title: BMP-6 inhibits microRNA-21 expression in breast cancer through repressing deltaEF1 and AP-1.
abstract: MicroRNAs (miRNAs), which are small noncoding RNA molecules, play important roles in the post-transcriptional regulation process. The microRNA-21 gene (miR-21) has been reported to be highly expressed in various solid tumors, including breast cancer. Bone morphogenetic protein-6 (BMP-6) has been identified as an inhibitor of breast cancer epithelial-mesenchymal transition (EMT) through rescuing E-cadherin expression. We initiated experiments to identify the relationships between miR-21 and BMP-6 in breast cancer progression. Real-time PCR analysis showed that miR-21 expression was very high in MDA-MB-231 cells that expressed little BMP-6. A reverse correlation between BMP-6 and miR-21 was also determined in breast cancer tissue samples. Moreover, BMP-6 inhibited miR-21 transcription in MDA-MB-231 cells. In order to investigate how BMP-6 inhibited the miR-21 promoter (miPPR-21), we constructed a series of miPPR-21 reporters. Luciferase assay results indicated that BMP-6 inhibited miPPR-21 activity through the E2-box and AP-1-binding sites. We also demonstrated that both deltaEF1 and TPA induced miR-21 expression. Using site-directed mutation and CHIP assay, we found that deltaEF1 induced miPPR-21 activity by binding to the E2-box on miPPR-21. Moreover, TPA triggered miPPR-21 activity through the AP-1 binding sites. BMP-6 treatment significantly reduced the binding of these factors to miPPR-21 by decreasing the expression of deltaEF1 and c-Fos/c-Jun. We also demonstrated that BMP-6-induced downregulation of miR-21 modified the activity of PDCD4 3'UTR and inhibited MDA-MB-231 cell invasion. deltaEF1 overexpression and TPA induction blocked this inhibitory effect of BMP-6. In conclusion, BMP-6-induced inhibition of miR-21 suggests that BMP-6 may function as an anti-metastasis factor by a mechanism involving transcriptional repression of miR-21 in breast cancer.
authors.affiliation: Laboratory of Medical Molecular Biology, Medical College of Nankai University, 94 Weijin Road, Tianjin 300071, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Du
authors.forename: Shuang
authors.initials: S
authors.lastname: Yang
authors.forename: Di
authors.initials: D
authors.lastname: An
authors.forename: Fen
authors.initials: F
authors.lastname: Hu
authors.forename: Wei
authors.initials: W
authors.lastname: Yuan
authors.forename: Chunli
authors.initials: C
authors.lastname: Zhai
authors.forename: Tianhui
authors.initials: T
authors.lastname: Zhu
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D055418:Bone Morphogenetic Protein 6 / Q000378:metabolism* / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015820:Cadherins / Q000378:metabolism; D045744:Cell Line, Tumor; D015536:Down-Regulation; D018398:Homeodomain Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed; D034741:RNA, Small Interfering / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000737:chemistry / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014162:Transfection; D000071799:Zinc Finger E-box-Binding Homeobox 1
chemical_list: D051017:Apoptosis Regulatory Proteins; D055418:Bone Morphogenetic Protein 6; D015820:Cadherins; D018398:Homeodomain Proteins; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; C114487:PDCD4 protein, human; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D018808:Transcription Factor AP-1; D014157:Transcription Factors; C486307:ZEB1 protein, human; D000071799:Zinc Finger E-box-Binding Homeobox 1; D013755:Tetradecanoylphorbol Acetate