affiliation: CHA Cancer Research Institute, CHA University, Seoul, Korea.
authors.forename: Mi-Kyung
authors.initials: MK
authors.lastname: Kwak
authors.affiliation: Cancer Research Institute, Kanazawa University, Kanazawa, Ishikawa, Japan.
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Naka
authors.affiliation: Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Korea.
authors.forename: Jungsoo
authors.initials: J
authors.lastname: Gim
authors.affiliation: Genome Resource and Analysis Unit, RIKEN Center for Developmental Biology, Kobe, Japan.
authors.forename: Mitsutaka
authors.initials: M
authors.lastname: Kadota
authors.affiliation: Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland.
authors.forename: Binwu
authors.initials: B
authors.lastname: Tang
authors.affiliation: Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland.
authors.forename: Kathleen C
authors.initials: KC
authors.lastname: Flanders
authors.affiliation: CHA Cancer Research Institute, CHA University, Seoul, Korea.
authors.forename: Tae-Aug
authors.initials: TA
authors.lastname: Kim
authors.affiliation: Department of Biology and Biomedical Science, Dong-A University, Busan, Korea.
authors.forename: Sun-Hee
authors.initials: SH
authors.lastname: Leem
authors.affiliation: Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Korea. Department of Statistics, Seoul National University, Seoul, Korea.
authors.forename: Taesung
authors.initials: T
authors.lastname: Park
authors.affiliation: Center for Advanced Biotechnology and Medicine, Susan Lehman Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey.
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.affiliation: Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland.
authors.forename: Lalage M
authors.initials: LM
authors.lastname: Wakefield
authors.affiliation: CHA Cancer Research Institute, CHA University, Seoul, Korea. aooshima@cha.ac.kr kimsj@cha.ac.kr.
authors.forename: Seong-Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: CHA Cancer Research Institute, CHA University, Seoul, Korea. Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, Maryland. aooshima@cha.ac.kr kimsj@cha.ac.kr.
authors.forename: Akira
authors.initials: A
authors.lastname: Ooshima
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009154:Mutation; D009362:Neoplasm Metastasis / Q000235:genetics / Q000473:pathology; D010766:Phosphorylation / Q000235:genetics; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D018125:Receptors, Transforming Growth Factor beta; C497790:SMAD3 protein, human; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta