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?-arrestin1 mediates metastatic growth of breast cancer cells by facilitating HIF-1-dependent VEGF expression.

ABSTRACT: ?-Arrestins 1 and 2 are multifunctional adaptor proteins originally discovered for their role in desensitizing seven-transmembrane receptor signaling via the heterotrimeric guanine nucleotide-binding proteins. Recently identified roles of ?-arrestins include regulation of cancer cell chemotaxis and proliferation. Herein, we report that ?-arrestin1 expression regulates breast tumor colonization in nude mice and cancer cell viability during hypoxia. ?-Arrestin1 robustly interacts with nuclear hypoxia-induced factor-1? (HIF-1?) that is stabilized during hypoxia and potentiates HIF-1-dependent transcription of the angiogenic factor vascular endothelial growth factor-A (VEGF-A). Increased expression of ?-arrestin1 in human breast cancer (infiltrating ductal carcinoma or IDC and metastatic IDC) correlates with increased levels of VEGF-A. While the anti-angiogenic drug thalidomide inhibits HIF-1-dependent VEGF transcription in breast carcinoma cells, it does not prevent HIF-1? stabilization, but leads to aberrant localization of HIF-1? to the perinuclear compartments and surprisingly stimulates nuclear export of ?-arrestin1. Additionally, imatinib mesylate that inhibits release of VEGF induces nuclear export of ?-arrestin1-HIF-1? complexes. Our findings suggest that ?-arrestin1 regulates nuclear signaling during hypoxia to promote survival of breast cancer cells via VEGF signaling and that drugs that induce its translocation from the nucleus to the cytoplasm could be useful in anti-angiogenic and breast cancer therapies.

SUBMITTER: Shenoy SK

PROVIDER: S-EPMC3179824 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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β-arrestin1 mediates metastatic growth of breast cancer cells by facilitating HIF-1-dependent VEGF expression.

Shenoy S K SK Han S S Zhao Y L YL Hara M R MR Oliver T T Cao Y Y Dewhirst M W MW

Oncogene 20110620 3

β-Arrestins 1 and 2 are multifunctional adaptor proteins originally discovered for their role in desensitizing seven-transmembrane receptor signaling via the heterotrimeric guanine nucleotide-binding proteins. Recently identified roles of β-arrestins include regulation of cancer cell chemotaxis and proliferation. Herein, we report that β-arrestin1 expression regulates breast tumor colonization in nude mice and cancer cell viability during hypoxia. β-Arrestin1 robustly interacts with nuclear hypo ...[more]

PMID: 21685944

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Project description:IntroductionCarcinoma-associated fibroblasts (CAFs) play a pivotal role in cancer progression by contributing to invasion, metastasis and angiogenesis. Solid tumors possess a unique microenvironment characterized by local hypoxia, which induces gene expression changes and biological features leading to poor outcomes. Hypoxia Inducible Factor 1 (HIF-1) is the main transcription factor that mediates the cell response to hypoxia through different mechanisms that include the regulation of genes strongly associated with cancer aggressiveness. Among the HIF-1 target genes, the G-protein estrogen receptor (GPER) exerts a stimulatory role in diverse types of cancer cells and in CAFs.MethodsWe evaluated the regulation and function of the key angiogenic mediator vascular endothelial growth factor (VEGF) in CAFs exposed to hypoxia. Gene expression studies, Western blotting analysis and immunofluorescence experiments were performed in CAFs and breast cancer cells in the presence of cobalt chloride (CoCl₂) or cultured under low oxygen tension (2% O₂), in order to analyze the involvement of the HIF-1α/GPER signaling in the biological responses to hypoxia. We also explored the role of the HIF-1α/GPER transduction pathway in functional assays like tube formation in human umbilical vein endothelial cells (HUVECs) and cell migration in CAFs.ResultsWe first determined that hypoxia induces the expression of HIF-1α and GPER in CAFs, then we ascertained that the HIF-1α/GPER signaling is involved in the regulation of VEGF expression in breast cancer cells and in CAFs exposed to hypoxia. We also assessed by ChIP assay that HIF-1α and GPER are both recruited to the VEGF promoter sequence and required for VEGF promoter stimulation upon hypoxic condition. As a biological counterpart of these findings, conditioned medium from hypoxic CAFs promoted tube formation in HUVECs in a HIF-1α/GPER dependent manner. The functional cooperation between HIF-1α and GPER in CAFs was also evidenced in the hypoxia-induced cell migration, which involved a further target of the HIF-1α/GPER signaling like connective tissue growth factor (CTGF).ConclusionsThe present results provide novel insight into the role elicited by the HIF-1α/GPER transduction pathway in CAFs towards the hypoxia-dependent tumor angiogenesis. Our findings further extend the molecular mechanisms through which the tumor microenvironment may contribute to cancer progression.

Project description:BACKGROUND:The G protein estrogen receptor GPER/GPR30 mediates estrogen action in breast cancer cells as well as in breast cancer-associated fibroblasts (CAFs), which are key components of microenvironment driving tumor progression. GPER is a transcriptional target of hypoxia inducible factor 1 alpha (HIF-1?) and activates VEGF expression and angiogenesis in hypoxic breast tumor microenvironment. Furthermore, IGF1/IGF1R signaling, which has angiogenic effects, has been shown to activate GPER in breast cancer cells. METHODS:We analyzed gene expression data from published studies representing almost 5000 breast cancer patients to investigate whether GPER and IGF1 signaling establish an angiocrine gene signature in breast cancer patients. Next, we used GPER-positive but estrogen receptor (ER)-negative primary CAF cells derived from patient breast tumours and SKBR3 breast cancer cells to investigate the role of GPER in the regulation of VEGF expression and angiogenesis triggered by IGF1. We performed gene expression and promoter studies, western blotting and immunofluorescence analysis, gene silencing strategies and endothelial tube formation assays to evaluate the involvement of the HIF-1?/GPER/VEGF signaling in the biological responses to IGF1. RESULTS:We first determined that GPER is co-expressed with IGF1R and with the vessel marker CD34 in human breast tumors (n?=?4972). Next, we determined that IGF1/IGF1R signaling engages the ERK1/2 and AKT transduction pathways to induce the expression of HIF-1? and its targets GPER and VEGF. We found that a functional cooperation between HIF-1? and GPER is essential for the transcriptional activation of VEGF induced by IGF1. Finally, using conditioned medium from CAFs and SKBR3 cells stimulated with IGF1, we established that HIF-1? and GPER are both required for VEGF-induced human vascular endothelial cell tube formation. CONCLUSIONS:These findings shed new light on the essential role played by GPER in IGF1/IGF1R signaling that induces breast tumor angiogenesis. Targeting the multifaceted interactions between cancer cells and tumor microenvironment involving both GPCRs and growth factor receptors has potential in future combination anticancer therapies.

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?-arrestin1 mediates metastatic growth of breast cancer cells by facilitating HIF-1-dependent VEGF expression.

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β-arrestin1 mediates metastatic growth of breast cancer cells by facilitating HIF-1-dependent VEGF expression.

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