HIF-1α/GPER signaling mediates the expression of VEGF induced by hypoxia in breast cancer associated fibroblasts (CAFs)

GPER Mediates a Feedforward FGF2/FGFR1 Paracrine Activation Coupling CAFs to Cancer Cells toward Breast Tumor Progression

The FGF2/FGFR1 paracrine loop is involved in the cross-talk between breast cancer cells and components of the tumor stroma as cancer-associated fibroblasts (CAFs). By quantitative PCR (qPCR), western blot, immunofluorescence analysis, ELISA and ChIP assays, we demonstrated that 17β-estradiol (E2) and the G protein estrogen receptor (GPER) agonist G-1 induce the up-regulation and secretion of FGF2 via GPER together with the EGFR/ERK/c-fos/AP-1 signaling cascade in (ER)-negative primary CAFs. Evaluating the genetic alterations from METABRIC and TCGA datasets, we then assessed that FGFR1 is the most frequently amplified FGFRs family member and its amplification/expression associates with shorter survival rates in breast cancer patients. Therefore, in order to assess the functional FGF2/FGFR1 interplay between CAFs and breast cancer cells, we generated the FGFR1-knockout MDA-MB-231 cells using CRISPR/Cas9 genome editing strategy. Using conditioned medium from estrogen-stimulated CAFs, we established that the activation of FGF2/FGFR1 paracrine signaling triggers the expression of the connective tissue growth factor (CTGF), leading to the migration and invasion of MDA-MB-231 cells. Our findings shed new light on the role elicited by estrogens through GPER in the activation of the FGF2/FGFR1 signaling. Moreover, our findings may identify further biological targets that could be considered in innovative combination strategies halting breast cancer progression.

Cancer-associated fibroblast regulation of tumor neo-angiogenesis as a therapeutic target in cancer

Adequate blood supply is essential for tumor survival, growth and metastasis. The tumor microenvironment (TME) is dynamic and complex, comprising cancer cells, cancer-associated stromal cells and their extracellular products. The TME serves an important role in tumor progression. Cancer-associated fibroblasts (CAFs) are the principal component of stromal cells within the TME, and contribute to tumor neo-angiogenesis by altering the proteome and degradome. The present paper reviews previous studies of the molecular signaling pathways by which CAFs promote tumor neo-angiogenesis and highlights therapeutic response targets. Also discussed are potential strategies for antitumor neo-angiogenesis to improve tumor treatment efficacy.

Dual role of twist1 in cancer-associated fibroblasts and tumor cells promoted epithelial-mesenchymal transition of esophageal cancer

Cancer-associated fibroblasts (CAFs) play critical roles in tumor progression. However, the role and mechanism underlying CAFs in esophageal cancer (EC) remain unclear. In this study, primary CAFs and normal esophageal fibroblasts (NOFs) were isolated and characterized by immunofluorescence, qRT-PCR and western blot. Clinical significance of twist1 in CAFs were evaluated by immunohistochemistry assay. Conditioned medium (CM) was collected from CAFs to evaluate the influence on epithelial-mesenchymal transition (EMT) of EC cells. EC cells were mixed with CAFs and subcutaneously injected into nude mice to assess the in vivo tumor growth. As the result, twist1 was overexpressed in CAFs compared with NOFs and exhibited adverse prognostic significance. In CAFs, twist1 promoted the expression and secretion of CXCL12. In EC cells, activated CXCL12/CXCR4 signaling promoted the EMT process through ERK/AKT - twist1 - MMP1/E-cadherin pathway. In addition, knockdown of twist1 in CAFs also suppressed in vivo tumor growth. In conclusion, our results revealed a dual role of twist1 in CAFs and EC cells to promote the EMT process.

G Protein-Coupled Estrogen Receptor: A Potential Therapeutic Target in Cancer

The G protein-coupled estrogen receptor (GPER) is a seven-transmembrane-domain receptor that mediates non-genomic estrogen related signaling. After ligand activation, GPER triggers multiple downstream pathways that exert diverse biological effects on the regulation of cell growth, migration and programmed cell death in a variety of tissues. A significant correlation between GPER and the progression of multiple cancers has likewise been reported. Therefore, a better understanding of the role GPER plays in cancer biology may lead to the identification of novel therapeutic targets, especially among estrogen-related cancers. Here, we review cell signaling and detail the functions of GPER in malignancies.

Dragon's Blood exerts cardio-protection against myocardial injury through PI3K-AKT-mTOR signaling pathway in acute myocardial infarction mice model

ETHNOPHARMACOLOGICAL RELEVANCE

Dragon's Blood (DB), the red resin of Dracaena cochinchinensis (Lour.) S. C., has been used in traditional Chinese medicine to treat acute myocardial infarction (AMI) for centuries. Evidence indicated that DB may exert cardio-protective effect by inhibiting inflammatory response during myocardial infarction. However, its pharmaceutical mechanism is still to be elucidated.

AIM OF THE STUDY

Due to its potential anti-inflammatory effect, Dragon's Blood extract (DBE) was applied on AMI mice model in this study and its mechanism on inflammation via PI3K-AKT-mTOR signaling pathway was to be validated.

MATERIALS AND METHODS

AMI mice model was established by ligation of left anterior descending (LAD) arteries. DBE was administered for 7 days before the surgery. Heart function was evaluated by 2D echocardiography. Levels of CK-MB and LDH1 in serum as well as TXB2, 6-keto-PGF1α and ET-1 in plasma were detected. Level of IL-6 in cardiac tissues was quantified by ELISA. Expressions of key proteins in PI3K-AKT-mTOR signaling pathway were detected by Western blot.

RESULTS

The result demonstrated that DBE could improve heart function in AMI mice model. Meanwhile, it could also regulate levels of CK-MB and LDH1, and restore balance between TXB2 and 6-keto-PGF1α. Further study suggested that DBE could inhibit inflammation and regulate expressions of key proteins in IL-6-JAK2/STAT3 pathway in cardiac tissue. Western blot results validated that DBE could activate PI3K-AKT-mTOR signaling pathway, thereby regulating the expressions of its downstream targets, including VEGF, COX2 and PPARγ.

CONCLUSION

DBE exerts cardio-protective efficacy by activating JAK2-STAT3 and PI3K-AKT-mTOR pathways in cardiac tissue. These findings provide insight into the pharmacological mechanism of DBE and validate the beneficial effects of DBE in the clinical application for AMI.

The association of HIF-1α expression with clinicopathological significance in prostate cancer: a meta-analysis

Background

Hypoxia-inducible factor-1α (HIF-1α) plays an important role in tumor growth, invasion, and metastasis. The aim of this study was to perform a meta-analysis to explore the association of HIF-1α expression with clinicopathological significance in patients with prostate cancer (PCa).

Methods

A detailed literature search was made in PubMed, Embase, Cochrane Library, China Biology Medicine disc (CBM), and China National Knowledge Infrastructure (CNKI) up to August 21, 2017. Odds ratios (ORs) with 95% CIs were calculated to evaluate the strength of the correlations. Analysis of pooled data was performed using Review Manager 5.3 software.

Results

Eventually, 14 studies were identified and involved in this meta-analysis. The rate of HIF-1α protein expression was significantly higher in PCa than in nonmalignant prostate tissues (OR=12.01, 95% CI: 8.22-17.55, P<0.00001). Similar results were found in different subgroups. There were significant differences between HIF-1α expression and clinicopathological significance. The expression of HIF-1α protein was significantly associated with Gleason score (Gleason ≥7 vs Gleason <7: OR=3.58, 95% CI: 2.35-5.46, P<0.00001). The frequency of HIF-1α protein expression was significantly higher in T3-T4 stages than in T1-T2 stages of PCa (OR=3.70, 95% CI: 1.53-8.96, P=0.004). The expression of HIF-1α protein was significantly associated with the presence of lymph node and/or bone metastasis of PCa (metastasis positive vs negative: OR=7.07, 95% CI: 4.08-12.25, P<0.00001).

Conclusion

Taken together, our findings have demonstrated the certain associations of HIF-1α expression with an increased risk and clinicopathological significance in PCa patients, indicating that HIF-1α may serve as a valuable biomarker for diagnosing PCa and monitoring the progression.

Exosome-related tumor microenvironment

The tumor microenvironment (tumor cells are located in the internal and external environment) is vital for the occurrence, growth and metastasis of tumors. An increasing number of studies have shown that exosomes are closely related to the tumor microenvironment. The mechanisms involved, however, are unclear. The focus of this review is on the exosome-related tumor microenvironment and other relevant factors, such as hypoxia, inflammation and angiogenesis. Many studies have suggested that exosomes are important mediators of metastasis, angiogenesis, and immune modulation in the tumor microenvironment. Additionally, exosomes can be isolated from bodily fluids of cancer patients, including urine, blood, saliva, milk, tumor effusion, cerebrospinal fluid, amniotic fluid and so on. Consequently, exosomes are potential biomarkers for clinical predictions and are also good drug carriers because they can cross the biofilm without triggering an immune response. Collectively, these findings illustrate that exosomes are crucial for developing potential targets for a new generation of pharmaceutical therapies that would improve the tumor microenvironment.

The impact of chemotherapy-associated hemoglobin on prognosis of colorectal cancer patients receiving adjuvant chemotherapy

BACKGROUND AND OBJECTIVE

The association of chemotherapy-associated hemoglobin and survival of colorectal cancer (CRC) receiving adjuvant chemotherapy is uncertain. We sought to explore the prognostic value of chemotherapy-associated hemoglobin in CRC receiving adjuvant chemotherapy and the best cut point affecting prognosis.

METHODS

Three hundred and twenty stage II and III CRC patients receiving adjuvant FOLFOX chemotherapy from March 2003 to March 2012 were enrolled. The associations between chemotherapy-associated hemoglobin (the absolute levels of post-chemotherapy) or chemotherapy-associated hemoglobin change (change between the pre- and post-chemotherapy hemoglobins) and disease free survival (DFS) or overall survival (OS) of CRC, and the best cut point were investigated.

RESULTS

Log rank test showed the best cut points for chemotherapy-associated hemoglobin and chemotherapy-associated hemoglobin change were respectively 90 g/L, 30 g/L. Cox regression model showed chemotherapy-associated hemoglobin < 90 g/L was the independent prognostic factor for DFS (HR, 2.221; 95% CI = 1.157-4.262), OS (HR, 2.058; 95% CI = 1.009-4.197), respectively, but no association of chemotherapy-associated hemoglobin change ⩾ 30g/L and DFS (HR, 2.063; 95% CI = 0.929-4.583), OS (HR, 1.386; 95% CI = 0.553-3.471) was found.

CONCLUSIONS

Chemotherapy-associated hemoglobin < 90 g/L has a significant prognostic value in CRC receiving adjuvant chemotherapy, which is a significant biomarker in the individualized management and may suggest the simple indication for the treatment of anemia in adjuvant chemotherapy in CRC.

Crosstalk between Notch, HIF-1α and GPER in Breast Cancer EMT

The Notch signaling pathway acts in both physiological and pathological conditions, including embryonic development and tumorigenesis. In cancer progression, diverse mechanisms are involved in Notch-mediated biological responses, including angiogenesis and epithelial-mesenchymal-transition (EMT). During EMT, the activation of cellular programs facilitated by transcriptional repressors results in epithelial cells losing their differentiated features, like cell–cell adhesion and apical–basal polarity, whereas they gain motility. As it concerns cancer epithelial cells, EMT may be consequent to the evolution of genetic/epigenetic instability, or triggered by factors that can act within the tumor microenvironment. Following a description of the Notch signaling pathway and its major regulatory nodes, we focus on studies that have given insights into the functional interaction between Notch signaling and either hypoxia or estrogen in breast cancer cells, with a particular focus on EMT. Furthermore, we describe the role of hypoxia signaling in breast cancer cells and discuss recent evidence regarding a functional interaction between HIF-1α and GPER in both breast cancer cells and cancer-associated fibroblasts (CAFs). On the basis of these studies, we propose that a functional network between HIF-1α, GPER and Notch may integrate tumor microenvironmental cues to induce robust EMT in cancer cells. Further investigations are required in order to better understand how hypoxia and estrogen signaling may converge on Notch-mediated EMT within the context of the stroma and tumor cells interaction. However, the data discussed here may anticipate the potential benefits of further pharmacological strategies targeting breast cancer progression.

Hypoxic Signalling in Tumour Stroma

Hypoxia is a common feature in solid tumors and is associated with cancer progression. The main regulators of the hypoxic response are hypoxia-inducible transcription factors (HIFs) that guide the cellular adaptation to hypoxia by gene activation. The actual oxygen sensing is performed by HIF prolyl hydroxylases (PHDs) that under normoxic conditions mark the HIF-α subunit for degradation. Cancer progression is not regulated only by the cancer cells themselves but also by the whole tumor microenvironment, which consists of cellular and extracellular components. Hypoxic conditions also affect the stromal compartment, where stromal cells are in close contact with the cancer cells. The important function of HIF in cancer cells has been shown by many animal models and described in hundreds of reviews, but less in known about PHDs and even less PHDs in stromal cells. Here, we review hypoxic signaling in tumors, mainly in the tumor stroma, with a focus on HIFs and PHDs.

Airway epithelial phosphoinositide 3-kinase-δ contributes to the modulation of fungi-induced innate immune response

Background

Respiratory fungal exposure is known to be associated with severe allergic lung inflammation. Airway epithelium is an essential controller of allergic inflammation. An innate immune recognition receptor, nucleotide-binding domain, leucine-rich-containing family, pyrin-domain-containing-3 (NLRP3) inflammasome, and phosphoinositide 3 kinase (PI3K)-δ in airway epithelium are involved in various inflammatory processes.

Objectives

We investigated the role of NLRP3 inflammasome in fungi-induced allergic lung inflammation and examined the regulatory mechanism of NLRP3 inflammasome, focusing on PI3K-δ in airway epithelium.

Methods

We used two in vivo models induced by exposure to Aspergillus fumigatus (Af) and Alternaria alternata (Aa), as well as an Af-exposed in vitro system. We also checked NLRP3 expression in lung tissues from patients with allergic bronchopulmonary aspergillosis (ABPA).

Results

Assembly/activation of NLRP3 inflammasome was increased in the lung of Af-exposed mice. Elevation of NLRP3 inflammasome assembly/activation was observed in Af-stimulated murine and human epithelial cells. Similarly, pulmonary expression of NLRP3 in patients with ABPA was increased. Importantly, neutralisation of NLRP3 inflammasome derived IL-1β alleviated pathophysiological features of Af-induced allergic inflammation. Furthermore, PI3K-δ blockade improved Af-induced allergic inflammation through modulation of NLRP3 inflammasome, especially in epithelial cells. This modulatory role of PI3K-δ was mediated through the regulation of mitochondrial reactive oxygen species (mtROS) generation. NLRP3 inflammasome was also implicated in Aa-induced eosinophilic allergic inflammation, which was improved by PI3K-δ blockade.

Conclusion

These findings demonstrate that fungi-induced assembly/activation of NLRP3 inflammasome in airway epithelium may be modulated by PI3K-δ, which is mediated partly through the regulation of mtROS generation. Inhibition of PI3K-δ may have potential for treating fungi-induced severe allergic lung inflammation.

Effects of thalidomide on growth and VEGF-A expression in SW480 colon cancer cells

Lymphatic and hematogenous spread are the most common ways for tumors to metastasize. Angiogenesis is essential for tumor growth and metastasis. Vascular endothelial growth factor (VEGF) particularly VEGF-A is important in the process of angiogenesis. The current research has indicated that thalidomide (THD) may be able to inhibit angiogenesis, stimulate the activity of the immune system and inhibit the adherence of cancer cells to stromal cells. These changes may lead to suppression of tumor occurrence and development. To date, to the best of our knowledge, the effects of THD on colon cancer SW480 cells have not been reported. In the present study, the effects of THD and a combination of THD and oxaliplatin (L-OHP) on the proliferation of SW480 cells have been investigated. Furthermore, the expression of VEGF-A and hypoxia-inducible factor 1 (HIF-1) was analyzed using MTT assay, quantitative polymerase chain reaction and western blot analysis. The results indicated that THD was able to inhibit SW480 cells in dose-and-time dependent manner and inhibit the expression of VEGF-A and HIF-1α. Furthermore, treatment with THD and L-OHP had synergistic inhibitory effect, which may provide a novel treatment strategy for advanced colorectal cancer.

Investigation of hypoxia networks in ovarian cancer via bioinformatics analysis

Background

Ovarian cancer is a leading cause of the death from gynecologic malignancies. Hypoxia is closely related to the malignant growth of cells. However, the molecular mechanism of hypoxia-regulated ovarian cancer cells remains unclear. Thus, this study was conducted to identify the key genes and pathways implicated in the regulation of hypoxia by bioinformatics analysis.

Methods

Using the datasets of GSE53012 downloaded from the Gene Expression Omnibus (GEO), the differentially expressed genes (DEGs) were screened by comparing the RNA expression from cycling hypoxia group, chronic hypoxia group, and control group. Subsequently, cluster analysis was performed followed by the construction of the protein-protein interaction (PPI) network of the overlapping DEGs between the cycling hypoxia and chronic hypoxia using ClusterONE. In addition, gene ontology (GO) functional and pathway enrichment analyses of the DEGs in the most remarkable module were performed using Database for Annotation, Visualization and Integrated Discovery (DAVID) software. Ultimately, the signaling pathways associated with hypoxia were verified by RT-PCR, WB, and MTT assays.

Results

A total of 931 overlapping DEGs were identified. Nine hub genes and seven node genes were screened by analyzing the PPI and pathway integration networks, including ESR1, MMP2, ErbB2, MYC, VIM, CYBB, EDN1, SERPINE1, and PDK. Additionally, 11 key pathways closely associated with hypoxia were identified, including focal adhesion, ErbB signaling, and proteoglycans in cancer, among which the ErbB signaling pathway was verified by RT-PCR, WB, and MTT assays. Furthermore, functional enrichment analysis revealed that these genes were mainly involved in the proliferation of ovarian cancer cells, such as regulation of cell proliferation, cell adhesion, positive regulation of cell migration, focal adhesion, and extracellular matrix binding.

Conclusion

The results show that hypoxia can promote the proliferation of ovarian cancer cells by affecting the invasion and adhesion functions through the dysregulation of ErbB signaling, which may be governed by the HIF-1α-TGFA-EGFR-ErbB2-MYC axis. These findings will contribute to the identification of new targets for the diagnosis and treatment of ovarian cancer.

Electronic supplementary material

The online version of this article (10.1186/s13048-018-0388-x) contains supplementary material, which is available to authorized users.

Nuclear factor 90 promotes angiogenesis by regulating HIF-1α/VEGF-A expression through the PI3K/Akt signaling pathway in human cervical cancer

Vascular endothelial growth factor A (VEGF-A), a fundamental component of angiogenesis, provides nutrients and oxygen to solid tumors, and enhances tumor cell survival, invasion, and migration. Nuclear factor 90 (NF90), a double-stranded RNA-binding protein, is strongly expressed in several human cancers, promotes tumor growth by reducing apoptosis, and increasing cell cycle process. The mechanisms by which cervical cancer cells inducing VEGF-A expression and angiogenesis upon NF90 upregulation remain to be fully established. We demonstrated that NF90 is upregulated in human cervical cancer specimens and the expression of NF90 is paralleled with that of VEGF-A under hypoxia. The expressions of hypoxia inducible factor-1α (HIF-1α) and VEGF-A are downregulated upon NF90 knockdown, which can be rescued by ectopic expression of NF90. Suppression of NF90 decreases the tube formation and cell migration of HUVECs. Moreover, the PI3K/Akt signaling pathway participates in the regulation. Knockdown of NF90 also reduces the tumor growth and angiogenesis of cervical cancer cell line in the mouse xenograft model. Taken together, suppression of NF90 in cervical cancer cell lines can decrease VEGF-A expression, inhibit angiogenesis, and reduce tumorigenic capacity in vivo.

GPER is involved in the functional liaison between breast tumor cells and cancer-associated fibroblasts (CAFs)

The aggressiveness of breast tumors is deeply influenced by the surrounding stroma. In this regard, the functional crosstalk between cancer cells and the tumor microenvironment has received considerable attention in recent years. Cancer-associated fibroblasts (CAFs) are active components of the tumor stroma as they play a main role in the initiation, progression, metastasis and recurrence of breast malignancy. Hence, a better understanding of the mechanisms through which host stroma may contribute to cancer development would lead to novel therapeutic approaches aimed to target both tumor cells and the adjacent microenvironment. The G protein estrogen receptor (GPER/GPR30) has been involved in estrogenic signaling in normal and malignant cells, including breast cancer. It is noteworthy that the potential of GPER to mediate stimulatory effects of estrogens has been also shown in CAFs derived from patients with breast tumors, suggesting that GPER may act at the cross-road between cancer cells and these important components of the tumor microenvironment. This review recapitulates recent findings underlying the breast tumor-promoting action of CAFs, in particular their functional liaison with breast cancer cells via GPER toward the occurrence of malignant features.

Twenty years of the G protein-coupled estrogen receptor GPER: Historical and personal perspectives

Estrogens play a critical role in many aspects of physiology, particularly female reproductive function, but also in pathophysiology, and are associated with protection from numerous diseases in premenopausal women. Steroids and the effects of estrogen have been known for ∼90 years, with the first evidence for a receptor for estrogen presented ∼50 years ago. The original ancestral steroid receptor, extending back into evolution more than 500 million years, was likely an estrogen receptor, whereas G protein-coupled receptors (GPCRs) trace their origins back into history more than one billion years. The classical estrogen receptors (ERα and ERβ) are ligand-activated transcription factors that confer estrogen sensitivity upon many genes. It was soon apparent that these, or novel receptors may also be responsible for the "rapid"/"non-genomic" membrane-associated effects of estrogen. The identification of an orphan GPCR (GPR30, published in 1996) opened a new field of research with the description in 2000 that GPR30 expression is required for rapid estrogen signaling. In 2005-2006, the field was greatly stimulated by two studies that described the binding of estrogen to GPR30-expressing cell membranes, followed by the identification of a GPR30-selective agonist (that lacked binding and activity towards ERα and ERβ). Renamed GPER (G protein-coupled estrogen receptor) by IUPHAR in 2007, the total number of articles in PubMed related to this receptor recently surpassed 1000. In this article, the authors present personal perspectives on how they became involved in the discovery and/or advancement of GPER research. These areas include non-genomic effects on vascular tone, receptor cloning, molecular and cellular biology, signal transduction mechanisms and pharmacology of GPER, highlighting the roles of GPER and GPER-selective compounds in diseases such as obesity, diabetes, and cancer and the obligatory role of GPER in propagating cardiovascular aging, arterial hypertension and heart failure through the stimulation of Nox expression.

GPER modulators: Opportunity Nox on the heels of a class Akt

The (patho)physiology of estrogen and its receptors is complex. It is therefore not surprising that therapeutic approaches targeting this hormone include stimulation of its activity through supplementation with either the hormone itself or natural or synthetic agonists, inhibition of its activity through the use of antagonists or inhibitors of its synthesis, and tissue-selective modulation of its activity with biased ligands. The physiology of this hormone is further complicated by the existence of at least three receptors, the classical nuclear estrogen receptors α and β (ERα and ERβ), and the 7-transmembrane G protein-coupled estrogen receptor (GPER/GPR30), with overlapping but distinct pharmacologic profiles, particularly of anti-estrogenic ligands. GPER-selective ligands, as well as GPER knockout mice, have greatly aided our understanding of the physiological roles of GPER. Such ligands have revealed that GPER activation mediates many of the rapid cellular signaling events (including Ca2+ mobilization, ERK and PI3K/Akt activation) associated with estrogen activity, as opposed to the nuclear ERs that are traditionally described to function as ligand-induced transcriptional factors. Many of the salutary effects of estrogen throughout the body are reproduced by the GPER-selective agonist G-1, which, owing to its minimal effects on reproductive tissues, can be considered a non-feminizing estrogenic compound, and thus of potential therapeutic use in both women and men. On the contrary, until recently GPER-selective antagonists had predominantly found preclinical application in cancer models where estrogen stimulates cell growth and survival. This viewpoint changed recently with the discovery that GPER is associated with aging, particularly that of the cardiovascular system, where the GPER antagonist G36 reduced hypertension and GPER deficiency prevented cardiac fibrosis and vascular dysfunction with age, through the downregulation of Nox1 and as a consequence superoxide production. Thus, similar to the classical ERs, both agonists and antagonists of GPER may be of therapeutic benefit depending on the disease or condition to be treated.

Stimulatory actions of IGF-I are mediated by IGF-IR cross-talk with GPER and DDR1 in mesothelioma and lung cancer cells

Insulin-like growth factor-I (IGF-I)/IGF-I receptor (IGF-IR) system has been largely involved in the pathogenesis and development of various tumors. We have previously demonstrated that IGF-IR cooperates with the G-protein estrogen receptor (GPER) and the collagen receptor discoidin domain 1 (DDR1) that are implicated in cancer progression. Here, we provide novel evidence regarding the molecular mechanisms through which IGF-I/IGF-IR signaling triggers a functional cross-talk with GPER and DDR1 in both mesothelioma and lung cancer cells. In particular, we show that IGF-I activates the transduction network mediated by IGF-IR leading to the up-regulation of GPER and its main target genes CTGF and EGR1 as well as the induction of DDR1 target genes like MATN-2, FBN-1, NOTCH 1 and HES-1. Of note, certain DDR1-mediated effects upon IGF-I stimulation required both IGF-IR and GPER as determined knocking-down the expression of these receptors. The aforementioned findings were nicely recapitulated in important biological outcomes like IGF-I promoted chemotaxis and migration of both mesothelioma and lung cancer cells. Overall, our data suggest that IGF-I/IGF-IR system triggers stimulatory actions through both GPER and DDR1 in aggressive tumors as mesothelioma and lung tumors. Hence, this novel signaling pathway may represent a further target in setting innovative anticancer strategies.

G Protein-Coupled Receptors at the Crossroad between Physiologic and Pathologic Angiogenesis: Old Paradigms and Emerging Concepts

G protein-coupled receptors (GPCRs) have been implicated in transmitting signals across the extra- and intra-cellular compartments, thus allowing environmental stimuli to elicit critical biological responses. As GPCRs can be activated by an extensive range of factors including hormones, neurotransmitters, phospholipids and other stimuli, their involvement in a plethora of physiological functions is not surprising. Aberrant GPCR signaling has been regarded as a major contributor to diverse pathologic conditions, such as inflammatory, cardiovascular and neoplastic diseases. In this regard, solid tumors have been demonstrated to activate an angiogenic program that relies on GPCR action to support cancer growth and metastatic dissemination. Therefore, the manipulation of aberrant GPCR signaling could represent a promising target in anticancer therapy. Here, we highlight the GPCR-mediated angiogenic function focusing on the molecular mechanisms and transduction effectors driving the patho-physiological vasculogenesis. Specifically, we describe evidence for the role of heptahelic receptors and associated G proteins in promoting angiogenic responses in pathologic conditions, especially tumor angiogenesis and progression. Likewise, we discuss opportunities to manipulate aberrant GPCR-mediated angiogenic signaling for therapeutic benefit using innovative GPCR-targeted and patient-tailored pharmacological strategies.

GPER mediates the angiocrine actions induced by IGF1 through the HIF-1α/VEGF pathway in the breast tumor microenvironment

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-1α) 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-1α/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-1α and its targets GPER and VEGF. We found that a functional cooperation between HIF-1α 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-1α 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.

MicroRNA-421 regulated by HIF-1α promotes metastasis, inhibits apoptosis, and induces cisplatin resistance by targeting E-cadherin and caspase-3 in gastric cancer

Hypoxia and dysregulation of microRNAs (miRNAs) have been identified as crucial factors in carcinogenesis. However, the potential mechanisms of HIF-1α and miR-421 in gastric cancer have not been well elucidated. In this study, we found that miR-421 was up-regulated by HIF-1α. Overexpression of miR-421 promoted metastasis, inhibited apoptosis, and induced cisplatin resistance in gastric cancer in vivo and in vitro. E-cadherin and caspase-3 were identified as targets of miR-421. Besides, relative mRNA expression of miR-421 was significantly increased in gastric cancer tumor tissues compared with non-tumor tissues in a cohort of gastric cancer specimens (n=107). The expression of miR-421 was higher in advanced gastric cancers compared with localized ones. Moreover, Kaplan–Meier analysis illustrated that those patients with low levels of miR-421 had a significant longer overall survival (p = 0.006) and time to relapse (p = 0.007). Therefore, miR-421 could serve as an important prognostic marker and a potential molecular target for therapy in gastric cancer.

Bisphenol A induces proliferative effects on both breast cancer cells and vascular endothelial cells through a shared GPER-dependent pathway in hypoxia

Based on the breast cancer cells and the vascular endothelial cells are both estrogen-sensitive, we proposed a close reciprocity existed between them in the tumor microenvironment, via shared molecular mechanism affected by environmental endocrine disruptors (EDCs). In this study, bisphenol A (BPA), via triggering G-protein estrogen receptor (GPER), stimulated cell proliferation and migration of bovine vascular endothelial cells (BVECs) and breast cancer cells (SkBr-3 and MDA-MB-231) and enhanced tumor growth in vivo. Moreover, the expression of both hypoxia inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) were up-regulated in a GPER-dependent manner by BPA treatment under hypoxic condition, and the activated GPER induced the HIF-1α expression by competitively binding to caveolin-1 (Cav-1) and facilitating the release of heat shock protein 90 (HSP90). These findings show that in a hypoxic microenvironment, BPA promotes HIF-1α and VEGF expressions through a shared GPER/Cav-1/HSP90 signaling cascade. Our observations provide a probable hypothesis that the effects of BPA on tumor development are copromoting relevant biological responses in both vascular endothelial and breast cancer cells.

Cancer-associated fibroblasts regulate the biological behavior of cancer cells and stroma in gastric cancer

Gastric cancer (GC) is a frequently diagnosed type of cancer in China, and is associated with a high mortality rate. The biological behavior of GC requires investigation in order to provide an evidence base for the development of strategies to prevent and treat GC. For this purpose, the present review outlines the process of tumor microenvironment (TME) evolution, including the dynamic biological behavior of different types of cancer cell and stroma. Cancer-associated fibroblasts (CAFs) serve as prominent stromal cellular components in the GC TME, and exhibit an essential function in GC progression. In the present study, the function of CAFs in cancer cell proliferation, cell migration, invasion, extracellular matrix remodeling, pathological angiogenesis and immune cell infiltration were investigated. The studies discussed in the present review demonstrate that the cross-talk between CAF, cancer cells and tumor stroma promotes GC progression.

Cancer-associated fibroblasts support vascular growth through mechanical force

The role of cancer-associated fibroblasts (CAFs) as regulators of tumor progression, specifically vascular growth, has only recently been described. CAFs are thought to be more mechanically active but how this trait may alter the tumor microenvironment is poorly understood. We hypothesized that enhanced mechanical activity of CAFs, as regulated by the Rho/ROCK pathway, contributes to increased blood vessel growth. Using a 3D in vitro tissue model of vasculogenesis, we observed increased vascularization in the presence of breast cancer CAFs compared to normal breast fibroblasts. Further studies indicated this phenomenon was not simply a result of enhanced soluble signaling factors, including vascular endothelial growth factor (VEGF), and that CAFs generated significantly larger deformations in 3D gels compared to normal fibroblasts. Inhibition of the mechanotransductive pathways abrogated the ability of CAFs to deform the matrix and suppressed vascularization. Finally, utilizing magnetic microbeads to mechanically stimulate mechanically-inhibited CAFs showed partial rescue of vascularization. Our studies demonstrate enhanced mechanical activity of CAFs may play a crucial and previously unappreciated role in the formation of tumor-associated vasculature which could possibly offer potential novel targets in future anti-cancer therapies.

GPER mediates differential effects of estrogen on colon cancer cell proliferation and migration under normoxic and hypoxic conditions

The estrogen receptor ERβ is the predominant ER subtype expressed in normal well-differentiated colonic epithelium. However, ERβ expression is lost under the hypoxic microenvironment as colorectal cancer (CRC) malignancy progresses. This raises questions about the role of signalling through other estrogen receptors such as ERα or G-protein coupled estrogen receptor (GPER, GPR30) by the estrogen 17β-estradiol (E2) under hypoxic conditions after ERβ is lost in CRC progression. We tested the hypothesis that E2 or hypoxia can act via GPER to contribute to the altered phenotype of CRC cells.

GPER expression was found to be up-regulated by hypoxia and E2 in a panel of CRC cell lines. The E2-modulated gene, Ataxia telangiectasia mutated (ATM), was repressed in hypoxia via GPER signalling. E2 treatment enhanced hypoxia-induced expression of HIF1-α and VEGFA, but repressed HIF1-α and VEGFA expression under normoxic conditions. The expression and repression of VEGFA by E2 were mediated by a GPER-dependent mechanism. E2 treatment potentiated hypoxia-induced CRC cell migration and proliferation, whereas in normoxia, cell migration and proliferation were suppressed by E2 treatment. The effects of E2 on these cellular responses in normoxia and hypoxia were mediated by GPER. In a cohort of 566 CRC patient tumor samples, GPER expression significantly associated with poor survival in CRC Stages 3-4 females but not in the stage-matched male population.

Our findings support a potentially pro-tumorigenic role for E2 in ERβ-negative CRC under hypoxic conditions transduced via GPER and suggest a novel route of therapeutic intervention through GPER antagonism.

The reverse Warburg effect is likely to be an Achilles' heel of cancer that can be exploited for cancer therapy

Although survival outcomes of cancer patients have been improved dramatically via conventional chemotherapy and targeted therapy over the last decades, there are still some tough clinical challenges that badly needs to be overcome, such as anticancer drug resistance, inevitable recurrences, cancer progression and metastasis. Simultaneously, accumulated evidence demonstrates that aberrant glucose metabolism termed ‘the Warburg effect’ in cancer cell is closely associated with malignant phenotypes. In 2009, a novel ‘two-compartment metabolic coupling’ model, also named ‘the reverse Warburg effect’, was proposed and attracted lots of attention. Based on this new model, we consider whether this new viewpoint can be exploited for improving the existent anti-cancer therapeutic strategies. Our review focuses on the paradigm shift from ‘the Warburg effect’ to ‘the reverse Warburg effect’, the features and molecular mechanisms of ‘the reverse Warburg effect’, and then we discuss its significance in fundamental researches and clinical practice.

Metastasized murine oral squamous cell carcinoma cells induce intratumoral polymorphonuclear myeloid derived suppressor cells

Myeloid derived suppressor cells (MDSCs) localize to hematopoietic organs and peripheral blood during inflammation or tumor tissues and lymph nodes in the presence of a tumor. However, whether there are differences in MDSCs found in the primary tumor and metastases is unknown. In the present study, we established a cell line of metastasized tumor cells to a lymph node, L5-11, which were derived from the Sq-1979 mouse buccal mucosa squamous cell carcinoma cell line. We then analyzed tumor immunogenicity, especially with regard to MDSCs, to clarify the differences between the primary tumor and metastases, using an isogenic heterotopic tumor transplantation model. Our data showed that the population of intratumoral MDSCs, especially polymorphonuclear MDSCs in the lymph node metastasis model were significantly increased compared with syngeneic grafts from the primary cell line Sq-1979 after 21 days. Furthermore, we identified that the lymph node metastasis cell line had increased expression of genes that promote the expansion of MDSCs, tumor growth and metastasis. Hence, these data suggest that tumor immunosuppression can occur via activation of MDSCs. However, further examination is required to clarify whether all or a subset of these factors from the lymph node metastasis tumor cells are required to induce intratumoral MDSCs.

Cytoplasmic GPER translocation in cancer-associated fibroblasts mediates cAMP/PKA/CREB/glycolytic axis to confer tumor cells with multidrug resistance

Multiple drug resistance is a challenging issue in the clinic. There is growing evidence that the G-protein-coupled estrogen receptor (GPER) is a novel mediator in the development of multidrug resistance in both estrogen receptor (ER)-positive and -negative breast cancers, and that cancer-associated fibroblasts (CAFs) in the tumor microenvironment may be a new agent that promotes drug resistance in tumor cells. However, the role of cytoplasmic GPER of CAFs on tumor therapy remains unclear. Here we first show that the breast tumor cell-activated PI3K/AKT (phosphoinositide 3-kinase/AKT) signaling pathway induces the cytoplasmic GPER translocation of CAFs in a CRM1-dependent pattern, and leads to the activation of a novel estrogen/GPER/cAMP/PKA/CREB signaling axis that triggers the aerobic glycolysis switch in CAFs. The glycolytic CAFs feed the extra pyruvate and lactate to tumor cells for augmentation of mitochondrial activity, and this energy metabolically coupled in a 'host-parasite relationship' between catabolic CAFs and anabolic cancer cells confers the tumor cells with multiple drug resistance to several conventional clinical treatments including endocrine therapy (tamoxifen), Her-2-targeted therapy (herceptin) and chemotherapy (epirubicin). Moreover, the clinical data from 18F-fluorodeoxyglucose positron emission tomography/computed tomography further present a strong association between the GPER/cAMP/PKA/CREB pathway of stromal fibroblasts with tumor metabolic activity and clinical treatment, suggesting that targeting cytoplasmic GPER in CAFs may rescue the drug sensitivity in patients with breast cancer. Thus, our data define novel insights into the stromal GPER-mediated multiple drug resistance from the point of reprogramming of tumor energy metabolism and provide the rationale for CAFs as a promising target for clinical therapy.

Adiponectin promotes VEGF-A-dependent angiogenesis in human chondrosarcoma through PI3K, Akt, mTOR, and HIF-α pathway

Chondrosarcoma is a type of highly malignant tumor with a potent capacity to invade locally and cause distant metastasis. Adiponectin is a protein hormone secreted predominantly by differentiated adipocytes. On the other hand, angiogenesis is a critical step in tumor growth and metastasis. However, the relationship of adiponectin with vascular endothelial growth factor-A (VEGF-A) expression and angiogenesis in human chondrosarcoma is mostly unknown. In this study we first demonstrated that the expression of adiponectin was correlated with tumor stage of human chondrosarcoma tissues. In addition, we also found that adiponectin increased VEGF-A expression in human chondrosarcoma cells and subsequently induced migration and tube formation in human endothelial progenitor cells (EPCs). Adiponectin promoted VEGF-A expression through adiponectin receptor (AdipoR), phosphoinositide 3 kinase (PI3K), Akt, mammalian target of rapamycin (mTOR), and hypoxia-inducible factor-1α (HIF)-1α signaling cascades. Knockdown of adiponectin decreased VEGF-A expression and also abolished chondrosarcoma conditional medium-mediated tube formation in EPCs in vitro as well as angiogenesis effects in the chick chorioallantoic membrane and Matrigel plug nude mice model in vivo. Therefore, adiponectin is crucial for tumor angiogenesis and growth, which may represent a novel target for anti-angiogenic therapy in human chondrosarcoma.

A positive feedback loop between ROS and Mxi1-0 promotes hypoxia-induced VEGF expression in human hepatocellular carcinoma cells

VEGF expression induced by hypoxia plays a critical role in promoting tumor angiogenesis. However, the molecular mechanism that modulates VEGF expression under hypoxia is still poorly understood. In this study, we found that VEGF induction in hypoxic HepG2 cells is ROS-dependent. ROS mediates hypoxia-induced VEGF by upregulation of Mxi1-0. Furthermore, PI3K/AKT/HIF-1α signaling pathway is involved in ROS-mediated Mxi1-0 and VEGF expression in hypoxic HepG2 cells. Finally, Mxi1-0 could in turn regulate ROS generation in hypoxic HepG2 cells, creating a positive feedback loop. Taken together, this study demonstrate a positive regulatory feedback loop in which ROS mediates hypoxia-induced Mxi1-0 via activation of PI3K/AKT/HIF-1α pathway, events that in turn elevate ROS generation and promote hypoxia-induced VEGF expression. These findings could provide a rationale for designing new therapies based on inhibition of hepatocellular carcinoma (HCC) angiogenesis.

Estrogen stabilizes hypoxia-inducible factor 1α through G protein-coupled estrogen receptor 1 in eutopic endometrium of endometriosis

OBJECTIVE

To investigate whether G protein-coupled estrogen receptor (GPER, also known as GPR30 and GPER1) stabilizes hypoxia-inducible factor 1α (HIF-1α) in eutopic endometrium (EuEM) of endometriosis.

DESIGN

Immunohistochemical analysis and experimental in vitro study.

SETTING

University hospital.

PATIENT(S)

Patients with or without endometriosis.

INTERVENTION(S)

The EuEM and normal control endometrium (CoEM) were obtained by curettage. Primary cultured endometrial stromal cells (ESCs) were treated with 17β-E₂, G1, or G15.

MAIN OUTCOME MEASURE(S)

The EuEM and CoEM were collected for immunohistochemistry. Western blot, polymerase chain reaction, ELISA, and dual luciferase experiments were used to detect expression of GPER, HIF-1α, vascular endothelial growth factor (VEGF), and matrix metalloproteinase 9 (MMP9) in ESCs. Estradiol and G1 were used as agonists of GPER, G15 as an antagonist. Migration of ESCs and endothelial tube formation of human umbilical vein endothelial cells cultured in medium collected from ESCs were measured.

RESULT(S)

Protein levels of GPER and HIF-1α were higher in EuEM than in CoEM. Protein levels of HIF-1α but not HIF-1α mRNA levels increased concurrently with GPER after E₂ and G1 treatment. Furthermore, expression and activity of VEGF and MMP9 increased under E₂ and G1 stimulation. However, these effects disappeared when GPER was blocked.

CONCLUSION(S)

G protein-coupled estrogen receptor stabilizes HIF-1α and thus promotes HIF-1α-induced VEGF and MMP9 in ESCs, which play critical roles in endometriosis.

GPER is involved in the stimulatory effects of aldosterone in breast cancer cells and breast tumor-derived endothelial cells

Aldosterone induces relevant effects binding to the mineralcorticoid receptor (MR), which acts as a ligand-gated transcription factor. Alternate mechanisms can mediate the action of aldosterone such as the activation of epidermal growth factor receptor (EGFR), MAPK/ERK, transcription factors and ion channels. The G-protein estrogen receptor (GPER) has been involved in the stimulatory effects of estrogenic signalling in breast cancer. GPER has been also shown to contribute to certain responses to aldosterone, however the role played by GPER and the molecular mechanisms implicated remain to be fully understood. Here, we evaluated the involvement of GPER in the stimulatory action exerted by aldosterone in breast cancer cells and breast tumor derived endothelial cells (B-TEC). Competition assays, gene expression and silencing studies, immunoblotting and immunofluorescence experiments, cell proliferation and migration were performed in order to provide novel insights into the role of GPER in the aldosterone-activated signalling. Our results demonstrate that aldosterone triggers the EGFR/ERK transduction pathway in a MR- and GPER-dependent manner. Aldosterone does not bind to GPER, it however induces the direct interaction between MR and GPER as well as between GPER and EGFR. Next, we ascertain that the up-regulation of the Na⁺/H⁺ exchanger-1 (NHE-1) induced by aldosterone involves MR and GPER. Biologically, both MR and GPER contribute to the proliferation and migration of breast and endothelial cancer cells mediated by NHE-1 upon aldosterone exposure. Our data further extend the current knowledge on the molecular mechanisms through which GPER may contribute to the stimulatory action elicited by aldosterone in breast cancer.

Protective effect of salidroside against bone loss via hypoxia-inducible factor-1α pathway-induced angiogenesis

Hypoxia-inducible factor (HIF)-1α plays a critical role in coupling angiogenesis with osteogenesis during bone development and regeneration. Salidroside (SAL) has shown anti-hypoxic effects in vitro and in vivo. However, the possible roles of SAL in the prevention of hypoxia-induced osteoporosis have remained unknown. Two osteoblast cell lines, MG-63 and ROB, were employed to evaluate the effects of SAL on cell viability, apoptosis, differentiation and mineralization in vitro. Rats subjected to ovariectomy-induced bone loss were treated with SAL in vivo. Our results showed that pre-treatment with SAL markedly attenuated the hypoxia-induced reductions in cell viability, apoptosis, differentiation and mineralization. SAL down-regulated HIF-1α expression and inhibited its translocation; however, SAL increased its transcriptional activity and, consequently, up-regulated vascular endothelial growth factor (VEGF). In vivo studies further demonstrated that SAL caused decreases in the mineral, alkaline phosphatase (ALP), and BGP concentrations in the blood of ovariectomized (OVX) rats. Moreover, SAL improved the trabecular bone microarchitecture and increased bone mineral density in the distal femur. Additionally, SAL administration partially ameliorated this hypoxia via the HIF-1α-VEGF signalling pathway. Our results indicate that SAL prevents bone loss by enhancing angiogenesis and osteogenesis and that these effects are associated with the activation of HIF-1α signalling.

Aspirin may inhibit angiogenesis and induce autophagy by inhibiting mTOR signaling pathway in murine hepatocarcinoma and sarcoma models

Aspirin is known to have inhibitory effects on growth development in various types of tumor. In previous studies, it was observed to inhibit angiogenesis by downregulating the expression of vascular endothelial growth factor-A (VEGF-A). In the present study, murine H₂₂ hepatocarcinoma and S180 sarcoma models were used to ascertain whether aspirin could inhibit angiogenesis and promote autophagy in tumors. Tumor-bearing mice were randomly divided into four groups with 10 mice per group: i) no treatment; ii) low-dose aspirin (100 mg/kg); iii) high-dose aspirin (400 mg/kg); iv) everolimus group (4 mg/kg). The effects of high-dose aspirin were validated through preliminary experiments. The drug treatment was administered every day for 14 days. The tumor size was measured every other day and then the tumor growth curve was plotted, and the tumor inhibitory rates were calculated. The expression levels of phosphorylated mammalian target of rapamycin (p-mTOR), hypoxia-inducible factor-1α (HIF-1α), VEGF-A, UNC-51-like kinase-1 (ULK1) and microtubule-associated protein 1 light chain 3A (LC3A) were detected by immunohistochemistry and western blot analysis, respectively. We observed that tumor growth delay was achieved in both H₂₂ hepatocarcinoma and S180 sarcoma models following treatment with aspirin. The tumor growth inhibition rates induced by low and high-dose aspirin and everolimus were 19.6, 33.6 and 53.7% (P<0.05) in H₂₂ hepatocarcinoma, and 25.7, 40.6 and 48.7% (P<0.05) in S180 sarcoma. The immunohistochemistry and western blot analysis data from the models revealed that the expression of p-mTOR, HIF-1α and VEGF-A was decreased, while the expression of ULK1 and LC3A was increased following treatment with aspirin and everolimus. The changes were more apparent in the high-dose aspirin and everolimus groups (P<0.01). The inhibitory action of aspirin and everolimus on tumor angiogenesis may be through inhibiting the expression of p-mTOR, HIF-1α and VEGF-A. Alternatively, aspirin may induce autophagy by inhibiting the mTOR signaling target and then increasing ULK1 and LC3A.

Copper activates HIF-1α/GPER/VEGF signalling in cancer cells

Copper promotes tumor angiogenesis, nevertheless the mechanisms involved remain to be fully understood. We have recently demonstrated that the G-protein estrogen receptor (GPER) cooperates with hypoxia inducible factor-1α (HIF-1α) toward the regulation of the pro-angiogenic factor VEGF. Here, we show that copper sulfate (CuSO4) induces the expression of HIF-1α as well as GPER and VEGF in breast and hepatic cancer cells through the activation of the EGFR/ERK/c-fos transduction pathway. Worthy, the copper chelating agent TEPA and the ROS scavenger NAC prevented the aforementioned stimulatory effects. We also ascertained that HIF-1α and GPER are required for the transcriptional activation of VEGF induced by CuSO4. In addition, in human endothelial cells, the conditioned medium from breast cancer cells treated with CuSO4 promoted cell migration and tube formation through HIF-1α and GPER. The present results provide novel insights into the molecular mechanisms involved by copper in triggering angiogenesis and tumor progression. Our data broaden the therapeutic potential of copper chelating agents against tumor angiogenesis and progression.

Dynamic monitoring of GPER-mediated estrogenic effects in breast cancer associated fibroblasts: An alternative role of estrogen in mammary carcinoma development

Cancer associated fibroblasts (CAFs) are crucial contributors to breast cancer development. Estrogen affects mammary stroma in both physiological and pathophysiological conditions. We show here that estrogen (G-protein coupled) receptor (GPER) could be detected by immunohistochemistry in stromal fibroblasts of primary breast cancers. The presence of GPER expression was further confirmed by immunofluorescence and quantitative PCR in CAFs isolated from primary breast cancers. Based on dynamic monitoring by real time cell analyzer (RTCA) system, 17-β-estradiol (E2) as well as GPER specific agonist G1 were observed to trigger transient cell index increasing within an hour in a dosage-dependent manner in breast CAFs. In addition, E2 and G1 stimulated intracellular calcium modulation and phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 within seconds and minutes in CAFs, respectively. Moreover, E2 and G1 promoted cell proliferation of breast CAFs measured by RTCA monitoring, cell viability assay and cell cycle analysis, and this promotion could be blocked by a GPER-selective antagonist G15. Interestingly, dynamic RTCA monitoring indicated that E2 increased adhesion of resuspended cells, and microscopy confirmed that E2 stimulated cell spreading. Both the adhesion and spreading were proposed to be mediated by GPER, since G1 also stimulated these effects similar to E2, and G15 reduced them. Moreover, GPER was found to mediate migration that was increased by E2 and G1 but reduced by G15 in RTCA cell migration assay and transwell assay. Accordingly, GPER mediates not only rapid actions but also slow effects including adhesion/spreading, proliferation and migration in breast CAFs. Estrogen is likely to affect tumor associated stroma and contributes to mammary carcinoma development through CAFs.

The G protein-coupled estrogen receptor as a modulator of neoplastic transformation

Estrogens play a crucial role in the regulation of physiological and pathophysiological processes. These hormones act through specific receptors, most notably the canonical estrogen receptors α and β (ERα and ERβ) and their truncated forms as well as the G protein-coupled estrogen receptor (GPER). Several studies have shown that GPER is expressed in many normal and cancer cells, including those of the breast, endometrium, ovary, testis and lung. Hormonal imbalance is one possible cause of cancer development. An accumulating body of evidence indicates that GPER is involved in the regulation of cancer cell proliferation, migration and invasion, it may act as a mediator of microRNA, and is believed to modulate the inflammation associated with neoplastic transformation. Furthermore, used in various treatment regimens anti-estrogens such as tamoxifen, raloxifen and fulvestrant (ICI 182.780), antagonists/modulators of canonical estrogen receptors, were found to be GPER agonists. This review presents the current knowledge about the potential role of GPER in neoplastic transformation.

Fibroblasts, an inconspicuous but essential player in colon cancer development and progression

Tumor microenvironments have a crucial role in cancer initiation and progression, and share many molecular and pathological features with wound healing process. Unless treated, tumors, however, do not heal in contrast to wounds that heal within a limited time framework. Wounds heal in coordination of a myriad of types of cells, particularly endothelial cells, leukocytes, and fibroblasts. Similar sets of cells also contribute to cancer initiation and progression, and as a consequence, anti-cancer treatment strategies have been proposed and tested by targeting endothelial cells and/or leukocytes. Compared with endothelial cells and leukocytes, less attention has been paid to the roles of cancer-associated fibroblasts (CAFs), fibroblasts present in tumor tissues, because their heterogeneity hinders the elucidation on them at cellular and molecular levels. Here, we will discuss the origin of CAFs and their crucial roles in cancer initiation and progression, and the possibility to develop a novel type of anti-cancer treatment by manipulating the migration and functions of CAFs.

An overlooked tumor promoting immunoregulation by non-hematopoietic stromal cells

Multidirectional complex communication between tumor-residing hematopoietic and non-hematopoietic stromal cells (NHSCs) decisively regulates cancer development, progression and therapeutic responses. HSCs predominantly participate in the immune regulations, while, NHSCs, provide parenchymal support or serve as a conduit for other cells or support angiogenesis. However, recent reports suggest NHSCs can additionally participate in ongoing tumor promoting immune reactions within tumor-microenvironment (TME). In this review, based on the state-of-art knowledge and accumulated evidence by us, we discuss the role of quite a few NHSCs in tumor from immunological perspectives. Understanding such consequence of NHSCs will surely pave the way in crafting effective cancer management.

GPER signalling in both cancer-associated fibroblasts and breast cancer cells mediates a feedforward IL1β/IL1R1 response

Cancer-associated fibroblasts (CAFs) contribute to the malignant aggressiveness through secreted factors like IL1β, which may drive pro-tumorigenic inflammatory phenotypes mainly acting via the cognate receptor named IL1R1. Here, we demonstrate that signalling mediated by the G protein estrogen receptor (GPER) triggers IL1β and IL1R1 expression in CAFs and breast cancer cells, respectively. Thereby, ligand-activation of GPER generates a feedforward loop coupling IL1β induction by CAFs to IL1R1 expression by cancer cells, promoting the up-regulation of IL1β/IL1R1 target genes such as PTGES, COX2, RAGE and ABCG2. This regulatory interaction between the two cell types induces migration and invasive features in breast cancer cells including fibroblastoid cytoarchitecture and F-actin reorganization. A better understanding of the mechanisms involved in the regulation of pro-inflammatory cytokines by GPER-integrated estrogen signals may be useful to target these stroma-cancer interactions.

G protein-coupled estrogen receptor is involved in modulating colonic motor function via nitric oxide release in C57BL/6 female mice

BACKGROUND

Estrogen may regulate gastrointestinal motor functions, but the mechanism(s) is not totally understood. Here, we investigated whether G protein-coupled estrogen receptor (GPER/GPR30) was involved in regulating colonic motor functions and explored the underlying physiological mechanisms.

METHODS

Adult female C57BL/6 mice were used. The expression and localization of GPER were examined by RT-PCR, western blot, and immuno-labeling. The role of GPER in modulating colonic motor functions was assessed by the bead propulsion test in vivo and organ bath experiments in vitro.

KEY RESULTS

GPER was expressed in colonic myenteric neurons. The colonic transit time (CTT) in proestrus and estrus was significantly longer than that in diestrus. In vivo treatment with the selective GPER blocker G15 significantly shortened CTT in proestrus and estrus. In ovariectomized mice, acute estrogen supplementation increased CTT, which could be abolished by G15 co-administration. The GPER agonist G-1 caused a concentration-dependent inhibition of carbachol -induced circular muscle strips contraction, which was abolished by tetrodotoxin and the neuronal nitric oxide synthase (nNOS) inhibitor N-propyl-l-arginine. G-1 stimulated NO production in isolated longitudinal muscle myenteric plexus and cultured myenteric neurons, which was dependent on nNOS. Immunofluorescence labeling showed co-localization of GPER with nNOS in the myenteric plexus.

CONCLUSIONS & INFERENCES

We suggest that activation of GPER exerts an inhibitory effect on colonic motility by promoting NO release from myenteric nitrergic nerves. These results raise a possibility that GPER may be involved in mediating the inhibitory effect of estrogen on colonic motor functions, via a non-genomic, neurogenic mechanism.

Recent Advances on the Role of G Protein-Coupled Receptors in Hypoxia-Mediated Signaling

G protein-coupled receptors (GPCRs) are cell surface proteins mainly involved in signal transmission; however, they play a role also in several pathophysiological conditions. Chemically heterogeneous molecules like peptides, hormones, lipids, and neurotransmitters activate second messengers and induce several biological responses by binding to these seven transmembrane receptors, which are coupled to heterotrimeric G proteins. Recently, additional molecular mechanisms have been involved in GPCR-mediated signaling, leading to an intricate network of transduction pathways. In this regard, it should be mentioned that diverse GPCR family members contribute to the adaptive cell responses to low oxygen tension, which is a distinguishing feature of several illnesses like neoplastic and cardiovascular diseases. For instance, the G protein estrogen receptor, namely G protein estrogen receptor (GPER)/GPR30, has been shown to contribute to relevant biological effects induced by hypoxia via the hypoxia-inducible factor (HIF)-1α in diverse cell contexts, including cancer. Likewise, GPER has been found to modulate the biological outcome of hypoxic/ischemic stress in both cardiovascular and central nervous systems. Here, we describe the role exerted by GPCR-mediated signaling in low oxygen conditions, discussing, in particular, the involvement of GPER by a hypoxic microenvironment.

GPER mediates the effects of 17β-estradiol in cardiac mitochondrial biogenesis and function

Considering the sexual dimorphism described in cardiac mitochondrial function and oxidative stress, we aimed to investigate the role of 17β-estradiol (E2) in these sex differences and the contribution of E2 receptors to these effects. As a model of chronic deprivation of ovarian hormones, we used ovariectomized (OVX) rats, half of which were treated with E2. Ovariectomy decreased markers of cardiac mitochondrial biogenesis and function and also increased oxidative stress, whereas E2 counteracted these effects. In H9c2 cardiomyocytes we observed that G-protein coupled estrogen receptor (GPER) agonist mimicked the effects of E2 in enhancing mitochondrial function and biogenesis, whereas GPER inhibitor neutralized them. These data suggest that E2 enhances mitochondrial function and decreases oxidative stress in cardiac muscle, thus it could be responsible for the sexual dimorphism observed in mitochondrial biogenesis and function in this tissue. These effects seem to be mediated through GPER stimulation.

The G protein estrogen receptor (GPER) is regulated by endothelin-1 mediated signaling in cancer cells

Endothelin-1 (ET-1) is a potent endogenous vasoconstrictor involved in many diseases, including certain cardiovascular disorders and cancer. As previous studies have shown that the G protein estrogen receptor (GPER) may regulate ET-1 dependent effects on the vascular system, we evaluated whether GPER could contribute to the effects elicited by ET-1 in breast cancer and hepatocarcinoma cells. Here, we demonstrate that ET-1 increases GPER expression through endothelin receptor A (ETAR) and endothelin receptor B (ETBR) along with the activation of PI3K/ERK/c-Fos/AP1 transduction pathway. In addition, we show that GPER is involved in important biological responses observed upon ET-1 exposure, as the migration of the aforementioned tumor cells and the formation of tube-like structures in human umbilical vein endothelial cells (HUVECs). Our data suggest that GPER may contribute to ET-1 action toward the progression of some types of tumor.

Pregnancy Augments G Protein Estrogen Receptor (GPER) Induced Vasodilation in Rat Uterine Arteries via the Nitric Oxide - cGMP Signaling Pathway

BACKGROUND

The regulation of vascular tone in the uterine circulation is a key determinant of appropriate uteroplacental blood perfusion and successful pregnancy outcome. Estrogens, which increase in the maternal circulation throughout pregnancy, can exert acute vasodilatory actions. Recently a third estrogen receptor named GPER (G protein-coupled estrogen receptor) was identified and, although several studies have shown vasodilatory effects in several vascular beds, nothing is known about its role in the uterine vasculature.

AIM

The aim of this study was to determine the function of GPER in uterine arteries mainly during pregnancy. Uterine arteries were isolated from nonpregnant and pregnant rats.

METHODS

Vessels were contracted with phenylephrine and then incubated with incremental doses (10-12-10-5 M) of the selective GPER agonist G1.

RESULTS

G1 induced a dose-dependent vasodilation which was: 1) significantly increased in pregnancy, 2) endothelium-dependent, 3) primarily mediated by NO/cGMP pathway and 4) unaffected by BKca channel inhibition.

CONCLUSION

This is the first study to show the potential importance of GPER signaling in reducing uterine vascular tone during pregnancy. GPER may therefore play a previously unrecognized role in the regulation of uteroplacental blood flow and normal fetus growth.

A calixpyrrole derivative acts as an antagonist to GPER, a G-protein coupled receptor: mechanisms and models

Estrogens regulate numerous pathophysiological processes, mainly by binding to and activating estrogen receptor (ER)α and ERβ. Increasing amounts of evidence have recently demonstrated that G-protein coupled receptor 30 (GPR30; also known as GPER) is also involved in diverse biological responses to estrogens both in normal and cancer cells. The classical ER and GPER share several features, including the ability to bind to identical compounds; nevertheless, some ligands exhibit opposed activity through these receptors. It is worth noting that, owing to the availability of selective agonists and antagonists of GPER for research, certain differential roles elicited by GPER compared with ER have been identified. Here, we provide evidence on the molecular mechanisms through which a calixpyrrole derivative acts as a GPER antagonist in different model systems, such as breast tumor cells and cancer-associated fibroblasts (CAFs) obtained from breast cancer patients. Our data might open new perspectives toward the development of a further class of selective GPER ligands in order to better dissect the role exerted by this receptor in different pathophysiological conditions. Moreover, calixpyrrole derivatives could be considered in future anticancer strategies targeting GPER in cancer cells.

A Bodipy as a luminescent probe for detection of the G protein estrogen receptor (GPER)

We report the rational design, based on docking simulations, and synthesis of the first fluorescent and selective probe of GPER for bioimaging purposes and functional dissecting studies. It has been conceived as a Bodipy derivative and obtained by accessible and direct synthesis. Its optical properties have been measured in different solvents, showing insensitivity to their polarity. Its binding to GPER was achieved by competition assays with [3H]E2 and [5,6-3H] nicotinic acid in ER-negative and GPER-positive SkBr3 breast cancer cells. SkBr3 cells, transfected with a GPER expression vector containing a FLAG tag, were used to confirm that the fluorophore binds to GPER in a specific manner.

Role of cancer-associated fibroblasts in invasion and metastasis of gastric cancer

Cancer-associated fibroblasts (CAFs) are important components of various types of tumors, including gastric cancer (GC). During tumorigenesis and progression, CAFs play critical roles in tumor invasion and metastasis via a series of functions including extracellular matrix deposition, angiogenesis, metabolism reprogramming and chemoresistance. However, the mechanism of the interaction between gastric cancer cells and CAFs remains largely unknown. MicroRNAs (miRNAs) are a class of non-coding small RNA molecules, and their expression in CAFs not only regulates the expression of a number of target genes but also plays an essential role in the communication between tumor cells and CAFs. In this review, we provide an overview of recent studies on CAF miRNAs in GC and the relevant signaling pathways in gastrointestinal tumors. Focusing the attention on these signaling pathways may help us better understand their role in tumor invasion and metastasis and identify new molecular targets for therapeutic strategies.