CXCR7 mediates SDF1-induced melanocyte migration

Evaluating CXCL12 for Effects on Reactive Gene Expression in Primary Astrocytes

Upon injury to the CNS, astrocytes undergo morphological and functional changes commonly referred to as astrocyte reactivity. Notably, these reactive processes include altered expression of factors that control immune processes and neuronal survival, as well as increased expression of the CXCL12 receptor, CXCR7/ACKR3. We now asked whether these events are related in that the astrocytic CXCL12 system modulates immune responses and/or neuronal survival. Short-term exposure of astrocytes cultured from the postnatal rat cortex to CXCL12 prominently increased the expression of serpine1/PAI1 on the mRNA level, but showed either no or only minor effects on the expression of additional reactive genes, selected from previous array studies. CXCL12-induced increases in PAI1 protein levels were only detectable in the additional presence of chemokines/cytokines, suggesting that translation of serpine1 mRNA depends on the cooperation of various factors. As expected, expression of most of the selected genes increased after acute or chronic activation of astrocytes with either LPS or a combination of IL-1β and TNFα. CXCL12 partially attenuated expression of some of the LPS and IL-1β/TNFα-induced genes under acute conditions, in particular those encoding CXCL9, CXCL10, CXCL11, and CCL5. Taken together, these findings argue for the involvement of the astrocyte CXCL12 system in the control of the immune response of the injured CNS, where it may control distinct steps.

CXCL12 inhibits hair growth through CXCR4

CXCL12 and its receptors, which are highly expressed in the skin, are associated with various cutaneous diseases, including androgenic alopecia. However, their expression and role during the hair cycle are unknown. This study aims to investigate the expression of CXCL12 and its receptor, CXCR4, in the vicinity of hair follicles and their effect on hair growth. CXCL12 was highly expressed in dermal fibroblasts (DFs) and its level was elevated throughout the catagen and telogen phases of the hair cycle. CXCR4 is expressed in the dermal papilla (DP) and outer root sheath (ORS). In hair organ culture, hair loss was induced by recombinant CXCL12 therapy, which delayed the telogen-to-anagen transition and decreased hair length. In contrast, the suppression of CXCL12 using a neutralizing antibody and siRNA triggered the telogen-to-anagen transition and increased hair length in hair organ culture. Neutralization of CXCR7, one of the two receptors for CXCL12, only slightly affected hair growth. However, inhibition of CXCR4, the other receptor for CXCL12, increased hair growth to a considerable extent. In addition, in hair organ culture, the conditioned medium from DFs with CXCL12 siRNA considerably increased the hair length and induced proliferation of DP and ORS cells. CXCL12, through CXCR4 activation, increased STAT3 and STAT5 phosphorylation in DP and ORS cells. In contrast, blocking CXCL12 and CXCR4 decreased the phosphorylation of STAT3 and STAT5. In summary, these findings suggest that CXCL12 inhibits hair growth via the CXCR4/STAT signaling pathway and that CXCL12/CXCR4 pathway inhibitors are a promising treatment option for hair growth.

Monocyte-derived SDF1 supports optic nerve regeneration and alters retinal ganglion cells' response to Pten deletion

Although mammalian retinal ganglion cells (RGCs) normally cannot regenerate axons nor survive after optic nerve injury, this failure is partially reversed by inducing sterile inflammation in the eye. Infiltrative myeloid cells express the axogenic protein oncomodulin (Ocm) but additional, as-yet-unidentified, factors are also required. We show here that infiltrative macrophages express stromal cell–derived factor 1 (SDF1, CXCL12), which plays a central role in this regard. Among many growth factors tested in culture, only SDF1 enhances Ocm activity, an effect mediated through intracellular cyclic AMP (cAMP) elevation and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) activation. SDF1 deficiency in myeloid cells (CXCL12flx/flxLysM-Cre−/+ mice) or deletion of the SDF1 receptor CXCR4 in RGCs (intraocular AAV2-Cre in CXCR4flx/flx mice) or SDF1 antagonist AMD3100 greatly suppresses inflammation-induced regeneration and decreases RGC survival to baseline levels. Conversely, SDF1 induces optic nerve regeneration and RGC survival, and, when combined with Ocm/cAMP, SDF1 increases axon regeneration to levels similar to those induced by intraocular inflammation. In contrast to deletion of phosphatase and tensin homolog (Pten), which promotes regeneration selectively from αRGCs, SDF1 promotes regeneration from non-αRGCs and enables the latter cells to respond robustly to Pten deletion; however, SDF1 surprisingly diminishes the response of αRGCs to Pten deletion. When combined with inflammation and Pten deletion, SDF1 enables many RGCs to regenerate axons the entire length of the optic nerve. Thus, SDF1 complements the effects of Ocm in mediating inflammation-induced regeneration and enables different RGC subtypes to respond to Pten deletion.

CXCL12 in Pancreatic Cancer: Its Function and Potential as a Therapeutic Drug Target

Simple Summary

Pancreatic cancer is a challenging disease to treat effectively. Fibroblasts associated with pancreatic cancer contribute to disease progression by secreting factors that enhance tumor cell survival and help tumor cells avoid detection by the immune system. This overview focuses on a chemokine, CXCL12, produced by cancer-associated fibroblasts and how CXCL12 signaling enhances pancreatic cancer progression by contributing to various hallmarks of cancer including, but not limited to, tumor growth and evasion of immune response. These pro-oncogenic functions of CXCL12 make it an attractive target in pancreatic cancer. We discuss the different approaches in development to therapeutically target CXCL12 and finally propose a novel approach, the use of the farnesyl transferase inhibitor tipifarnib to inhibit CXCL12 expression in pancreatic fibroblasts.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a disease with limited therapeutic options and dismal long-term survival. The unique tumor environment of PDAC, consisting of desmoplastic stroma, immune suppressive cells, and activated fibroblasts, contributes to its resistance to therapy. Activated fibroblasts (cancer-associated fibroblasts and pancreatic stellate cells) secrete chemokines and growth factors that support PDAC growth, spread, chemoresistance, and immune evasion. In this review, we focus on one such chemokine, CXCL12, secreted by the cancer-associated fibroblasts and discuss its contribution to several of the classical hallmarks of PDAC and other tumors. We review the various therapeutic approaches in development to target CXCL12 signaling in PDAC. Finally, we propose an unconventional use of tipifarnib, a farnesyl transferase inhibitor, to inhibit CXCL12 production in PDAC.

H2 O2 -induced oxidative stress disrupts mitochondrial functions and impairs migratory potential of human epidermal melanocytes

Reactive oxygen species (ROS) have already been demonstrated to impede the migratory ability in non-melanocytic cell lines by depleting mitochondrial ATP production. Therefore, understanding the mitochondrial metabolic response to migration in the presence of ROS should be a key to understanding repigmentation in vitiligo. This study aimed to investigate the energy mechanism associated with the ROS-mediated attenuation of melanocyte migration. After melanocytes were pretreated with H₂ O₂ , their ATP production, migratory ability, ultrastructural changes and Mitochondrial Permeability Potential were analysed. The results showed that, in parallel with the decreased ATP production, the migratory ability of melanocytes was significantly inhibited by oxidative stress. Supplementation with exogenous ATP reversed the suppressed ATP-dependent migration of melanocytes. Melanocytes were then stressed with H₂ O₂ and Agilent Whole Human Genome microarray analysis identified 763 up-regulated mRNAs and 1117 down-regulated mRNAs. Among them, 11 of the encoded proteins were involved in mitochondrial ATP production and their expression levels were verified. The decreased expression of NADH dehydrogenase 2(ND₂₎ , cytochrome c oxidase 1(COX1) and cytochrome c oxidase 3(COX3) was shown to be involved in the depletion of mitochondrial ATP production, which was coupled with the impaired migratory potential. These results indicate that the migration of melanocytes relies heavily on an inexhaustible supply of ATP from mitochondria.

Xmrks the Spot: Fish Models for Investigating Epidermal Growth Factor Receptor Signaling in Cancer Research

Studies conducted in several fish species, e.g., Xiphophorus hellerii (green swordtail) and Xiphophorus maculatus (southern platyfish) crosses, Oryzias latipes (medaka), and Danio rerio (zebrafish), have identified an oncogenic role for the receptor tyrosine kinase, Xmrk, a gene product closely related to the human epidermal growth factor receptor (EGFR), which is associated with a wide variety of pathological conditions, including cancer. Comparative analyses of Xmrk and EGFR signal transduction in melanoma have shown that both utilize STAT5 signaling to regulate apoptosis and cell proliferation, PI3K to modulate apoptosis, FAK to control migration, and the Ras/Raf/MEK/MAPK pathway to regulate cell survival, proliferation, and differentiation. Further, Xmrk and EGFR may also modulate similar chemokine, extracellular matrix, oxidative stress, and microRNA signaling pathways in melanoma. In hepatocellular carcinoma (HCC), Xmrk and EGFR signaling utilize STAT5 to regulate cell proliferation, and Xmrk may signal through PI3K and FasR to modulate apoptosis. At the same time, both activate the Ras/Raf/MEK/MAPK pathway to regulate cell proliferation and E-cadherin signaling. Xmrk models of melanoma have shown that inhibitors of PI3K and MEK have an anti-cancer effect, and in HCC, that the steroidal drug, adrenosterone, can prevent metastasis and recover E-cadherin expression, suggesting that fish Xmrk models can exploit similarities with EGFR signal transduction to identify and study new chemotherapeutic drugs.

Functions of the CXCL12 Receptor ACKR3/CXCR7-What Has Been Perceived and What Has Been Overlooked

The CXCL12 system is central to the development of many organs and is further crucially engaged in pathophysiological processes underlying cancer, inflammation, and cardiovascular disorders. This disease-associated role presently focuses major interest on the two CXCL12 receptors, CXCR4 and atypical chemokine receptor 3 (ACKR3)/CXCR7, as promising therapeutic targets. Major obstacles in these ongoing efforts are confusing reports on the differential use of either ACKR3/CXCR7 and/or CXCR4 across various cells as well as on the specific function(s) of ACKR3/CXCR7. Although basically no doubts remain that CXCR4 represents a classic chemokine receptor, functions assigned to ACKR3/CXCR7 range from those of a strictly silent scavenger receptor eventually modulating CXCR4 signaling to an active and independent signaling receptor. In this review, we depict a thorough analysis of our present knowledge on different modes of organization and functions of the cellular CXCL12 system. We further highlight the potential role of ACKR3/CXCR7 as a "crosslinker" of different receptor systems. Finally, we discuss mechanisms with the potency to impinge on the cellular organization of the CXCL12 system and hence might represent additional future therapeutic targets. SIGNIFICANCE STATEMENT: Delineating the recognized functions of atypical chemokine receptor 3 and CXCR4 in CXCL12 signaling is central to the more detailed understanding of the role of the CXCL12 system in health and disease and will help to guide future research efforts.

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.

CXCL11 promotes tumor progression by the biased use of the chemokine receptors CXCR3 and CXCR7

The chemokine, CXCL11, is highly expressed in different solid tumors and controls tumor growth, metastasis, and lymphocyte infiltration. Although of potential clinical interest, it is presently unknown whether these tumor-promoting activities involve the CXCL11 receptors, CXCR3 and/or CXCR7. This issue is further intrigued by the fact that CXCR3 exists in the two functionally divergent splice variants, CXCR3A and CXCR3B, which exert pro- and anti-tumorigenic influences, respectively. To unravel the role of the various CXCL11 receptors in tumor progression, we have now defined their role in CXCL11-induced chemotaxis of the tumor cell lines, A549, C33-A, DLD-1, MDA-MB-231, and PC-3. CXCL11-induced cell migration was either sensitive to the CXCR3 antagonist, ÀMG487 (DLD-1), the CXCR7 antagonist, CCX771 (C33-A, PC-3), or both (A549, MDA-231). Moreover, in C33-A and PC-3 cells, but not in the other tumor cells, pharmacological activation and inhibition of CXCR3B prevented and potentiated CXCL11-induced cell migration, respectively. Both immunocytochemistry and Western blot analysis finally revealed that the observed cell type specific organization of the CXCL11 system is not the result of differences in expression levels or subcellular location of CXCL11 receptors. Our findings imply that the therapeutic use of CXCR3 antagonists in cancer patients requires exact knowledge of the organization of the CXCR3 system in the respective tumor.

CXCL12 regulates differentiation of human immature melanocyte precursors as well as their migration

Melanocyte stem cells (McSCs) are localized in the bulge region of hair follicles and supply melanocytes, which determine hair color by synthesizing melanin. Ectopic differentiation of McSCs, which are usually undifferentiated in the bulge region, causes depletion of McSCs and results in hair graying. Therefore, to prevent hair graying, it is essential to maintain McSCs in the bulge region, but the mechanism of McSC maintenance remains unclear. To address this issue, we investigated the role of CXCL12, a chemokine which was previously suggested to induce migration of melanocyte lineage cells, as a niche component of McSCs. Immunohistological analysis revealed that CXCL12 was highly expressed in the bulge region of human hair follicles. CXCL12 mRNA expression level was significantly lower in white hairs plucked from human scalps than in black hairs. CXCL12 attracted the migration of early-passage normal human epidermal melanocytes (eNHEMs), an in vitro model of McSCs, which had characteristics of immature melanocyte precursors. We also found that CXCL12 suppressed their differentiation. These results suggest that CXCL12 regulates differentiation of McSCs as well as their proper localization, and maintaining McSCs by regulating CXCL12 expression level in the bulge region may be a key to preventing hair graying.

Targeting Chemokines and Chemokine Receptors in Melanoma and Other Cancers

The tumor microenvironment is highly heterogeneous. It is composed of a diverse array of immune cells that are recruited continuously into lesions. They are guided into the tumor through interactions between chemokines and their receptors. A variety of chemokine receptors are expressed on the surface of both tumor and immune cells rendering them sensitive to multiple stimuli that can subsequently influence their migration and function. These features significantly impact tumor fate and are critical in melanoma control and progression. Indeed, particular chemokine receptors expressed on tumor and immune cells are strongly associated with patient prognosis. Thus, potential targeting of chemokine receptors is highly attractive as a means to quench or eliminate unconstrained tumor cell growth.

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

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

Requirement of zebrafish pcdh10a and pcdh10b in melanocyte precursor migration

Melanocytes derive from neural crest cells, which are a highly migratory population of cells that play an important role in pigmentation of the skin and epidermal appendages. In most vertebrates, melanocyte precursor cells migrate solely along the dorsolateral pathway to populate the skin. However, zebrafish melanocyte precursors also migrate along the ventromedial pathway, in route to the yolk, where they interact with other neural crest derivative populations. Here, we demonstrate the requirement for zebrafish paralogs pcdh10a and pcdh10b in zebrafish melanocyte precursor migration. pcdh10a and pcdh10b are expressed in a subset of melanocyte precursor and somatic cells respectively, and knockdown and TALEN mediated gene disruption of pcdh10a results in aberrant migration of melanocyte precursors resulting in fully melanized melanocytes that differentiate precociously in the ventromedial pathway. Live cell imaging analysis demonstrates that loss of pchd10a results in a reduction of directed cell migration of melanocyte precursors, caused by both increased adhesion and a loss of cell-cell contact with other migratory neural crest cells. Also, we determined that the paralog pcdh10b is upregulated and can compensate for the genetic loss of pcdh10a. Disruption of pcdh10b alone by CRISPR mutagenesis results in somite defects, while the loss of both paralogs results in enhanced migratory melanocyte precursor phenotype and embryonic lethality. These results reveal a novel role for pcdh10a and pcdh10b in zebrafish melanocyte precursor migration and suggest that pcdh10 paralogs potentially interact for proper transient migration along the ventromedial pathway.

Mechanisms of CXCR7 induction in malignant melanoma development

Malignant melanoma (MM) is a highly malignant skin tumor. The mechanism of MM pathogenesis and its signaling pathways are not well characterized. C-X-C chemokine receptor type 7 (CXCR7) has been reported to regulate cancer cell invasion. The present study sought to investigate the effects of CXCR7 on MM development. First, CXCR7 expression levels were assessed in the skin tumor tissue of patients with MM. Then, CXCR7 small hairpin RNA was used in M14 melanoma cells in a Transwell culture model and in a transplanted mouse model to test the effects of CXCR7. In addition, immunohistochemistry staining, reverse transcription-quantitative polymerase chain reaction and western blotting were used. The results revealed that CXCR7 expression levels were significantly higher in MM tissue compared with squamous cell carcinoma or basal cell carcinoma tissue. Knocking down CXCR7 in M14 cells significantly inhibited cell migration and invasion in the Transwell culture model. Furthermore, CXCR7 knockdown also significantly reduced the transplanted tumor size, weight and vascular number in the mouse model. It was concluded that CXCR7 interacts with C-X-C motif chemokine ligand 12 to activate the chemokine receptor signaling pathway, and to increase melanoma cell migration, invasion and development.

High Expression of Stromal Cell-Derived Factor 1 (SDF-1) and NF-κB Predicts Poor Prognosis in Cervical Cancer

Background

SDF-1 and NF-κB are associated with the prognosis of a wide range of cancers, but their value in cervical cancer remains controversial. The aim of this study was to investigate the expression of SDF-1and NF-κB in cervical cancer and their significance in clinical prognosis.

Material/Methods

The expression of SDF-1and NF-κB in 105 formalin-fixed, paraffin-embedded cervical cancer tissues and the adjacent tissues was examined by immunohistochemistry (IHC). The results were semi-quantitatively scored and analyzed by chi-square test. The overall survival times (OS) were collected by follow-up and analyzed by Kaplan-Meier analysis.

Results

The expression level of both SDF-1and NF-κB in cervical cancer are higher than that in the adjacent tissues (P<0.05). SDF-1 expression are correlated with tumor size and FIGO histology grade (P<0.05). NF-κB expression are correlated with tumor size and FIGO histology grade, and lymph node metastasis (LNM) status (P<0.05). The patients with a positive expression of SDF-1or NF-κB tended to have much shorter survival time than patients with negative expression. In addition, multivariate Cox regression analysis demonstrated that SDF-1 expression and lymph node metastasis are independent predictors of the OS in cervical cancer patients.

Conclusions

The expression of SDF-1 is significantly associated with tumor size and FIGO histology grade. The expression of NF-κB is significantly associated with tumor size, FIGO histology grade, and lymph node metastasis. The positive SDF-1or NF-κB expression is significantly correlated with poor prognosis. These may be valuable biomarkers for the prognosis and the potential therapeutic targets of cervical cancer.

Interferon-inducible T-cell alpha chemoattractant (ITAC) induces the melanocytic migration and hypopigmentation through destabilizing p53 via histone deacetylase 5: a possible role of ITAC in pigment-related disorders

BACKGROUND

Cell migration plays a major role in the immune response and in tumorigenesis. Interferon-inducible T-cell alpha chemoattractant (ITAC) elicits a strong chemotactic response from immune cells.

OBJECTIVES

To examine the effect of ITAC on melanocyte migration and pigmentation and its involvement in related disorders, and to investigate potential key players in these processes.

METHODS

Human melanocytes or melanoma cells were treated with ITAC and a migration assay was carried out. Global gene expression analysis was performed to find genes regulated by ITAC treatment. The function of key players involved in ITAC-induced cellular processes was addressed using knockdown or overexpression experiments in combination with ITAC treatment. ITAC expression in the inflammation-associated hypopigmentary disorder, vitiligo, was examined.

RESULTS

Among CXCR3 ligands, only ITAC induced melanocyte migration. ITAC treatment upregulated the expression of histone deacetylase 5 (HDAC5) and downregulated that of p53, a known target of HDAC5. Through knockdown or overexpression of HDAC5 and p53, we confirmed that HDAC5 mediates ITAC-induced migration by decreasing levels of p53 via deacetylation. In addition, ITAC treatment could decrease pigmentation in a p53- and HDAC5-dependent manner. Finally, the increased migration of human melanoma cells by ITAC treatment and the increased ITAC expression in the epidermis of vitiligo skin were verified.

CONCLUSIONS

This study provides in vitro evidence for the migratory and hypopigmentation effects of ITAC on melanocytic cells, gives translational insights into the roles of ITAC in pathological conditions, and suggests that HDAC5 and its substrate p53 are potent targets for regulating ITAC-induced cellular processes.

Carvedilol-responsive microRNAs, miR-199a-3p and -214 protect cardiomyocytes from simulated ischemia-reperfusion injury

The nonselective β-adrenergic receptor antagonist (β-blocker) carvedilol has been shown to protect against myocardial injury, but the detailed underlying mechanisms are unclear. We recently reported that carvedilol stimulates the processing of microRNA (miR)-199a-3p and miR-214 in the heart via β-arrestin1-biased β1-adrenergic receptor (β1AR) cardioprotective signaling. Here, we investigate whether these β-arrestin1/β1AR-responsive miRs mediate the beneficial effects of carvedilol against simulated ischemia/reperfusion (sI/R). Using cultured cardiomyocyte cell lines and primary cardiomyocytes, we demonstrate that carvedilol upregulates miR-199a-3p and miR-214 in both ventricular and atrial cardiomyocytes subjected to sI/R. Overexpression of the two miRs in cardiomyocytes mimics the effects of carvedilol to activate p-AKT survival signaling and the expression of a downstream pluripotency marker Sox2 in response to sI/R. Moreover, carvedilol-mediated p-AKT activation is abolished by knockdown of either miR-199a-3p or miR-214. Along with previous studies to directly link the cardioprotective actions of carvedilol to upregulation of p-AKT/stem cell markers, our findings suggest that the protective roles of carvedilol during ischemic injury are in part attributed to activation of these two protective miRs. Loss of function of miR-199a-3p and miR-214 also increases cardiomyocyte apoptosis after sI/R. Mechanistically, we demonstrate that miR-199a-3p and miR-214 repress the predictive or known apoptotic target genes ddit4 and ing4, respectively, in cardiomyocytes. These findings suggest pivotal roles for miR-199a-3p and miR-214 as regulators of cardiomyocyte survival and contributors to the functional benefits of carvedilol therapy.

The Effect of MCP-1/CCR2 on the Proliferation and Senescence of Epidermal Constituent Cells in Solar Lentigo

Solar lentigo (SL) is a representative photoaging skin disorder. Alteration of the main epidermal constituent cells-keratinocytes and melanocytes-in relation to the photoaged dermal environment or chemokine/cytokine network is suggested as its pathogenesis. Among these, we focused on monocyte chemoattractant protein-1 (MCP-1), as it is known to be associated with tissue aging. For the first time, we report that the MCP-1 receptor, CCR2, is expressed in normal human melanocytes. In SL tissue, there was an increase of CCR2+Melan A+ melanocytes with positivity to Rb protein compared to peri-lesional normal skin. MCP-1 induced the proliferation of normal human melanocytes without a significant change in the melanin content. MCP-1 treatment in normal human keratinocytes showed an increase in senescence-associated β-galactosidase staining and p53 and p21 protein expressions. In summary, MCP-1 may participate in the development of SL by affecting epidermal constituent cells, for example, by inducing melanocyte proliferation and keratinocyte senescence.

Overview and potential unifying themes of the atypical chemokine receptor family

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

Strategies to improve the immunosuppressive properties of human mesenchymal stem cells

Mesenchymal stem cells (MSCs) are of particular interest for the treatment of immune-related diseases because of their immunosuppressive capacities. However, few clinical trials of MSCs have yielded satisfactory results. A number of clinical trials using MSCs are currently in progress worldwide. Unfortunately, protocols and methods, including optimized culture conditions for the harvest of MSCs, have not been standardized. In this regard, complications in the ex vivo expansion of MSCs and MSC heterogeneity have been implicated in the failure of clinical trials. In this review, potential strategies to obtain MSCs with improved immunosuppressive properties and the potential roles of specific immunomodulatory genes, which are differentially upregulated in certain culture conditions, will be discussed.

PAX3 and FOXD3 Promote CXCR4 Expression in Melanoma

Metastatic melanoma is an aggressive and deadly disease. The chemokine receptor CXCR4 is active in melanoma metastasis, although the mechanism for the promotion and maintenance of CXCR4 expression in these cells is mostly unknown. Here, we find melanoma cells express two CXCR4 isoforms, the common version and a variant that is normally restricted to cells during development or to mature blood cells. CXCR4 expression is driven through a highly conserved intronic enhancer element by the transcription factors PAX3 and FOXD3. Inhibition of these transcription factors slows melanoma cell growth, migration, and motility, as well as reduces CXCR4 expression. Overexpression of these transcription factors drives the production of increased CXCR4 levels. Loss of PAX3 and FOXD3 transcription factor activity results in a reduction in cell motility, migration, and chemotaxis, all of which are rescued by CXCR4 overexpression. Here, we discover a molecular pathway wherein PAX3 and FOXD3 promote CXCR4 gene expression in melanoma.

Human skin melanocyte migration towards stromal cell-derived factor-1α demonstrated by optical real-time cell mobility assay: modulation of their chemotactic ability by α-melanocyte-stimulating hormone

To identify potential regulators of normal human melanocyte behaviour, we have developed an in vitro human melanocyte migration assay, using the optically accessible, real-time cell motility assay device TAXIScan. Coating of the glass surface with an extracellular matrix that served as scaffolding molecule was essential to demonstrate efficient melanocyte migration. Among several chemokines tested, stromal cell-derived factor (SDF)-1α/CXCL12 was the most effective driver of human normal skin melanocytes. Incubation of melanocytes with α-melanocyte-stimulating hormone (MSH) before the assay specifically enhanced CXCR4 expression and consequently chemotaxis towards SDF-1α/CXCL12. These results suggest that α-MSH acts on melanocytes to produce melanin as well as stimulates the cells to migrate to the site where they work through CXCR4 up-regulation, which is a new dynamic mode of action of α-MSH on melanocyte physiology.

Melanoma cells break down LPA to establish local gradients that drive chemotactic dispersal

The high mortality of melanoma is caused by rapid spread of cancer cells, which occurs unusually early in tumour evolution. Unlike most solid tumours, thickness rather than cytological markers or differentiation is the best guide to metastatic potential. Multiple stimuli that drive melanoma cell migration have been described, but it is not clear which are responsible for invasion, nor if chemotactic gradients exist in real tumours. In a chamber-based assay for melanoma dispersal, we find that cells migrate efficiently away from one another, even in initially homogeneous medium. This dispersal is driven by positive chemotaxis rather than chemorepulsion or contact inhibition. The principal chemoattractant, unexpectedly active across all tumour stages, is the lipid agonist lysophosphatidic acid (LPA) acting through the LPA receptor LPAR1. LPA induces chemotaxis of remarkable accuracy, and is both necessary and sufficient for chemotaxis and invasion in 2-D and 3-D assays. Growth factors, often described as tumour attractants, cause negligible chemotaxis themselves, but potentiate chemotaxis to LPA. Cells rapidly break down LPA present at substantial levels in culture medium and normal skin to generate outward-facing gradients. We measure LPA gradients across the margins of melanomas in vivo, confirming the physiological importance of our results. We conclude that LPA chemotaxis provides a strong drive for melanoma cells to invade outwards. Cells create their own gradients by acting as a sink, breaking down locally present LPA, and thus forming a gradient that is low in the tumour and high in the surrounding areas. The key step is not acquisition of sensitivity to the chemoattractant, but rather the tumour growing to break down enough LPA to form a gradient. Thus the stimulus that drives cell dispersal is not the presence of LPA itself, but the self-generated, outward-directed gradient.

The chemokine receptor CXCR7 interacts with EGFR to promote breast cancer cell proliferation

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 β-arrestin2 in cells with EGFR over expression we were able to nearly deplete the CXCR7-EGFR colocalization events, suggesting that β-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.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-198) contains supplementary material, which is available to authorized users.

Sema3E/PlexinD1 regulates the migration of hem-derived Cajal-Retzius cells in developing cerebral cortex

During the development of the cerebral cortex, Cajal-Retzius (CR) cells settle in the preplate and coordinate the precise growth of the neocortex. Indeed, CR cells migrate tangentially from specific proliferative regions of the telencephalon (for example, the cortical hem (CH)) to populate the entire cortical surface. This is a very finely tuned process regulated by an emerging number of factors that has been sequentially revealed in recent years. However, the putative participation of one of the major families of axon guidance molecules in this process, the Semaphorins, was not explored. Here we show that Semaphorin-3E (Sema3E) is a natural negative regulator of the migration of PlexinD1-positive CR cells originating in the CH. Our results also indicate that Sema3E/PlexinD1 signalling controls the motogenic potential of CR cells in vitro and in vivo. Indeed, absence of Sema3E/PlexinD1 signalling increased the migratory properties of CR cells. This modulation implies negative effects on CXCL12/CXCR4 signalling and increased ADF/Cofilin activity.

The effect of TC14012 on alkali burn-induced corneal neovascularization in mice

AIMS

To observe the effect of TC14012 (a CXCR4 antagonist and CXCR7 agonist) on alkali burn-induced corneal neovascularization (CNV) in a mouse model.

METHODS

CNV was induced in vivo by alkali burns on the corneas of BALB/c mice. A total of 54 mice treated with alkali burns were randomly divided into 3 groups, each of which received one of the following treatments: bilateral subconjunctival injections of TC14012 for 3 consecutive days, bilateral subconjunctival injections of balanced saline (BS) for 3 consecutive days or no treatment (blank control). The areas of CNV were measured on days 3, 7 and 14 after the alkali burns. CXCR4, CXCR7, vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP) mRNAs were detected and quantified by real-time reverse transcription PCR on days 7 and 14. Additionally, the expression of the proteins CXCR4, CXCR7, VEGF, β-arrestin 2, total ERK1/2 and phospho-ERK1/2 was determined by Western blotting.

RESULTS

On day 7 after the alkali burns, the CNV area, VEGF, MMP-2 and MMP-9 mRNA levels, and VEGF, β-arrestin 2 and phospho-ERK1/2 protein levels were increased in the TC14012 group compared with the nontreatment and BS groups. However, on day 14, the CNV area, CXCR4, CXCR7, VEGF, MMP-2 and MMP-9 mRNA levels, and the CXCR4, CXCR7, VEGF and β-arrestin 2 protein levels were significantly decreased in the TC14012 group.

CONCLUSIONS

TC14012 initially enhanced alkali burn-induced CNV but reduced CNV in later stages. In addition to CXCR4, CXCR7 is involved in the pathogenesis of CNV.

The role of the non-canonical Wnt-planar cell polarity pathway in neural crest migration

The neural crest is an embryonic stem cell population whose migratory behaviour has been likened to malignant invasion. The neural crest, as does cancer, undergoes an epithelial-to-mesenchymal transition and migrates to colonize almost all the tissues of the embryo. Neural crest cells exhibit collective cell migration, moving in streams of high directionality. The migratory neural crest streams are kept in shape by the presence of negative signals in their vicinity. The directionality of the migrating neural crest is achieved by contact-dependent cell polarization, in a phenomenon called contact inhibition of locomotion. Two cells experiencing contact inhibition of locomotion move away from each other after collision. However, if the cell density is high only cells exposed to a free edge can migrate away from the cluster leading to the directional migration of the whole group. Recent work performed in chicks, zebrafish and frogs has shown that the non-canonical Wnt-PCP (planar cell polarity) pathway plays a major role in neural crest migration. PCP signalling controls contact inhibition of locomotion between neural crest cells by localizing different PCP proteins at the site of cell contact during collision and locally regulating the activity of Rho GTPases. Upon collision RhoA (ras homologue family member A) is activated, whereas Rac1 is inhibited at the contact between two migrating neural crest cells, leading to the collapse of protrusions and the migration of cells away from one another. The present review summarizes the mechanisms that control neural crest migration and focuses on the role of non-canonical Wnt or PCP signalling in this process.

Atorvastatin inhibits CXCR7 induction to reduce macrophage migration

We have recently reported that CXCR7, the alternate high affinity SDF-1 receptor, is induced during monocyte-to-macrophage differentiation, leading to increased macrophage phagocytosis linked to atherosclerosis. Statins, the most widely used medications for atherosclerosis, were shown to have pleiotropic beneficial effects independent of their cholesterol-lowering activity. This study aimed to determine whether induction of CXCR7 during macrophage differentiation is inhibited by statins and its significance on macrophage physiology. Here we show for the first time that atorvastatin dose-dependently inhibited CXCR7 mRNA and protein expression in THP-1 macrophages, without affecting the other SDF-1 receptor, CXCR4. Pharmacotherapy relevant dose of atorvastatin affected neither cell viability nor macrophage differentiation. Suppression of CXCR7 expression was completely reversed by supplementation with mevalonate. Inhibition of squalene synthase, the enzyme committed to cholesterol biosynthesis, also decreased CXCR7 induction, albeit not as efficacious as atorvastatin. However, the geranylgeranyl transferase inhibitor, GGTI-286, the farnesyl transferase inhibitor, FTI-276, and the Rho kinase inhibitor, Y-27632, all failed to mimic the effect of atorvastatin, suggesting that the protein prenylation pathways are not critical for atorvastatin inhibition of CXCR7 induction. Interestingly, the dramatic effect of atorvastatin was only partially mimicked by other statins including pravastatin, fluvastatin, mevastatin, and simvastatin. Furthermore, activation of CXCR7 by SDF-1, TC14012, or I-TAC all prompted macrophage migration, which was significantly suppressed by atorvastatin treatment, but not by the CXCR4 antagonist. We conclude that atorvastatin modulates macrophage migration by down-regulating CXCR7 expression, suggesting a new CXCR7-dependent mechanism of atorvastatin to benefit atherosclerosis treatment beyond its lipid lowering effect.

Intracellular coexpression of CXC- and CC- chemokine receptors and their ligands in human melanoma cell lines and dynamic variations after xenotransplantation

Background

Chemokines have been implicated in tumor progression and metastasis. In melanoma, chemokine receptors have been implicated in organ selective metastasis by regulating processes such as chemoattraction, adhesion and survival.

Methods

In this study we have analyzed, using flow cytometry, the systems formed by the chemokine receptors CXCR3, CXCR4, CXCR7, CCR7 and CCR10 and their ligands in thirteen human melanoma cell lines (five established from primary tumors and eight established from metastasis from different tissues). WM-115 and WM-266.4 melanoma cell lines (obtained from a primary and a metastatic melanoma respectively) were xenografted in nude mice and the tumors and cell lines derived from them were also analyzed.

Results

Our results show that the melanoma cell lines do not express or express in a low degree the chemokine receptors on their cell surface. However, melanoma cell lines show intracellular expression of all the aforementioned receptors and most of their respective ligands. When analyzing the xenografts and the cell lines obtained from them we found variations in the intracellular expression of chemokines and chemokine receptors that differed between the primary and metastatic cell lines. However, as well as in the original cell lines, minute or no expression of the chemokine receptors was observed at the cell surface.

Conclusions

Coexpression of chemokine receptors and their ligands was found in human melanoma cell lines. However, this expression is intracellular and receptors are not found at the cell membrane nor chemokines are secreted to the cell medium. The levels of expressed chemokine receptors and their ligands show dynamic variations after xenotransplantation that differ depending on the origin of the cell line (from primary tumor or from metastasis).

Stromal derived factor-1 (SDF-1) and its receptors CXCR4 and CXCR7 in endometrial cancer patients

PURPOSE

One of the most important function of stromal derived factor-1 (SDF-1) and its receptors, is regulating the process of metastasis formation. The aim of our study was to investigate the correlation between SDF-1, CXCR4 and CXCR7 protein levels measured by immunohistochemistry with the clinicopathological features and the survival of endometrial cancer patients.

MATERIALS AND METHODS

92 patients aged 37-84 (mean 65.1±9.5) were enrolled to our study between January 2000 and December 2007. After the diagnosis of endometrial cancer, all women underwent total abdominal hysterectomy, with bilateral salpingoophorectomy and pelvic lymph node dissection. In all patients clinical stage (according to FIGO classification), histologic grade, myometrial invasion, lymph node and distant metastases were determined.Furthermore, the survival time was assessed. Immunohistochemical analyses of SDF-1, CXCR4 and CXCR7 were performed on archive formalin fixed paraffin embedded tissue sections.

RESULTS

Statistically significant correlations (p<0.01) were reported between SDF-1 and the clinical stage of disease, lymph node metastases, distant metastases, deep myometrial invasion (≥50%), cervical involvement, involvement of adnexa. Statistically significant correlation (p<0.01) was found between SDF-1 expression and the risk of the recurrence. Higher SDF-1 expression was associated with a higher risk of recurrence (p = 0.0001). The results of CXCR4 and CXCR7 expression didn't reveal any significant differences(p>0.05) between the proteins expression in the primary tumor cells and the clinicopathological features. Moreover, the Kaplan-Meier analyses demonstrated a stepwise impairment of cancer overall survival (OS) with increasing SDF-1 expression.

CONCLUSION

The important role of SDF-1 as a predictor of negative clinicopathological characteristics of a tumor suggests that the expression of this stromal factor should be included in the panel of accessory pathomorphological tests and could be helpful in establishing a more accurate prognosis in endometrial cancer patients.

The signaling pathway of stromal cell-derived factor-1 and its role in kidney diseases

The chemokine stromal cell-derived factor-1 (SDF-1) regulates the trafficking of progenitor cell (PGC) during embryonic development, cell chemotaxis, and postnatal homing into injury sites. SDF-1 also regulates cell growth, survival, adhesion and angiogenesis. However, in different tissues/cells, the role of SDF-1 is different, such as that it is increased in most of the tumors and associated with cancer metastasis, whereas it is essential for the development of vasculature. For kidney diseases, its role remains controversial. Signaling pathways might be very important in the pathogenesis of kidney diseases. We performed this review to provide a relatively complete signaling pathway flowchart for SDF-1 to the investigators who were interested in the role of SDF-1 in the pathogenesis of kidney diseases. Here, we reviewed the signal transduction pathway of SDF-1 and its role in the pathogenesis of kidney diseases.

Xmrk-induced melanoma progression is affected by Sdf1 signals through Cxcr7

Chemokine signals mediated by Sdf1/Cxcl12 through the chemokine receptor Cxcr4 are thought to play an instructive role in tumor migration and organ-specific metastasis. We have used a small aquarium fish model to contribute to a better understanding of how the course of melanoma development is influenced by Sdf1 signals in vivo. We studied oncogene-induced skin tumor appearance and progression in the transgenic medaka (Oryzias latipes) melanoma model. Similar to humans, invasive medaka melanomas show increased levels of sdf1, cxcr4, and cxcr7 gene expression. Stable transgenic fish lines overexpressing sdf1 exclusively in pigment cells showed a reduction in melanoma appearance and progression. Remarkably, diminished levels of functional Cxcr7, but not of Cxcr4b, resulted in strongly reduced melanoma invasiveness and a repression of melanoma. Our results thereby indicate that Sdf1 signals via Cxcr7 are able to constrain melanoma growth in vivo and that these signals influence tumor outcome.

Directional tissue migration through a self-generated chemokine gradient

The directed migration of cell collectives is a driving force of embryogenesis. The predominant view in the field is that cells in embryos navigate along pre-patterned chemoattractant gradients. One hypothetical way to free migrating collectives from the requirement of long-range gradients would be through the self-generation of local gradients that travel with them, a strategy that potentially allows self-determined directionality. However, a lack of tools for the visualization of endogenous guidance cues has prevented the demonstration of such self-generated gradients in vivo. Here we define the in vivo dynamics of one key guidance molecule, the chemokine Cxcl12a, by applying a fluorescent timer approach to measure ligand-triggered receptor turnover in living animals. Using the zebrafish lateral line primordium as a model, we show that migrating cell collectives can self-generate gradients of chemokine activity across their length via polarized receptor-mediated internalization. Finally, by engineering an external source of the atypical receptor Cxcr7 that moves with the primordium, we show that a self-generated gradient mechanism is sufficient to direct robust collective migration. This study thus provides, to our knowledge, the first in vivo proof for self-directed tissue migration through local shaping of an extracellular cue and provides a framework for investigating self-directed migration in many other contexts including cancer invasion.

Misregulation of SDF1-CXCR4 signaling impairs early cardiac neural crest cell migration leading to conotruncal defects

RATIONALE

Cardiac neural crest cells (NCs) contribute to heart morphogenesis by giving rise to a variety of cell types from mesenchyme of the outflow tract, ventricular septum, and semilunar valves to neurons of the cardiac ganglia and smooth muscles of the great arteries. Failure in cardiac NC development results in outflow and ventricular septation defects commonly observed in congenital heart diseases. Cardiac NCs derive from the vagal neural tube, which also gives rise to enteric NCs that colonize the gut; however, so far, molecular mechanisms segregating these 2 populations and driving cardiac NC migration toward the heart have remained elusive.

OBJECTIVE

Stromal-derived factor-1 (SDF1) is a chemokine that mediates oriented migration of multiple embryonic cells and mice deficient for Sdf1 or its receptors, Cxcr4 and Cxcr7, exhibit ventricular septum defects, raising the possibility that SDF1 might selectively drive cardiac NC migration toward the heart via a chemotactic mechanism.

METHODS AND RESULTS

We show in the chick embryo that Sdf1 expression is tightly coordinated with the progression of cardiac NCs expressing Cxcr4. Cxcr4 loss-of-function causes delayed migration and enhanced death of cardiac NCs, whereas Sdf1 misexpression results in their diversion from their normal pathway, indicating that SDF1 acts as a chemoattractant for cardiac NCs. These alterations of SDF1 signaling result in severe cardiovascular defects.

CONCLUSIONS

These data identify Sdf1 and its receptor Cxcr4 as candidate genes responsible for cardiac congenital pathologies in human.