title: BMP-6 promotes E-cadherin expression through repressing deltaEF1 in breast cancer cells.
abstract: BACKGROUND
  Bone morphogenetic protein-6 (BMP-6) is critically involved in many developmental processes. Recent studies indicate that BMP-6 is closely related to tumor differentiation and metastasis.
  
  
  METHODS
  Quantitative RT-PCR was used to determine the expression of BMP-6, E-cadherin, and deltaEF1 at the mRNA level in MCF-7 and MDA-MB-231 breast cancer cells, as well as in 16 breast cancer specimens. Immunoblot analysis was used to measure the expression of deltaEF1 at the protein level in deltaEF1-overexpressing and deltaEF1-interfered MDA-MB-231 cells. Luciferase assay was used to determine the rhBMP-6 or deltaEF1 driven transcriptional activity of the E-cadherin promoter in MDA-MB-231 cells. Quantitative CHIP assay was used to detect the direct association of deltaEF1 with the E-cadherin proximal promoter in MDA-MB-231 cells.
  
  
  RESULTS
  MCF-7 breast cancer cells, an ER+ cell line that expressed high levels of BMP-6 and E-cadherin exhibited very low levels of deltaEF1 transcript. In contrast, MDA-MB-231 cells, an ER- cell line had significantly reduced BMP-6 and E-cadherin mRNA levels, suggesting an inverse correlation between BMP-6/E-cadherin and deltaEF1. To determine if the same relationship exists in human tumors, we examined tissue samples of breast cancer from human subjects. In 16 breast cancer specimens, the inverse correlation between BMP-6/E-cadherin and deltaEF1 was observed in both ER+ cases (4 of 8 cases) and ER- cases (7 of 8 cases). Further, we found that BMP-6 inhibited deltaEF1 transcription, resulting in an up-regulation of E-cadherin mRNA expression. This is consistent with our analysis of the E-cadherin promoter demonstrating that BMP-6 was a potent transcriptional activator. Interestingly, ectopic expression of deltaEF1 was able to block BMP-6-induced transactivation of E-cadherin, whereas RNA interference-mediated down-regulation of endogenous deltaEF1 in breast cancer cells abolished E-cadherin transactivation by BMP-6. In addition to down-regulating the expression of deltaEF1, BMP-6 also physically dislodged deltaEF1 from E-cadherin promoter to allow the activation of E-cadherin transcription.
  
  
  CONCLUSIONS
  We conclude that repression of deltaEF1 plays a key role in mediating BMP-6-induced transcriptional activation of E-cadherin in breast cancer cells. Consistent with the fact that higher level of deltaEF1 expression is associated with more invasive phenotype of breast cancer cells, our collective data suggests that deltaEF1 is likely the switch through which BMP-6 restores E-cadherin-mediated cell-to-cell adhesion and prevents breast cancer metastasis.
authors.affiliation: Medical College of Nankai University, Tianjin, China. yangshuang@nankai.edu.cn
authors.forename: Shuang
authors.initials: S
authors.lastname: Yang
authors.forename: Jun
authors.initials: J
authors.lastname: Du
authors.forename: Zhaoqi
authors.initials: Z
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Yuan
authors.forename: Yuhuan
authors.initials: Y
authors.lastname: Qiao
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Songyuan
authors.initials: S
authors.lastname: Gao
authors.forename: Jian
authors.initials: J
authors.lastname: Yin
authors.forename: Baocun
authors.initials: B
authors.lastname: Sun
authors.forename: Tianhui
authors.initials: T
authors.lastname: Zhu
mesh_terms: D000328:Adult; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins / Q000235:genetics*; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D015820:Cadherins / Q000235:genetics*; D018270:Carcinoma, Ductal, Breast / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D020648:Peptide Elongation Factor 1 / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D012334:RNA, Neoplasm / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015533:Transcriptional Activation; D015854:Up-Regulation
chemical_list: C525816:BMP6 protein, human; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins; D015820:Cadherins; D020648:Peptide Elongation Factor 1; D012333:RNA, Messenger; D012334:RNA, Neoplasm