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The chemokine receptor CXCR7 interacts with EGFR to promote breast cancer cell proliferation

BACKGROUND: Recent advances have revealed a significant contribution of chemokines and their receptors in tumor growth, survival after chemotherapy, and organ-specific metastasis. The CXC chemokine receptor-7 (CXCR7) is the latest chemokine receptor implicated in cancer. Although over expressed in b...

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Autores principales: Salazar, Nicole, Muñoz, Daniel, Kallifatidis, Georgios, Singh, Rajendra K, Jordà, Mercè, Lokeshwar, Bal L
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4167278/
https://www.ncbi.nlm.nih.gov/pubmed/25168820
http://dx.doi.org/10.1186/1476-4598-13-198
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author Salazar, Nicole
Muñoz, Daniel
Kallifatidis, Georgios
Singh, Rajendra K
Jordà, Mercè
Lokeshwar, Bal L
author_facet Salazar, Nicole
Muñoz, Daniel
Kallifatidis, Georgios
Singh, Rajendra K
Jordà, Mercè
Lokeshwar, Bal L
author_sort Salazar, Nicole
collection PubMed
description BACKGROUND: Recent advances have revealed a significant contribution of chemokines and their receptors in tumor growth, survival after chemotherapy, and organ-specific metastasis. The CXC chemokine receptor-7 (CXCR7) is the latest chemokine receptor implicated in cancer. Although over expressed in breast cancer cell lines and tumor tissues, its mechanism of action in breast cancer (BrCa) growth and metastasis is unclear. Studies in other cancers have implicated CXCR7 in cell proliferation, anti-apoptotic activity and cell-cell adhesion. The present study was initiated to examine the pattern of CXCR7 expression and its role in regulation of growth signaling in breast cancer. METHODS: The contribution of CXCR7 in BrCa cell proliferation was investigated in representative cell lines using real time quantitative PCR (q-PCR), proliferation assays, immunohistochemistry and immunoblotting. Phenotypic changes were examined after CXCR7 specific cDNA and siRNA transfection and expression levels were monitored by q-PCR. Further, the association of CXCR7 with epidermal growth factor receptor (EGFR) and modulation of its activity were investigated by western blotting, immunofluorescence, and in-situ proximity ligation assays in human BrCa cells and tissues. RESULTS: CXCR7 was expressed in both, estrogen receptor (ER) positive and negative BrCa cell lines. CXCR7 was also expressed unevenly in normal breast tissues and to a much higher extent in ER + cancer tissues. Depletion of CXCR7 in MCF7 BrCa cells by RNA interference decreased proliferation and caused cell cycle arrest. Further, proximity ligation assay (PLA) revealed colocalization of CXCR7 with EGFR in cancer tissues and cancer cell lines. CXCR7 depletion reduced levels of phospho-EGFR at Tyrosine1110 after EGF-stimulation and also reduced phosphorylation of ERK1/2, indicating a potentially direct impact on mitogenic signaling in MCF7 cells. Using siRNA to knockdown β-arrestin2 in cells with EGFR over expression we were able to nearly deplete the CXCR7-EGFR colocalization events, suggesting that β-arrestin2 acts as a scaffold to enhance CXCR7 dependent activation of EGFR after EGF stimulation. CONCLUSIONS: These results demonstrate coupling of CXCR7 with EGFR to regulate proliferation of BrCa cells and suggest an important ligand-independent role of CXCR7 in BrCa growth. Thus, the CXCR7-EGFR axis is a promising target for breast cancer therapy. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1476-4598-13-198) contains supplementary material, which is available to authorized users.
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spelling pubmed-41672782014-09-19 The chemokine receptor CXCR7 interacts with EGFR to promote breast cancer cell proliferation Salazar, Nicole Muñoz, Daniel Kallifatidis, Georgios Singh, Rajendra K Jordà, Mercè Lokeshwar, Bal L Mol Cancer Research BACKGROUND: Recent advances have revealed a significant contribution of chemokines and their receptors in tumor growth, survival after chemotherapy, and organ-specific metastasis. The CXC chemokine receptor-7 (CXCR7) is the latest chemokine receptor implicated in cancer. Although over expressed in breast cancer cell lines and tumor tissues, its mechanism of action in breast cancer (BrCa) growth and metastasis is unclear. Studies in other cancers have implicated CXCR7 in cell proliferation, anti-apoptotic activity and cell-cell adhesion. The present study was initiated to examine the pattern of CXCR7 expression and its role in regulation of growth signaling in breast cancer. METHODS: The contribution of CXCR7 in BrCa cell proliferation was investigated in representative cell lines using real time quantitative PCR (q-PCR), proliferation assays, immunohistochemistry and immunoblotting. Phenotypic changes were examined after CXCR7 specific cDNA and siRNA transfection and expression levels were monitored by q-PCR. Further, the association of CXCR7 with epidermal growth factor receptor (EGFR) and modulation of its activity were investigated by western blotting, immunofluorescence, and in-situ proximity ligation assays in human BrCa cells and tissues. RESULTS: CXCR7 was expressed in both, estrogen receptor (ER) positive and negative BrCa cell lines. CXCR7 was also expressed unevenly in normal breast tissues and to a much higher extent in ER + cancer tissues. Depletion of CXCR7 in MCF7 BrCa cells by RNA interference decreased proliferation and caused cell cycle arrest. Further, proximity ligation assay (PLA) revealed colocalization of CXCR7 with EGFR in cancer tissues and cancer cell lines. CXCR7 depletion reduced levels of phospho-EGFR at Tyrosine1110 after EGF-stimulation and also reduced phosphorylation of ERK1/2, indicating a potentially direct impact on mitogenic signaling in MCF7 cells. Using siRNA to knockdown β-arrestin2 in cells with EGFR over expression we were able to nearly deplete the CXCR7-EGFR colocalization events, suggesting that β-arrestin2 acts as a scaffold to enhance CXCR7 dependent activation of EGFR after EGF stimulation. CONCLUSIONS: These results demonstrate coupling of CXCR7 with EGFR to regulate proliferation of BrCa cells and suggest an important ligand-independent role of CXCR7 in BrCa growth. Thus, the CXCR7-EGFR axis is a promising target for breast cancer therapy. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1476-4598-13-198) contains supplementary material, which is available to authorized users. BioMed Central 2014-08-28 /pmc/articles/PMC4167278/ /pubmed/25168820 http://dx.doi.org/10.1186/1476-4598-13-198 Text en © Salazar et al.; licensee BioMed Central Ltd. 2014 This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Salazar, Nicole
Muñoz, Daniel
Kallifatidis, Georgios
Singh, Rajendra K
Jordà, Mercè
Lokeshwar, Bal L
The chemokine receptor CXCR7 interacts with EGFR to promote breast cancer cell proliferation
title The chemokine receptor CXCR7 interacts with EGFR to promote breast cancer cell proliferation
title_full The chemokine receptor CXCR7 interacts with EGFR to promote breast cancer cell proliferation
title_fullStr The chemokine receptor CXCR7 interacts with EGFR to promote breast cancer cell proliferation
title_full_unstemmed The chemokine receptor CXCR7 interacts with EGFR to promote breast cancer cell proliferation
title_short The chemokine receptor CXCR7 interacts with EGFR to promote breast cancer cell proliferation
title_sort chemokine receptor cxcr7 interacts with egfr to promote breast cancer cell proliferation
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4167278/
https://www.ncbi.nlm.nih.gov/pubmed/25168820
http://dx.doi.org/10.1186/1476-4598-13-198
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