title: TGFβ-induced c-Myb affects the expression of EMT-associated genes and promotes invasion of ER+ breast cancer cells.
abstract: Advanced breast cancer cells acquire metastatic properties in response to TGFβ. We show here that the expression of c-Myb increases in TGFβ-treated ER (+) breast cancer cells by protein stabilization, transcription activation and release from miR200-dependent down-regulation. In particular, we mapped 2 sites for miR200b, miR200c and miR429 binding in the 3' UTR of the human c-myb gene. These microRNAs decreased the expression of c-Myb when transfected in MCF-7 cells. In addition, luciferase activity from a vector containing the 3' UTR of the c-myb gene was inhibited by miR200s through a binding-dependent mechanism. siRNA- and shRNA-mediated down-regulation was used to investigate the role of c-Myb for the effects induced by TGFβ in ER(+) breast cancer MCF-7 and ZR-75.1 cells. Transfection with c-Myb siRNAs blocked the increase of Slug (SNAI2) and Bcl-2 expression and reversed the decrease in E-cadherin expression induced by TGF-β treatment. Conversely, c-Myb down-regulation decreased invasion and anchorage-independent growth of breast cancer cells expressing a constitutively active TGFβ receptor I. Finally, apoptosis induced by etoposide increased in c-Myb-silenced TGFβ-treated ER(+) cell lines. In summary, exposure of ER(+) breast cancer cells to TGFβ induces an increase of c-Myb expression which is required for expression of EMT-associated markers, in vitro invasion and anchorage-independent growth. Furthermore, our findings suggest a potentially detrimental effect of TGFβ and c-Myb co-expression in breast cancer.
authors.affiliation: ENEA Research Center Casaccia, Laboratory of Radiation Biology and Biomedicine, Casaccia, Rome, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Cesi
authors.forename: Arianna
authors.initials: A
authors.lastname: Casciati
authors.forename: Fabiola
authors.initials: F
authors.lastname: Sesti
authors.forename: Barbara
authors.initials: B
authors.lastname: Tanno
authors.forename: Bruno
authors.initials: B
authors.lastname: Calabretta
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Raschellà
mesh_terms: D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D001943:Breast Neoplasms / Q000473:pathology*; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003001:Cloning, Molecular; D058750:Epithelial-Mesenchymal Transition; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D005047:Etoposide / Q000494:pharmacology; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D020570:Genes, myb; D006801:Humans; D016086:Lentivirus / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009361:Neoplasm Invasiveness; D011499:Protein Processing, Post-Translational; D055550:Protein Stability; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: D014408:Biomarkers, Tumor; D015820:Cadherins; D047628:Estrogen Receptor alpha; C533896:MIRN200 microRNA, human; C546363:MIRN429 microRNA, human; D035683:MicroRNAs; D020598:Proto-Oncogene Proteins c-myb; D034741:RNA, Small Interfering; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D005047:Etoposide