Molecular characterization and expression analysis of Asian swamp eel (Monopterus albus) CXC chemokine receptor (CXCR) 1a, CXCR1b, CXCR2, CXCR3a, CXCR3b, and CXCR4 after bacteria and poly I:C challenge

The CXC chemokine receptors (CXCRs) play critical roles in innate and adaptive immune systems. In this study, six Asian swamp eel (Monopterus albus) CXCRs (MaCXCR1-4) were identified and their molecular characterization and expression patterns were analyzed. The open reading frames (ORFs) of MaCXCR1a, MaCXCR1b, MaCXCR2, MaCXCR3a, MaCXCR3b, and MaCXCR4 were 1074 bp (base pairs), 1080 bp, 1125 bp, 1146 bp, 1083 bp, and 1140 bp, and encoded proteins of 357 aa (amino acids), 359 aa, 374 aa, 381 aa, 360 aa, and 379 aa, respectively. All these CXCRs have seven conserved transmembrane domains and four cysteines (with the exception of MaCXCR3b). Multiple sequence alignment revealed that the MaCXCRs possess a typical G-protein receptor family 1 signature and a DRY motif. There are also one to four potential N-glycosylation sites in the extracellular regions of the MaCXCRs, mainly distributed in the N-terminus and extracellular hydrophilic loop (ECL) 2 region. Phylogenetic analysis demonstrated that the MaCXCRs were clustered together with homologous proteins from other fish. Taken together with the amino acid identity and similarity analysis, these results suggested that the MaCXCRs are conserved with other homologous genes, in which CXCR4 is more conserved than CXCR1-3. The MaCXCRs loci showed conserved synteny among teleost fish, and we found that human CXCR1 shares a common ancestor with fish CXCR1a. MaCXCRs were constitutively expressed in a wide range of tissues (especially in immune-related tissues) with different expression levels, suggesting that the MaCXCRs have different roles in un-stimulated tissues, and may play vital roles under normal conditions. MaCXCRs showed different fold changes in the spleen after Aeromonas veronii and polyinosinic-polycytidylic acid (poly I:C) challenge, which suggested that MaCXCR1a and MaCXCR3a have longer antiviral activities compared with their antibacterial functions, and that MaCXCR1b possesses stronger antiviral than antibacterial activity. MaCXCR4 may play vital roles during bacterial and viral infection; however, MaCXCR2 has relatively small effect in antibacterial and antiviral responses. The differential responses of these genes to bacteria and poly I:C implied the differences in the mechanisms of defense against viruses and bacteria.

Genome-wide Estrogen Receptor-α activation is sustained, not cyclical

Estrogen Receptor-alpha (ER) drives 75% of breast cancers. Stimulation of the ER by estra-2-diol forms a transcriptionally-active chromatin-bound complex. Previous studies reported that ER binding follows a cyclical pattern. However, most studies have been limited to individual ER target genes and without replicates. Thus, the robustness and generality of ER cycling are not well understood. We present a comprehensive genome-wide analysis of the ER after activation, based on 6 replicates at 10 time-points, using our method for precise quantification of binding, Parallel-Factor ChIP-seq. In contrast to previous studies, we identified a sustained increase in affinity, alongside a class of estra-2-diol independent binding sites. Our results are corroborated by quantitative re-analysis of multiple independent studies. Our new model reconciles the conflicting studies into the ER at the TFF1 promoter and provides a detailed understanding in the context of the ER's role as both the driver and therapeutic target of breast cancer.

Breast Cancer: An Examination of the Potential of ACKR3 to Modify the Response of CXCR4 to CXCL12

Upon binding with the chemokine CXCL12, the chemokine receptor CXCR4 has been shown to promote breast cancer progression. This process, however, can be affected by the expression of the atypical chemokine receptor ACKR3. Given ACKR3's ability to form heterodimers with CXCR4, we investigated how dual expression of both receptors differed from their lone expression in terms of their signalling pathways. We created single and double CXCR4 and/or ACKR3 Chinese hamster ovary (CHO) cell transfectants. ERK and Akt phosphorylation after CXCL12 stimulation was assessed and correlated with receptor internalization. Functional consequences in cell migration and proliferation were determined through wound healing assays and calcium flux. Initial experiments showed that CXCR4 and ACKR3 were upregulated in primary breast cancer and that CXCR4 and ACKR3 could form heterodimers in transfected CHO cells. This co-expression modified CXCR4's Akt activation after CXCL12's stimulation but not ERK phosphorylation (p < 0.05). To assess this signalling disparity, receptor internalization was assessed and it was observed that ACKR3 was recycled to the surface whilst CXCR4 was degraded (p < 0.01), a process that could be partially inhibited with a proteasome inhibitor (p < 0.01). Internalization was also assessed with the ACKR3 agonist VUF11207, which caused both CXCR4 and ACKR3 to be degraded after internalization (p < 0.05 and p < 0.001), highlighting its potential as a dual targeting drug. Interestingly, we observed that CXCR4 but not ACKR3, activated calcium flux after CXCL12 stimulation (p < 0.05) and its co-expression could increase cellular migration (p < 0.01). These findings suggest that both receptors can signal through ERK and Akt pathways but co-expression can alter their kinetics and internalization pathways.

Adaptation and Constraint in the Atypical Chemokine Receptor Family in Mammals

Atypical chemokine receptors (ACKRs) are a subclass of G protein-coupled receptors characterized by promiscuity of ligand binding and an obvious inability to signal after ligand binding. Although some discoveries regarding this family in Homo sapiens and other species have been reported in some studies, the evolution and function of multiple ACKR in mammals have not yet been clearly understood. We performed an evolutionary analysis of ACKR genes (ACKR1, ACKR2, ACKR3, and ACKR4) in mammals. Ninety-two full-length ACKR genes from 27 mammal species were retrieved from the Genbank and Ensemble databases. Phylogenetic analysis showed that there were four well-conserved subfamilies in mammals. Synteny analysis revealed that ACKR genes formed conserved linkage groups with their adjacent genes across mammalian species, facilitating the identification of ACKRs in as yet unannotated genome datasets. Analysis of the site-specific profiles established by posterior probability revealed the positive-selection sites to be distributed mainly in the ligand binding region of ACKR1. This study highlights the molecular evolution of the ACKR gene family in mammals and identifies the critical amino acid residues likely to be relevant to ligand binding. Further experimental verification of these findings may provide valuable information regarding the ACKR's biochemical and physiological functions.

Alternative splicing of helicase-like transcription factor (Hltf): Intron retention-dependent activation of immune tolerance at the feto-maternal interface

Hltf is regulated by intron retention, and global Hltf-deletion causes perinatal lethality from hypoglycemia. In heart, full-length Hltf is a transcriptional regulator of Hif-1α that controls transport systems. Thus, we tested the hypothesis that Hltf deletion from placenta caused or exacerbated neonatal hypoglycemia via Hif-1α regulation of nutrient transporters. RNA-seq data analyses identified significant changes in transcript expression and alternative splicing (AS) in E18.5 placentome. iPathwayGuide was used for gene ontology (GO) analysis of biological processes, molecular functions and cellular components. Elim pruning algorithm identified hierarchical relationships. The methylome was interrogated by Methyl-MiniSeq Epiquest analysis. GO analysis identified gene enrichment within biological processes. Protein expression was visualized with immunohistochemistry. Although two Hltf mRNA isoforms are quantifiable in most murine tissues, only the truncated Hltf isoform is expressed in placenta. The responsible intron retention event occurs in the absence of DNA methylation. iPathwayGuide analysis identified 157 target genes of 11,538 total genes with measured expression. These were obtained using a threshold of 0.05 for statistical significance (p-value) and a long fold change of expression with absolute value of at least 0.6. Hltf deletion altered transcription of trophoblast lineage-specific genes, and increased transcription of the Cxcr7 (p = 0.004) gene whose protein product is a co-receptor for human and simian immunodeficiency viruses. Concomitant increased Cxcr7 protein was identified with immunolabeling. Hltf deletion had no effect on transcription or site-specific methylation patterns of Hif-1α, the major glucose transporters, or System A amino acid transporters. There was no measureable evidence of uteroplacental dysfunction or fetal compromise. iPathGuide analysis revealed Hltf suppresses cytolysis (10/21 genes; p-value 1.900e-12; p-value correction: Elim pruning; GO:019835) including the perforin-granzyme pathway in uterine natural killer cells. Our findings 1) prove the truncated Hltf protein isoform is a transcription factor, 2) establish a functional link between AS of Hltf and immunosuppression at the feto-maternal interface, 3) correlate intron retention with the absence of DNA methylation, and 4) underscore the importance of differential splicing analysis to identify Hltf's functional diversity.

CXCR7 expression in diffuse large B-cell lymphoma identifies a subgroup of CXCR4+ patients with good prognosis

The CXCR4/CXCL12 axis has been extensively associated with different types of cancer correlating with higher aggressiveness and metastasis. In diffuse large B-cell lymphoma (DLBCL), the expression of the chemokine receptor CXCR4 is involved in the dissemination of malignant B cells and is a marker of poor prognosis. CXCR7 is a chemokine receptor that binds to the same ligand as CXCR4 and regulates de CXCR4-CXCL12 axis. These findings together with the report of CXCR7 prognostic value in several tumor types, led us to evaluate the expression of CXCR7 in diffuse large B-cell lymphoma biopsies. Here, we describe that CXCR7 receptor is an independent prognostic factor that associates with good clinical outcome. Moreover, the expression of CXCR7 associates with increased survival in CXCR4+ but not in CXCR4- DLBCL patients. Thus, the combined immunohistochemical evaluation of both CXCR7 and CXCR4 expression in DLBCL biopsies may improve their prognostic value as single markers. Finally, we show that CXCR7 overexpression in vitro is able to diminish DLBCL cell survival and increase their sensitivity to antitumor drugs. Hence, further studies on the CXCR7 receptor may establish its role in DLBCL and the molecular mechanisms that modulate CXCR4 activity.

Genetically engineered two-warhead evasins provide a method to achieve precision targeting of disease-relevant chemokine subsets

Both CC and CXC-class chemokines drive inflammatory disease. Tick salivary chemokine-binding proteins (CKBPs), or evasins, specifically bind subsets of CC- or CXC-chemokines, and could precisely target disease-relevant chemokines. Here we have used yeast surface display to identify two tick evasins: a CC-CKBP, P1243 from Amblyomma americanum and a CXC-CKBP, P1156 from Ixodes ricinus. P1243 binds 11 CC-chemokines with Kd < 10 nM, and 10 CC-chemokines with Kd between 10 and 100 nM. P1156 binds two ELR + CXC-chemokines with Kd < 10 nM, and four ELR + CXC-chemokines with Kd between 10 and 100 nM. Both CKBPs neutralize chemokine activity with IC50 < 10 nM in cell migration assays. As both CC- and CXC-CKBP activities are desirable in a single agent, we have engineered "two-warhead" CKBPs to create single agents that bind and neutralize subsets of CC and CXC chemokines. These results show that tick evasins can be linked to create non-natural proteins that target subsets of CC and CXC chemokines. We suggest that "two-warhead" evasins, designed by matching the activities of parental evasins to CC and CXC chemokines expressed in disease, would achieve precision targeting of inflammatory disease-relevant chemokines by a single agent.

IL6 derived from cancer-associated fibroblasts promotes chemoresistance via CXCR7 in esophageal squamous cell carcinoma

Various factors and cellular components in the tumor microenvironment are key drivers associated with drug resistance in many cancers. Here, we analyzed the factors and molecular mechanisms involved in chemoresistance in patients with esophageal squamous cell carcinoma (ESCC). We found that interleukin 6 (IL6) derived mainly from cancer-associated fibroblasts played the most important role in chemoresistance by upregulating C-X-C motif chemokine receptor 7 (CXCR7) expression through signal transducer and activator of transcription 3/nuclear factor-κB pathway. CXCR7 knockdown resulted in the inhibition of IL6-induced proliferation and chemoresistance. In addition, CXCR7 silencing significantly decreased gene expression associated with stemness, chemoresistance and epithelial-mesenchymal transition and suppressed the proliferation ability of ESCC cells in three-dimensional culture systems and angiogenesis assay. In clinical samples, ESCC patients with high expression of CXCR7 and IL6 presented a significantly worse overall survival and progression-free survival upon receiving cisplatin after operation. These results suggest that the IL6-CXCR7 axis may provide a promising target for the treatment of ESCC.

Inhibition of chemokine (C-X-C motif) receptor four (CXCR4) at the fetal-maternal interface during early gestation in sheep: alterations in expression of chemokines, angiogenic factors and their receptors

Chemokine (C-X-C motif) ligand 12 (CXCL12) and its receptor, chemokine (C-X-C motif) receptor 4 (CXCR4), are involved in significant biological processes associated with early pregnancy including increasing trophoblast invasion and stimulating placental vascularization. To further elucidate functions of CXCL12-CXCR4 signaling during early gestation, our objective was to inhibit CXCR4 in vivo using a CXCR4 antagonist, AMD3100. We hypothesized that inhibition of CXCR4 would negatively affect chemokine and angiogenic factor regulation imperative for placental development in sheep. Osmotic pumps containing PBS (control) or AMD3100 (CXCR4 antagonist) were surgically installed ipsilateral to the corpus luteum on d 12 of gestation and administered treatments directly into the uterine lumen. Maternal (caruncle and intercaruncle) and fetal membrane tissues were collected on d 23 of gestation and mRNA and protein expression were analyzed for vascular endothelial growth factor (VEGF), kinase insert domain receptor (KDR), fms related tyrosine kinase 1 (FLT1), fibroblast growth factor 2 (FGF2), angiopoietin 1 (ANGPT1), hypoxia inducible factor 1 ɑ subunit (HIF1A), CXCL12, and its corresponding receptors (CXCR4 and CXCR7). Immunohistochemical procedures were performed for analysis of CXCL12 and cell proliferation. In caruncle tissue ipsilateral to the pump, mRNA for KDR, ANGPT1, HIF1A, and CXCL12 increased (P < 0.05) in treated ewes compared to control, whereas caruncle tissue contralateral to the pump had increased expression (P < 0.05) of KDR, and CXCL12 in treated ewes. In fetal membrane, CXCR4 mRNA and protein decreased (P < 0.05), while VEGF protein decreased (P < 0.05) in caruncle and fetal membrane tissue from treated ewes. Results from this study highlight the importance of CXCL12-CXCR4 signaling at the fetal-maternal interface. Inhibiting this axis may disrupt typical regulation of angiogenic factors needed for placental development and embryo growth.

CXCR7/CXCL12 axis is involved in lymph node and liver metastasis of gastric carcinoma

AIM

To investigate the role of CXC chemokine receptor (CXCR)-7 and CXCL12 in lymph node and liver metastasis of gastric carcinoma.

METHODS

In 160 cases of gastric cancer, the expression of CXCR7 and CXCL12 in tumor and matched tumor-adjacent non-cancer tissues, in the lymph nodes around the stomach and in the liver was detected using immunohistochemistry to analyze the relationship between CXCR7/CXCL12 expression and clinicopathological features and to determine whether CXCR7 and CXCL12 constitute a biological axis to promote lymph node and liver metastasis of gastric cancer. Furthermore, the CXCR7 gene was silenced and overexpressed in human gastric cancer SGC-7901 cells, and cell proliferation, migration and invasiveness were measured by the MTT, wound healing and Transwell assays, respectively.

RESULTS

CXCR7 expression was up-regulated in gastric cancer tissues (P = 0.011). CXCR7/CXCL12 expression was significantly related to high tumor stage and lymph node (r = 0.338, P = 0.000) and liver metastasis (r = 0.629, P = 0.000). The expression of CXCL12 in lymph node and liver metastasis was higher than that in primary gastric cancer tissues (χ2 = 6.669, P = 0.010; χ2 = 25379, P = 0.000), and the expression of CXCL12 in lymph node and liver metastasis of gastric cancer was consistent with the positive expression of CXCR7 in primary gastric cancer (r = 0.338, P = 0.000; r = 0.629, P = 0.000). Overexpression of the CXCR7 gene promoted cell proliferation, migration and invasion. Silencing of the CXCR7 gene suppressed SGC-7901 cell proliferation, migration and invasion. Human gastric cancer cell lines expressed CXCR7 and showed vigorous proliferation and migratory responses to CXCL12.

CONCLUSION

The CXCR7/CXCL12 axis is involved in lymph node and liver metastasis of gastric cancer. CXCR7 is considered a potential therapeutic target for the treatment of gastric cancer.

CXC motif chemokine receptor 4 gene polymorphism and cancer risk

BACKGROUND

Previous epidemiological studies have reported the relationship between CXC motif chemokine receptor 4 (CXCR4) synonymous polymorphism (rs2228014), and risk of cancer, but the results remained conflicting and controversial. Therefore, this study was devised to evaluate the genetic effects of the rs2228014 polymorphism on cancer risk in a large meta-analysis.

METHODS

The computer-based databases (EMBASE, Web of Science, and PubMed) were searched for all relevant studies evaluating rs2228014 and susceptibility to cancer. In the analysis, pooled odds ratios (ORs) with its corresponding 95% confidence intervals (CIs) were calculated in 5 genetic models to assess the genetic risk. Egger regression and Begg funnel plots test were conducted to appraise the publication bias.

RESULTS

Data on rs2228014 polymorphism and overall cancer risk were available for 3684 cancer patients and 5114 healthy controls participating in 11 studies. Overall, a significantly increased risk of cancer was associated with rs2228014 polymorphism in homozygote model (OR = 2.01, 95% CI: 1.22-3.33) and in recessive model (OR = 1.97, 95% CI: 1.23-3.16). When stratified by ethnicity, the results were positive only in Asian populations (heterozygote model: OR = 1.36, 95% CI: 1.13-1.65; homozygote model: OR = 2.43, 95% CI: 1.21-4.91; dominant model: OR = 1.47, 95% CI: 1.13-1.90; recessive model: OR = 2.25, 95% CI: 1.13-4.48; and allele model: OR = 1.48, 95% CI: 1.10-1.99). Besides, in the subgroup analysis by source of control, the result was significant only in population-based control (homozygote model: OR = 2.39, 95% CI: 1.06-5.40; recessive model: pooled OR = 2.24, 95% CI: 1.02-4.96).

CONCLUSION

In general, our results first indicated that the rs2228014 polymorphism in CXCR4 gene is correlated with an increased risk of cancer, especially among Asian ethnicity. Large, well-designed epidemiological studies are required to verify the current findings.

Blocking CXCR7-mediated adipose tissue macrophages chemotaxis attenuates insulin resistance and inflammation in obesity

Adipose tissue macrophages (ATMs) have been considered to have a pivotal role in the chronic inflammation development during obesity. Although chemokine-chemokine receptor interaction has been studied in ATMs infiltration, most chemokine receptors remain incompletely understood and little is known about their mechanism of actions that lead to ATMs chemotaxis and pathogenesis of insulin resistance during obesity. In this study, we reported that CXCR7 expression is upregulated in adipose tissue, and specifically in ATMs during obesity. In addition, CXCL11 or CXCL12-induced ATMs chemotaxis is mediated by CXCR7 in obesity but not leanness, whereas CXCR3 and CXCR4 are not involved. Additional mechanism study shows that NF-κB activation is essential in ATMs chemotaxis, and manipulates chemotaxis of ATMs via CXCR7 expression regulation in obesity. Most importantly, CXCR7 neutralizing therapy dose dependently leads to less infiltration of macrophages into adipose tissue and thus reduces inflammation and improves insulin sensitivity in obesity. In conclusion, these findings demonstrated that blocking CXCR7-mediated ATMs chemotaxis ameliorates insulin resistance and inflammation in obesity.

CXCR7/p-ERK-Signaling Is a Novel Target for Therapeutic Vasculogenesis in Patients with Coronary Artery Disease

Coronary artery disease (CAD) is characterized by insufficient vasculogenic response to ischemia, which is typically accompanied by dysfunction of endothelial outgrowth cells (EOCs). CXC chemokine receptor 7 (CXCR7) is a key modulator of the neovascularization of EOCs to perfusion defect area. However, the mechanism underlying the role of EOCs in CAD-related abnormal vasculogenesis is still not clear. Here, we investigated the alteration of EOCs-related vasculogenic capacity in patients with CAD and its potential mechanism. Compared with EOCs isolated from healthy subjects, EOCs from CAD patients showed an impaired vasculogenic function in vitro. CXCR7 expression of EOCs from CAD patients was downregulated. Meanwhile, the phosphorylation of extracellular signal-regulated kinase (ERK), downstream of CXCR7 signaling, was also reduced. CXCR7 expression introduced by adenovirus increased the phosphorylation of ERK, which was parallel to improved function of EOCs. The enhanced adhesion and vasculogenesis of EOCs can be blocked by short interfering RNA (siRNA) against CXCR7 and ERK inhibitor PD098059. Therefore, our study demonstrates that the upregulation of CXCR7 signaling contributes to increased vasculogenic capacity of EOCs from CAD patients, indicating that CXCR7 signaling may be a novel therapeutic vasculogenic target for CAD.

[Expression of CXCR7 in Gastric Cancer Cells and Its Effect on the Migration and Invasion of SGC-7901 Cells]

OBJECTIVES

To determine the expression of chemokine (C-X-C motif) receptor 7 (CXCR7) in five gastric cancer cell lines with various degrees of differentiation, and the effect of silencing CXCR7 on the migration and invasion of SGC-7901 cells.

METHODS

The expression of CXCR7 in gastric cell lines (HGC-27, MGC-803, SGC-7901, BGC-823 and MKN-28) was detected by Western bolt and RT-PCR. The SGC-7901 cells were transfected with liposome of CXCR7 siRNA to silence CXCR7 gene, and then treated with stromal-derived factor-1 (SDF-1)-the ligand of CXCR7. Transwell assay was used for determining the migratory and invasive ability of SGC-7901 cells in the four groups: NC siRNA, NC siRNA+SDF-1, CXCR7 siRNA and CXCR7 siRNA+SDF-1.

RESULTS

CXCR7 was expressed in the five gastric cancer cell lines, with the highest intensity in SGC-7901. The migrated and invasive cells increased in the NC siRNA+SDF-1 group and reduced in the CXCR7-siRNA group compared with the NC siRNA group (P<0.05). The CXCR7-siRNA+SDF-1 group had less migrated and invasive cells than the NC siRNA+SDF-1 group (P<0.05).

CONCLUSIONS

CXCR7 is highly expressed in SGC-7901. SDF-1 promotes the migratory and invasive capability of SGC-7901 cells, but such an effect can be inhibited by silencing it with CXCR7siRNA.

New Insights into Mechanisms and Functions of Chemokine (C-X-C Motif) Receptor 4 Heteromerization in Vascular Smooth Muscle

Recent evidence suggests that C-X-C chemokine receptor type 4 (CXCR4) heteromerizes with α_1A/B-adrenoceptors (AR) and atypical chemokine receptor 3 (ACKR3) and that CXCR4:α_1A/B-AR heteromers are important for α₁-AR function in vascular smooth muscle cells (VSMC). Structural determinants for CXCR4 heteromerization and functional consequences of CXCR4:α_1A/B-AR heteromerization in intact arteries, however, remain unknown. Utilizing proximity ligation assays (PLA) to visualize receptor interactions in VSMC, we show that peptide analogs of transmembrane-domain (TM) 2 and TM4 of CXCR4 selectively reduce PLA signals for CXCR4:α_1A-AR and CXCR4:ACKR3 interactions, respectively. While both peptides inhibit CXCL12-induced chemotaxis, only the TM2 peptide inhibits phenylephrine-induced Ca²⁺-fluxes, contraction of VSMC and reduces efficacy of phenylephrine to constrict isolated arteries. In a Cre-loxP mouse model to delete CXCR4 in VSMC, we observed 60% knockdown of CXCR4. PLA signals for CXCR4:α_1A/B-AR and CXCR4:ACKR3 interactions in VSMC, however, remained constant. Our observations point towards TM2/4 of CXCR4 as possible contact sites for heteromerization and suggest that TM-derived peptide analogs permit selective targeting of CXCR4 heteromers. A molecular dynamics simulation of a receptor complex in which the CXCR4 homodimer interacts with α_1A-AR via TM2 and with ACKR3 via TM4 is presented. Our findings further imply that CXCR4:α_1A-AR heteromers are important for intrinsic α₁-AR function in intact arteries and provide initial and unexpected insights into the regulation of CXCR4 heteromerization in VSMC.

Commercially available antibodies directed against α-adrenergic receptor subtypes and other G protein-coupled receptors with acceptable selectivity in flow cytometry experiments

Several previous reports suggested that many commercially available antibodies directed against G protein-coupled receptors (GPCR) lack sufficient selectivity. Accordingly, it has been proposed that receptor antibodies should be validated by at least one of several criteria, such as testing tissues or cells after knockout or silencing of the corresponding gene. Here, we tested whether 12 commercially available antibodies directed against α-adrenergic receptor (AR) subtypes (α1A/B/D, α2A/B/C), atypical chemokine receptor 3 (ACKR3), and vasopressin receptor 1A (AVPR1A) suffice these criteria. We detected in flow cytometry experiments with human vascular smooth muscle cells that the fluorescence signals from each of these antibodies were reduced by 46 ± 10 %-91 ± 2 % in cells treated with commercially available small interfering RNA (siRNA) specific for each receptor, as compared with cells that were incubated with non-targeting siRNA. The tested antibodies included anti-ACKR3 (R&D Systems, mab42273), for which specificity has previously been demonstrated. Staining with this antibody resulted in 72 ± 5 % reduction of the fluorescence signal after ACKR3 siRNA treatment. Furthermore, staining with anti-α1A-AR (Santa Cruz, sc1477) and anti-ACKR3 (Abcam, ab38089), which have previously been reported to be non-specific, resulted in 70 ± 19 % and 80 ± 4 % loss of the fluorescence signal after α1A-AR and ACKR3 siRNA treatment, respectively. Our findings demonstrate that the tested antibodies show reasonable selectivity for their receptor target under our experimental conditions. Furthermore, our observations suggest that the selectivity of GPCR antibodies depends on the method for which the antibody is employed, the species from which cells/tissues are obtained, and on the type of specimens (cell, tissue/cell homogenate, or section) tested.

Prognostic significance of CXCL12, CXCR4, and CXCR7 in patients with breast cancer

BACKGROUND

The chemokine CXCL12 and its receptors CXCR4 and CXCR7 play important roles in cancer invasion and metastasis. This study investigated the mRNA expressions of CXCL12, CXCR4, and CXCR7 to illustrate the role of these biomarkers in breast cancer metastasis and prognosis.

METHODS

The mRNA expressions of CXCL12, CXCR4, and CXCR7 in 115 primary breast cancer and regional lymph node specimens were detected by quantitative reverse-transcription polymerase chain reaction. Survival time was analyzed by Kaplan-Meier survival curves using log-rank test. Univariable and multivariable Cox regression analyses were performed to assess independent prognostic factors for survival.

RESULTS

The expression levels of CXCR4 and CXCR7 in breast cancer tissues were significantly higher than that in adjacent normal tissues (P=0.022 and P<0.001, respectively), while the expression level of CXCL12 in breast cancer tissues did not differ from that in adjacent normal tissues (P=0.156). Furthermore, CXCL12 exhibited significant differences in expression between primary tumor and lymph node metastasis tumor (P=0.039). CXCR4 and CXCR7 expressions in metastasis tumor were also higher, although no significant difference was observed (P=0.067 and P=0.054, respectively). Kaplan-Meier survival analysis revealed that patients exhibiting high CXCR4 and CXCR7 expression experienced a shorter survival period compared with those with low expression. When analyzed with a Cox regression model, the expressions of CXCL12, CXCR4 and CXCR7 were independent prognostic factors for overall survival.

CONCLUSIONS

The mRNA expressions of CXCL12, CXCR4, and CXCR7 play important roles in the progression and metastasis of breast cancer and may act as predictive factors significantly affecting the prognosis.

Lipopolysaccharide Promotes Choroidal Neovascularization by Up-Regulation of CXCR4 and CXCR7 Expression in Choroid Endothelial Cell

Stromal cell-derived factor-1 (SDF-1) has been confirmed to participate in the formation of choroidal neovascularization (CNV) via its two receptors: CXC chemokine receptors 4 (CXCR4) and CXCR7. Previous studies have indicated that the activation of Toll-like receptors (TLRs) by lipopolysaccharide (LPS) might elevate CXCR4 and/or CXCR7 expression in tumor cells, enhancing the response to SDF-1 to promote invasion and cell dissemination. However, the impact of LPS on the CXCR4 and CXCR7 expression in endothelial cells and subsequent pathological angiogenesis formation remains to be elucidated. The present study shows that LPS enhanced the CXCR4 and CXCR7 expression via activation of the TLR4 pathway in choroid-retinal endothelial (RF/6A) cells. In addition, the transcriptional regulation of CXCR4 and CXCR7 by LPS was found to be mediated by phosphorylation of the extracellular signal-related kinase (ERK) 1/2 and activation of nuclear factor kappa B (NF-κB) signaling pathways, which were blocked by ERK- or NF-κB-specific inhibitors. Furthermore, the increased CXCR4 and CXCR7 expression resulted in increased SDF-1-induced RF/6A cells proliferation, migration and tube formation. In vivo, LPS-treated rat had significantly higher mRNA levels of CXCR4 and CXCR7 expression and lager laser-induced CNV area than vehicle-treated rat. SDF-1 blockade with a neutralizing antibody attenuated the progression of CNV in LPS-treated rat after a single intravitreal injection. Altogether, these results demonstrated that LPS might influence CNV formation by enhancing CXCR7 and CXCR7 expression in endothelial cells, possibly providing a new perspective for the treatment of CNV-associated diseases.

The CXCR4/CXCR7/CXCL12 Axis Is Involved in a Secondary but Complex Control of Neuroblastoma Metastatic Cell Homing

Neuroblastoma (NB) is one of the most deadly solid tumors of the young child, for which new efficient and targeted therapies are strongly needed. The CXCR4/CXCR7/CXCL12 chemokine axis has been involved in the progression and organ-specific dissemination of various cancers. In NB, CXCR4 expression was shown to be associated to highly aggressive undifferentiated tumors, while CXCR7 expression was detected in more differentiated and mature neuroblastic tumors. As investigated in vivo, using an orthotopic model of tumor cell implantation of chemokine receptor-overexpressing NB cells (IGR-NB8), the CXCR4/CXCR7/CXCL12 axis was shown to regulate NB primary and secondary growth, although without any apparent influence on organ selective metastasis. In the present study, we addressed the selective role of CXCR4 and CXCR7 receptors in the homing phase of metastatic dissemination using an intravenous model of tumor cell implantation. Tail vein injection into NOD-scid-gamma mice of transduced IGR-NB8 cells overexpressing CXCR4, CXCR7, or both receptors revealed that all transduced cell variants preferentially invaded the adrenal gland and typical NB metastatic target organs, such as the liver and the bone marrow. However, CXCR4 expression favored NB cell dissemination to the liver and the lungs, while CXCR7 was able to strongly promote NB cell homing to the adrenal gland and the liver. Finally, coexpression of CXCR4 and CXCR7 receptors significantly and selectively increased NB dissemination toward the bone marrow. In conclusion, CXCR4 and CXCR7 receptors may be involved in a complex and organ-dependent control of NB growth and selective homing, making these receptors and their inhibitors potential new therapeutic targets.

The CXC chemokine receptors of fish: Insights into CXCR evolution in the vertebrates

This article will review current knowledge on CXCR in fish, that represent three distinct vertebrate groups: Agnatha (jawless fishes), Chondrichthyes (cartilaginous fishes) and Osteichthyes (bony fishes). With the sequencing of many fish genomes, information on CXCR in these species in particular has expanded considerably. In mammals, 6 CXCRs have been described, and their homologues will be initially reviewed before considering a number of atypical CXCRs and a discussion of CXCR evolution.

Identification of common regulators of genes in co-expression networks affecting muscle and meat properties

Understanding the genetic contributions behind skeletal muscle composition and metabolism is of great interest in medicine and agriculture. Attempts to dissect these complex traits combine genome-wide genotyping, expression data analyses and network analyses. Weighted gene co-expression network analysis (WGCNA) groups genes into modules based on patterns of co-expression, which can be linked to phenotypes by correlation analysis of trait values and the module eigengenes, i.e. the first principal component of a given module. Network hub genes and regulators of the genes in the modules are likely to play an important role in the emergence of respective traits. In order to detect common regulators of genes in modules showing association with meat quality traits, we identified eQTL for each of these genes, including the highly connected hub genes. Additionally, the module eigengene values were used for association analyses in order to derive a joint eQTL for the respective module. Thereby major sites of orchestrated regulation of genes within trait-associated modules were detected as hotspots of eQTL of many genes of a module and of its eigengene. These sites harbor likely common regulators of genes in the modules. We exemplarily showed the consistent impact of candidate common regulators on the expression of members of respective modules by RNAi knockdown experiments. In fact, Cxcr7 was identified and validated as a regulator of genes in a module, which is involved in the function of defense response in muscle cells. Zfp36l2 was confirmed as a regulator of genes of a module related to cell death or apoptosis pathways. The integration of eQTL in module networks enabled to interpret the differentially-regulated genes from a systems perspective. By integrating genome-wide genomic and transcriptomic data, employing co-expression and eQTL analyses, the study revealed likely regulators that are involved in the fine-tuning and synchronization of genes with trait-associated expression.

Long term intravital multiphoton microscopy imaging of immune cells in healthy and diseased liver using CXCR6.Gfp reporter mice

Liver inflammation as a response to injury is a highly dynamic process involving the infiltration of distinct subtypes of leukocytes including monocytes, neutrophils, T cell subsets, B cells, natural killer (NK) and NKT cells. Intravital microscopy of the liver for monitoring immune cell migration is particularly challenging due to the high requirements regarding sample preparation and fixation, optical resolution and long-term animal survival. Yet, the dynamics of inflammatory processes as well as cellular interaction studies could provide critical information to better understand the initiation, progression and regression of inflammatory liver disease. Therefore, a highly sensitive and reliable method was established to study migration and cell-cell-interactions of different immune cells in mouse liver over long periods (about 6 hr) by intravital two-photon laser scanning microscopy (TPLSM) in combination with intensive care monitoring. The method provided includes a gentle preparation and stable fixation of the liver with minimal perturbation of the organ; long term intravital imaging using multicolor multiphoton microscopy with virtually no photobleaching or phototoxic effects over a time period of up to 6 hr, allowing tracking of specific leukocyte subsets; and stable imaging conditions due to extensive monitoring of mouse vital parameters and stabilization of circulation, temperature and gas exchange. To investigate lymphocyte migration upon liver inflammation CXCR6.gfp knock-in mice were subjected to intravital liver imaging under baseline conditions and after acute and chronic liver damage induced by intraperitoneal injection(s) of carbon tetrachloride (CCl4). CXCR6 is a chemokine receptor expressed on lymphocytes, mainly on Natural Killer T (NKT)-, Natural Killer (NK)- and subsets of T lymphocytes such as CD4 T cells but also mucosal associated invariant (MAIT) T cells1. Following the migratory pattern and positioning of CXCR6.gfp+ immune cells allowed a detailed insight into their altered behavior upon liver injury and therefore their potential involvement in disease progression.

Mesenchymal stromal cell secretome up-regulates 47 kDa CXCR4 expression, and induce invasiveness in neuroblastoma cell lines

Neuroblastoma accounts for 15% of childhood cancer deaths and presents with metastatic disease of the bone and the bone marrow at diagnosis in 70% of the cases. Previous studies have shown that the Mesenchymal Stromal Cell (MSC) secretome, triggers metastases in several cancer types such as breast and prostate cancer, but the specific role of the MSC factors in neuroblastoma metastasis is unclear. To better understand the effect of MSC secretome on chemokine receptors in neuroblastoma, and its role in metastasis, we studied a panel of 20 neuroblastoma cell lines, and compared their invasive potential towards MSC-conditioned-RPMI (mRPMI) and their cytokine receptor expression profiles. Western blot analysis revealed the expression of multiple CXCR4 isoforms in neuroblastoma cells. Among the five major isoforms, the expression of the 47 kDa isoform showed significant correlation with high invasiveness. Pretreatment with mRPMI up-regulated the expression of the 47 kDa CXCR4 isoform and also increased MMP-9 secretion, expression of integrin α3 and integrin β1, and the invasive potential of the cell; while blocking CXCR4 either with AMD 3100, a CXCR4 antagonist, or with an anti-47 kDa CXCR4 neutralizing antibody decreased the secretion of MMP-9, the expression of integrin α3 and integrin β1, and the invasive potential of the cell. Pretreatment with mRPMI also protected the 47 kDa CXCR4 isoform from ubiquitination and subsequent degradation. Our data suggest a modulatory role of the MSC secretome on the expression of the 47 kDa CXCR4 isoform and invasion potential of the neuroblastoma cells to the bone marrow.

CXCR4 promotes renal tubular cell survival in male diabetic rats: implications for ligand inactivation in the human kidney

Binding of the receptor CXCR4 to its ligand stromal cell-derived factor 1 (SDF-1) promotes cell survival and is under the influence of a number of regulatory processes including enzymatic ligand inactivation by endopeptidases such as matrix metalloproteinase 9 (MMP-9). In light of the pivotal role that the SDF-1/CXCR4 axis plays in renal development and in the pathological growth of renal cells, we explored the function of this pathway in diabetic rats and in biopsies from patients with diabetic nephropathy, hypothesizing that the pro-survival effects of CXCR4 in resident cells would attenuate renal injury. Renal CXCR4 expression was observed to be increased in diabetic rats, whereas antagonism of the receptor unmasked albuminuria and accelerated tubular epithelial cell death. In cultured cells, CXCR4 blockade promoted tubular cell apoptosis, up-regulated Bcl-2-associated death promoter, and prevented high glucose/SDF-1-augmented phosphorylation of the pro-survival kinase, Akt. Although CXCR4 expression was also increased in biopsy tissue from patients with diabetic nephropathy, serine 339 phosphorylation of the receptor, indicative of ligand engagement, was unaffected. Coincident with these changes in receptor expression but not activity, MMP-9 was also up-regulated in diabetic nephropathy biopsies. Supporting a ligand-inactivating effect of the endopeptidase, exposure of cultured cells to recombinant MMP-9 abrogated SDF-1 induced Akt phosphorylation. These observations demonstrate a potentially reno-protective role for CXCR4 in diabetes that is impeded in its actions in the human kidney by the coincident up-regulation of ligand-inactivating endopeptidases. Therapeutically intervening in this interplay may limit tubulointerstitial injury, the principal determinant of renal decline in diabetes.

Co-expression of CXCR4 and CXCR7 in human endometrial stromal cells is modulated by steroid hormones

Endometrium modulated by estrogen (E) and progesterone (P) is important for implantation and pregnancy. The present study compared the expression of chemokine CXCL12 and chemokine receptor CXCR4 and CXCR7 between human cycling and early pregnant endometria by immunohistochemistry (IHC). Then the modulation of E and P on expression of CXCL12, CXCR4 and CXCR7 in human endometrial stromal cells (ESCs) was explored at both mRNA and protein level. The result of IHC showed that human ESCs of the menstrual period did not express CXCL12, CXCR4 or CXCR7 protein, however, the expression of CXCR4 and CXCR7 but not CXCL12 in ESCs increased in the proliferative and secretory phase, and the expression intensity for CXCR4 and CXCR7 in ESCs was the highest in the first trimester. Moreover, E and P were able to up-regulate the mRNA and protein expression of CXCR4 and protein expression of CXCR7 in ESCs (P<0.01). Thus, ESCs spatiotemporally co-express CXCR4 and CXCR7 rather than CXCL12, and E and P are able to regulate the expression of CXCR4 and CXCR7 in ESCs, suggesting the modulation of steroid hormones on chemokine receptor expression in ESCs.