title: Positive feedback activation of estrogen receptors by the CXCL12-CXCR4 pathway.
abstract: Induction of estrogen-regulated gene transcription by estrogen receptors ERalpha and ERbeta plays an important role in breast cancer development and growth. High expression of the chemokine receptor CXCR4 and its ligand CXCL12/stromal cell-derived factor 1 (SDF-1) has also been correlated with aggressive breast tumor phenotypes. Here, we describe a positive regulatory loop between the CXCR4/SDF-1 signaling pathway and ER transcriptional competence in human breast cancer cells. Treatment of breast carcinoma MCF-7 cells with SDF-1 increased ER transcriptional activity and expression of ER target genes, including SDF-1 itself. These effects were blocked by the antiestrogen ICI-182780 and by CXCR4 silencing and, conversely, estrogen-induced gene expression and growth of MCF-7 cells were impaired on CXCR4 inhibition. Both ERalpha and ERbeta were activated by SDF-1 in the presence of CXCR4 and by overexpression of a constitutively active CXCR4, indicating that CXCR4 signals to both receptors. In particular, ERbeta was able to translate the effects of SDF-1 on its own expression, as well as enhance activator protein 1 (AP-1) containing genes cyclin D1 and c-Myc in the presence of tamoxifen. This correlated with an increased ERbeta occupancy of responsive promoters at both estrogen-responsive and AP-1 elements. Ser-87, a conserved mitogen-activated protein kinase site in ERbeta, was highly phosphorylated by SDF-1, revealing an essential role of the AF-1 domain in response to CXCR4 activation. These results identify a complete autocrine loop between the CXCR4/SDF-1 and ERalpha/ERbeta signaling pathways that dictates ER-dependent gene expression and growth of breast cancer cells.
authors: Research Center, CHU Ste-Justine, and Department of Biochemistry, University of Montreal, Montréal, Quebec, Canada.
authors: Karine
authors: K
authors: Sauvé
authors: Julie
authors: J
authors: Lepage
authors: Mélanie
authors: M
authors: Sanchez
authors: Nikolaus
authors: N
authors: Heveker
authors: André
authors: A
authors: Tremblay
mesh_terms: D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D054377:Chemokine CXCL12 / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D047629:Estrogen Receptor beta / Q000235:genetics / Q000378:metabolism; D004967:Estrogens / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D019718:Receptors, CXCR4 / Q000235:genetics*; D011960:Receptors, Estrogen / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics*; D013629:Tamoxifen / Q000494:pharmacology; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism
chemical_list: C515255:CXCL12 protein, human; C527276:CXCR4 protein, human; D054377:Chemokine CXCL12; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D004967:Estrogens; D019718:Receptors, CXCR4; D011960:Receptors, Estrogen; D018808:Transcription Factor AP-1; D013629:Tamoxifen; D012694:Serine