title: GATA3 protein as a MUC1 transcriptional regulator in breast cancer cells.
abstract: BACKGROUND
  Recent studies have demonstrated that members of the GATA-binding protein (GATA) family (GATA4 and GATA5) might have pivotal roles in the transcriptional upregulation of mucin genes (MUC2, MUC3 and MUC4) in gastrointestinal epithelium. The zinc-finger GATA3 transcription factor has been reported to be involved in the growth control and differentiation of breast epithelial cells. In SAGE (serial analysis of gene expression) studies we observed an intriguing significant correlation between GATA3 and MUC1 mRNA expression in breast carcinomas. We therefore designed the present study to elucidate whether MUC1 expression is regulated by GATA3 in breast cancer cells.
  
  
  METHODS
  Promoter sequence analysis of the MUC1 gene identified six GATA cis consensus elements in the 5' flanking region (GATA1, GATA3 and four GATA-like sequences). Chromatin immunoprecipitation and electrophoretic mobility-shift assays were employed to study the presence of a functional GATA3-binding site. GATA3 and MUC1 expression was analyzed in vitro with a GATA3 knockdown assay. Furthermore, expression of GATA3 and MUC1 genes was analyzed by real-time RT-PCR and immunohistochemistry on breast cancer-specific tissue microarrays.
  
  
  RESULTS
  We confirmed the presence of a functional GATA3-binding site on the MUC1 promoter region in the MCF7 cell line. We determined that GATA3 knockdown assays led to a decrease in MUC1 protein expression in MCF7 and T47D cells. In addition, we detected a statistically significant correlation in expression between GATA3 and MUC1 genes at the mRNA and protein levels both in normal breast epithelium and in breast carcinomas (p = 0.01). GATA3 expression was also highly associated with estrogen receptor and progesterone receptor status (p = 0.0001) and tumor grade (p = 0.004) in breast carcinomas.
  
  
  CONCLUSIONS
  Our study provides evidence indicating that GATA3 is probably a mediator for the transcriptional upregulation of MUC1 expression in some breast cancers.
authors.affiliation: Department of Carcinogenesis, The University of Texas MD Anderson Cancer Center, Science Park--Research Division, Smithville, TX 78957, USA. mabba777@hotmail.com
authors.forename: Martín C
authors.initials: MC
authors.lastname: Abba
authors.forename: María I
authors.initials: MI
authors.lastname: Nunez
authors.forename: Andrea G
authors.initials: AG
authors.lastname: Colussi
authors.forename: María V
authors.initials: MV
authors.lastname: Croce
authors.forename: Amada
authors.initials: A
authors.lastname: Segal-Eiras
authors.forename: C Marcelo
authors.initials: CM
authors.lastname: Aldaz
mesh_terms: D000951:Antigens, Neoplasm / Q000235:genetics*; D001943:Breast Neoplasms / Q000235:genetics*; D005260:Female; D050990:GATA3 Transcription Factor / Q000235:genetics*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D018396:Mucin-1; D009077:Mucins / Q000235:genetics*; D014158:Transcription, Genetic; D015854:Up-Regulation
chemical_list: D000951:Antigens, Neoplasm; D050990:GATA3 Transcription Factor; C494749:GATA3 protein, human; C060192:MUC1 protein, human; D018396:Mucin-1; D009077:Mucins