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

GPER-novel membrane oestrogen receptor

The recent discovery of the G protein-coupled oestrogen receptor (GPER) presents new challenges and opportunities for understanding the physiology, pathophysiology and pharmacology of many diseases. This review will focus on the expression and function of GPER in hypertension, kidney disease, atherosclerosis, vascular remodelling, heart failure, reproduction, metabolic disorders, cancer, environmental health and menopause. Furthermore, this review will highlight the potential of GPER as a therapeutic target.

HIF-1 in cancer therapy: two decade long story of a transcription factor

BACKGROUND

Oxygen (O₂) homeostasis is an indispensable requirement of eukaryotes. O₂ concentration in cellular milieu is defined as normoxia (∼21% O₂), physoxia (∼1-13% O₂) or hypoxia (∼0.1-1% O₂). Hypoxia, a striking micro-environmental feature in tumorigenesis, is countered by tumor cells via induction of O₂ governed transcription factor, hypoxia inducible factor-1 (HIF-1). Post discovery, HIF-1 has emerged as a promising anticancer therapeutic target during the last two decades. Recent reports have highlighted that enhanced levels of HIF-1 correlate with tumor metastasis leading to poor patient prognosis.

MATERIAL AND METHODS

A systematic search in PubMed and SciFinder for the literature on HIF-1 biology and therapeutic importance in cancer was carried out.

RESULTS

This review highlights the initial description as well as the recent insights into HIF-1 biology and regulation. We have focused on emerging data regarding varied classes of HIF-1 target genes affecting various levels of crosstalk among tumorigenic pathways. We have emphasized on the fact that HIF-1 acts as a networking hub coordinating activities of multiple signaling molecules influencing tumorigenesis. Emerging evidences indicate role of many HIF-induced proteomic and genomic alterations in malignant progression by mediating a myriad of genes stimulating angiogenesis, anaerobic metabolism and survival of cancer cells in O₂-deficient microenvironment.

CONCLUSIONS

Better understanding of the crucial role of HIF-1 in carcinogenesis could offer promising new avenues to researchers and aid in elucidating various open issues regarding the use of HIF-1 as an anticancer therapeutic target. In spite of large efforts in this field, many questions still remain unanswered. Hence, future investigations are necessary to devise, assess and refine methods for translating previous research efforts into novel clinical practices in cancer treatment.

Clinical significance of HIF-1α expression in gastric malignant transformation in people from high altitude area of Qinghai

AIM

To detect the expression of hypoxia inducible factor-1α (HIF-1α) in gastric malignant transformation in people from high altitude area of Qinghai, China.

METHODS

RT-PCR was used to detect the expression of HIF-1α gene in 7 cell lines and 27 pairs of GC and matched tumor adjacent normal gastric mucosa tissues. Using tissue microarray including 57 normal gastric mucosa tissues, 37 chronic atrophic gastritis tissues, 34 intestinal metaplasia tissues, and 146 gastric cancer (GC) tissues, immunohistochemistry (IHC) was performed to detect the level of HIF-1α protein expression.

RESULTS

The expression of HIF-1α at the mRNA level was different in GC cell lines. HIF-1αexpression in AGS, SGC7901, and N87 cells was higher than that in MGC803, BGC823, PAMC82 and MKN45 cells. The level of HIF-1α expression was significantly higher in GC tissues (66.6%, 18/27) compared with normal gastric mucosa tissues (26.3%, 15/57; P < 0.001). IHC data showed that the positive rate of HIF-1α was 64.8% (24/37) in chronic atrophic gastritis tissues, 61.7% (21/34) in intestinal metaplasia tissues, and 56.8% (83/146) in GC tissues, all of which were significantly higher than that in normal tissues (26.3%, 15/57). Expression of HIF-1α was positively associated with age in GC (P < 0.05). Kaplan-Meier analysis showed that patients with a low level of HIF-1α had apparently better survival than those with a high level (P < 0.0001). HIF-1α protein (RR = 3.229, 95%CI: 2.024-5.151) was identified to be an independent risk factor for the outcome of GC patients.

CONCLUSION

High HIF-1α expression is associated with gastric malignant transformation and poor prognosis in high altitude areas.

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.

Involvement of c-Fos in the Promotion of Cancer Stem-like Cell Properties in Head and Neck Squamous Cell Carcinoma

Purpose: Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide. Although improvements in surgical techniques, chemotherapy and radiation delivery, and supportive care have improved quality of life for patients with HNSCC, regional and distant recurrence remain common. Recent evidence suggests that cancer stem-like cells (CSC) play a significant role in recurrence and chemoresistance. We previously observed that c-Fos was highly upregulated in the HNSCC sphere-forming cells. Consequences of c-Fos upregulation for the biology of HNSCC-CSCs are poorly understood. In this study, we investigated the role of c-Fos in renewal of stemness of HNSCC and tumor growth.Experimental Design and Results: We generated stable HNSCC cell lines ectopically expressing the c-Fos gene. Exogenous expression of c-Fos in nontumorigenic MDA1386Tu cells makes these cells tumorigenic in nude mice. Furthermore, subcutaneous transplantation of c-Fos-overexpressing Cal27 cells (tumorigenic) into immunocompromised mice enhanced tumor growth as compared with parental cells. Mechanistic investigations demonstrated that c-Fos overexpression enhanced the epithelial-mesenchymal transition (EMT) state and expression of CSC markers (Nanog, c-Myc, Sox2, and Notch1). Ectopic expression of c-Fos in HNSCC cells also displays increased sphere formation. We further observed that overexpression of c-Fos increased the expression of pERK and cyclin D1 in HNSCC cells.Conclusions: Together, our results strongly suggest a novel role of c-Fos as a regulator of EMT and cancer stem cell reprogramming in HNSCC cells, which may hold potential as a CSC-directed therapeutic approach to improve HNSCC treatment. Clin Cancer Res; 23(12); 3120-8. ©2016 AACR.

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.

Double-edged role of G protein-coupled estrogen receptor 1 in breast cancer prognosis: an analysis of 167 breast cancer samples and online data sets

G protein-coupled estrogen receptor 1 (GPER1) is widely expressed in breast cancer; however, its prognostic significance in breast cancer patients remains controversial. In this study, expression levels of GPER1 were analyzed by using real-time polymerase chain reaction in 167 primary breast cancer samples, and overall survival (OS), recurrence-free survival (RFS), distant metastasis-free survival (DMFS), and disease-free survival (DFS) were analyzed by using Kaplan-Meier curves and multivariable Cox regression. In addition, a meta-analysis was conducted with all available online data sets found in the Web sites kmplot.com and www.prognoscan.org. The results showed that there was no significant correlation between GPER1 expression and OS, RFS, DMFS, and DFS in the total breast cancer patient population. In contrast, the meta-analysis of online data sets found that expression levels of GPER1 were slightly associated with better RFS in the total breast cancer population (P=0.021). Interestingly, higher expression of GPER1 was associated with poorer DFS in HER2-positive subtype of breast cancer (P=0.047) but with better DMFS (P=0.040) and DFS (P=0.035) in HER2-negative subtype of breast cancer. In addition, it was found that HER2 overexpression in MDA-MB-231 cell increased GPER1, which may help explain protumor effect of GPER1 in HER2-overexpressed patients. The overall results suggested that the expression of GPER1 has distinct prognostic values in HER2-positive and HER2-negative breast cancer patients.

Characterization of Human and Yeast Mitochondrial Glycine Carriers with Implications for Heme Biosynthesis and Anemia

Heme is an essential molecule in many biological processes, such as transport and storage of oxygen and electron transfer as well as a structural component of hemoproteins. Defects of heme biosynthesis in developing erythroblasts have profound medical implications, as represented by sideroblastic anemia. The synthesis of heme requires the uptake of glycine into the mitochondrial matrix where glycine is condensed with succinyl coenzyme A to yield δ-aminolevulinic acid. Herein we describe the biochemical and molecular characterization of yeast Hem25p and human SLC25A38, providing evidence that they are mitochondrial carriers for glycine. In particular, the hem25Δ mutant manifests a defect in the biosynthesis of δ-aminolevulinic acid and displays reduced levels of downstream heme and mitochondrial cytochromes. The observed defects are rescued by complementation with yeast HEM25 or human SLC25A38 genes. Our results identify new proteins in the heme biosynthetic pathway and demonstrate that Hem25p and its human orthologue SLC25A38 are the main mitochondrial glycine transporters required for heme synthesis, providing definitive evidence of their previously proposed glycine transport function. Furthermore, our work may suggest new therapeutic approaches for the treatment of congenital sideroblastic anemia.

GPER, IGF-IR, and EGFR transduction signaling are involved in stimulatory effects of zinc in breast cancer cells and cancer-associated fibroblasts

Zinc (Zn) is an essential trace mineral that contributes to the regulation of several cellular functions; however, it may be also implicated in the progression of breast cancer through different mechanisms. It has been largely reported that the classical estrogen receptor (ER), as well as the G protein estrogen receptor (GPER, previously known as GPR30) can exert a main role in the development of breast tumors. In the present study, we demonstrate that zinc chloride (ZnCl₂ ) involves GPER in the activation of insulin-like growth factor receptor I (IGF-IR)/epidermal growth factor receptor (EGFR)-mediated signaling, which in turn triggers downstream pathways like ERK and AKT in breast cancer cells, and main components of the tumor microenvironment namely cancer-associated fibroblasts (CAFs). Further corroborating these findings, ZnCl₂ stimulates a functional crosstalk of GPER with IGF-IR and EGFR toward the transcription of diverse GPER target genes. Then, we show that GPER contributes to the stimulatory effects induced by ZnCl₂ on cell-cycle progression, proliferation, and migration of breast cancer cells as well as migration of CAFs. Together, our data provide novel insights into the molecular mechanisms through which zinc may exert stimulatory effects in breast cancer cells and CAFs toward tumor progression. © 2016 Wiley Periodicals, Inc.

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.

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.

Inhibiting effect of Endostar combined with ginsenoside Rg3 on breast cancer tumor growth in tumor-bearing mice

OBJECTIVE

To study the inhibiting effect of Endostar combined with ginsenoside Rg3 on breast cancer tumor growth in tumor-bearing mice.

METHODS

Female mice were selected as experimental animals, and breast cancer tumor-bearing mouse models were established and then divided into groups A, B, C and D that respectively received saline, recombinant human endostatin, ginsenosides Rg3 and recombinant human endostatin combined with Rg3 intervention; 7 d, 14 d and 21 d after intervention, tumor tissue volume was measured; 21 d after intervention, mice were killed, tumor tissue was collected, and mRNA contents of angiogenesis molecules, invasion molecules, autophagy marker molecules and autophagy signaling pathway molecules were detected.

RESULTS

At 7 d, 14 d and 21 d after intervention, tumor tissue volume of groups B, C and D was lower than that of group A, and tumor tissue volume of group D was lower than that of groups B and C; mRNA contents of VEGFA, VEGFB, VEGFC, MMP2, MMP9, p62, mTOR, PI3K, Akt, JNK and Beclin-1 in tumor tissue of groups B, C and D were significantly lower than those of group A, and LC3-II/LC3-I was significantly higher than that of group A; mRNA contents of VEGFA, VEGFB, VEGFC, MMP2, MMP9, p62, mTOR, PI3K, Akt, JNK and Beclin-1 in tumor tissue of group D were significantly lower than those of groups B and C, and LC3-II/LC3-I was higher than that of groups B and C.

CONCLUSIONS

Endostar combined with ginsenoside Rg3 has stronger inhibiting effect on breast cancer tumor growth in tumor-bearing mice than single drug, and it can inhibit angiogenesis and cell invasion, and enhance cell autophagy.

Predictive significance of combined LAPTM4B and VEGF expression in patients with cervical cancer

Lysosome-associated protein transmembrane 4ß-35 (LAPTM4B-35) is overexpressed in several solid malignancies. This study determines the expression level of LAPTM4B-35 in the cervical cancer during tumor development and progression. The present study investigated the clinicopathological significance of the coexpression of LAPTM4B-35 and VEGF in patients with cervical cancer. Immunohistochemistry was used to evaluate the expression of LAPTM4B-35 and VEGF in 62 cervical intraepithelial neoplasia (CIN) and 226 cervical carcinoma in comparison with 45 normal cervical specimens. The correlation of combined LAPTM4B-35 and VEGF with clinicopathologic characteristics was analyzed using a chi-squared test. Patient survival was determined using Kaplan-Meier method and log-rank test. A Cox regression analysis was performed to determine the prognostic significance of the factors. Combined LAPTM4B-35 and VEGF expression was significantly associated with FIGO stage (P = 0.014), tumor histologic grade (P = 0.033), lymph node metastasis (P = 0.045), and recurrence (P = 0.010). Kaplan-Meier survival analysis showed that patients with cervical cancer expressing both LAPTM4B-35 and VEGF exhibited both poor overall survival (OS) and disease-free survival (DFS) (P = 0.015 and P = 0.016, respectively). Cox analysis demonstrated that combined LAPTM4B-35 and VEGF expression was an independent factor for both OS and DFS (P = 0.015 and P = 0.016, respectively). Overexpression of LAPTM4B-35combined with positive VEGF expression may serve as a new biological marker to predict the prognosis of cervical carcinoma patients.