title: Loss of N-Myc interactor promotes epithelial-mesenchymal transition by activation of TGF-β/SMAD signaling.
abstract: Epithelial-mesenchymal transition is one of the critical cellular programs that facilitate the progression of breast cancer to an invasive disease. We have observed that the expression of N-myc interactor (NMI) decreases significantly during progression of breast cancer, specifically in invasive and metastatic stages. Recapitulation of this loss in breast cell lines with epithelial morphology (MCF10A (non-tumorigenic) and T47D (tumorigenic)) by silencing NMI expression causes mesenchymal-like morphological changes in 3D growth, accompanied by upregulation of SLUG and ZEB2 and increased invasive properties. Conversely, we found that restoring NMI expression attenuated the mesenchymal attributes of metastatic breast cancer cells, accompanied by distinctly circumscribed 3D growth with basement membrane deposition and decreased invasion. Further investigations into the downstream signaling modulated by NMI revealed that NMI expression negatively regulates SMAD signaling, which is a key regulator of cellular plasticity. We demonstrate that NMI blocks TGF-β/SMAD signaling via upregulation of SMAD7, a negative feedback regulator of the pathway. We also provide evidence that NMI activates STAT signaling, which negatively modulates TGF-β/SMAD signaling. Taken together, our findings suggest that loss of NMI during breast cancer progression could be one of the driving factors that enhance the invasive ability of breast cancer by aberrant activation of TGF-β/SMAD signaling.
authors.affiliation: Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Devine
authors.affiliation: 1] Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA [2] Department of Surgery, University of South Alabama, Mobile, AL, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Rostas
authors.affiliation: Department of Pathology and Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Metge
authors.affiliation: Department of Pathology and Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: S
authors.initials: S
authors.lastname: Das
authors.affiliation: Department of Mathematics and Statistics, University of South Alabama, Mobile, AL, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Mulekar
authors.affiliation: Department of Pathology, University of South Alabama, Mobile, AL, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Tucker
authors.affiliation: Department of Pathology and Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: W E
authors.initials: WE
authors.lastname: Grizzle
authors.affiliation: Department of Radiation Oncology, University of Alabama at Birmingham, AL, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Buchsbaum
authors.affiliation: Department of Pathology and Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Shevde
authors.affiliation: Department of Pathology and Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Samant
mesh_terms: D002460:Cell Line; D058750:Epithelial-Mesenchymal Transition; D020868:Gene Silencing; D006801:Humans; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D016271:Proto-Oncogene Proteins c-myc; D051785:Smad Proteins; D016212:Transforming Growth Factor beta