CREB-1 and AP-1 transcription factors JunD and Fra-2 regulate bone sialoprotein gene expression in human breast cancer cells.
Bone sialoprotein (BSP) expression is detected in a variety of human osteotropic cancers. High expression of BSP in breast and prostate primary carcinomas is associated with progression and bone metastases development. In this study, we examined the transcriptional regulation of BSP gene expression in MDA-MB-231 and MCF-7 human breast cancer cells compared with Saos-2 human osteoblast-like cells. BSP human promoter deletion analyses delineated a -56/-84 region, which comprises a cAMP response element (CRE) that was sufficient for maximal promoter activity in breast cancer cell lines. We found that the basic fibroblast growth factor response element (FRE) also located in the proximal promoter was a crucial regulator of human BSP promoter activity in Saos-2 but not in breast cancer cells. Promoter activity experiments in combination with DNA mobility shift assays demonstrated that BSP promoter activity is under the control of the CRE element, through CREB-1, JunD and Fra-2 binding, in MDA-MB-231, MCF-7 and in Saos-2 cells. Forskolin, a protein kinase A pathway activator, failed to enhance BSP transcriptional activity suggesting that CRE site behaves as a constitutive rather than an inducible element in these cell lines. Over-expression of JunD and Fra-2 increased BSP promoter activity and upregulated endogenous BSP protein expression in MCF-7 and Saos-2 cells while siRNA-mediated inhibition of both factors expression significantly reduced BSP protein level in MDA-MB-231. Collectively, these data provide with new transcriptional mechanisms, implicating CREB and AP-1 factors, that control BSP gene expression in breast cancer cells.
Detry
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Metastasis Research Laboratory, Center of Experimental Cancer Research, University of Liège, Belgium.
Lamour
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Castronovo
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Bellahcène
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D001943:Breast Neoplasms / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D045744:Cell Line, Tumor; D017362:Cyclic AMP Response Element-Binding Protein / Q000276:immunology / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D051921:Fos-Related Antigen-2 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D058574:Integrin-Binding Sialoprotein; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D012795:Sialoglycoproteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000276:immunology / Q000378:metabolism*
D017362:Cyclic AMP Response Element-Binding Protein; D051921:Fos-Related Antigen-2; C546871:IBSP protein, human; D058574:Integrin-Binding Sialoprotein; D016755:Proto-Oncogene Proteins c-jun; D034741:RNA, Small Interfering; D012795:Sialoglycoproteins; D018808:Transcription Factor AP-1; D017868:Cyclic AMP-Dependent Protein Kinases