Differential expression of RDC1/CXCR7 in the human placenta

Atypical chemokine receptors in cancer

Atypical chemokine receptors (ACKRs) are a group of seven-transmembrane spanning serpentine receptors that are structurally homologous to classical G-protein-coupled receptors and bind cognate chemokines with high affinities but do not signal via G-proteins or mediate cell migration. However, ACKRs efficiently modify the availability and function of chemokines in defined microanatomical environments, can signal via intracellular effectors other than G-proteins, and play complex roles in physiology and disease, including in cancer. In this review, we summarize the findings on the diverse contributions of individual ACKRs to cancer development, progression, and tumor-host interactions. We discuss how changes in ACKR expression within tumor affect cancer growth, tumor vascularization, leukocyte infiltration, and metastasis formation, ultimately resulting in differential disease outcomes. Across many studies, ACKR3 expression was shown to support tumor growth and dissemination, whereas ACKR1, ACKR2, and ACKR4 in tumors were more likely to contribute to tumor suppression. With few notable exceptions, the insights on molecular and cellular mechanisms of ACKRs activities in cancer remain sparse, and the intricacies of their involvement are not fully appreciated. This is particularly true for ACKR1, ACKR2 and ACKR4. A better understanding of how ACKR expression and functions impact cancer should pave the way for their future targeting by new and effective therapies.

Chemokines as the critical factors during bladder cancer progression: an overview

Bladder cancer (BCa) is one of the most frequent urogenital malignancies which is mainly observed among men. There are various genetic and environmental risk factors associated with BCa progression. Transurethral endoscopic resection and open ablative surgery are the main treatment options for muscle invasive BCa. BCG therapy is also employed following the endoscopic resection to prevent tumor relapse. The tumor microenvironment is the main interaction site of tumor cells and immune system in which the immune cells are recruited via chemokines and chemokine receptors. In present review we summarized the main chemokines and chemokine receptors which have been associated with histopathological features of BCa patients in the world. This review highlights the chemokines and chemokine receptors as critical markers in early detection and therapeutic purposes among BCa patients and clarifies their molecular functions during BCa progression and metastasis.

Wogonin reverses the drug resistance of chronic myelogenous leukemia cells to imatinib through CXCL12-CXCR4/7 axis in bone marrow microenvironment

Background

In the current study, chronic myeloid leukemia (CML) cells (K562 and KU812) co-cultured with human bone marrow stromal cells (BMSCs) were significantly less sensitive to imatinib (IM). The activation of the CXCL12-CXCR4/7 axis plays an important role in the protective effect of the bone marrow microenvironment (BME) on CML cells. The aim of this study was to investigate whether Wogonin could increase the sensitivity of CML cells to IM when they were co-cultured with BME and explore its underlying mechanism.

Methods

A model of CML cells co-cultured with BMSCs was applied in vitro. Flow cytometric, western blotting, immunofluorescence, and RT-PCR assays were used to explore the protective effects of BME on CML cells.

Results

The results showed that Wogonin could reverse the resistance of CML cells to IM under co-culture conditions by inhibiting Transforming growth factor-β (TGF-β) secretion in the BME, preventing the translocation of Smad4 into nucleus and subsequently reducing the expression of CXCR4 and CXCR7 in CML cells. Moreover, the reverse effect of Wogonin was demonstrated by inhibiting the activation of CXCL12-CXCR4/7 axis via restraining the TGF-β/Smad4/Id3 pathway in vitro. In vivo studies also showed that Wogonin decreased the expression of CXCR4 and CXCR7 in mice bone marrow with low systemic toxicity, and the mechanism was consistent with the in vitro study.

Conclusions

Wogonin increases the sensitivity of CML cells to IM in BME by controlling the TGF-β/Smad4/Id3 pathway and decreasing the expression of CXCR4 and CXCR7. These results co-supported the point that Wogonin could be a potential candidate of reversal agents on treatment of IM-resistant CML.

CXCL12 in normal and pathological pregnancies: A review

The survival of allogeneic fetuses during pregnancy is a rather paradoxical phenomenon with a complex mechanism. Chemokine ligand12 (CXCL12) and its receptors CXC chemokine receptor (CXCR)4 and 7 are extensively found in placenta tissues and cells, including trophoblast cells, vascular endothelial cells, and decidual stromal and decidual immune cells (eg, NK cells and regulatory T cells). Evidence has illustrated that the CXClL12/CXCR4/CXCR7 axis could enhance the cross talk at the maternal-fetal interface through multiple processes, such as invasion and placental angiogenesis, which appears to be critical signaling components in placentation and fetal outcome. In addition, an increasing number of studies have demonstrated that the CXCL12/CXCR4/CXCR7 axis also stands out for its pleiotropic roles in several pregnancy-associated diseases (eg, recurrent spontaneous abortion (RSA), pre-eclampsia (PE), and preterm labor). In the present review, the different biological properties and signaling in physiological and pathological pregnancy conditions of CXCL12/CXCR4/CXCR7 axis were discussed, with the aim of obtaining a further understanding of the regulatory mechanisms and highlighting their potential as a target for therapeutic approaches.

Expression and Functional Analysis of CXCL12 and Its Receptors in Human Term Trophoblast Cells

Chemokine CXCL12 and its receptors CXCR4/CXCR7 play a pivotal role in many physiological and pathological situations, while the expression and function in human term trophoblast cells remain largely unknown. In the study, the expression and function of CXCL12 and its receptors CXCR4/CXCR7 in human term trophoblast cells were investigated. Immunocytochemistry and flow cytometry showed that the expression of CXCL12/CXCR4/CXCR7 could be detected in term trophoblast cells while expression level differed. The secretion of CXCL12 in human term trophoblast cells was confirmed by enzyme-linked immunosorbent assay (ELISA). In order to reveal the function of CXCL12, exogenetic recombinant human CXCL12 protein (rhCXCL12) was added to the cultured term trophoblast cells; results showed that cell proliferation ability was increased while cell apoptosis rate was decreased. Moreover, the effects of rhCXCL12 on term trophoblast cells could be diminished or attenuated by antibodies against CXCL12, CXCR4, or CXCR7, respectively. Therefore, these results revealed the important role of CXCL12 on human term trophoblast cells. Our study will provide new insights into understanding the role of CXCL12 on human term trophoblast cells.

Emerging roles of atypical chemokine receptor 3 (ACKR3) in normal development and physiology

The discovery that atypical chemokine receptors (ACKRs) can initiate alternative signaling pathways rather than classical G-protein coupled receptor (GPCR) signaling has changed the paradigm of chemokine receptors and their roles in modulating chemotactic responses. The ACKR family has grown over the years, with discovery of new functions and roles in a variety of pathophysiological conditions. However, the extent to which these receptors regulate normal physiology is still continuously expanding. In particular, atypical chemokine receptor 3 (ACKR3) has proven to be an important receptor in mediating normal biological functions, including cardiac development and migration of cortical neurons. In this review, we illustrate the versatile and intriguing role of ACKR3 in physiology.

Placental chemokine compartmentalisation: A novel mammalian molecular control mechanism

Atypical chemokine receptor 2 (ACKR2) is a chemokine-scavenging receptor. ACKR2–/–embryos display a reduction in size of a novel, to our knowledge, embryonic skin macrophage population referred to as ‘intermediate’ cells. CC chemokine receptor 2 (CCR2)–/–embryos display an identical phenotype, indicating that these cells require CCR2 to enable them to populate embryonic skin. Further analysis revealed that ACKR2–/–embryos have higher circulating concentrations of the CCR2 ligand, CC ligand 2 (CCL2); thus, ACKR2 regulates intraembryonic CCL2 levels. We show that ACKR2 is strongly expressed by trophoblasts and that it blocks movement of inflammatory chemokines, such as CCL2, from the maternal decidua into the embryonic circulation. We propose that trophoblastic ACKR2 is responsible for ensuring chemokine compartmentalisation on the maternal decidua, without which chemokines enter the embryonic circulation, disrupting gradients essential for directed intraembryonic cell migration. Overall, therefore, we describe a novel, to our knowledge, molecular mechanism whereby maternal decidual chemokines can function in a compartmentalised fashion without interfering with intraembryonic leukocyte migration. These data suggest similar functions for other atypical chemokine receptors in the placenta and indicate that defects in such receptors may have unanticipated developmental consequences.

A novel mechanism for molecular compartmentalisation in the placenta involves an atypical chemokine receptor that scavenges chemokines, blocking their drainage from the maternal face of the placenta into the embryo and thus protecting intraembryonic cellular migration processes.

Atypical chemokine receptors 1, 2, 3 and 4: Expression and regulation in the endometrium during the estrous cycle and pregnancy and with somatic cell nucleus transfer-cloned embryos in pigs

Atypical chemokine receptor (ACKR) 1, ACKR2, ACKR3, and ACKR4, chemokine decoy receptors that lack G-protein-mediated signaling pathways, internalize and degrade chemokines to control their availability and function. Chemokines play important roles in the endometrium during the estrous cycle and pregnancy, but the expression and regulation of ACKRs have not been determined in pigs. Therefore, we examined the expression of ACKRs in the endometrium throughout the estrous cycle and pregnancy and in conceptus tissues in pigs. ACKR1, ACKR2, ACKR3, and ACKR4 mRNA was expressed in the endometrium, with higher levels of ACKR3 on day 12 of the estrous cycle than in pregnancy and higher levels of ACKR4 on day 15 of pregnancy than in the estrous cycle. ACKR1, ACKR2, and ACKR3, but not ACKR4, mRNA was detected in conceptus and chorioallantoic tissues during pregnancy. ACKR2 and ACKR3 mRNA and ACKR4 protein were mainly localized to luminal epithelial cells and weakly to glandular epithelial cells in the endometrium. Increasing doses of progesterone increased the expression of ACKR2 and ACKR4 and decreased the expression of ACKR3 in endometrial tissues. On day 12 of pregnancy, the expression of ACKR4 mRNA was lower in the endometria of gilts with somatic cell nucleus transfer-derived conceptuses than in the endometria of gilts carrying conceptuses derived from natural mating. These results indicate that the expression of ACKRs is dynamically regulated at the maternal-conceptus interface, suggesting that ACKR proteins might play critical roles in regulating endometrial chemokines to support the establishment and maintenance of pregnancy in pigs.

Prognostic significance of CXCR7 in cancer patients: a meta-analysis

Background

CXC chemokine receptor 7 (CXCR7) is frequently overexpressed in a variety of tumors. Nevertheless, whether CXCR7 can be used as a tumor prognosis marker has not been systematically assessed. The current meta-analysis was performed to obtain an accurate evaluation of the relationship between CXCR7 level and the prognosis of cancer patients.

Methods

Embase, Web of Science, and PubMed were systematically searched according to a defined search strategy up to June 11, 2018. Then, the required data were extracted from all qualified studies which were screened out based on the defined inclusion and exclusion criteria. Finally, the hazard ratios (HR) with 95% confidence intervals (CI) were used to evaluate the prognostic significance of CXCR7 in tumor patients.

Results

A total of 28 original research studies comprising 33 cohorts and 5685 patients were included in this meta-analysis. The results showed that CXCR7 overexpression was significantly related to worse overall survival (OS) (HR 1.72; 95% CI 1.49–1.99), disease-free survival (DFS) (HR 5.58; 95% CI 3.16–9.85), progression-free survival (PFS) (HR 2.83; 95% CI 1.66–4.85) and recurrence-free survival (RFS) (HR 1.58; 95% CI 1.34–1.88) in cancer patients. Furthermore, for certain types of cancer, significant associations between higher CXCR7 expression and worse OS of glioma (HR 1.77; 95% CI 1.43–2.19), breast cancer (HR 1.45; 95% CI 1.28–1.63), esophageal cancer (HR 2.72; 95% CI 1.11–6.66) and pancreatic cancer (HR 1.46; 95% CI 1.12–1.90) were found. However, for lung cancer and hepatocellular cancer, there was no significant relationship between CXCR7 expression level and OS, (HR 2.40; 95% CI 0.34–17.07) and (HR 1.37; 95% CI 0.84–2.24) respectively.

Conclusions

Increased CXCR7 level could predict poor prognosis of tumor patients and might be regarded as a novel prognostic biomarker for tumor patients.

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.

Cell-specific expression and signal transduction of C-C motif chemokine ligand 2 and atypical chemokine receptors in the porcine endometrium during early pregnancy

Chemokines and atypical chemokine receptors (ACKRs; also known as chemokine decoy receptors) play an important role in reproductive immunology by recruiting leukocytes during early pregnancy. The aim of this study was to determine the expression of C-C motif chemokine ligand 2 (CCL2) and ACKRs in the endometrium during estrous cycle and early pregnancy, and to investigate the functional effects of CCL2 on porcine uterine luminal epithelial (pLE) cells. Our results indicated that CCL2, ACKR1, ACKR3, and ACKR4 were strongly detected in the glandular and luminal epithelium of the endometrium during early pregnancy compared to that in non-pregnant pigs. Recombinant CCL2 improved pLE cell proliferation via activation of the PI3K and MAPK pathways and suppression of endoplasmic reticulum (ER) stress by reducing the expression of ER stress regulatory genes. Collectively, these results provide novel insights into CCL2-mediated signaling mechanisms in the porcine endometrium at the maternal-fetal interface during early pregnancy.

Targeting CXCR7 improves the efficacy of breast cancer patients with tamoxifen therapy

Chemokine (C-X-C motif) receptor 7 (CXCR7) has been established to be involved in breast cancer (BCa) progression. However, the role of CXCR7 in different subtype of BCa still remains unclear. Here we note that CXCR7 expression is significantly amplified in Luminal type BCa tissues as compared with Her2 and TNBC types through data-mining in TCGA datasets, and its protein level positively correlates with ERα expression by staining of human BCa tissue. Interestingly, alteration of CXCR7 expression in Luminal type BCa cells is able to modulate the expression of ERα through ubiquitination at post-translational level. Additionally, overexpression of CXCR7 in these cells greatly induces 4-OHT insensitivity in vitro and is associated with earlier recurrence in patients with tamoxifen therapy. Notably, silencing ERα expression potentially rescues the sensitivity of the above cells to 4-OHT, suggesting that elevated level of ERα is responsible for CXCR7-induced 4-OHT insensitivity in Luminal type BCa. Finally, mechanistic analyses show that the reduced BRCA1 (ubiquitin E3 ligase) and elevated OTUB1 (deubiquitinase) expression, which are regulated by CXCR7/ERK1/2 signaling pathway, are responsible for stabilizing ERα protein. In conclusion, our results suggest that targeting CXCR7 may serve as a potential therapeutic strategy for improving the efficacy of BCa patients with tamoxifen therapy.

Biological/pathological functions of the CXCL12/CXCR4/CXCR7 axes in the pathogenesis of bladder cancer

CXC chemokine ligand 12 (CXCL12) is an important member of the CXC subfamily of chemokines, and has been extensively studied in various human body organs and systems, both in physiological and clinical states. Ligation of CXCL12 to CXCR4 and CXCR7 as its receptors on peripheral immune cells gives rise to pleiotropic activities. CXCL12 itself is a highly effective chemoattractant which conservatively attracts lymphocytes and monocytes, whereas there exists no evidence to show attraction for neutrophils. CXCL12 regulates inflammation, neo-vascularization, metastasis, and tumor growth, phenomena which are all pivotally involved in cancer development and further metastasis. Generation and secretion of CXCL12 by stromal cells facilitate attraction of cancer cells, acting through its cognate receptor, CXCR4, which is expressed by both hematopoietic and non-hematopoietic tumor cells. CXCR4 stimulates tumor progression by different mechanisms and is required for metastatic spread to organs where CXCL12 is expressed, thereby allowing tumor cells to access cellular niches, such as the marrow, which favor tumor cell survival and proliferation. It has also been demonstrated that CXCL12 binds to another seven-transmembrane G-protein receptor or G-protein-coupled receptor, namely CXCR7. These studies indicated critical roles for CXCR4 and CXCR7 mediation of tumor metastasis in several types of cancers, suggesting their contributions as biomarkers of tumor behavior as well as potential therapeutic targets. Furthermore, CXCL12 itself has the capability to stimulate survival and growth of neoplastic cells in a paracrine fashion. CXCL12 is a supportive chemokine for tumor neovascularization via attracting endothelial cells to the tumor microenvironment. It has been suggested that elevated protein and mRNA levels of CXCL12/CXCR4/CXCR7 are associated with human bladder cancer (BC). Taken together, mounting evidence suggests a role for CXCR4, CXCR7, and their ligand CXCL12 during the genesis of BC and its further development. However, a better understanding is still required before exploring CXCL12/CXCR4/CXCR7 targeting in the clinic.

Oroxylin A reverses the drug resistance of chronic myelogenous leukemia cells to imatinib through CXCL12/CXCR7 axis in bone marrow microenvironment

Imatinib (IM), a tyrosine-kinase inhibitor, is used in treatment of multiple cancers, most notably Philadelphia chromosome-positive (Ph⁺ ) chronic myelogenous leukemia (CML). However, the majority of patients continue to present with minimal residual disease occurred in the bone marrow (BM) microenvironment. One of the key factors that contribute to leukemia cell drug resistance is chemokine CXCL12. In the current study, co-culturing CML cell K562 and KU812 with BM stromal cell M2-10B4 attenuated IM-induced apoptosis. CXCL12/CXCR7 pathway was activated in co-culture models, which was further proved to be related to drug resistance by silencing CXCR7. ERK phosphorylation and downstream apoptosis related proteins' activation were also observed in co-culture group after the activation of CXCR7. Moreover, oroxylin A, a bioactive flavonoid isolated from the root of Scutellaria baicalensis Georgi, was found to be effective in reversing BM stroma induced CML resistance to IM. After cells were treated with weakly toxic concentration of oroxylin A, cell apoptosis induced by IM in co-culture model was enhanced. And the activated CXCL12/CXCR7 pathway, the expression of p-ERK and downstream apoptosis related proteins were suppressed. The in vivo study also showed that oroxylin A increased apoptosis of CML cells with low systemic toxicity, and the mechanism was consistent with the in vitro study. In conclusion, oroxylin A improved sensitivity of CML cells to IM treatment in BM microenvironment through regulating CXCL12/CXCR7 pathway. © 2016 Wiley Periodicals, Inc.

Non-human primates in HIV research: Achievements, limits and alternatives

An ideal model for HIV-1 research is still unavailable. However, infection of non-human primates (NHP), such as macaques, with Simian Immunodeficiency Virus (SIV) recapitulates most virological, immunological and clinical hallmarks of HIV infection in humans. It has become the most suitable model to study the mechanisms of transmission and physiopathology of HIV/AIDS. On the other hand, natural hosts of SIV, such as African green monkeys and sooty mangabeys that when infected do not progress to AIDS, represent an excellent model to elucidate the mechanisms involved in the capacity of controlling inflammation and disease progression. The use of NHP-SIV models has indeed enriched our knowledge in the fields of: i) viral transmission and viral reservoirs, ii) early immune responses, iii) host cell-virus interactions in tissues, iv) AIDS pathogenesis, v) virulence factors, vi) prevention and vii) drug development. The possibility to control many variables during experimental SIV infection, together with the resemblance between SIV and HIV infections, make the NHP model the most appropriate, so far, for HIV/AIDS research. Nonetheless, some limitations in using these models have to be considered. Alternative models for HIV/AIDS research, such as humanized mice and recombinant forms of HIV-SIV viruses (SHIV) for NHP infection, have been developed. The improvement of SHIV viruses that mimic even better the natural history of HIV infection and of humanized mice that develop a greater variety of human immune cell lineages, is ongoing. None of these models is perfect, but they allow contributing to the progress in managing or preventing HIV infection.

Chemokine and chemokine receptors in autoimmunity: the case of primary biliary cholangitis

Chemokines represent a major mediator of innate immunity and play a key role in the selective recruitment of cells during localized inflammatory responses. Beyond critical extracellular mediators of leukocyte trafficking, chemokines and their cognate receptors are expressed by a variety of resident and infiltrating cells (monocytes, lymphocytes, NK cells, mast cells, and NKT cells). Chemokines represent ideal candidates for mechanistic studies (particularly in murine models) to better understand the pathogenesis of chronic inflammation and possibly become biomarkers of disease. Nonetheless, therapeutic approaches targeting chemokines have led to unsatisfactory results in rheumatoid arthritis, while biologics against pro-inflammatory cytokines are being used worldwide with success. In this comprehensive review we will discuss the evidence supporting the involvement of chemokines and their specific receptors in mediating the effector cell response, utilizing the autoimmune/primary biliary cholangitis setting as a paradigm.

Overview and potential unifying themes of the atypical chemokine receptor family

Chemokines modulate immune responses through their ability to orchestrate the migration of target cells. Chemokines directly induce cell migration through a distinct set of 7 transmembrane domain G protein-coupled receptors but are also recognized by a small subfamily of atypical chemokine receptors, characterized by their inability to support chemotactic activity. Atypical chemokine receptors are now emerging as crucial regulatory components of chemokine networks in a wide range of physiologic and pathologic contexts. Although a new nomenclature has been approved recently to reflect their functional distinction from their conventional counterparts, a systematic view of this subfamily is still missing. This review discusses their biochemical and immunologic properties to identify potential unifying themes in this emerging family.

C-X-C motif receptor 7 in gastrointestinal cancer

Chemokine receptors are key mediators of normal physiology and numerous pathological conditions, including inflammation and cancer. This receptor family is an emerging target for anticancer drug development. C-X-C motif receptor 7 (CXCR7) is an atypical chemokine receptor that was first cloned from a canine cDNA library as an orphan receptor and was initially named receptor dog cDNA 1 (RDC1). Shortly after demonstrating that RDC1 binds with its ligand, stromal cell-derived factor-1α and interferon-inducible T-cell α chemoattractant, RDC1 was officially deorphanized and renamed CXCR7, as the seventh receptor in the CXC class of the chemokine receptor family. Recent accumulating evidence has demonstrated that CXCR7 expression is augmented in the majority of tumor cells compared with their normal counterparts and is involved in cell proliferation, survival, migration, invasion and angiogenesis during the initiation and progression of breast, lung and prostate cancer. In the present review, the expression and role of CXCR7, as well as its clinical relevance in cancer of the gastrointestinal system, were investigated. In addition, the potential of this chemokine receptor as a therapeutic target in the treatment of gastrointestinal cancer was discussed.

Androgen receptor and chemokine receptors 4 and 7 form a signaling axis to regulate CXCL12-dependent cellular motility

Background

Identifying cellular signaling pathways that become corrupted in the presence of androgens that increase the metastatic potential of organ-confined tumor cells is critical to devising strategies capable of attenuating the metastatic progression of hormone-naïve, organ-confined tumors. In localized prostate cancers, gene fusions that place ETS-family transcription factors under the control of androgens drive gene expression programs that increase the invasiveness of organ-confined tumor cells. C-X-C chemokine receptor type 4 (CXCR4) is a downstream target of ERG, whose upregulation in prostate-tumor cells contributes to their migration from the prostate gland. Recent evidence suggests that CXCR4-mediated proliferation and metastasis of tumor cells is regulated by CXCR7 through its scavenging of chemokine CXCL12. However, the role of androgens in regulating CXCR4-mediated motility with respect to CXCR7 function in prostate-cancer cells remains unclear.

Methods

Immunocytochemistry, western blot, and affinity-purification analyses were used to study how androgens influenced the expression, subcellular localization, and function of CXCR7, CXCR4, and androgen receptor (AR) in LNCaP prostate-tumor cells. Moreover, luciferase assays and quantitative polymerase chain reaction (qPCR) were used to study how chemokines CXCL11 and CXCL12 regulate androgen-regulated genes (ARGs) in LNCaP prostate-tumor cells. Lastly, cell motility assays were carried out to determine how androgens influenced CXCR4-dependent motility through CXCL12.

Results

Here we show that, in the LNCaP prostate-tumor cell line, androgens coordinate the expression of CXCR4 and CXCR7, thereby promoting CXCL12/CXCR4-mediated cell motility. RNA interference experiments revealed functional interactions between AR and CXCR7 in these cells. Co-localization and affinity-purification experiments support a physical interaction between AR and CXCR7 in LNCaP cells. Unexpectedly, CXCR7 resided in the nuclear compartment and modulated AR-mediated transcription. Moreover, androgen-mediated cell motility correlated positively with the co-localization of CXCR4 and CXCR7 receptors, suggesting that cell migration may be linked to functional CXCR4/CXCR7 heterodimers. Lastly, CXCL12-mediated cell motility was CXCR7-dependent, with CXCR7 expression required for optimal expression of CXCR4 protein.

Conclusions

Overall, our results suggest that inhibition of CXCR7 function might decrease the metastatic potential of organ-confined prostate cancers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1201-5) contains supplementary material, which is available to authorized users.

Endothelial expression of CXCR7 and the regulation of systemic CXCL12 levels

The concentration of CXCL12/SDF-1 in the bloodstream is tightly regulated, given its central role in leucocyte and stem/progenitor cell egress from bone marrow and recruitment to sites of inflammation or injury. The mechanism responsible for this regulation is unknown. Here we show that both genetic deletion and pharmacological inhibition of CXCR7, a high-affinity CXCL12 receptor, caused pronounced increases in plasma CXCL12 levels. The rise in plasma CXCL12 levels was associated with an impairment in the ability of leucocytes to migrate to a local source of CXCL12. Using a set of complementary and highly sensitive techniques, we found that CXCR7 protein is expressed at low levels in multiple organs in both humans and mice. In humans, CXCR7 was detected primarily on venule endothelium and arteriole smooth muscle cells. CXCR7 expression on venule endothelium was also documented in immunodeficient mice and CXCR7(+/lacZ) mice. The vascular expression of CXCR7 therefore gives it immediate access to circulating CXCL12. These studies suggest that endothelial CXCR7 regulates circulating CXCL12 levels and that CXCR7 inhibitors might be used to block CXCL12-mediated cell migration for therapeutic purposes.

CXCL12-CXCR7 signaling activates ERK and Akt pathways in human choriocarcinoma cells

Abstract CXCL12 acts as a physiological ligand for the chemokine receptor CXCR7. Chemokine receptor expression by human trophoblast and other placental cells have important implications for understanding the regulation of placental growth and development. We had previously reported the differential expression of CXCR7 in different stages of the human placenta suggesting its possible role in regulation of placental growth and development. In this study, we determined the expression of CXCR7 in human choriocarcinoma JAR cells at the mRNA level and protein level and the downstream signaling pathway mediated by CXCL12-CXCR7 interaction. We observed that binding of CXCL12 to CXCR7 activates the ERK and Akt cell-survival pathways in JAR cells. Inhibition of the ERK and Akt pathways using specific inhibitors (Wortmanin & PD98509) led to the activation of the p38 pathway. Our findings suggest a possible role of CXCR7 in activating the cell survival pathways ERK and Akt in human choriocarcinoma JAR cells.

Expression of stromal cell-derived factor-1 receptors CXCR4 and CXCR7 on circulating platelets of patients with acute coronary syndrome and association with left ventricular functional recovery

BACKGROUND

Surface expression of stromal cell-derived factor-1 (SDF-1) on platelets is enhanced during ischaemic events and might play an important role in peripheral homing and myocardial repair. As SDF-1 effects are mediated through CXCR4/CXCR7, we investigated platelet expression of SDF-1/CXCR4/CXCR7 in patients with coronary artery disease (CAD).

METHODS AND RESULTS

Expression of SDF-1, CXCR4, and CXCR7 in platelets was investigated by western blot analysis, immunofluorescence confocal microscopy, and flow cytometry among healthy subjects and patients with acute coronary syndrome (ACS) and stable CAD. In a cohort study, platelet surface expression of CXCR4, CXCR7, and SDF-1 was measured in 215 patients with symptomatic CAD (stable CAD = 112, ACS = 103) at the time of percutaneous coronary intervention. Course of left ventricular ejection fraction (LVEF) was followed up during intrahospital stay and at 3 months. Both CXCR4 and CXCR7 are surface expressed on human platelets and to a higher degree in CAD patients when compared with healthy controls. Platelet surface expression of CXCR7 but not CXCR4 was enhanced in patients with ACS when compared with patients with stable CAD (mean fluorescence intensity 17.8 vs. 15.3, P = 0.004 and 29.0 vs. 26.3, P = 0.122, respectively). CXCR4 and CXCR7 significantly correlated with their ligand SDF-1 on platelets (ρ = 0.273, P < 0.001 and ρ = 0.454, P < 0.001, respectively). Additionally, high CXCR7 expression above the median correlated with the absolute improvement of LVEF% after 5 days and 3 months (46.2, 49.8, 53.7; P = 0.003).

CONCLUSION

These findings indicate that platelet surface expression of CXCR4 and CXCR7 might differentially contribute to SDF-1-mediated effects on regenerative mechanisms following ACS. Studies are warranted to further evaluate the regulatory mechanisms of CXCR4/-7 expression and its prognostic impact on CAD.

CXCR7 impact on CXCL12 biology and disease

It is known that the chemokine receptor CXCR7 (RDC1) can be engaged by both chemokines CXCL12 (SDF-1) and CXCL11 (I-TAC), but the exact expression pattern and function of CXCR7 is controversial. CXCR7 expression seems to be enhanced during pathological inflammation and tumor development, and emerging data suggest this receptor is an attractive therapeutic target for autoimmune diseases and cancer. CXCR7/CXCR4 heterodimerization, β-arrestin-mediated signaling, and modulation of CXCL12 responsiveness by CXCR7 suggest that the monogamous CXCR4/CXCL12 signaling axis is an oversimplified model that needs to be revisited. Consequently, research into CXCR7 biology is of great interest and further studies are warranted. This review summarizes recent findings about the CXCR7 receptor and analyses its impact on understanding the roles of CXCL12 biology in health and disease.

Human cytomegalovirus infection inhibits CXCL12- mediated migration and invasion of human extravillous cytotrophoblasts

Background

During the first trimester of pregnancy, a series of tightly regulated interactions govern the formation of a highly invasive population of fetal-derived extravillous cytotrophoblasts (EVT). Successful pregnancy is dependent on efficient invasion of the uterine wall and maternal spiral arteries by EVT. Dysregulated trophoblast invasion is associated with intrauterine growth restriction, birth defects, spontaneous abortion and preeclampsia. A number of soluble growth factors, cytokines, and chemokines modulate this process, fine-tuning the temporal and spatial aspects of cytotrophoblast invasion. In particular, the CXCL12/CXCR4 axis has been shown to specifically modulate cytotrophoblast differentiation, invasion, and survival throughout early pregnancy. Infection with human cytomegalovirus (HCMV) has been associated with impaired differentiation of cytotrophoblasts down the invasive pathway, specifically dysregulating the response to mitogens including epidermal growth factor (EGF) and hepatocyte growth factor (HGF). In this study, the effect of HCMV infection on the CXCL12-mediated migration and invasion of the EVT cell line SGHPL-4 was investigated.

Results

Infection with HCMV significantly decreased secretion of CXCL12 by SGHPL-4 cells, and induced a striking perinuclear accumulation of the chemokine. HCMV infection significantly increased mRNA and total cell surface expression of the two known receptors for CXCL12: CXCR4 and CXCR7. Functionally, HCMV-infected SGHPL-4 cells were unable to migrate or invade in response to a gradient of soluble CXCL12 in transwell assays.

Conclusions

Collectively, these studies demonstrate that HCMV impairs EVT migration and invasion induced by CXCL12. As HCMV has the ability to inhibit EVT migration and invasion through dysregulation of other relevant signaling pathways, it is likely that the virus affects multiple signaling pathways to impair placentation and contribute to some of the placental defects seen in HCMV-positive pregnancies.

The biochemistry and biology of the atypical chemokine receptors

A subset of chemokine receptors, initially called "silent" on the basis of their apparent failure to activate conventional signalling events, has recently attracted growing interest due to their ability to internalize, degrade, or transport ligands and thus modify gradients and create functional chemokine patterns in tissues. These receptors recognize distinct and complementary sets of ligands with high affinity, are strategically expressed in different cellular contexts, and lack structural determinants supporting Gα(i) activation, a key signalling event in cell migration. This is in keeping with the hypothesis that they have evolved to fulfil fundamentally different functions to the classical signalling chemokine receptors. Based on these considerations, these receptors (D6, Duffy antigen receptor for chemokines (DARC), CCX-CKR1 and CXCR7) are now collectively considered as an emerging class of 'atypical' chemokine receptors. In this article, we review the biochemistry and biology of this emerging chemokine receptor subfamily.

CXCL12 receptor preference, signal transduction, biological response and the expression of 5T4 oncofoetal glycoprotein

CXCL12 is a pleiotropic chemokine capable of eliciting multiple signal transduction cascades and functions, via interaction with either CXCR4 or CXCR7. Factors that determine CXCL12 receptor preference, intracellular signalling route and biological response are poorly understood but are of central importance in the context of therapeutic intervention of the CXCL12 axis in multiple disease states. We have recently demonstrated that 5T4 oncofoetal glycoprotein facilitates functional CXCR4 expression leading to CXCL12 mediated chemotaxis in mouse embryonic cells. Using wild type (WT) and 5T4 knockout (5T4KO) murine embryonic fibroblasts (MEFs), we now show that CXCL12 binding to CXCR4 activates both the ERK and AKT pathways within minutes, but while these pathways are intact, they are non-functional in 5T4KO cells treated with CXCL12. Importantly, in the absence of 5T4 expression, CXCR7 is upregulated and becomes the predominant receptor for CXCL12, activating a distinct signal transduction pathway with slower kinetics involving transactivation of the epidermal growth factor receptor (EGFR), eliciting proliferation rather than chemotaxis. Thus the surface expression of 5T4 marks the use of the CXCR4 rather than the CXCR7 receptor, with distinct consequences for CXCL12 exposure, relevant to the spread and growth of a tumour. Consistent with this hypothesis, we have identified human small cell lung carcinoma cells with similar 5T4/CXCR7 reciprocity that is predictive of biological response to CXCL12 and determined that 5T4 expression is required for functional chemotaxis in these cells.

Role of chemokine receptor CXCR7 in bladder cancer progression

Bladder cancer is one of the most common tumors of the genitourinary tract; however, the molecular events underlying growth and invasion of the tumor remain unclear. Here, role of the CXCR7 receptor in bladder cancer was further explored. CXCR7 protein expression was examined using high-density tissue microarrays. Expression of CXCR7 showed strong epithelial staining that correlated with bladder cancer progression. In vitro and in vivo studies in bladder cancer cell lines suggested that alterations in CXCR7 expression were associated with the activities of proliferation, apoptosis, migration, invasion, angiogenesis and tumor growth. Moreover, CXCR7 expression was able to regulate expression of the proangiogenic factors IL-8 or VEGF, which may involve in the regulation of tumor angiogenesis. Finally, we found that signaling by the CXCR7 in bladder cancer cells activates AKT, ERK and STAT3 pathways. The AKT and ERK pathways may reciprocally regulate, which are responsible for in vitro and in vivo epithelial to mesenchymal transition (EMT) process of bladder cancer. Simultaneously targeting the two pathways by using U0126 and LY294002 inhibitors or using CCX733, a selective CXCR7 antagonist drastically reduced CXCR7-induced EMT process. Taken together, our data show for the first time that CXCR7 plays a role in the development of bladder cancer. Targeting CXCR7 or its downstream-activated AKT and ERK pathways may prove beneficial to prevent metastasis and provide a more effective therapeutic strategy for bladder cancer.

Histomorphometric and immunohistochemical analysis of infectious agents, T-cell subpopulations and inflammatory adhesion molecules in placentas from HIV-seropositive pregnant women

BACKGROUND

The aim of this study was to compare histomorphometric changes and the results of immunohistochemical tests for VCAM, ICAM-1, CD4 and CD8 in normal placentas from HIV-seropositive pregnant women.

METHODS

Samples of normal placentas were divided into 2 groups: healthy HIV-seronegative pregnant women (control group = C = 60) and HIV-seropositive women (experimental group = E = 57). Conventional histological sections were submitted to morphometric analysis and evaluated in terms of the immunohistochemical expression of ICAM-1, VCAM, CD4 and CD8.

RESULTS

The villi in group E were smaller than those in group C. The median for the CD8+ T cell count was higher in group E than in group C (p = 0.03). Immunohistochemical expression of ICAM-1 was observed in 57% of the cases in group E, compared with 21% of those in group C (p = 0.001). There was no difference in VCAM expression or CD4+ cell counts between groups and no correlation between the data for antiretroviral therapy and morphometric or immunohistochemical data.

CONCLUSIONS

The morphometric data showed that placentas of HIV-seropositive pregnant women tend to have smaller villi than those of seronegative women. In addition, immunohistochemical testing for infectious agents helped to identify cases that were positive for microorganisms (6/112) that routine pathological examination had failed to detect. The anti-p24 antibody had a limited ability to detect HIV viral protein in this study (2/57). Correlation of immunohistochemical expression of CD8+ T cells and ICAM-1 with the presence of HIV in the placenta revealed that those expressions can act as biomarkers of inflammatory changes. There was no correlation between the data for antiretroviral therapy and morphometric or immunohistochemical data.

CXCR7 mediated Giα independent activation of ERK and Akt promotes cell survival and chemotaxis in T cells

Chemokine receptors CXCR7 and CXCR4 bind to the same ligand stromal cell derived factor-1alpha (SDF-1α/CXCL12). We assessed the downstream signaling pathways mediated by CXCL12-CXCR7 interaction in Jurkat T cells. All experiments were carried out after functionally blocking the CXCR4 receptor. CXCL12, on binding CXCR7, induced phosphorylation of extra cellular regulated protein kinases (ERK 1/2) and Akt. Selective inhibition of each signal demonstrated that phosphorylated ERK 1/2 is essential for chemotaxis and survival of T cells whereas activation of Akt promotes only cell survival. Another interesting finding of this study is that CXCL12-CXCR7 interaction under normal physiological conditions does not activate the p38 pathway. Furthermore, we observed that the CXCL12 signaling via CXCR7 is Giα independent. Our findings suggest that CXCR7 promotes cell survival and does not induce cell death in T cells. The CXCL12 signaling via CXCR7 may be crucial in determining the fate of the activated T cells.

A new locus in chromosome 2q37-qter is associated with posterior polar cataract

PURPOSE

To study the genetic basis of autosomal dominant posterior polar cataracts in two Chinese pedigrees.

MATERIALS AND METHODS

Peripheral blood samples were collected and genomic DNA was isolated. A genome-wide scan, using microsatellite markers at approximately 10-cm intervals and additional microsatellite markers for the positive region, was performed. Haplotype data were processed using Cyrillic software (version 2.1) to define the region of the disease gene. Mutation analysis was carried out for candidate genes. Sequencing data were analyzed with the software Sequence Scanner v1.0.

RESULTS

A maximum two-point LOD score (Z (max)) of 2.53 and 2.03 was obtained at marker D2S125 with recombination θ = 0.00 in the two families. The possible disease genes were located at approximately 8.44-cM between the marker D2S125 and the terminal of chromosome 2q, namely, 2q37-qter. Candidate genes, such as Gamma-crystallins (CRYGA-D), septin 2 (SEPT2), aquaporin 12B (AQP12B), and chemokine orphan receptor 7 (CXCR7), were sequenced but no causative mutations were found.

CONCLUSIONS

Our results suggest that an unidentified gene in chromosome 2q37-qter is associated with posterior polar cataract, which may have an implication in understanding the genetic and molecular mechanisms of cataracts.

Isolation and characterization of human trophoblast side-population (SP) cells in primary villous cytotrophoblasts and HTR-8/SVneo cell line

Recently, numerous studies have identified that immature cell populations including stem cells and progenitor cells can be found among “side-population” (SP) cells. Although SP cells isolated from some adult tissues have been reported elsewhere, isolation and characterization of human trophoblast SP remained to be reported. In this study, HTR-8/SVneo cells and human primary villous cytotrophoblasts (vCTBs) were stained with Hoechst 33342 and SP and non-SP (NSP) fractions were isolated using a cell sorter. A small population of SP cells was identified in HTR-8/SVneo cells and in vCTBs. SP cells expressed several vCTB-specific markers and failed to express syncytiotrophoblast (STB) or extravillous cytotrophopblast (EVT)-specific differentiation markers. SP cells formed colonies and proliferated on mouse embryonic fibroblast (MEF) feeder cells or in MEF conditioned medium supplemented with heparin/FGF2, and they also showed long-term repopulating property. SP cells could differentiate into both STB and EVT cell lineages and expressed several differentiation markers. Microarray analysis revealed that IL7R and IL1R2 were exclusively expressed in SP cells and not in NSP cells. vCTB cells sorted as positive for both IL7R and IL1R2 failed to express trophoblast differentiation markers and spontaneously differentiated into both STB and EVT in basal medium. These features shown by the SP cells suggested that IL7R and IL1R2 are available as markers to detect the SP cells and that vCTB progenitor cells and trophoblast stem cells were involved in the SP cell population.

CXCR7 and syndecan-4 are potential receptors for CXCL12 in human cytotrophoblasts

The placenta forms the interface between the mother and the fetus. During placental development cytotrophoblasts differentiate to form the syncytium or to invade the decidual wall to breach maternal vessels and establish the blood flow in the intervillous space. This process is still not well understood but it is proposed that chemokines and their receptors are involved in guiding cytotrophoblasts to the decidua and maternal vessels as well as attracting immunocompetent cells to the implantation site. CXCL12 is a chemokine expressed by cytotrophoblasts and is involved in cytotrophoblast invasion, differentiation and survival. One of its receptors, CXCR4, has been detected on cytotrophoblasts. Recent data show that CXCR7 and syndecan-4 might partially mediate CXCL12 function in other cell types. In this study, we examined CXCR7 and syndecan-4 expression at the maternal-fetal interface via immmunolocalization in placental tissue sections and in isolated cytotrophoblasts. We further used immunoblot analyses to confirm the data. We were able to show that cytotrophoblasts express both receptors and that upregulation occurs during the differentiation process of cytotrophoblasts towards the invasive phenotype. On a functional level CXCR7 seems not to be involved in JAR cell chemotaxis, suggesting a different function of this receptor. In conclusion, we propose that CXCL12 binds to CXCR4, but also to CXCR7 and syndecan-4. These three receptors could mediate different functions of CXCL12, such as cell migration, directed invasion, proliferation and survival. The latter molecules might also be involved in the development of placental pathologies, such as preeclampsia or choriocarcinoma growth.

Expression of CXCL12 and CXCR4 in human endometrium; effects of CXCL12 on MMP production by human endometrial cells

BACKGROUND

Although several studies have suggested that CXCL12 and its receptor, CXCR4, may play a role in embryo implantation, there are limited reports of expression of CXCR4 and CXCL12 in human endometrium. The aim of this study was to investigate CXCL12 and CXCR4 expression in human endometrium and to see if CXCL12 could affect matrix metalloproteinase (MMP) production by endometrial stromal and epithelial cells.

METHODS

Quantitative real-time RT-PCR (qRT-PCR) was used to detect the expression of CXCL12 and CXCR4 mRNA in endometrial biopsy samples obtained from fertile women (n = 30). Immunohistochemical analysis was carried out to determine where in the endometrium CXCL12 and CXCR4 were expressed. Primary cell culture followed by qRT-PCR and zymography was used to investigate whether CXCL12 affected MMP-2 and -9 production by endometrial stromal and epithelial cells.

RESULTS

Both CXCL12 and CXCR4 were detected in the endometrium. There was no difference in CXCL12 expression at different times in the cycle, but expression of CXCR4 mRNA was significantly higher in the early proliferative (P < 0.01) compared with late proliferative and secretory phases of the cycle. CXCL12 expression was strongest in the epithelial compartment, and weaker in blood vessel walls. CXCR4 immunostaining was strong in the epithelium and blood vessel walls and weaker in the stroma. CXCL12 (10 and 100 ng/ml) had no effect on mRNA expression or activity of MMP-2 or MMP-9 in either stromal or epithelial cells.

CONCLUSIONS

The results show that the expression of CXCL12 in human endometrium does not alter during the menstrual cycle, while the endometrial expression of its receptor, CXCR4, is highest in the early proliferative phase. In contrast to its effects in other cells, CXCL12 had no effect on MMP-2 or MMP-9 production by endometrial stromal or epithelial cells.

CXCL12 / CXCR4 / CXCR7 chemokine axis and cancer progression

Chemokines, small pro-inflammatory chemoattractant cytokines that bind to specific G-protein-coupled seven-span transmembrane receptors, are major regulators of cell trafficking and adhesion. The chemokine CXCL12 (also called stromal-derived factor-1) is an important α-chemokine that binds primarily to its cognate receptor CXCR4 and thus regulates the trafficking of normal and malignant cells. For many years, it was believed that CXCR4 was the only receptor for CXCL12. Yet, recent work has demonstrated that CXCL12 also binds to another seven-transmembrane span receptor called CXCR7. Our group and others have established critical roles for CXCR4 and CXCR7 on mediating tumor metastasis in several types of cancers, in addition to their contributions as biomarkers of tumor behavior as well as potential therapeutic targets. Here, we review the current concepts regarding the role of CXCL12 / CXCR4 / CXCR7 axis activation, which regulates the pattern of tumor growth and metastatic spread to organs expressing high levels of CXCL12 to develop secondary tumors. We also summarize recent therapeutic approaches to target these receptors and/or their ligands.

HIV-1 co-receptor usage: influence on mother-to-child transmission and pediatric infection

Viral CCR5 usage is not a predictive marker of mother to child transmission (MTCT) of HIV-1. CXCR4-using viral variants are little represented in pregnant women, have an increased although not significant risk of transmission and can be eventually also detected in the neonates. Genetic polymorphisms are more frequently of relevance in the child than in the mother. However, specific tissues as the placenta or the intestine, which are involved in the prevalent routes of infection in MTCT, may play an important role of selective barriers. The virus phenotype of the infected children, like that of adults, can evolve from R5 to CXCR4-using phenotype or remain R5 despite clinical progression to overt immune deficiency. The refined classification of R5 viruses into R5(narrow) and R5(broad) resolves the enigma of the R5 phenotype being associated with the state of immune deficiency. Studies are needed to address more in specific the relevance of these factors in HIV-1 MTCT and pediatric infection of non-B subtypes.