title: Stat3 regulates ErbB-2 expression and co-opts ErbB-2 nuclear function to induce miR-21 expression, PDCD4 downregulation and breast cancer metastasis.
abstract: Membrane overexpression of the receptor tyrosine kinase ErbB-2 (MErbB-2) accounts for a clinically aggressive breast cancer (BC) subtype (ErbB-2-positive) with increased incidence of metastases. We and others demonstrated that nuclear ErbB-2 (NErbB-2) also plays a key role in BC and is a poor prognostic factor in ErbB-2-positive tumors. The signal transducer and activator of transcription 3 (Stat3), another player in BC, has been recognized as a downstream mediator of MErbB-2 action in BC metastasis. Here, we revealed an unanticipated novel direction of the ErbB-2 and Stat3 interaction underlying BC metastasis. We found that Stat3 binds to its response elements (GAS) at the ErbB-2 promoter to upregulate ErbB-2 transcription in metastatic, ErbB-2-positive BC. We validated these results in several BC subtypes displaying metastatic and non-metastatic ability, highlighting Stat3 general role as upstream regulator of ErbB-2 expression in BC. Moreover, we showed that Stat3 co-opts NErbB-2 function by recruiting ErbB-2 as its coactivator at the GAS sites in the promoter of microRNA-21 (miR-21), a metastasis-promoting microRNA (miRNA). Using an ErbB-2 nuclear localization domain mutant and a constitutively activated ErbB-2 variant, we found that NErbB-2 role as a Stat3 coactivator and also its direct role as transcription factor upregulate miR-21 in BC. This reveals a novel function of NErbB-2 as a regulator of miRNAs expression. Increased levels of miR-21, in turn, downregulate the expression of the metastasis-suppressor protein programmed cell death 4 (PDCD4), a validated miR-21 target. Using an in vivo model of metastatic ErbB-2-postive BC, in which we silenced Stat3 and reconstituted ErbB-2 or miR-21 expression, we showed that both are downstream mediators of Stat3-driven metastasis. Supporting the clinical relevance of our results, we found an inverse correlation between ErbB-2/Stat3 nuclear co-expression and PDCD4 expression in ErbB-2-positive primary invasive BCs. Our findings identify Stat3 and NErbB-2 as novel therapeutic targets to inhibit ErbB-2-positive BC metastasis.
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: L
authors.initials: L
authors.lastname: Venturutti
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: L V
authors.initials: LV
authors.lastname: Romero
authors.affiliation: Research Area, Institute of Oncology 'Angel H. Roffo', University of Buenos Aires, Buenos Aires, Argentina.
authors.forename: A J
authors.initials: AJ
authors.lastname: Urtreger
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: M F
authors.initials: MF
authors.lastname: Chervo
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: R I
authors.initials: RI
authors.lastname: Cordo Russo
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: M F
authors.initials: MF
authors.lastname: Mercogliano
authors.affiliation: Servicio de Patología, Sanatorio Mater Dei, Buenos Aires, Argentina.
authors.forename: G
authors.initials: G
authors.lastname: Inurrigarro
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: M G
authors.initials: MG
authors.lastname: Pereyra
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: C J
authors.initials: CJ
authors.lastname: Proietti
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: F
authors.initials: F
authors.lastname: Izzo
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: M C
authors.initials: MC
authors.lastname: Díaz Flaqué
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: V
authors.initials: V
authors.lastname: Sundblad
authors.affiliation: Departamento de Anatomía Patológica (BIOREN), Universidad de La Frontera, Temuco, Chile.|Departamento de Anatomía Patológica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago de Chile, Chile.|Advanced Center for Chronic Diseases (ACCDIS), Pontificia Universidad Católica de Chile, Santiago de Chile, Chile.
authors.forename: J C
authors.initials: JC
authors.lastname: Roa
authors.affiliation: Departamento de Anatomía Patológica (BIOREN), Universidad de La Frontera, Temuco, Chile.
authors.forename: P
authors.initials: P
authors.lastname: Guzmán
authors.affiliation: Research Area, Institute of Oncology 'Angel H. Roffo', University of Buenos Aires, Buenos Aires, Argentina.
authors.forename: E D
authors.initials: ED
authors.lastname: Bal de Kier Joffé
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: E H
authors.initials: EH
authors.lastname: Charreau
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: R
authors.initials: R
authors.lastname: Schillaci
authors.affiliation: Laboratory of Molecular Mechanisms of Carcinogenesis, Instituto de Biología y Medicina Experimental, CONICET, Buenos Aires, Argentina.
authors.forename: P V
authors.initials: PV
authors.lastname: Elizalde
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis* / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D035683:MicroRNAs / Q000096:biosynthesis* / Q000235:genetics; D008875:Middle Aged; D009362:Neoplasm Metastasis; D016601:RNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics; D050796:STAT3 Transcription Factor / Q000235:genetics*; D015398:Signal Transduction; D015533:Transcriptional Activation / Q000235:genetics; D014162:Transfection
chemical_list: D051017:Apoptosis Regulatory Proteins; D035683:MicroRNAs; D016601:RNA-Binding Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D050796:STAT3 Transcription Factor; C524940:MIRN21 microRNA, human; C114487:PDCD4 protein, human; C508053:ERBB2 protein, human