Stacer AC, etal., Oncogene. 2016 Mar 31;35(13):1716-24. doi: 10.1038/onc.2015.236. Epub 2015 Jun 29.
Atypical chemokine receptor CXCR7 (ACKR3) functions as a scavenger receptor for chemokine CXCL12, a molecule that promotes multiple steps in tumor growth and metastasis in breast cancer and multiple other malignancies. Although normal vascular endothelium expres
ses low levels of CXCR7, marked upregulation of CXCR7 occurs in tumor vasculature in breast cancer and other tumors. To investigate effects of endothelial CXCR7 in breast cancer, we conditionally deleted this receptor from vascular endothelium of adult mice, generating CXCR7(DeltaEND/DeltaEND) animals. CXCR7(DeltaEND/DeltaEND) mice appeared phenotypically normal, although these animals exhibited a modest 35+/-3% increase in plasma CXCL12 as compared with control. Using two different syngeneic, orthotopic tumor implant models of breast cancer, we discovered that CXCR7(DeltaEND/DeltaEND) mice had significantly greater local recurrence of cancer following resection, elevated numbers of circulating tumor cells and more spontaneous metastases. CXCR7(DeltaEND/DeltaEND) mice also showed greater experimental metastases following intracardiac injection of cancer cells. These results establish that endothelial CXCR7 limits breast cancer metastasis at multiple steps in the metastatic cascade, advancing understanding of CXCL12 pathways in tumor environments and informing ongoing drug development targeting CXCR7 in cancer.
Chatterjee M, etal., Biochem Soc Trans. 2015 Aug;43(4):720-6. doi: 10.1042/BST20150113. Epub 2015 Aug 3.
Platelet-derived SDF-1alpha (stromal cell derived factor-alpha) mediates inflammation, immune defence and repair mechanisms at site of tissue injury. This review summarizes the relative expression of CXC chemokine receptor 4 (CXCR4) and CXCR7 in platelets, their
dynamic trafficking in presence of ligands like chemokine C-X-C-motif ligand 11 (CXCL11), CXCL12 and MIF (macrophage migration inhibitory factor); how these receptors differentially mediate the functional and survival response to the chemokines CXCL11, CXCL12 and MIF. We further elaborate and emphasize the prognostic significance of platelet surface expression of CXCR4-CXCR7 in the context of coronary artery disease (CAD). SDF-1alpha/CXCL12, CXCL11, MIF effects mediated through CXCR4 and CXCR7 may play a regulatory role at the site of vascular and tissue inflammation, immune defence and repair where activated platelets reach as forerunners and function as critical players.
Differentiation of oligodendroglial precursor cells (OPCs), a crucial prerequisite for central nervous system (CNS) remyelination in diseases such as Multiple Sclerosis (MS), is modulated by a multitude of extrinsic and intrinsic factors. In a previous study we revealed that the chemokine CXCL12 sti
mulates rodent OPC differentiation via activation of its receptor CXCR7. We could now demonstrate that CXCR7 is also expressed on NogoA- and Nkx2.2-positive oligodendroglial cells in human MS brains and that stimulation of cultured primary fetal human OPCs with CXCL12 promotes their differentiation as measured by surface marker expression and morphologic complexity. Pharmacological inhibition of CXCR7 effectively blocks these CXCL12-dependent effects. Our findings therefore suggest that a specific activation of CXCR7 could provide a means to promote oligodendroglial differentiation facilitating endogenous remyelination activities.
Chen D, etal., Sci Rep. 2015 Nov 18;5:16813. doi: 10.1038/srep16813.
Stromal cell-derived factor 1 (SDF-1) is a chemokine that can be expressed in injured cardiomyocytes after myocardial infarction (MI). By combining with its receptor CXCR4, SDF-1 induced stem and progenitor cells migration. CXCR7, a novel receptor for SDF-1, has
been identified recently. We aimed to explore the roles of SDF-1/CXCR4 and SDF-1/CXCR7 pathway and their crosstalk in CSCs migration. In the present study, CXCR4 and CXCR7 expression were identified in CSCs. Transwell assay showed that SDF-1 caused CSCs migration in a dose- and time-dependent manner, which could be significantly suppressed by CXCR4 or CXCR7 siRNA. Phospho-ERK, phospho-Akt and Raf-1 significantly elevated in CSCs with SDF-1 stimulation. Knockdown of CXCR4 or CXCR7 significantly decreased phospho-ERK or phospho-Akt, respectively, and eventually resulted in the inhibition of CSCs migration. Moreover, western blot showed that MK2206 (Akt inhibitor) increased the expression of phospho-ERK and Raf-1, whereas PD98059 (ERK inhibitor) had no effect on phospho-Akt and Raf-1. GW5074 (Raf-1 inhibitor) upregulated the expression of phospho-ERK, but had no effect on phospho-Akt. The present study indicated that SDF-1/CXCR7/Akt and SDF-1/CXCR4/ERK pathway played important roles in CSCs migration. Akt phosphorylation inhibited Raf-1 activity, which in turn dephosphorylated ERK and negatively regulated CSCs migration.
Chen Q, etal., Stem Cells. 2015 Aug;33(8):2574-85. doi: 10.1002/stem.2022. Epub 2015 May 13.
Neural progenitor cell (NPC) migration is an essential process for brain development, adult neurogenesis, and neuroregeneration after brain injury. Stromal cell-derived factor-1 (SDF-1, CXCL12) and its traditional receptor CXCR4 are well known to regulate NPC migration. However, the discovery of ... (more)
pan style='font-weight:700;'>CXCR7, a newly identified CXCL12 receptor, adds to the dynamics of the existing CXCL12/CXCR4 pair. Antagonists for either CXCR4 or CXCR7 blocked CXCL12-mediated NPC migration in a transwell chemotaxis assay, suggesting that both receptors are required for CXCL12 action. We derived NPC cultures from Cxcr4 knockout (KO) mice and used transwell and stripe assays to determine the cell migration. NPCs derived from Cxcr4 KO mice polarized and migrated in response to CXCL12 gradient, suggesting that CXCR7 could serve as an independent migration receptor. Furthermore, Cxcr4 KO NPCs transplanted into the adult mouse striatum migrated in response to the adjacent injection of CXCL12, an effect that was blocked by a CXCR7 antagonist, suggesting that CXCR7 also mediates NPC migration in vivo. Molecular mechanism studies revealed that CXCR7 interact with Rac1 in the leading edge of the polarized NPCs in the absence of CXCR4. Both CXCR7 and Rac1 are required for extracellular signal-regulated kinases (ERK) 1/2 activation and subsequent NPC migration, indicating that CXCR7 could serve as a functional receptor in CXCL12-mediated NPC migration independent of CXCR4. Together these results reveal an essential role of CXCR7 for CXCL12-mediated NPC migration that will be important to understand neurogenesis during development and in adulthood.
Oculomotor synkinesis is the involuntary movement of the eyes or eyelids with a voluntary attempt at a different movement. The chemokine receptor CXCR4 and its ligand CXCL12 regulate oculomotor nerve development; mice with loss of either molecule have oculomotor synkinesis. In a consanguineous famil
y with congenital ptosis and elevation of the ptotic eyelid with ipsilateral abduction, we identified a co-segregating homozygous missense variant (c.772G>A) in ACKR3, which encodes an atypical chemokine receptor that binds CXCL12 and functions as a scavenger receptor, regulating levels of CXCL12 available for CXCR4 signaling. The mutant protein (p.V258M) is expressed and traffics to the cell surface but has a lower binding affinity for CXCL12. Mice with loss of Ackr3 have variable phenotypes that include misrouting of the oculomotor and abducens nerves. All embryos show oculomotor nerve misrouting, ranging from complete misprojection in the midbrain, to aberrant peripheral branching, to a thin nerve, which aberrantly innervates the lateral rectus (as seen in Duane syndrome). The abducens nerve phenotype ranges from complete absence, to aberrant projections within the orbit, to a normal trajectory. Loss of ACKR3 in the midbrain leads to downregulation of CXCR4 protein, consistent with reports that excess CXCL12 causes ligand-induced degradation of CXCR4. Correspondingly, excess CXCL12 applied to ex vivo oculomotor slices causes axon misrouting, similar to inhibition of CXCR4. Thus, ACKR3, through its regulation of CXCL12 levels, is an important regulator of axon guidance in the oculomotor system; complete loss causes oculomotor synkinesis in mice, while reduced function causes oculomotor synkinesis in humans.
In the tumor microenvironment, chemokine system has a critical role in tumorigenesis and metastasis. The acquisition of stem-like properties by cancer cells is involved in metastasis and drug resistance, which are pivotal problems that result in poor outcomes in patients with lung cancer. Patients w
ith advanced lung cancer present high plasma levels of transforming growth factor-beta1 (TGFbeta1), which correlate with poor prognostic features. Therefore, TGFbeta1 may be important in the tumor microenvironment, where chemokines are widely expressed. However, the role of chemokines in TGFbeta1-induced tumor progression still remains unclear. In our study, TGFbeta1 upregulated CXC chemokine receptor expression, migration, invasion, epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) formation in lung adenocarcinoma. We found that CXCR7 was the most upregulated chemokine receptor induced by TGFbeta1. CXCR7 knockdown resulted in reduction of migration, invasion and EMT induced by TGFbeta1, whereas CXCR4 knockdown did not reverse TGFbeta1-promoted EMT. CXCR7 silencing significantly decreased cancer sphere-forming capacity, stem-like properties, chemoresistance and TGFbeta1-induced CSC tumor initiation in vivo. In clinical samples, high TGFbeta1 and CXCR7 expression was significantly associated with the late stages of lung adenocarcinoma. Moreover, TGFbeta1 and CXCR7 coexpression was positively correlated with the CSC marker, CD44, which is associated with lymph node metastasis. Besides, patients with high expression of both CXCR7 and TGFbeta1 presented a significantly worse survival rate. These results suggest that the TGFbeta1-CXCR7 axis may be a prognostic marker and may provide novel targets for combinational therapies to be used in the treatment of advanced lung cancer in the future.
Wu W, etal., Int J Clin Exp Pathol. 2015 Oct 1;8(10):13217-24. eCollection 2015.
BACKGROUND: The chemokine CXCL12 and its receptors CXCR4 and CXCR7 play important roles in cancer invasion and metastasis. This study investigated the mRNA expressions of CXCL12, CXCR4, and CXCR7 to illustrate the role of th
ese biomarkers in breast cancer metastasis and prognosis. METHODS: The mRNA expressions of CXCL12, CXCR4, and CXCR7 in 115 primary breast cancer and regional lymph node specimens were detected by quantitative reverse-transcription polymerase chain reaction. Survival time was analyzed by Kaplan-Meier survival curves using log-rank test. Univariable and multivariable Cox regression analyses were performed to assess independent prognostic factors for survival. RESULTS: The expression levels of CXCR4 and CXCR7 in breast cancer tissues were significantly higher than that in adjacent normal tissues (P=0.022 and P<0.001, respectively), while the expression level of CXCL12 in breast cancer tissues did not differ from that in adjacent normal tissues (P=0.156). Furthermore, CXCL12 exhibited significant differences in expression between primary tumor and lymph node metastasis tumor (P=0.039). CXCR4 and CXCR7 expressions in metastasis tumor were also higher, although no significant difference was observed (P=0.067 and P=0.054, respectively). Kaplan-Meier survival analysis revealed that patients exhibiting high CXCR4 and CXCR7 expression experienced a shorter survival period compared with those with low expression. When analyzed with a Cox regression model, the expressions of CXCL12, CXCR4 and CXCR7 were independent prognostic factors for overall survival. CONCLUSIONS: The mRNA expressions of CXCL12, CXCR4, and CXCR7 play important roles in the progression and metastasis of breast cancer and may act as predictive factors significantly affecting the prognosis.
Cajal-Retzius (CR) cells are essential for cortical development and lamination. These pioneer neurons arise from distinct progenitor sources, including the cortical hem and the ventral pallium at pallium-subpallium boundary (PSB). CXCR4, the canonical receptor for the chemokine CXCL12, controls the
superficial location of hem-derived CR cells. However, recent studies showed that CXCR7, a second CXCL12 receptor, is also expressed in CR cells at early developmental stages. We thus investigated the role of CXCR7 during CR cell development using multiple loss-of-function approaches. Cxcr7 gene inactivation led to aberrant localization of Reelin-positive cells within the pallium. In addition, Cxcr7(-/-) mice were characterized by significant accumulation of ectopic CR cells in the lateral part of the dorsal pallium compared with Cxcr4 knockout mice. Loss-of-function approaches, using either gene targeting or pharmacological receptor inhibition, reveal that CXCR7 and CXCR4 act both in CR positioning. Finally, conditional Cxcr7 deletion in cells derived from Dbx1-expressing progenitors indicates an essential role of CXCR7 in controlling the positioning of a subpopulation of PSB-derived CR cells. Our data demonstrate that CXCR7 has a role in the positioning of hem and PSB-derived CR cells, CXCL12 regulating CR cell subpial localization through the combined action of CXCR4 and CXCR7.
The chemokine stromal cell-derived factor-1 (SDF-1)/CXCL12 acting via its G-protein coupled receptor (GPCR) CXCR4 has been implicated in neurogenesis, neuromodulation, brain inflammation, HIV-1 encephalopathy and tumor growth. CXCR7 was identified as an alternat
e receptor for SDF-1/CXCL12. Characterization of CXCR7-deficient mice demonstrated a role for CXCR7 in fetal endothelial biology, cardiac development, and B-cell localization. Despite its ligand binding properties, CXCR7 does not seem to signal like a conventional GPCR. It has been suggested that CXCR7 may not function alone but in combination with CXCR4. Here, we investigated the regional localization of CXCR7 receptors in adult mouse brain using CXCR7-EGFP transgenic mice. We found that the receptors were expressed in various brain regions including olfactory bulb, cerebral cortex, hippocampus, subventricular zone (SVZ), hypothalamus and cerebellum. Extensive CXCR7 expression was associated with cerebral blood vessels. Using cell type specific markers, CXCR7 expression was found in neurons, astrocytes and oligodendrocyte progenitors. GAD-expressing neurons exhibited CXCR7 expression in the hippocampus. Expression of CXCR7 in the dentate gyrus included cells that expressed nestin, GFAP and cells that appeared to be immature granule cells. In mice with Experimental Autoimmune Encephalomyelitis (EAE), CXCR7 was expressed by migrating oligodendrocyte progenitors in the SVZ. We then compared the distribution of SDF-1/CXCL12 and CXCR7 using bitransgenic mice expressing both CXCR7-EGFP and SDF-1-mRFP. Enhanced expression of SDF-1/CXCL12 and CXCR7 was observed in the corpus callosum, SVZ and cerebellum. Overall, the expression of CXCR7 in normal and pathological nervous system suggests CXCR4-independent functions of SDF-1/CXCL12 mediated through its interaction with CXCR7.
Qin Y, etal., Cell Physiol Biochem. 2015;37(1):117-30. doi: 10.1159/000430338. Epub 2015 Aug 17.
BACKGROUND/AIMS: Mesenchymal stem cells (MSCs) possess immunomodulatory properties on a diverse array of immune cell lineages, including regulatory T and B cells (Tregs and Bregs, respectively). However, their specific effects and mechanisms underlying induction of Bregs remain unclear. The immune r
egulatory function of MSCs is exerted through both cell-cell contact and the release of soluble factors. The main objective of this study was to examine the role of the SDF-1-CXCR4/CXCR7 axis in the secretory action of MSCs, and potential effects on the immunoregulatory function of these cells. METHODS: MSCs were isolated from mouse bone marrow and characterized according to their multilineage differentiation potential and their surface antigen expression. CD19(+) B cells purified from mice splenocytes were co-cultured with MSCs at various ratios in the presence of LPS and alphaCD40. After 4 days, intracellular IL-10 production and cell surface CD1d and CD5 expression by CD19(+) B cells were determined using flow cytometry, and the secretion of IL-10, IL-6, IgM, and IgG were assessed with ELISA. MSCs were treated with different concentrations of stromal derived factor-1alpha (SDF-1alpha) stimuli or transiently overexpressed with CXCR7. and their cell viability and immune regulatory effects of MSCs on Bregs were assessed. RESULTS: MSCs induced IL-10-producing regulatory B cells and primarily stimulated the CD1d(+)CD5(+)B cell subset of IL-10+Breg cells to express IL-10. IL-10, IL-6, and IgM secretion were additionally induced by MSCs. The CXCR7 pathway was required for MSC viability and the production of paracrine factors under SDF-1alpha culture condition. Low concentrations of SDF-1alpha promoted the immunomodulatory effect of MSCs, leading to a further increase in IL-10-producing regulatory B cells and IL-10 secretion. In contrast, high concentrations of SDF-1alpha inhibited MSCs induction of IL-10(+)Breg cells. Notably, CXCR7 overexpression in MSCs reversed the inhibitory effect of high concentrations of SDF-1alpha and promoted the immunomodulatory effect of these cells. CONCLUSION: MSCs induce IL-10(+)Breg cells, which contribute to the generation of an immunosuppressive environment. SDF-1alpha and its receptor, CXCR7 play important roles in the immunomodulatory function of MSCs by regulating their paracrine actions.
Neve Polimeno M, etal., Cell Mol Immunol. 2015 Jul;12(4):474-82. doi: 10.1038/cmi.2014.102. Epub 2014 Nov 3.
Hepatocellular carcinoma (HCC) is a heterogeneous disease with a poor prognosis and limited markers for predicting patient survival. Because chemokines and chemokine receptors play numerous and integral roles in HCC disease progression, the CXCR4-CXCL12-CXCR7 a
xis was studied in HCC patients. CXCR4 and CXCR7 expression was analyzed by immunohistochemistry in 86 HCC patients (training cohort) and validated in 42 unrelated HCC patients (validation cohort). CXCR4 levels were low in 22.1% of patients, intermediate in 30.2%, and high in 47.7%, whereas CXCR7 levels were low in 9.3% of patients, intermediate in 44.2% and high in 46.5% of the patients in the training cohort. When correlated to patient outcome, only CXCR4 affected overall survival (P=0.03). CXCR4-CXCL12-CXCR7 mRNA levels were examined in 33/86 patients. Interestingly, the common CXCR4-CXCR7 ligand CXCL12 was expressed at significantly lower levels in tumor tissues compared to adjacent normal liver (P=0.032). The expression and function of CXCR4 and CXCR7 was also analyzed in several human HCC cell lines. CXCR4 was expressed in Huh7, Hep3B, SNU398, SNU449 and SNU475 cells, whereas CXCR7 was expressed in HepG2, Huh7, SNU449 and SNU475 cells. Huh7, SNU449 and SNU475 cells migrated toward CXCL12, and this migration was inhibited by AMD3100/anti-CXCR4 and by CCX771/anti-CXCR7. Moreover, SNU449 and Huh7 cells exhibited matrix invasion in the presence of CXCL12 and CXCL11, a ligand exclusive to CXCR7. In conclusion, CXCR4 affects the prognosis of HCC patients but CXCR7 does not. Therefore, the CXCR4-CXCL12-CXCR7 axis plays a role in the interaction of HCC with the surrounding normal tissue and represents a suitable therapeutic target.
Salazar N, etal., Mol Cancer. 2014 Aug 28;13:198. doi: 10.1186/1476-4598-13-198.
BACKGROUND: Recent advances have revealed a significant contribution of chemokines and their receptors in tumor growth, survival after chemotherapy, and organ-specific metastasis. The CXC chemokine receptor-7 (CXCR7) is the latest chemokine receptor implicated
in cancer. Although over expressed in breast cancer cell lines and tumor tissues, its mechanism of action in breast cancer (BrCa) growth and metastasis is unclear. Studies in other cancers have implicated CXCR7 in cell proliferation, anti-apoptotic activity and cell-cell adhesion. The present study was initiated to examine the pattern of CXCR7 expression and its role in regulation of growth signaling in breast cancer. METHODS: The contribution of CXCR7 in BrCa cell proliferation was investigated in representative cell lines using real time quantitative PCR (q-PCR), proliferation assays, immunohistochemistry and immunoblotting. Phenotypic changes were examined after CXCR7 specific cDNA and siRNA transfection and expression levels were monitored by q-PCR. Further, the association of CXCR7 with epidermal growth factor receptor (EGFR) and modulation of its activity were investigated by western blotting, immunofluorescence, and in-situ proximity ligation assays in human BrCa cells and tissues. RESULTS: CXCR7 was expressed in both, estrogen receptor (ER) positive and negative BrCa cell lines. CXCR7 was also expressed unevenly in normal breast tissues and to a much higher extent in ER + cancer tissues. Depletion of CXCR7 in MCF7 BrCa cells by RNA interference decreased proliferation and caused cell cycle arrest. Further, proximity ligation assay (PLA) revealed colocalization of CXCR7 with EGFR in cancer tissues and cancer cell lines. CXCR7 depletion reduced levels of phospho-EGFR at Tyrosine1110 after EGF-stimulation and also reduced phosphorylation of ERK1/2, indicating a potentially direct impact on mitogenic signaling in MCF7 cells. Using siRNA to knockdown beta-arrestin2 in cells with EGFR over expression we were able to nearly deplete the CXCR7-EGFR colocalization events, suggesting that beta-arrestin2 acts as a scaffold to enhance CXCR7 dependent activation of EGFR after EGF stimulation. CONCLUSIONS: These results demonstrate coupling of CXCR7 with EGFR to regulate proliferation of BrCa cells and suggest an important ligand-independent role of CXCR7 in BrCa growth. Thus, the CXCR7-EGFR axis is a promising target for breast cancer therapy.
Yang D, etal., Int J Clin Exp Pathol. 2015 Oct 1;8(10):13051-8. eCollection 2015.
Previous studies have shown that chemokine receptor CXCR7 plays critical roles in tumor development. However, the clinicopathological and prognostic significance of CXCR7 in colorectal carcinoma (CRC) has not been fully unde
rstood. The aim of our study is to investigate the expression of CXCR7 and its clinical significance in CRC. First, quantitative RT-PCR and Western blot assays were performed to determine the expression of CXCR7 mRNA and protein in 20 paired of CRC tissues and corresponding adjacent non-tumor tissues. Next, immunohistochemistry was performed to detect the expression of CXCR7 protein in another 96 cases of CRC tissues, and analyze its correlation with clinicopathological factors of patients. Finally, the correlation of CXCR7 with 5-year overall survival (OS) and progression free survival (PFS) was statistically analyzed by the Kaplan-Meier method and Cox proportional hazards model. Results showed that the expression levels of CXCR7 mRNA and protein were significantly higher in CRC tissues than in normal tissues. Positive CXCR7 expression was observed to be significantly correlated with lymph nodal metastasis (P < 0.001), distant metastasis (P = 0.017), and advanced TNM stage (P < 0.001). Patients with positive expression of CXCR7 were demonstrated to be associated with worse OS and PFS (P < 0.001, P < 0.001, respectively). Moreover, multivariate survival analysis revealed that CXCR7 expression level might be an independent predictive factor for OS and PFS of CRC patients. Collectively, positive CXCR7 expression in CRC was correlated with tumor development and poor prognosis of patients.
Rhabdomyosarcomas (RMS) are soft tissue malignant tumors of childhood and adolescents. The mechanisms underlying their aggressiveness are still poorly understood. Chemokines are chemotactic proteins involved in pathological processes that have been intensely studied in several types of cancers becau
se of their influence in migration, angiogenesis, or metastases. We analyzed the expression of the chemokine receptors CXCR3, CXCR4 and CXCR7 and their ligands CXCL9, CXCL10, CXCL11 and CXCL12, in 15 RMS samples derived from nine patients. Expression was measured in tumors and primary cultures of RMS by Real-Time Polymerase Chain Reaction, immunostaining and flow cytometry. Our results show that these receptors are widely expressed in RMS. A significant difference between CXCL12/CXCR4, CXCL12/CXCR7, CXCL11/CXCR7 expression ratios was found in alveolar versus embryonal RMS and similarly between CXCL12/CXCR4 and CXCL11/CXCR3 ratios in primary versus recurrent tumors. These findings suggest a possible association between the interrelation of chemokine/chemokine-receptor and an aggressive biological behavior in RMS.
Inaguma S, etal., Oncotarget. 2015 Oct 20;6(32):33648-57. doi: 10.18632/oncotarget.5203.
The up-regulation of chemokine receptors CXCR4 and CXCR7 impacts on the distant metastasis and prognosis of breast cancer, though knowledge about the regulatory mechanism of their expressions is limited. Meanwhile, the GLI transcription factors of Hedgehog sign
aling have been reported to play a pivotal role in the development and progression of many types of human cancer. In breast cancer, the increased expression of GLI1 correlated with metastasis and unfavorable overall prognosis, though its molecular mechanism is also not fully understood. Based on our findings that GLI1 enhanced the lung metastasis of breast cancer cells in a mouse model system, we comprehensively screened for genes up-regulated by GLI1 in breast cancer cells, and as such identified CXCR4, CXCR7/ACKR3, and actin-binding protein LCP1/L-PLASTIN, all of which have been reported to be involved in CXCL12-stimulating signaling. In breast cancer cells, we found that GLI1 and GLI2 up-regulated these expressions, while treatment with GLI-specific inhibitor GANT61 reduced the expressions. As for CXCR4, we confirmed it as a direct target of GLI1 through the reporter assay and the chromatin immunoprecipitation assay. We also found that GLI1 enhanced CXCL12-induced ERK phosphorylation and cell migration, both of which were blocked by either CXCR4-specific inhibitor or knockdown of CXCR7 or LCP1. These evidences suggest an indispensable role of GLI1 in the migration and metastasis of breast cancer cells through CXCL12/CXCR4 signaling enhancement.
D'Alterio C, etal., Int J Cancer. 2014 Jul 15;135(2):379-90. doi: 10.1002/ijc.28689. Epub 2014 Jan 10.
Despite the optimization of the local treatment of advanced rectal cancer (LARC), combination of preoperative chemoradiotherapy (CRT) and surgery, approximately one third of patients will develop distant metastases. Since the chemokine receptor CXCR4 has been implicated in metastasis development and
prognosis in colorectal cancer, the role of the entire axis CXCR4-CXCL12-CXCR7 was evaluated to identify high relapse risk rectal cancer patients. Tumor specimens of 68 LARC patients undergoing surgery after neoadjuvant-CRT were evaluated for CXCR4, CXCR7, and CXCL12 expression through immunohistochemistry. Multivariable prognostic model was developed using classical prognostic factors along with chemokine receptor expression profiles. High CXCR4 correlated with a shorter relapse-free survival (RFS) (p = 0.0006) and cancer specific survival (CSS) (p = 0.0004). Concomitant high CXCR4-negative/low CXCR7 or high CXCR4-negative/low CXCL12 significantly impaired RFS (p = 0.0003 and p = 0.0043) and CSS (p = 0.0485 and p = 0.0026). High CXCR4/N+ identified the worst prognostic category for RFS (p < 0.0001) and CSS (p = 0.0003). The optimal multivariable predictive model for RFS was a five-variable model consisting of gender, pT stage, N status, CXCR4, and CXCR7 (AUC = 0.92, 95% CI = 0.77-0.98). The model is informative and supportive for adjuvant treatment and identifies CXCR4 as a new therapeutic target in rectal cancer.
Faaij CM, etal., Pediatr Blood Cancer. 2010 Aug;55(2):344-8. doi: 10.1002/pbc.22500.
Chemokine receptor/ligand interactions orchestrate the migration of cells to peripheral tissues such as the skin. We analysed chemokine receptor expression by acute myeloid leukaemic (AML) cells present in peripheral blood (n = 7), bone marrow (n = 6), or skin (n = 11) obtained from 15 paediatric AM
L patients with skin involvement and in 10 AML patients without skin involvement. High percentages of circulating CCR2(pos) AML cells were only detected in patients with extramedullary disease. Skin-residing AML cells displayed a different set of receptors in situ, namely: CCR5, CXCR4, CXCR7 and CX3CR1. These results suggest the involvement of different chemokine/chemokine receptor interactions in homing and retention of AML blasts in the skin.
PURPOSE: Ewing sarcoma (EWS) is the second most common sarcoma of bone in children and young adults. Patients with disseminated disease at diagnosis or early relapse have a poor prognosis. Our goal was to identify novel predictive biomarkers for these patients, focusing on chemokines, specifically g
enes involved in the CXCR4-pathway because of their established role in metastasis and tumour growth. METHODS: Total RNA isolated from therapy-naive tumour samples (n=18; panel I) and cell lines (n=21) was used to study expression of CXCR4-pathway related genes and CXCR4 splice variants (CXCR4-2: Small and CXCR4-1: Large) by RT-Q-PCR. Expression levels were correlated to overall survival (OS) and event free survival (EFS). Study results were validated in an independent series of 26 tumour samples (panel II) from therapy-naive tumour samples. RESULTS: CXCL12, CXCR4, CXCR7 and CXCL14 were expressed and high CXCR7 and CXCL14 expression showed a positive correlation with EFS and OS and a negative correlation with metastasis development. Both splice variants CXCR4 were expressed in cell lines and tumour samples and CXCR4-1/CXCR4-2 ratio was significantly higher in tumour samples compared to cell lines and correlated with an improved EFS and OS. The results from the test panel were validated in an independent sample panel. CONCLUSIONS: We identified a set of genes involved in CXCR4 signalling that may be used as a marker to predict survival and metastasis development in Ewing sarcoma.
Dieckow J, etal., Invest Ophthalmol Vis Sci. 2016 Jan 1;57(1):56-65. doi: 10.1167/iovs.15-18129.
PURPOSE: Trefoil factor family (TFF) peptides, and in particular TFF3, are characteristic secretory products of mucous epithelia that promote antiapoptosis, epithelial migration, restitution, and wound healing. For a long time, a receptor for TFF3 had not yet been identified. However, the chemokine
receptor CXCR4 has been described as a low affinity receptor for TFF2. Additionally, CXCR7, which is able to heterodimerize with CXCR4, has also been discussed as a potential TFF2 receptor. Since there are distinct structural similarities between the three known TFF peptides, this study evaluated whether CXCR4 and CXCR7 may also act as putative TFF3 receptors. METHODS: We evaluated the expression of both CXCR4 and CXCR7 in samples of human ocular surface tissues and cell lines, using RT-PCR, immunohistochemistry, and Western blot analysis. Furthermore, we studied possible binding interactions between TFF3 and the receptor proteins in an x-ray structure-based modeling system. Functional studies of TFF3-CXCR4/CXCR7 interaction were accomplished by cell culture-based migration assays, flow cytometry, and evaluation of activation of the mitogen-activated protein (MAP) kinase signaling cascade. RESULTS: We detected both receptors at mRNA and protein level in all analyzed ocular surface tissues, and in lesser amount in ocular surface cell lines. X-ray structure-based modeling revealed CXCR4 and CXCR7 dimers as possible binding partners to TFF3. Cell culture-based assays revealed enhanced cell migration under TFF3 stimulation in a conjunctival epithelial cell line, which was completely suppressed by blocking CXCR4 and/or CXCR7. Flow cytometry showed increased proliferation rates after TFF3 treatment, while blocking both receptors had no effect on this increase. Trefoil factor family 3 also activated the MAP kinase signaling cascade independently from receptor activity. CONCLUSIONS: Dimers CXCR4 and CXCR7 are involved in TFF3-dependent activation of cell migration, but not cell proliferation. The ERK1/2 pathway is activated in the process, but not influenced by CXCR4 or CXCR7. These results implicate a dependence of TFF3 activity as to cell migration on the chemokine receptors CXCR4 and CXCR7 at the ocular surface.
Lu J, etal., Exp Mol Pathol. 2016 Feb;100(1):184-91. doi: 10.1016/j.yexmp.2015.12.013. Epub 2015 Dec 22.
Preeclampsia is a pregnancy disorder with sudden onset of maternal hypertension and proteinuria, which is characterized by defective cytotrophoblast invasion, increased apoptosis in cytotrophoblast, and diminished syncytial differentiation. In this study, samples from 11 mild preeclamptic patients,
18 severe preeclamptic patients, and 21 normal pregnant women were collected. The expression level of CXCL12 and its two receptors (CXCR4 and CXCR7) in these samples and their relationship with apoptosis were investigated. Morphological change of trophoblast cells that was observed by scanning electron microscope (SEM) indicated a significant tendency of apoptosis in the preeclamptic placenta. Immunohistochemical staining showed that expression level of three proteins was significantly lower in severe preeclamptic placentas compared with normal placentas (P<0.05), whereas no significant difference was found between mild preeclamptic and normal placentas (P>0.05). Real time quantitative PCR (RT-qPCR) and Western blot showed that both mRNA and protein expression level of CXCR4, CXCR7, and CXCL12 of trophoblasts were lower in the severe preeclampsia group than that in the normal group (P<0.05 for mRNA, P<0.01 for protein). In conclusion, our data revealed that the roles of CXCR4, CXCR7, and CXCL12 are associated with trophoblastic cells apoptosis and may be linked to the occurrence and development of severe preeclampsia.
Bao J, etal., Biochem Biophys Res Commun. 2016 Jan 1;469(1):1-7. doi: 10.1016/j.bbrc.2015.11.059. Epub 2015 Nov 23.
Multiple sclerosis (MS) is the prototypical in fl ammatory demyelinating disease of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE), widely used as an animal model of MS, classically manifests as an ascending paralysis that is characterized by extensive infiltratio
n of the CNS by inflammatory cells. Although several studies uncover the significant role of microglia in the development of EAE, the cellular mechanisms of microglia that govern EAE pathogenesis remain unknown. In the current study, we report that CXCR7 expression is dynamic regulated in activated microglia during CNS autoimmunity and positively correlates with the clinical severity of EAE. In addition, microglial chemotaxis is mediated by CXCR7 during CNS autoimmunity, signaling through extracellular signal-regulated kinase (ERK)1/2 activation, whereas p38 mitogen-activated protein kinase (MAPK) and (c-Jun N-terminal kinase) JNK are not involved. Most importantly, CXCR7 neutralizing treatment ameliorates the clinical severity of EAE along with ERK1/2 phosphorylation reduction. Collectively, our data demonstrate that CXCR7 suppression modulates microglial chemotaxis to ameliorate EAE.
The chemokine receptor CXCR7 interacts with the chemokines CXCL11 and CXCL12. During development, this ligand receptor system (C-X-C) provokes cell-type-specific responses in terms of migration, adhesion or ligand sequestration. It is active in zebrafish and rod
ents but no data are available for its presence or function in primate testes. Real-time quantitative polymerase chain reaction was performed in monkeys to detect CXCL11, CXCL12 and CXCR7. At the protein level, CXCL12 and CXCR7 were localized in the testes of the marmoset (Callitrix jacchus) whereas CXCR7 patterns were determined for various stages in human testes. Morphometry and flow cytometry were applied to quantify CXCR7-positive cells in monkeys. Transcript levels and protein expression of CXCR7 were detectable throughout testicular development. In both species, CXCR7 protein expression was restricted to premeiotic germ cells. In immature marmoset testes, 69.9% +/- 9% of the total germ cell population were labelled for CXCR7, whereas in the adult, 4.7% +/- 2.7% were positive for CXCR7. CXCL12 mRNA was detectable in all developmental stages in marmosets. The CXCL12 protein was exclusively localized to Sertoli cells. This pattern of CXCL12/CXCR7 indicates their involvement in regulatory processes that possibly orchestrate the interaction between undifferentiated germ cells and Sertoli cells.
Flüh C, etal., Int J Oncol. 2016 Apr;48(4):1408-16. doi: 10.3892/ijo.2016.3354. Epub 2016 Jan 25.
The chemokine CXCL12 (also termed SDF-1, stromal cell-derived factor-1) and its receptors CXCR4 and CXCR7 are known to play a pivotal role in tumor progression including glioblastomas (GBM). Previous investigations focused on the expression and functional roles
of CXCR4 and CXCR7 in different GBM cell subpopulations, but comparative analysis in matched primary versus recurrent GBM samples are still lacking. Thus, here we investigated the expression of CXCR4 and CXCR7 on mRNA and protein level using matched primary and recurrent GBM pairs. Additionally, as GBM CXCR4-positive stem-like cells are supposed to give rise to recurrence, we compared the expression of both receptors in primary and recurrent GBM cells expressing either neural (MUSASHI-1) or embryonic stem cell markers (KLF-4, OCT-4, SOX-2, NANOG). We were able to show that both CXCR4 and CXCR7 were expressed at considerable mRNA and protein levels. CXCR7 was downregulated in relapse cases, and different groups regarding CXCR4/CXCR7 expression differences between primary and recurrent samples could be distinguished. A co-expression of both receptors was rare. In line with this, CXCR4 was co-expressed with all investigated neural and embryonic stem cell markers in both primary and recurrent tissues, whereas CXCR7 was mostly found on stem cell marker-negative cells, but was co-expressed with KLF-4 on a distinct GBM cell subpopulation. These results point to an individual role of CXCR4 and CXCR7 in stem cell marker-positive GBM cells in glioma progression and underline the opportunity to develop new therapeutic tools for GBM intervention.
Chronic rejection remains a major obstacle in transplant medicine. Recent studies suggest a crucial role of the chemokine SDF-1 on neointima formation after injury. Here, we investigate the potential therapeutic effect of inhibiting the SDF-1/CXCR4/CXCR7 axis wi
th an anti-SDF-1 Spiegelmer (NOX-A12) on the development of chronic allograft vasculopathy. Heterotopic heart transplants from H-2bm12 to B6 mice and aortic transplants from Balb/c to B6 were performed. Mice were treated with NOX-A12. Control animals received a nonfunctional Spiegelmer (revNOX-A12). Samples were retrieved at different time points and analysed by histology, RT-PCR and proliferation assay. Blockade of SDF-1 caused a significant decrease in neointima formation as measured by intima/media ratio (1.0 +/- 0.1 vs. 1.8 +/- 0.1, P < 0.001 AoTx; 0.35 +/- 0.05 vs. 1.13 +/- 0.27, P < 0.05 HTx). In vitro treatment of primary vascular smooth muscle cells with NOX-A12 showed a significant reduction in proliferation (0.42 +/- 0.04 vs. 0.24 +/- 0.03, P < 0.05). TGF-beta, TNF-alpha and IL-6 levels were significantly reduced under SDF-1 inhibition (3.42 +/- 0.37 vs. 1.67 +/- 0.33, P < 0.05; 2.18 +/- 0.37 vs. 1.0 +/- 0.39, P < 0.05; 2.18 +/- 0.26 vs. 1.6 +/- 0.1, P < 0.05). SDF-1/CXCR4/CXCR7 plays a critical role in the development of chronic allograft vasculopathy (CAV). Therefore, pharmacological inhibition of SDF-1 with NOX-A12 may represent a therapeutic option to ameliorate chronic rejection changes.
Shakir M, etal., Pancreas. 2015 May;44(4):528-34. doi: 10.1097/MPA.0000000000000298.
Novel therapies need to be developed for patients with pancreatic cancer because of the poor outcomes of current regimens. Pancreatic cancer cells respond to the C-X-C chemokine receptor type 4 (CXCR4)/C-X-C chemokine receptor type 7 (CXCR7)/C-X-C motif chemok
ine 12 (CXCL12)/high-mobility group box 1 signaling axis and this axis presents a novel target for therapy. C-X-C motif chemokine 12 stimulates CXCR4/CXCR7-bearing cells in a paracrine manner. C-X-C chemokine receptor type 4 and CXCR7 are transmembrane G protein-coupled receptors that, upon interaction with ligand CXCL12, activate downstream protein kinases that promote a more aggressive behavior. C-X-C chemokine receptor type 4 is expressed on most pancreatic cancer cells, whereas CXCR7 is primarily expressed on tumor-associated endothelium. High-mobility group box 1 promotes the CXCR4 and CXCL12 interaction, promoting angiogenesis and lymphangiogenesis. Hypoxia-inducible factor 1 is a potent stimulator of CXCR4 and CXCL12 expression, promoting more aggressive behavior. This receptor/ligand interaction can be disrupted by CXCR4 antagonists available and in clinical use to harvest bone marrow stem cells. Novel imaging strategies are now being developed at several centers to evaluate response to therapy and identify early recurrence. Thus, the CXCR4/CXCR7/CXCL12 interaction plays a critical role in cancer cell progression, proliferation, invasion, as well as metastasis and is a suitable target for therapy, imaging, as well as development of novel diagnostics.
