Role of chemokine receptor CXCR7 in bladder cancer progression

An emerging paradigm of CXCL12 involvement in the metastatic cascade

The chemokine CXCL12, also known as stromal cell-derived factor 1 (SDF1), has emerged as a pivotal regulator in the intricate molecular networks driving cancer progression. As an influential factor in the tumor microenvironment, CXCL12 plays a multifaceted role that spans beyond its traditional role as a chemokine inducing invasion and metastasis. Indeed, CXCL12 has been assigned functions related to epithelial-to-mesenchymal transition, cancer cell stemness, angiogenesis, and immunosuppression, all of which are currently viewed as specialized biological programs contributing to the "metastatic cascade" among other cancer hallmarks. Its interaction with its cognate receptor, CXCR4, initiates a cascade of events that not only shapes the metastatic potential of tumor cells but also defines the niches within the secondary organs that support metastatic colonization. Given the profound implications of CXCL12 in the metastatic cascade, understanding its mechanistic underpinnings is of paramount importance for the targeted elimination of rate-limiting steps in the metastatic process. This review aims to provide a comprehensive overview of the current knowledge surrounding the role of CXCL12 in cancer metastasis, especially its molecular interactions rationalizing its potential as a therapeutic target.

Chemokine receptor CXCR7 activates Aurora Kinase A and promotes neuroendocrine prostate cancer growth

CXCR7 is an atypical chemokine receptor that recruits β-arrestin (ARRB2) and internalizes into clathrin-coated intracellular vesicles where the complex acts as a scaffold for cytoplasmic kinase assembly and signal transduction. Here, we report that CXCR7 was elevated in the majority of prostate cancer (PCa) cases with neuroendocrine features (NEPC). CXCR7 markedly induced mitotic spindle and cell cycle gene expression. Mechanistically, we identified Aurora Kinase A (AURKA), a key regulator of mitosis, as a novel target that was bound and activated by the CXCR7-ARRB2 complex. CXCR7 interacted with proteins associated with microtubules and golgi, and, as such, the CXCR7-ARRB2-containing vesicles trafficked along the microtubules to the pericentrosomal golgi apparatus, where the complex interacted with AURKA. Accordingly, CXCR7 promoted PCa cell proliferation and tumor growth, which was mitigated by AURKA inhibition. In summary, our study reveals a critical role of CXCR7-ARRB2 in interacting and activating AURKA, which can be targeted by AURKA inhibitors to benefit a subset of patients with NEPC.

The Role of CXC Chemokines in Cancer Progression

CXC chemokines are small chemotactic and secreted cytokines. Studies have shown that CXC chemokines are dysregulated in multiple types of cancer and are closely correlated with tumor progression. The CXC chemokine family has a dual function in tumor development, either tumor-promoting or tumor-suppressive depending on the context of cellular signaling. Recent evidence highlights the pro-tumorigenic properties of CXC chemokines in most human cancers. CXC chemokines were found to play pivotal roles in promoting angiogenesis, stimulating inflammatory responses, and facilitating tumor metastases. Enhanced expression of CXC chemokines is always signatured with inferior survival and prognosis. The levels of CXC chemokines in cancer patients are in dynamic change according to the tumor contexts (e.g., chemotherapy resistance and tumor recurrence after surgery). Thus, CXC chemokines have great potential to be used as diagnostic and prognostic biomarkers and therapeutic targets. Currently, the molecular mechanisms underlying the effect of CXC chemokines on tumor inflammation and metastasis remain unclear and application of antagonists and neutralizing antibodies of CXC chemokines signaling for cancer therapy is still not fully established. This article will review the roles of CXC chemokines in promoting tumorigenesis and progression and address the future research directions of CXC chemokines for cancer treatment.

Cancer-Associated Membrane Protein as Targeted Therapy for Bladder Cancer

Bladder cancer (BC) recurrence is one of the primary clinical problems encountered by patients following chemotherapy. However, the mechanisms underlying their resistance to chemotherapy remain unclear. Alteration in the pattern of membrane proteins (MPs) is thought to be associated with this recurrence outcome, often leading to cell dysfunction. Since MPs are found throughout the cell membrane, they have become the focus of attention for cancer diagnosis and treatment. Identifying specific and sensitive biomarkers for BC, therefore, requires a major collaborative effort. This review describes studies on membrane proteins as potential biomarkers to facilitate personalised medicine. It aims to introduce and discuss the types and significant functions of membrane proteins as potential biomarkers for future medicine. Other types of biomarkers such as DNA-, RNA- or metabolite-based biomarkers are not included in this review, but the focus is mainly on cell membrane surface protein-based biomarkers.

Effects of SDF-1/CXCR7 on the Migration, Invasion and Epithelial-Mesenchymal Transition of Gastric Cancer Cells

We found that SDF-1/CXCR7 axis played an important role in the growth and proliferation of gastric cancer in the previous studies. The objectives of this study were to explore the effects of SDF-1/CXCR7 on the metastatic ability of gastric cancer cells and the possible mechanisms. CXCR7 expression in SGC-7901 gastric cancer cells was stably knocked down via lentiviral vectors. The cell migration and invasion abilities were detected by transwell migration and invasion assays. The expressions of matrix metalloproteinase 2 (MMP-2), MMP-9, vascular endothelial growth factor (VEGF), epithelial-mesenchymal transition (EMT) markers and Akt phosphorylation were detected with real-time PCR and/or western blot. We found that SDF-1 markedly enhanced the migration and invasion abilities of SGC-7901 gastric cancer cells; CXCR7 knockdown inhibited these effects. SDF-1/CXCR7 increased the expressions of MMP-2, MMP-9 and VEGF. SDF-1/CXCR7 also downregulated E-cadherin expression but upregulated N-cadherin, vimentin and Snail expressions, suggesting that SDF-1/CXCR7 could promote the development of EMT in gastric cancer cells. Furthermore, SDF-1/CXCR7 could promote Akt phosphorylation. Our results indicated that SDF-1/CXCR7 enhanced the migration, invasion and EMT of gastric cancer cells and thus CXCR7 supression may be a strategy for inhibiting gastric cancer metastasis.

Immunotoxins Immunotherapy against Hepatocellular Carcinoma: A Promising Prospect

Hepatocellular carcinoma (HCC) is one of the most common cancers in the world. Therefore, fighting against such cancer is reasonable. Chemotherapy drugs are sometimes inefficient and often accompanied by undesirable side effects for patients. On the other hand, the emergence of chemoresistant HCC emphasizes the need for a new high-efficiency treatment strategy. Immunotoxins are armed and rigorous targeting agents that can purposefully kill cancer cells. Unlike traditional chemotherapeutics, immunotoxins because of targeted toxicity, insignificant cross-resistance, easy production, and other favorable properties can be ideal candidates against HCC. In this review, the characteristics of proper HCC-specific biomarkers for immunotoxin targeting were dissected. After that, the first to last immunotoxins developed for the treatment of liver cancer were discussed. So, by reviewing the strengths and weaknesses of these immunotoxins, we attempted to provide keynotes for designing an optimal immunotoxin against HCC.

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.

The Role of the CXCL12/CXCR4/CXCR7 Chemokine Axis in Cancer

Chemokines are a family of small, secreted cytokines which regulate a variety of cell functions. The C-X-C motif chemokine ligand 12 (CXCL12) binds to C-X-C chemokine receptor type 4 (CXCR4) and C-X-C chemokine receptor type 7 (CXCR7). The interaction of CXCL12 and its receptors subsequently induces downstream signaling pathways with broad effects on chemotaxis, cell proliferation, migration, and gene expression. Accumulating evidence suggests that the CXCL12/CXCR4/CXCR7 axis plays a pivotal role in tumor development, survival, angiogenesis, metastasis, and tumor microenvironment. In addition, this chemokine axis promotes chemoresistance in cancer therapy via complex crosstalk with other pathways. Multiple small molecules targeting CXCR4/CXCR7 have been developed and used for preclinical and clinical cancer treatment. In this review, we describe the roles of the CXCL12/CXCR4/CXCR7 axis in cancer progression and summarize strategies to develop novel targeted cancer therapies.

Neutralization of CXCL12 attenuates established pulmonary hypertension in rats

AIMS

The progressive accumulation of cells in pulmonary vascular walls is a key pathological feature of pulmonary arterial hypertension (PAH) that results in narrowing of the vessel lumen, but treatments targeting this mechanism are lacking. The C-X-C motif chemokine 12 (CXCL12) appears to be crucial in these processes. We investigated the activity of two CXCL12 neutraligands on experimental pulmonary hypertension (PH), using two complementary animal models.

METHODS AND RESULTS

Male Wistar rats were injected with monocrotaline (MCT) or were subjected to SU5416 followed by 3-week hypoxia to induce severe PH. After PH establishment, assessed by pulsed-wave Doppler echocardiography, MCT-injected or SU5416 plus chronic hypoxia (SuHx) rats were randomized to receive CXCL12 neutraligands chalcone 4 or LIT-927 (100 mg/kg/day), the C-X-C motif chemokine receptor 4 (CXCR4) antagonist AMD3100 (5 mg/kg/day), or vehicle, for 2 or 3 weeks, respectively. At the end of these treatment periods, echocardiographic and haemodynamic measurements were performed and tissue samples were collected for protein expression and histological analysis. Daily treatment of MCT-injected or SuHx rats with established PH with chalcone 4 or LIT-927 partially reversed established PH, reducing total pulmonary vascular resistance, and remodelling of pulmonary arterioles. Consistent with these observations, we found that neutralization of CXCL12 attenuates right ventricular hypertrophy, pulmonary vascular remodelling, and decreases pulmonary artery smooth muscle cell (PA-SMC) proliferation in lungs of MCT-injected rats and SuHx rats. Importantly, CXCL12 neutralization with either chalcone 4 or LIT-927 inhibited the migration of PA-SMCs and pericytes in vitro with a better efficacy than AMD3100. Finally, we found that CXCL12 neutralization decreases vascular pericyte coverage and macrophage infiltration in lungs of both MCT-injected and SuHx rats.

CONCLUSION

We report here a greater beneficial effect of CXCL12 neutralization vs. the conventional CXCR4 blockade with AMD3100 in the MCT and SuHx rat models of severe PH, supporting a role for CXCL12 in the progression of vascular complications in PH and opening to new therapeutic options.

Relevance of the CXCR4/CXCR7-CXCL12 axis and its effect in pathophysiological conditions

The impact of the C-X-C receptor (CXCR) 7 and its close co-player CXCR4 in different physiological and pathophysiological processes has been extensively investigated within the last decades. Following activation by their shared ligand C-X-C ligand (CXCL) 12, both chemokine receptors can induce various routes of cell signaling and/or scavenge CXCL12 from the extracellular environment. This contributes to organ development and maintenance of homeostasis. Alterations of the CXCR4/CXCR7-CXCL12 axis have been detected in diseases such as cancer, central nervous system and cardiac disorders, and autoimmune diseases. These alterations include changes of the expression pattern, distribution, or downstream effects. The progression of the diseases can be regulated in preclinical models by the use of various modulators suggesting that this axis serves as a promising therapeutic target. It is therefore of great interest to investigate CXCR4/CXCR7/CXCL12 modulators in clinical development, with several CXCR4 and CXCL12 modulators such as plerixafor, ulocuplumab, balixafortide, and olaptesed pegol having already reached this stage. An overview is presented of the most important diseases whose outcomes can be positively or negatively regulated by the CXCR4/CXCR7-CXCL12 axis and summarizes preclinical and clinical data of modulators of that axis. Contrary to CXCR4 and CXCL12 modulators, CXCR7 modulators have, thus far, not been extensively studied. Therefore, more (pre)clinical investigations are needed.

Discovery of Diphenylacetamides as CXCR7 Inhibitors with Novel β-Arrestin Antagonist Activity

The atypical chemokine receptor CXCR7 has been studied in various disease settings including immunological diseases and heart disease. Efforts to elucidate the role of CXCR7 have been limited by the lack of suitable chemical tools with a range of pharmacological profiles. A high-throughput screen was conducted to discover novel chemical matter with the potential to modulate CXCR7 receptor activity. This led to the identification of a series of diphenylacetamides confirmed in a CXCL12 competition assay indicating receptor binding. Further evaluation of this series revealed a lack of activity in the functional assay measuring β-arrestin recruitment. The most potent representative, compound 10 (K _i = 597 nM), was determined to be an antagonist in the β-arrestin assay (IC₅₀ = 622 nM). To our knowledge, this is the first reported small molecule β-arrestin antagonist for CXCR7, useful as an in vitro chemical tool to elucidate the effects of CXCL12 displacement with β-arrestin antagonism in models for diseases such as cardiac injury and suitable as starting point for hit optimization directed toward an in vivo tool compound for studying CXCR7 receptor pharmacology.

Expression and regulation effects of chemokine receptor 7 in colon cancer cells

In China the incidence and mortality rates of colon cancer have been increasing annually. Studies have revealed that CXCR7 is expressed in many tumors. The aim of the present study was to investigate the function of CXCR7 in colon cancer. The expression level of chemokine receptor 7 (CXCR7) in Caco-2 and HCT116 cells was investigated to elucidate the effect of CXCR7 on cell biological behavior. Reverse transcription-quantitative PCR and western blot analysis were used to detect the expression level of CXCR7 in Caco-2 and HCT116 cells after transfection with small interfering (si)RNA. To analyze the in vitro biological function of CXCR7, cell proliferation was measured using a Cell Counting Kit-8 assay, and cell invasion and migration were measured using Matrigel, and Transwell and wound healing assays. siRNAs were successfully transfected into Caco-2 and HCT116 cells and resulted in a decrease in CXCR7 protein and mRNA expression. Downregulation of CXCR7 inhibited Caco-2 and HCT116 cell proliferation, invasion, and migration. Regulation of CXCR7 expression may affect the biological behavior of Caco-2 and HCT116 cells, suggesting that CXCR7 has a potential role in molecular therapy in colon cancer.

Atypical chemokine receptors in tumor cell growth and metastasis

Atypical chemokine receptors (ACKRs) are seven-transmembrane cell surface protein receptors expressed in immune cells, normal mesenchymal cells, and several tumor cells. As of this writing, six ACKRs have been characterized by diverse activities. They bind both cysteine-cysteine (CC) type and cysteine-X-cysteine (CXC)-type chemokines, either alone, or together with a ligand bound-functional G-protein coupled (typical) chemokine receptor. The major structural difference between ACKRs and typical chemokine receptors is the substituted DRYLAIV amino acid motif in the second intracellular loop of the ACKR. Due to this substitution, these receptors cannot bind Gαi-type G-proteins responsible for intracellular calcium mobilization and cellular chemotaxis. Although initially characterized as non-signaling transmembrane receptors (decoy receptors) that attenuate ligand-induced signaling by GPCRs, studies of all ACKRs have shown ligand-independent and ligand-dependent transmembrane signaling in both non-tumor and tumor cells. The precise function and mechanism of the differential expression of ACKRs in many tumors are not understood well. The use of antagonists of ACKRs ligands has shown limited antitumor potential; however, depleting ACKR expression resulted in a reduction in experimental tumor growth and metastasis. The ACKRs represent a unique class of transmembrane signaling proteins that regulate growth, survival, and metastatic processes in tumor cells, affecting multiple pathways of tumor growth. Therefore, closer investigations of ACKRs have a high potential for identifying therapeutics which affect the intracellular signaling, preferentially via the ligand-independent mechanism.

Role of JAK/STAT3 Signaling in the Regulation of Metastasis, the Transition of Cancer Stem Cells, and Chemoresistance of Cancer by Epithelial-Mesenchymal Transition

The JAK/STAT3 signaling pathway plays an essential role in various types of cancers. Activation of this pathway leads to increased tumorigenic and metastatic ability, the transition of cancer stem cells (CSCs), and chemoresistance in cancer via enhancing the epithelial–mesenchymal transition (EMT). EMT acts as a critical regulator in the progression of cancer and is involved in regulating invasion, spread, and survival. Furthermore, accumulating evidence indicates the failure of conventional therapies due to the acquisition of CSC properties. In this review, we summarize the effects of JAK/STAT3 activation on EMT and the generation of CSCs. Moreover, we discuss cutting-edge data on the link between EMT and CSCs in the tumor microenvironment that involves a previously unknown function of miRNAs, and also discuss new regulators of the JAK/STAT3 signaling pathway.

CXC Chemokine Receptors in the Tumor Microenvironment and an Update of Antagonist Development

Chemokine receptors, a diverse group within the seven-transmembrane G protein-coupled receptor superfamily, are frequently overexpressed in malignant tumors. Ligand binding activates multiple downstream signal transduction cascades that drive tumor growth and metastasis, resulting in poor clinical outcome. These receptors are thus considered promising targets for anti-tumor therapy. This article reviews recent studies on the expression and function of CXC chemokine receptors in various tumor microenvironments and recent developments in cancer therapy using CXC chemokine receptor antagonists.

CXCR7 regulates epileptic seizures by controlling the synaptic activity of hippocampal granule cells

C–X–C motif chemokine receptor 7 (CXCR7), which mediates the immune response in the brain, was recently reported to regulate neurological functions. However, the role of CXCR7 in epilepsy remains unclear. Here, we found that CXCR7 was upregulated in the hippocampal dentate gyrus (DG) of mice subjected to kainic acid (KA)-induced epilepsy and in the brain tissues of patients with temporal lobe epilepsy. Silencing CXCR7 in the hippocampal DG region exerted an antiepileptic effect on the KA-induced mouse model of epilepsy, whereas CXCR7 overexpression produced a seizure-aggravating effect. Mechanistically, CXCR7 selectively regulated N-methyl-d-aspartate receptor (NMDAR)-mediated synaptic neurotransmission in hippocampal dentate granule cells by modulating the cell membrane expression of the NMDAR subunit2A, which requires the activation of extracellular signal-regulated kinase 1/2 (ERK1/2). Thus, CXCR7 may regulate epileptic seizures and represents a novel target for antiepileptic treatments.

The potential role of stromal cell-derived factor-1α/CXCR4/CXCR7 axis in adipose-derived mesenchymal stem cells

To investigate the potential role of stromal cell-derived factor-1α (SDF-1α)/CXCR4/CXCR7 axis in adipose-derived mesenchymal stem cells (ADSCs), quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was employed to screen the effective small interfering RNA against CXCR4 and CXCR7 in ADSCs. The messenger RNA (mRNA) and proteins abundances of AKT (p-AKT), ERK (p-ERK), JNK (p-JNK), and p38 (p-p38) in different groups were identified by qRT-PCR, western blot, and immunofluorescence staining method. Meanwhile, cell migration and cell proliferation with SDF-1 treated were examined by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and transwell permeable assay, respectively. Moreover, the interaction between CXCR4 and CXCR7 was examined by a GST pull-down assay. CXCR4 small interfering RNA3 (siRNA3) and CXCR7 siRNA3 have been proved to the most effective tools for knockdown CXCR4 and CXCR7 expressions. mRNA abundance of JNK and p38 could be affected by SDF-1α/CXCR4/CXCR7 axis. However, western blot analysis of p-AKT, p-ERK, p-JNK, and p-p38 in CXCR43-treated ADSCs was significantly higher than that in the control group. Moreover, the immunofluorescence staining analysis revealed that the expressions of p-ATK and p-JNK proteins were significantly higher in NC- and SDF-1-treated subgroups than that in the CXCR4 and CXCR7 groups. p-ATK and p-JNK proteins in CXCR4 group were similar to that in CXCR7 group. Cell migration analysis of CXCR4-treated ADSCs suggested that knockdown CXCR4 could effectively promote cell migration (p < .05). Moreover, CXCR4 could interact with CXCR7. The results in this study could provide a better understanding of SDF-1α/CXCR4/CXCR7 axis during ADSCs development.

Chemokine receptor 7 targets the vascular endothelial growth factor via the AKT/ERK pathway to regulate angiogenesis in colon cancer

Background

Studies have shown that CXCR7 is expressed in many tumors. The aim of the present study was to investigate the function of CXCR7 in colon cancer. Although evidence indicates that CXCR7 promotes angiogenesis in colon cancer, the mechanism involved in this process remains unclear.

Methods

The expression of CXCR7 in colon cancer was evaluated by quantitative reverse‐transcription polymerase chain reaction and western blotting. After transfection, cell proliferation, migration, and lumen formation were measured in vitro. Immunohistochemistry and western blotting were used to identify the functional target of CXCR7 in vivo and in vitro.

Results

In this study, CXCR7 was differentially expressed in four colon cancer cell lines. The proliferation and migration experiments showed that overexpression of CXCR7 enhanced cell growth and migration. Moreover, the tube formation assays showed that co‐culture of colon cancer cells overexpressing CXCR7 with human umbilical vein endothelial cells significantly promoted tube formation in the latter cells. Conversely, the stable knockdown of CXCR7 significantly reduced this malignant activity. In addition, we found that CXCR7 activates the AKT and ERK pathways in colon cancer cells. The phosphorylation of AKT and ERK, as well as the expression of the vascular endothelial growth factor, can be inhibited using the LY294002 and U0126 inhibitors. Furthermore, the angiogenic ability of CXCR7‐induced colon cancer cells was eliminated.

Conclusion

Expression of CXCR7 contributes to colon cancer growth and angiogenesis, by activating the AKT and ERK pathways. CXCR7 provides a potential therapeutic target against colon cancer.

Forkhead box P3 gene silencing inhibits the expression of chemokines and chemokine receptors associated with cell growth, migration, and apoptosis in hepatocellular carcinoma cells

The aberrant expression of forkhead box P3 (FOXP3) leads to the formation of malignant tumors. FOXP3 expression levels are also elevated in hepatocellular carcinoma (HCC). The aim of the present study was to investigate the effects of FOXP3 silencing on cell proliferation, migration, apoptosis and chemokine/chemokine receptor expression in the MHCC-97H HCC cell line. Three FOXP3 short hairpin (sh)RNA constructs were designed: Sh-FOXP3-1-pGreenPuro, sh-FOXP3-2-pGreenPuro, and sh-FOXP3-3-pGreenPuro. MHCC-97H cells were transfected with shRNA-FOXP3, and the mRNA and protein expression levels of C-X-C motif chemokine (CXC) ligand 12 (CXCL12), CXCL11, CXC receptor 4 (CXCR4) and CXCR7 were measured. Cell Counting Kit-8, terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling and Transwell assays were used to evaluate cell proliferation, apoptosis and migration, respectively. Of the three FOXP3 lentivirus carriers constructed, sh-FOXP3-1 significantly reduced FOXP3 expression levels and was chosen for further experiments. sh-FOXP3-1 inhibited cell proliferation, promoted apoptosis and inhibited cell migration compared with the negative control. The mRNA and protein expression levels of CXCL12, CXCL11, CXCR4 and CXCR7 were decreased significantly in response to FOXP3 silencing. FOXP3 silencing may therefore inhibit cell growth, induce apoptosis and inhibit migration in HCC cells, possibly by impairing the chemokine/chemokine receptor axes.

Impact of CXCR4 and CXCR7 knockout by CRISPR/Cas9 on the function of triple-negative breast cancer cells

Background

Breast cancer is one of the most common malignancies threatening women's health. Triple-negative breast cancer (TNBC) is a special type of breast cancer with high invasion and metastasis. CXCL12 and its receptors CXCR4 and CXCR7 play a crucial role in the progress of breast cancer. The aim of this study was to investigate the effect of CXCR4 and CXCR7 on the function of TNBC.

Materials and methods

We used the CRISPR/Cas9 technique to carry out a single knockout of the CXCR4 or CXCR7 gene and co-knockout of CXCR4 and CXCR7 genes in the TNBC cell line (MDA-MB-231). The single knockout and co-knockout cells were screened and verified by PCR sequencing and Western blot assay, the effect of single knockout and co-knockout on the proliferation of TNBC cells was examined using the Cell Counting Kit-8 and colony formation assays, the migration and invasion of TNBC cells were examined by the transwell and wound-healing assays, the changes in the cell cycle distribution after knockout were detected by flow cytometry, and the difference in the migration and invasion of single knockout and co-knockout induced by CXCL12 was observed by adding CXCL12 in the experimental group.

Results

The single knockout of the CXCR4 or CXCR7 gene significantly reduced the cell proliferation, growth, migration, and invasion and delayed the conversion of the G1/S cycle, while the co-knockout inhibited these biological abilities more significantly. In both the knockout and control groups, the migration and invasion of CXCL12-added cells were significantly stronger than those of the non-CXCL12-added cells, and CXCL12 induced lesser migration and invasion in the CXCR4 and CXCR7 co-knockout group than in the single knockout groups.

Conclusion

The knockout of the CXCR4 and CXCR7 genes affects the binding capacity and functions of CXCL12, inhibits the malignant progression of TNBC cells significantly, and may become a potential target for the treatment of TNBC.

Context-Dependent Signaling of CXC Chemokine Receptor 4 and Atypical Chemokine Receptor 3

G protein-coupled receptors (GPCRs) are regulated by complex molecular mechanisms, both in physiologic and pathologic conditions, and their signaling can be intricate. Many factors influence their signaling behavior, including the type of ligand that activates the GPCR, the presence of interacting partners, the kinetics involved, or their location. The two CXC-type chemokine receptors, CXC chemokine receptor 4 (CXCR4) and atypical chemokine receptor 3 (ACKR3), both members of the GPCR superfamily, are important and established therapeutic targets in relation to cancer, human immunodeficiency virus infection, and inflammatory diseases. Therefore, it is crucial to understand how the signaling of these receptors works to be able to specifically target them. In this review, we discuss how the signaling pathways activated by CXCR4 and ACKR3 can vary in different situations. G protein signaling of CXCR4 depends on the cellular context, and discrepancies exist depending on the cell lines used. ACKR3, as an atypical chemokine receptor, is generally reported to not activate G proteins but can broaden its signaling spectrum upon heteromerization with other receptors, such as CXCR4, endothelial growth factor receptor, or the α ₁-adrenergic receptor (α ₁-AR). Also, CXCR4 forms heteromers with CC chemokine receptor (CCR) 2, CCR5, the Na⁺/H⁺ exchanger regulatory factor 1, CXCR3, α ₁-AR, and the opioid receptors, which results in differential signaling from that of the monomeric subunits. In addition, CXCR4 is present on membrane rafts but can go into the nucleus during cancer progression, probably acquiring different signaling properties. In this review, we also provide an overview of the currently known critical amino acids involved in CXCR4 and ACKR3 signaling.

CXCR7 contributes to the aggressive phenotype of cholangiocarcinoma cells

Development of cholangiocarcinoma (CCA) is dependent on a cross-talk with stromal cells, which release different chemokines including CXCL12, that interacts with two different receptors, CXCR4 and CXCR7. The aim of the present study was to investigate the role of CXCR7 in CCA cells. CXCR7 is overexpressed by different CCA cell lines and in human CCA specimens. Knock-down of CXCR7 in HuCCT-1 cells reduced migration, invasion, and CXCL12-induced adhesion to collagen I. Survival of CCA was also reduced in CXCR7-silenced cells. The ability of CXCL12 to induce cell migration and survival was also blocked by CCX733, a CXCR7 antagonist. Similar effects of CXCR7 activation were observed in CCLP-1 cells and in primary iCCA cells. Enrichment of tumor stem-like cells by a 3D culture system resulted in increased CXCR7 expression compared to cells grown in monolayers, and genetic knockdown of CXCR7 robustly reduced sphere formation both in HuCCT-1 and in CCLP-1 cells. In HuCCT-1 cells CXCR7 was found to interact with β-arrestin 2, which was necessary to mediate CXCL12-induced migration, but not survival. In conclusion, CXCR7 is widely expressed in CCA, and contributes to the aggressive phenotype of CCA cells, inducing cell migration, invasion, adhesion, survival, growth and stem cell-like features. Cell migration induced by CXCR7 requires interaction with β-arrestin 2.

CXCR7 promotes melanoma tumorigenesis via Src kinase signaling

Chemokine receptors have been documented to exert critical functions in melanoma progression. However, current drugs targeting these receptors have limited efficacy in clinical applications, suggesting the urgency to further explore the roles of chemokine receptors in melanoma. Here we found that C–X–C chemokine receptor 7 (CXCR7) was the most highly expressed chemokine receptor in murine melanoma cell lines. In addition, the expression level of CXCR7 was positively correlated with melanoma progression in the clinical samples. High CXCR7 expression was associated with shorter overall survival in melanoma patients. Increased expression of CXCR7 augmented melanoma proliferation in vitro and tumor growth in vivo, whereas knockout of CXCR7 exhibited significant inhibitory effects. Moreover, our data elucidated that CXCR7 activated Src kinase phosphorylation in a β-arrestin2-dependent manner. The administration of the Src kinase inhibitor PP1 or siRNA specific for β-arrestin2 abolished CXCR7-promoted cell proliferation. Importantly, CXCR7 also regulated melanoma angiogenesis and the secretion of vascular endothelial growth factor (VEGF). Subsequent investigations revealed a novel event that the activation of the CXCR7-Src axis stimulated the phosphorylation of eukaryotic translation initiation factor 4E (eIF4E) to accelerate the translation of hypoxia-inducible factor 1α (HIF-1α), which enhanced the secretion of VEGF from melanoma cells. Collectively, our results illuminate the crucial roles of CXCR7 in melanoma tumorigenesis, and indicate the potential of targeting CXCR7 as new therapeutic strategies for melanoma treatment.

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.

Chemosensitivity is differentially regulated by the SDF-1/CXCR4 and SDF-1/CXCR7 axes in acute lymphoblastic leukemia with MLL gene rearrangements

Although recent advances in chemotherapy have markedly improved outcome of acute lymphoblastic leukemia (ALL), infantile ALL with MLL gene rearrangements (MLL+ALL) is refractory to chemotherapy. We have shown that specific cytokines FLT3 ligand and TGFβ1 both of which are produced from bone marrow stromal cells synergistically induced MLL+ALL cells into chemo-resistant quiescence, and that treatment of MLL+ALL cells with inhibitors against FLT3 and/or TGFβ1 receptor partially but significantly converts them toward chemo-sensitive. In the present study, we showed that MLL+ALL cells expressed CXCR4 and CXCR7, both receptors for the same chemokine stromal cell derived factor-1 (SDF-1), but their biological events were differentially regulated by the SDF-1/CXCR4 and SDF-1/CXCR7 axes and particularly exerted an opposite effect for determining chemo-sensitivity of MLL+ALL cells; enhancement via the SDF-1/CXCR4 axis vs. suppression via the SDF-1/CXCR7 axis. Because cytosine-arabinoside-induced apoptosis of MLL+ALL cells was inhibited by pretreatment with the CXCR4 inhibitor but rather accelerated by pretreatment with the CXCR7 inhibitor, an application of the CXCR7 inhibitor may become a good treatment option in future for MLL+ALL patients. MLL+ALL has a unique gene profile distinguishable from other types of ALL and AML, and should be investigated separately in responses to biological active agents including chemokine inhibitors.

CXCR7 is not obligatory for CXCL12-CXCR4-induced epithelial-mesenchymal transition in human ovarian cancer

Although the CXCL12-CXCR4/CXCR7 chemokine axis is demonstrated to play an integral role in tumor progression, the controversy exists and the role of CXCL12-CXCR4/CXCR7 signaling axis in epithelial-mesenchymal transition (EMT) of human ovarian cancer has not been explored. Here, we showed that in ovarian cancer CXCL12 induced EMT phenotypes including the spindle-like cell morphology, podia and stress fiber formation, a decrease in E-cadherin expression, and increases in mesenchymal N-cadherin and vimentin expressions. These effects of CXCL12 could be antagonized by the CXCR4 antagonist AMD3100, but not by the anti-CXCR7 antibody. The expressions of the EMT markers were significantly down-regulated by the CXCR4 siRNA, and up-regulated by the pcDNA3.1/CXCR4 plasmid, whereas not affected by the CXCR7 siRNA. Furthermore, intraperitoneal administration of AMD3100 inhibited tumor dissemination and growth in the nude mice inoculated with ovarian IGROV-1 cells with a concomitant reduction in EMT marker expressions. Collectively, these data suggest that CXCR4, rather than CXCR7, plays a key role in CXCL12-activated EMT phenotypes, and targeting the CXCL12-CXCR4 chemokine axis represents a potential therapeutic strategy to prevent ovarian cancer progression.

CXCR7 silencing inhibits the migration and invasion of human tumor endothelial cells derived from hepatocellular carcinoma by suppressing STAT3

C-X-C chemokine receptor type 7 (CXCR7) is reported to be overexpressed in tumor endothelial cells (TECs), which are the primary target cells of antivascular chemotherapy. However, the role of CXCR7 in TECs is not fully understood. In the present study, CXCR7 expression was inhibited in TECs derived from hepatocellular carcinoma (HCC) using short hairpin (sh)RNA plasmids to investigate the role of CXCR7 in the regulation of migration and invasion of TECs as well as its underlying mechanisms. The data showed that the downregulation of CXCR7 significantly inhibited the migration and invasion of TECs. Further study showed that silencing CXCR7 resulted in decreased phosphorylated signal transducer and activator of transcription 3 (STAT3) at Tyr705 and its downstream target genes in TECs, including matrix metalloproteinase‑2 (MMP2) and vascular endothelial growth factor (VEGF). However, restoring STAT3 phosphorylation abolished the CXCR7‑shRNA‑induced decrease in TECs migration and invasion, as well as the downregulation of MMP2 and VEGF in TECs. These findings indicate that CXCR7 may regulate the migration and invasion of TECs derived from HCC via the STAT3 signaling pathway and that CXCR7 could be a potential target for the antivascular therapy of HCC.

CXCR7 regulates breast tumor metastasis and angiogenesis in vivo and in vitro

The chemokine receptor CXCR7 is regarded as a scavenger receptor for CXCL12, and induces numerous key steps in tumor growth and metastasis. However, the exact molecular mechanism of CXCR7 regulation in breast tumor angiogenesis remains unknown. In the present study, the function of CXCR7 in breast tumors was investigated in vitro and in vivo. The breast cancer MDA-MB-231 cell line was used. Pharmacological inhibition of CXCR7 by CCX771 reduced breast tumor invasion, adhesion and metastasis. Furthermore, CXCR7 was essential for the tube formation of HUVECs in vitro, and for blood vessel formation in a Matrigel plug assay in vivo. In addition, vascular endothelial growth factor expression was also decreased in CCX771-treated MDA-MB-231 cells, indicating that CCX771 regulates tumor angiogenesis. The present results indicated that CXCR7 regulated breast cancer metastasis at multiple stages; additional understanding of CXCR7 in tumor environments may develop anti-metastatic therapy.

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.

CXCR7 as a chemokine receptor for SDF-1 promotes gastric cancer progression via MAPK pathways

OBJECTIVE

As the alternate receptor for stromal cell-derived factor-1 (SDF-1) except CXCR4, CXCR7 has been shown to be involved in the progression of some malignancies. However, the role of SDF-1/CXCR7 in gastric cancer (GC) remains unclear.

MATERIALS AND METHODS

CXCR7 expression was examined in 83 human GC tissues and adjacent non-cancer tissues (ANCTs) by immunohistochemistry, in three human GC cell lines (MGC-803, BGC-823 and SGC-7901) by reverse transcription-PCR and western blot. CXCR7 was stably knocked down via lentiviral vectors. The cells proliferation was evaluated using CCK-8 and colony formation assay; MAPK pathways (ERK1/2, p38 and SAPK/JNK) were detected using western blot. Besides, the xenograft model of nude mice for GC growth was performed.

RESULTS

CXCR7 expression in GC tissues was significantly higher than that in ANCTs and associated with tumor size, TNM stage and lymph node metastasis. CXCR7 and CXCR4 were both detectable in three GC cell lines and SGC-7901 cells expressed CXCR7 the most abundantly. SDF-1 promoted the proliferation of SGC-7901 cells, the phosphorylation of ERK1/2, p38 and CXCR7 knockdown distinctly reversed these changes; the proliferation stimulated with SDF-1 was attenuated by U0126 (MEK1/2 inhibitor). Furthermore, CXCR7 knockdown inhibited the growth of GC subcutaneous xenografts and decreased the microvessel density and VEGF expression in vivo.

CONCLUSION

CXCR7 was identified as a novel promoter in GC initiation and progression.

iTRAQ-coupled 2D LC/MS-MS analysis of CXCR7-transfected papillary thyroid carcinoma cells: A new insight into CXCR7 regulation of papillary thyroid carcinoma progression and identification of potential biomarkers

Previous studies have demonstrated that C-X-C chemokine receptor type 7 (CXCR7) regulates papillary thyroid carcinoma (PTC) growth and metastasis; however, the molecular mechanisms underlying this regulation remain unclear. In the present study, the protein expression profiles of the PTC cell line GLAG-66 and GLAG-66 cells stably transfected with CXCR7 cDNA were analyzed and compared using isobaric tag for relative and absolute quantification-coupled two-dimensional liquid chromatography-tandem mass spectrometry. In total, 2,983 proteins were quantified and 130 proteins were identified to be differentially expressed, of which 87 were significantly upregulated and 43 were significantly downregulated. Gene Ontology enrichment analysis revealed that the differentially expressed proteins were primarily enriched in a number of biological processes, including metabolism-related processes, cellular component organization, transport, cellular development process and the immune response. The differentially expressed proteins identified included fibronectin 1, basigin, periplakin and serpin family B member 5, all of which are associated with cellular junctions and cancer progression. In addition, transgelin-2 and AHNAK nucleoprotein 2 were identified as potential novel biomarkers for the prognosis and treatment of PTC.

MiR-1-3p inhibits the proliferation and invasion of bladder cancer cells by suppressing CCL2 expression

We attempted to analyze the effects of miR-1-3p and CCL2 on the proliferation, migration, and invasion of bladder cancer cells. A total of 18 pairs of bladder cancer tissues with corresponding adjacent tissues and the 6 cases of normal tissues were collected. The expressions of miR-1-3p and CCL2 in the cancer tissues were evaluated using quantitative real-time polymerase chain reaction and western blot. The relationship between miR-1-3p and CCL2 was assessed using luciferase reporter assay. The UM-UC-3 bladder cancer cells were transfected with CCL2 small interfering RNA and miR-1-3p mimics. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, colony formation assay, wound healing assay, Transwell assay, and the flow cytometry test were used to detect the proliferation, migration, invasion, and apoptosis of bladder cancer cells. Bladder cancer tissues had lower levels of miR-1-3p but higher levels of CCL2 than normal tissues ( p < 0.05). The transfection of miR-1-3p mimics and CCL2 small interfering RNA remarkably suppressed cell proliferation and invasion and promoted apoptosis of cells ( p < 0.05). Results of the luciferase reporter gene assay demonstrated that miR-1-3p targeted CCL2. MiR-1-3p suppresses the proliferation and invasion of urinary bladder cancer cells by targeting CCL2.

CXCR7 maintains osteosarcoma invasion after CXCR4 suppression in bone marrow microenvironment

The major cause of death in osteosarcoma is the invasion and metastasis. Better understanding of the molecular mechanism of osteosarcoma invasion is essential in developing effective tumor-suppressive therapies. Interaction between chemokine receptors plays a crucial role in regulating osteosarcoma invasion. Here, we investigated the relationship between CXCR7 and CXCR4 in osteosarcoma invasion induced by bone marrow microenvironment. Human bone marrow mesenchymal stem cells were co-cultured with osteosarcoma cells to mimic actual bone marrow microenvironment. Osteosarcoma cell invasion and CXCL12/CXCR4 activation were observed within this co-culture model. Interestingly, in this co-culture model, osteosarcoma cell invasion was not inhibited by suppressing CXCR4 expression with neutralizing antibody or specific inhibitor AMD3100. Downstream signaling extracellular signal-regulated kinase and signal transducer and activator of transcription 3 were not significantly affected by CXCR4 inhibition. However, suppressing CXCR4 led to CXCR7 upregulation. Constitutive expression of CXCR7 could maintain osteosarcoma cell invasion when CXCR4 was suppressed. Simultaneously, inhibiting CXCR4 and CXCR7 compromised osteosarcoma invasion in co-culture system and suppressed extracellular signal-regulated kinase and signal transducer and activator of transcription 3 signals. Moreover, bone marrow microenvironment, not CXCL12 alone, is required for CXCR7 activation after CXCR4 suppression. Taken together, suppressing CXCR4 is not enough to impede osteosarcoma invasion in bone marrow microenvironment since CXCR7 is activated to sustain invasion. Therefore, inhibiting both CXCR4 and CXCR7 could be a promising strategy in controlling osteosarcoma invasion.

Clinical significance of expression of chemokine factor receptor 7 in gastric cancer: A meta-analysis

AIM

To investigate the expression of chemokine factor receptor 7 (CXCR7) in gastric cancer and evaluate its clinical significance.

METHODS

PubMed, EMBASE, Web of Science, CNKI, CBM, VIP, and Wanfang were searched for case-control studies on the significance of expression of CXCR7 in gastric cancer. Meta-analysis was conducted using RevManv.5.3 software to yield odds ratio (OR) and 95% confidence interval (95%CI).

RESULTS

A total of four case-control studies involving 320 gastric cancer tissues and 105 normal gastric tissues were included. The results of meta-analyses showed that the positive rate of CXCR7 expression was higher in gastric cancer tissues than in normal gastric tissues (OR = 46.35, 95%CI: 19.99-107.43), and CXCR7 expression in gastric cancer tissues was significantly associated with deep invasion (OR = 0.17, 95%CI: 0.05-0.58), lymph node metastasis (OR = 0.23, 95%CI: 0.12-0.44), and advanced clinical stage (OR = 0.29, 95%CI: 0.16-0.54). However, no significant correlation was found between CXCR7 expression and the degree of differentiation in gastric cancer.

CONCLUSION

The expression of CXCR7 in gastric cancer is higher than that in normal tissue. CXCR7 expression is associated with depth of invasion, lymph node metastasis and clinical stage, indicating that CXCR7 may play a role in gastric cancer metastasis.

Identification and Validation of Gene Expression Patterns in Cystitis Glandularis Patients and Controls

Our aim was to investigate differences in gene expression in bladder tissues between cystitis glandularis (CG) patients and healthy controls. Subsequent RNA was isolated from urinary bladder samples from CG patients and healthy controls, followed by RNA sequencing analysis. There were 4263 differentially expressed genes in urinary bladder between CG patients and controls, and 8 genes were verified with real-time PCR, Western blot, and enzyme-linked immunosorbent assay (ELISA) analysis. Gene set enrichment analysis (GSEA) revealed that 25 signaling pathways were upregulated in CG patients, and 17 signaling pathways were found upregulated in healthy controls. The mRNA expression levels of the indicated genes, including CCND1, CCNA1, EGFR, AR, CX3CL1, CXCL6, and CXCL1, were significantly increased in urinary bladder from CG and bladder cancer (BC) patients compared with healthy controls, while TP53 was decreased. CX3CL1, CXCL6, and CXCL1 concentrations in peripheral blood from CG and BC patients were significantly increased compared with healthy controls. The protein expression levels of CCND1, EGFR, and AR were significantly increased in urinary bladder from CG and BC patients compared with healthy controls. In conclusion, the gene expression profile of CG patients has established a foundation to study the gene mechanism of CG and BC progression.

CCR7 as a predictive biomarker associated with computed tomography for the diagnosis of lymph node metastasis in bladder carcinoma

The aim of the present study was to investigate whether the expression levels of CC-chemokine receptor 7 (CCR7) combined with computed tomography (CT) was associated with lymph node metastasis in bladder transitional cell carcinoma (BTCC). For this purpose, 115 cases of BTCC were analyzed at the Department of Urology of Xiangya Hospital, Central South University (Changsha, China). Preoperative CT scans of abdomen and pelvis, immunohistochemistry of CCR7 expression in the tumor specimens and pathological findings for lymph node metastasis were assessed. In addition, the sensitivity, specificity and accuracy of CCR7 and CT for the diagnosis of lymph node metastasis in BTCC were evaluated separately and jointly. The expression levels of CCR7 were observed to be significantly higher in BTCC than in normal controls (P<0.01). Multivariate analysis indicated that the overexpression of CCR7 was an independent predictor for lymph node metastasis in BTCC (P<0.05). The sensitivity, specificity and accuracy of CCR7 combined with CT scan for the diagnosis of lymph node metastasis in BTCC were 92.3, 83.6 and 70.0%, respectively. By contrast, the sensitivity, specificity and accuracy of CCR7 alone were 88.1, 69.9 and 76.5%, respectively, while the sensitivity, specificity and accuracy of CT alone were 52.4, 79.5 and 69.6%, respectively. The results of the present study indicated that CCR7 is an independent predictor of lymph node metastasis in BTCC. Therefore, the use of CCR7 combined with CT may improve the accuracy of the diagnosis of lymph node metastasis in BTCC.

The chemokine receptor CXCR7 is a critical regulator for the tumorigenesis and development of papillary thyroid carcinoma by inducing angiogenesis in vitro and in vivo

Papillary thyroid carcinoma (PTC) is a well-differentiated neoplasm, but it can transfer early to cervical lymph nodes. Accumulating evidences have confirmed the important roles of CXCR7 in tumor cell proliferation, invasion, metastasis, and angiogenesis. Our previous study demonstrated CXCR7 modulated proliferation, apoptosis, and invasion of PTC cells. In this study, we evaluated the effect of expression of CXCR7 in PTC cells on angiogenesis and whether its expression had an influence on the tumor growth of PTC in vivo. We evaluated the effect of CXCR7 on interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF) secretion, angiogenesis, and tumor growth by ELISA, endothelial tube formation assay, and a xenograft tumor model in nude mice. Immunohistochemistry was used to assess expression of CD34 in tumor of mice. In vitro and in vivo studies in PTC cells suggested that the alteration of CXCR7 expression was correlated with angiogenesis and tumor growth. Moreover, CXCR7 mediated the expression of IL-8 and VEGF, which might be involved in the regulation of tumor angiogenesis. These findings suggest that CXCR7 affects the growth of PTC cells and participates in the tumorigenesis of PTC, probably through regulating angiogenesis by the proangiogenic VEGF or IL-8.

CXCR7 functions in colon cancer cell survival and migration

C-X-C chemokine receptor 7 (CXCR7) is a known promoter of tumor progression and metastasis; however, little is known about its role in colon cancer. The aim of the present study was to investigate the function of CXCR7 in human colon cancer cells. CXCR7 mRNA levels were examined in HT-29 and SW-480 human colon cancer cell lines using a quantitative polymerase chain reaction. CXCR7-knockdown was performed with small interfering RNA and lentiviral-mediated gene delivery. Immunofluorescence (IF) was conducted to examine CXCR7 expression and localization in colon cancer cells. Cell survival and migration were evaluated using MTT and migration assays, respectively. HT-29 cells expressed higher levels of CXCR7 mRNA and were therefore used in subsequent experiments. IF staining revealed that the CXCR7 protein was expressed on the cell membrane, and its expression decreased following CXCR7-short hairpin RNA lentiviral transfection. Lentiviral CXCR7-knockdown resulted in decreased cell survival and migration; however, MTT assays revealed that the lentiviral vector itself was cytotoxic. This cytotoxicity was indicated as the cell survival of the negative control group cells was significantly decreased compared with that of the blank control group cells (P<0.05). In conclusion, it is becoming increasingly evident that CXCR7 plays a role in colon cancer promotion, suggesting that CXCR7 is a promising biomarker for chemokine receptor-based drug development. Furthermore, the fact that CXCR7 is expressed on the membrane and not intracellularly makes it a prime target for drug-based intervention.

Chronic inflammation in urothelial bladder cancer

The association between inflammation and cancer has been pointed out in epidemiological and clinical studies, revealing how chronic inflammation may contribute to carcinogenesis in various malignancies. However, the molecular events leading to malignant transformation in a chronically inflamed environment are not fully understood. In urothelial carcinoma of the urinary bladder, inflammation plays a dual role. On the one hand, chronic inflammation is a well-established risk factor for the development of bladder cancer (BC), as seen in Schistosoma haematobium infection. On the other, intravesical therapy by bacillus Calmette-Guérin (BCG), which induces inflammation, offers protection against cancer recurrence. The large variety of pro-inflammatory mediators expressed by BC and immune cells binds to specific receptors which control signalling pathways. These activate transcription of a plethora of downstream factors. This review summarizes recent data regarding inflammation and urothelial carcinoma, with special emphasis on the role the inflammatory response plays in BC recurrence risk and progression.

Gene expression profile analyze the molecular mechanism of CXCR7 regulating papillary thyroid carcinoma growth and metastasis

Background

To detect genetic expression profile alterations after papillary thyroid carcinoma (PTC) cells transfected with chemokine receptor CXCR7 gene by gene microarray, and gain insights into molecular mechanisms of how CXCR7 regulating PTC growth and metastasis.

Methods

The Human OneArray microarray was used for a complete genome-wide transcript profiling of CXCR7 transfected PTCs (K1-CXCR7 cells), defined as experimental group. Non CXCR7 transfected PTCs (K1 cells) were used as control group. Differential analysis for per gene was performed with a random variance model and t test, p values were adjusted to control the false discovery rate. Gene ontology (GO) on differentially expressed genes to identify the biological processes in modulating the progression of papillary thyroid carcinoma. Pathway analysis was used to evaluate the signaling pathway that differentially expressed genes were involved in. In addition, quantitative real-time polymerase chain reaction (q-PCR) and Western blot were used to verify the top differentially expression genes.

Results

Comparative analysis revealed that the expression level of 1149 genes was changed in response to CXCR7 transfection. After unsupervised hierarchical clustering analysis, 270 differentially expressed genes were filtered, of them 156 genes were up-regulated whereas 114 genes were down-regulated in K1-CXCR7 cells. GO enrichment analysis revealed the differentially expressed genes were mainly involved in biopolymer metabolic process, signal transduction and protein metabolism. Pathway enrichment analysis revealed differentially expressed genes were mainly involved in ECM-receptor interaction, Focal adhesion, MAPK signaling pathway and Cytokine-cytokine receptor interaction pathway. More importantly, the expression level of genes closely associated with tumor growth and metastasis was altered significantly in K1-CXCR7 cells, including up-regulated genes FN1, COL1A1, COL4A1, PDGFRB, LTB, CXCL12, MMP-11, MT1-MMP and down-regulated genes ITGA7, and Notch-1.

Conclusions

Gene expression profiling analysis of papillary thyroid carcinoma can further delineate the mechanistic insights on how CXCR7 regulating papillary thyroid carcinoma growth and metastasis. CXCR7 may regulate growth and metastasis of papillary thyroid carcinoma via the activation of PI3K/AKT pathway and its downstream NF-κB signaling, as well as the down-regulation of Notch signaling.

Downregulation of cathepsin L suppresses cancer invasion and migration by inhibiting transforming growth factor‑β‑mediated epithelial‑mesenchymal transition

Cathepsin L, a lysosomal acid cysteine protease, was found to be overexpressed in several types of human carcinomas. However, its functional roles in tumor progression and the underlying mechanisms remain largely unclear. In the present study, we investigated a novel functional aspect of cathepsin L in regulating transforming growth factor‑β (TGF‑β)‑induced epithelial‑mesenchymal transition (EMT) in A549 and MCF‑7 cells and examined its possible mechanisms. We found that TGF‑β‑induced cell morphologic changes of EMT were associated with the increased protein level of cathepsin L in A549 and MCF‑7 cells, suggesting that cathepsin L may be involved in the regulation of EMT. Furthermore, we showed that silencing of cathepsin L blocked TGF‑β‑induced cell migration, invasion and actin remodeling and inhibited TGF‑β‑mediated EMT. We also demonstrated that the mechanism of how cathepsin L knockdown regulates EMT may be explained by the suppression of EMT‑inducing molecules, such as Snail, which is associated with the phosphatidylinositol 3‑kinase (PI3K)‑AKT and Wnt signaling pathways. Moreover, we proved that cathepsin L knockdown in A549 cells significantly inhibited xenograft tumor growth and EMT in vivo. The results showed a new mechanism to determine cathepsin L involvement in the regulation of cancer invasion and migration. These results showed that cathepsin L knockdown is important in regulating EMT and suggest that cathepsin L may be utilized as a new target for enhancing the efficacy of chemotherapeutics against epithelial cancer.

CCL18 promotes epithelial-mesenchymal transition, invasion and migration of pancreatic cancer cells in pancreatic ductal adenocarcinoma

CCL18 is a chemokine that is primarily expressed in monocytes, macrophages and immature dendritic cells and plays a crucial role in immune and inflammation responses. Recently, CCL18 was found to play pivotal roles in the development of several kinds of cancers, but its expression status and role during the tumorigenesis of pancreatic cancer remain unknown. In this study, we performed immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) to evaluate the expression of CCL18 in human pancreatic ductal adenocarcinoma (PDAC) tissues and preoperative serum, respectively. The results showed that both cancer epithelial cells and mesenchymal macrophages in PDAC tissues positively expressed CCL18. Serum CCL18 levels were significantly higher in patients with PDAC in comparison to healthy controls. The expression of CCL18 in both cancer epithelial cells and mesenchymal cells was correlated with lymph node metastasis, histopathological grading and overall survival in 62 PDAC patients. In vitro assays showed that the gene and protein expression of CCL18 from U937 and THP-1 cell- derived macrophages were significantly higher than that from unstimulated U937 cells and THP-1 cells. In contrast, pancreatic cancer cell lines showed little to no CCL18 expression even after IL4 stimulation. Intriguingly, pancreatic cancer cell lines expressed the potential CCL18 receptors PITPNM3, CCR6 and GPR3. Furthermore, treatment with recombinant human CCL18 promoted the migration and invasion of pancreatic cancer cells, but had no effect on cell proliferation. Consistent with these results, CCL18 induced the expression of the epithelial-mesenchymal transition (EMT) related gene SNAIL1. Our findings suggest that the serum level of CCL18 is a potential biomarker for the diagnosis and prognosis of PDAC, and that the combined functions of CCL18 in mesenchymal and cancer cells might accelerate the progression of PDAC by promoting the epithelial-mesenchymal transition, invasion and migration of pancreatic cancer cells.

Chemokine receptor 7 promotes tumor migration and invasiveness via the RhoA/ROCK pathway in metastatic squamous cell carcinoma of the head and neck

Metastatic squamous cell carcinoma of the head and neck (SCCHN) has been shown to express chemokine receptor 7 (CCR7), which can activate signaling pathways to promote invasion and survival of SCCHN cells. We hypothesized that the RhoA/Rho-associated kinase (ROCK) pathway is involved in the CCR7-induced invasion and migration of metastatic SCCHN cells. Thus, using migration, matrigel invasion and scrape wound-healing assays, we elucidated the role of RhoA in mediating CCR7-associated cellular mobility. Pull-down assays and western blotting were used to measure RhoA and its downstream expression. Immunohistochemical staining and analysis were useful in identifying the correlation between CCR7 and RhoA expression and clinicopathological factors. The results showed that inhibition of RhoA/ROCK reduced the tumor cell migration and invasiveness induced by CCL19. Activated RhoA, proline-rich tyrosine kinase-2 (Pyk2) and cofilin induced by CCL19 were elevated, and increased RhoA, Pyk2 and cofilin activity was eliminated by CCR7mAb, RhoA/ROCK and Pyk2 inhibitors, indicating involvement of the RhoA/ROCK-Pyk2-cofilin cascade. In summary, CCR7 via RhoA/ROCK-Pyk2 cofilin pathway promotes invasion and migration of metastatic SCCHN cells.

Chemokines in tumor progression and metastasis

Chemokines play a vital role in tumor progression and metastasis. Chemokines are involved in the growth of many cancers including breast cancer, ovarian cancer, pancreatic cancer, melanoma, lung cancer, gastric cancer, acute lymphoblastic leukemia, colon cancer, non-small lung cancer, non-hodgkin's lymphoma, etc. The expression of chemokines and their receptors is altered in many malignancies and leads to aberrant chemokine receptor signaling. This review focuses on the role of chemokines in key processes that facilitate tumor progression including proliferation, senescence, angiogenesis, epithelial mesenchymal transition, immune evasion and metastasis.

CCR7 regulates cell migration and invasion through JAK2/STAT3 in metastatic squamous cell carcinoma of the head and neck

Squamous cell carcinoma of the head and neck (SCCHN) frequently involves metastasis at diagnosis. Our previous research has demonstrated that CCR7 plays a key role in regulating SCCHN metastasis, and this process involves several molecules, such as PI3K/cdc42, pyk2, and Src. In this study, the goals are to identify whether JAK2/STAT3 also participates in CCR7's signal network, its relationship with other signal pathways, and its role in SCCHN cell invasion and migration. The results showed that stimulation of CCL19 could induce JAK2/STAT3 phosphorylation, which can be blocked by Src and pyk2 inhibitors. After activation, STAT3 was able to promote low expression of E-cadherin and had no effect on vimentin. This JAk2/STAT3 pathway not only mediated CCR7-induced cell migration but also mediated invasion speed. The immunohistochemistry results also showed that the phosphorylation of STAT3 was correlated with CCR7 expression in SCCHN, and CCR7 and STAT3 phosphorylation were all associated with lymph node metastasis. In conclusion, JAk2/STAT3 plays a key role in CCR7 regulating SCCHN metastasis.

CXCR7 stimulates MAPK signaling to regulate hepatocellular carcinoma progression

The CXCL12/CXCR4 axis has been posited widely to have significant roles in many primary tumors and metastases. It is known that CXCR7 can also be engaged by CXCL12, but the exact function of CXCR7 is controversial. This prompted us to investigate the expression, specific function and signal transduction of CXCR7 in hepatocellular carcinoma (HCC). In this study, CXCR7 and CXCR4 were differentially expressed in nine cell lines of HCC, and that elevated expression of both CXCR7 and CXCL4 were correlated with highly metastatic ability of HCC cells. Moreover, CXCR7 expression was significantly upregulated in metastatic HCC samples compared with the non-metastatic ones by staining of high-density tissue microarrays constructed from a cohort of 48 human HCC specimens. CXCR7 overexpression enhanced cell growth and invasiveness in vitro, and tumorigenicity and lung metastasis in vivo. By contrast, CXCR7 stable knockdown markedly reduced these malignant behaviors. In addition, it was observed that alterations in CXCR7 expression were positively correlated with the phosphorylation levels of mitogen-activated protein kinase (MAPK) pathway proteins. Targeting extracellular regulated kinase pathway by using U0126 inhibitor or using CCX771, a selective CXCR7 antagonist, drastically reduced CXCR7-mediated cell proliferation. Importantly, by using human biotin-based antibody arrays, several differentially expressed proteins were identified in CXCR7-overexpression and depletion groups. Comparative analysis indicated that upstream regulators including TP53 and IL-6 were involved in CXCR7 signal transduction. CXCR7 expression was further proved to regulate expression of vascular endothelial growth factor A and galectin-3, which may contribute to tumor angiogenesis and invasiveness. Consequently, elevated expression of CXCR7 contributes to HCC growth and invasiveness via activation of MAPK and angiogenesis signaling pathways. Targeting CXCR7 may prevent metastasis and provide a potential therapeutic strategy for HCC.

Silencing of CXCR7 gene represses growth and invasion and induces apoptosis in colorectal cancer through ERK and β-arrestin pathways

The CXC chemokine receptor 7 (CXCR7) has been reported to be involved in cell growth, metastasis and apoptosis in certain cancers. However, the function and molecular mechanisms of CXCR7 in human colorectal cancer (CRC) are still undefined. In the present study, sixty-eight cases of CRC tissues and corresponding adjacent non-cancer tissues (ANCT) were collected, and the expression of CXCR7 was assessed using immunohistochemistry (IHC) in biopsy samples. Furthermore, CXCR7 gene was silenced by small hairpin RNA-mediated lentiviral vector (Lv-shCXCR7), by transfection into human CRC cells (SW480 and HT-29). The levels of p-ERK, β-arrestin, proliferating cell nuclear antigen (PCNA), matrix metallopeptidase-2 (MMP-2) and caspase-3 (CAS-3) were detected by western blotting. Cell proliferative activities and invasive capability were respectively measured by MTT and Transwell assays. Cell apoptosis was analyzed by flow cytometry. The results demonstrated that CXCR7 expression was significantly upregulated in CRC tissues compared with the ANCT (54.4 vs. 36.8%, P=0.041), and correlated with Dukes staging and depth of invasion (P=0.007; P=0.002). Silencing of CXCR7 gene suppressed cell proliferation and invasion, and induced cell apoptosis in CRC cells with decreased expression of p-ERK, β-arrestin, PCNA and MMP-2 but increased expression of CAS-3. The tumor volumes in the SW480 subcutaneous tumor models treated with Lv-shCXCR7 were significantly smaller than those of the negative control (NC) and PBS groups (P<0.01). In conclusion, our findings indicate that upregulation of CXCR7 expression is associated with tumor invasion, and silencing of the CXCR7 gene represses the development of CRC cells through ERK and β-arrestin pathways, suggesting that CXCR7 may serve as a potential therapeutic target for the treatment of CRC.

The role of chemoattractant receptors in shaping the tumor microenvironment

Chemoattractant receptors are a family of seven transmembrane G protein coupled receptors (GPCRs) initially found to mediate the chemotaxis and activation of immune cells. During the past decades, the functions of these GPCRs have been discovered to not only regulate leukocyte trafficking and promote immune responses, but also play important roles in homeostasis, development, angiogenesis, and tumor progression. Accumulating evidence indicates that chemoattractant GPCRs and their ligands promote the progression of malignant tumors based on their capacity to orchestrate the infiltration of the tumor microenvironment by immune cells, endothelial cells, fibroblasts, and mesenchymal cells. This facilitates the interaction of tumor cells with host cells, tumor cells with tumor cells, and host cells with host cells to provide a basis for the expansion of established tumors and development of distant metastasis. In addition, many malignant tumors of the nonhematopoietic origin express multiple chemoattractant GPCRs that increase the invasiveness and metastasis of tumor cells. Therefore, GPCRs and their ligands constitute targets for the development of novel antitumor therapeutics.