The alpha-chemokine, stromal cell-derived factor-1alpha, binds to the transmembrane G-protein-coupled CXCR-4 receptor and activates multiple signal transduction pathways

Exosomes Secreted from CXCR4 Overexpressing Mesenchymal Stem Cells Promote Cardioprotection via Akt Signaling Pathway following Myocardial Infarction

Background and Objective. Exosomes secreted from mesenchymal stem cells (MSC) have demonstrated cardioprotective effects. This study examined the role of exosomes derived from MSC overexpressing CXCR4 for recovery of cardiac functions after myocardial infarction (MI). Methods. In vitro, exosomes from MSC transduced with lentiviral CXCR4 (Exo(CR4)) encoding a silencing sequence or null vector were isolated and characterized by transmission electron microscopy and dynamic light scattering. Gene expression was then analyzed by qPCR and Western blotting. Cytoprotective effects on cardiomyocytes were evaluated and effects of exosomes on angiogenesis analyzed. In vivo, an exosome-pretreated MSC-sheet was implanted into a region of scarred myocardium in a rat MI model. Angiogenesis, infarct size, and cardiac functions were then analyzed. Results. In vitro, Exo(CR4) significantly upregulated IGF-1α and pAkt levels and downregulated active caspase 3 level in cardiomyocytes. Exo(CR4) also enhanced VEGF expression and vessel formation. However, effects of Exo(CR4) were abolished by an Akt inhibitor or CXCR4 knockdown. In vivo, Exo(CR4) treated MSC-sheet implantation promoted cardiac functional restoration by increasing angiogenesis, reducing infarct size, and improving cardiac remodeling. Conclusions. This study reveals a novel role of exosomes derived from MSC(CR4) and highlights a new mechanism of intercellular mediation of stem cells for MI treatment.

CXCL12/CXCR4 axis in the pathogenesis of acute lymphoblastic leukemia (ALL): a possible therapeutic target

Acute lymphoblastic leukemia (ALL) is the commonest childhood malignancy, accounting for approximately 80 % of leukemia in the pediatric group, and its etiology is unknown. This neoplasia is characterized by male predominance, high-risk features and poor outcome, mainly in recurrence patients and adults. In recent years, advances in the success of childhood ALL treatment were verified, and the rate of cure is over 80 % of individuals. However, there is a considerable scope for improving therapeutic outcome in this neoplasia. Improvements in ALL therapy might readily be achieved by developing additional biomarkers that can predict and refine prognosis in patients with ALL. In normal hematopoietic cells, cytokines provide the stimulus for proliferation, survival, self-renewal, differentiation and functional activation. Abnormalities of cytokines are characteristic in all forms of leukemia, including ALL. The stromal cell-derived factor-1 (SDF-1 or CXCL12) is a member of the CXC chemokine family that binds to CXC chemokine receptor 4 (CXCR4). The CXCL12/CXCR4 axis appears to play a role in dissemination of solid tumors and hematopoietic diseases. Understanding the mechanisms by which ALL cells are disseminated will provide additional information to expand therapeutic approach. Therefore, this review summarizes information relating to ALL cell biology, focusing specifically in a cytokine receptor important axis, CXCL12/CXCR4, that may have implications for novel treatment strategies to improve life expectancy of patients with this neoplasia.

The chemokine receptors CXCR4/CXCR7 and their primary heterodimeric ligands CXCL12 and CXCL12/high mobility group box 1 in pancreatic cancer growth and development: finding flow

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 chemokine 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.

Optimizing multiple sclerosis diagnosis: gene expression and genomic association

OBJECTIVE

The diagnosis of multiple sclerosis (MS) at disease onset is sometimes masqueraded by other diagnostic options resembling MS clinically or radiologically (NonMS). In the present study we utilized findings of large-scale Genome-Wide Association Studies (GWAS) to develop a blood gene expression-based classification tool to assist in diagnosis during the first demyelinating event.

METHODS

We have merged knowledge of 110 MS susceptibility genes gained from MS GWAS studies together with our experimental results of differential blood gene expression profiling between 80 MS and 31 NonMS patients. Multiple classification algorithms were applied to this cohort to construct a diagnostic classifier that correctly distinguished between MS and NonMS patients. Accuracy of the classifier was tested on an additional independent group of 146 patients including 121 MS and 25 NonMS patients.

RESULTS

We have constructed a 42 gene-transcript expression-based MS diagnostic classifier. The overall accuracy of the classifier, as tested on an independent patient population consisting of diagnostically challenging cases including NonMS patients with positive MRI findings, achieved a correct classification rate of 76.0 ± 3.5%.

INTERPRETATION

The presented diagnostic classification tool complements the existing diagnostic McDonald criteria by assisting in the accurate exclusion of other neurological diseases at presentation of the first demyelinating event suggestive of MS.

Construction of a CXCL12-KDEL fusion gene to inhibit head and neck squamous cell carcinoma metastasis by intracellular sequestration of CXCR4

The CXCL12-CXCR4 biological axis consisting of the chemotactic factor CXCL12 and its specific receptor CXCR4 plays an important role in oral cancer metastasis. High expression of CXCR4 may help oral squamous cancer cells invade local tissues and metastasize to lymph nodes. No obvious association was observed between CXCL12 expression and lymph node metastasis, suggesting that CXCL12 chemotaxis may only be related to CXCR4 expression on the tumor cell membrane. KDEL can be retained by receptors on the surface of the intracellular endoplasmic reticulum (ER) and also be called an ER retention signal sequence. So we adopted the KDEL sequence in this study to generate a CXCL12-KDEL fusion protein in combination with a traceable E-tag label. As such, CXCL12 was retained in the ER. Specific receptor CXCR4 binds to the CXCL12-KDEL, was also retained in the ER, and was thus prevented from reaching the oral squamous cancer cell surface. We reduced the cell surface level of CXCR4 and called the technique “intracellular sequestration.” By this way, we have finished blocking of CXCL12-CXCR4 biological axis and inhibiting lymph node metastasis of oral carcinoma.

Sulforaphane and its methylcarbonyl analogs inhibit the LPS-stimulated inflammatory response in human monocytes through modulating cytokine production, suppressing chemotactic migration and phagocytosis in a NF-κB- and MAPK-dependent manner

Sulforaphane [SF; 1-isothiocyanato-4-(methylsulfinyl)-butane], an aliphatic isothiocyanate (ITC) naturally derived from cruciferous vegetables and largely known for its chemopreventive potential also appears to possess anti-inflammatory potential. In this study, structural analogs of SF {compound 1 [1-isothiocyanato-4-(methylcarbonyl)-butane] and 2 [1-isothiocyanato-3-(methylcarbonyl)-propane]} containing a carbonyl group in place of the sulfinyl group in SF, were evaluated for their anti-inflammatory activities. In RAW 264.7 cells, the ITCs at non-toxic concentrations caused an inhibition of NO and prostaglandin E2 (PGE2) release through suppressing expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), as well as a reduction in matrix metalloproteinase-9 (MMP-9) expression, secretion and gelatinolytic activity. Further work performed on human monocytes isolated from blood of healthy donors revealed that the ITCs not only suppressed the expression and release of pro-inflammatory mediators IL-1β, IL-6, TNF-α and MMP-9, but also suppressed their antibody-independent phagocytic and chemotactic migratory abilities. These anti-inflammatory activities were mediated through suppression of the NF-κB and MAPK signaling pathways. In addition, the ITCs were revealed to interact with the cysteines in inhibitor of nuclear factor-κB kinase β subunit (IKKβ), which could contribute at least partly to the suppression of NF-κB signaling. In conclusion, results obtained in this study provide deeper insights into the anti-inflammatory properties of SF and its methylcarbonyl analogs and the underlying mechanisms. These compounds thus serve as promising candidates for clinical applications in controlling inflammatory conditions.

Plasma stromal cell-derived factor 1α/CXCL12 level predicts long-term adverse cardiovascular outcomes in patients with coronary artery disease

OBJECTIVE

Stromal derived factor-1α/CXCL12 is a chemoattractant responsible for homing of progenitor cells to ischemic tissues. We aimed to investigate the association of plasma CXCL12 with long-term cardiovascular outcomes in patients with coronary artery disease (CAD).

METHODS

785 patients aged: 63 ± 12 undergoing coronary angiography were independently enrolled into discovery (N = 186) and replication (N = 599) cohorts. Baseline levels of plasma CXCL12 were measured using Quantikine CXCL12 ELISA assay (R&D systems). Patients were followed for cardiovascular death and/or myocardial infarction (MI) for a mean of 2.6 yrs. Cox proportional hazard was used to determine independent predictors of cardiovascular death/MI.

RESULTS

The incidence of cardiovascular death/MI was 13% (N = 99). High CXCL12 level based on best discriminatory threshold derived from the ROC analysis predicted risk of cardiovascular death/MI (HR = 4.81, p = 1 × 10(-6)) independent of traditional risk factors in the pooled cohort. Addition of CXCL12 to a baseline model was associated with a significant improvement in c-statistic (AUC: 0.67-0.73, p = 0.03). Addition of CXCL12 was associated with correct risk reclassification of 40% of events and 10.5% of non-events. Similarly for the outcome of cardiovascular death, the addition of the CXCL12 to the baseline model was associated with correct reclassification of 20.7% of events and 9% of non-events. These results were replicated in two independent cohorts.

CONCLUSION

Plasma CXCL12 level is a strong independent predictor of adverse cardiovascular outcomes in patients with CAD and improves risk reclassification.

Identification of LY2510924, a novel cyclic peptide CXCR4 antagonist that exhibits antitumor activities in solid tumor and breast cancer metastatic models

Emerging evidence demonstrates that stromal cell-derived factor 1 (SDF-1) and CXCR4, a chemokine and chemokine receptor pair, play important roles in tumorigenesis. In this report, we describe a small cyclic peptide, LY2510924, which is a potent and selective CXCR4 antagonist currently in phase II clinical studies for cancer. LY2510924 specifically blocked SDF-1 binding to CXCR4 with IC50 value of 0.079 nmol/L, and inhibited SDF-1-induced GTP binding with Kb value of 0.38 nmol/L. In human lymphoma U937 cells expressing endogenous CXCR4, LY2510924 inhibited SDF-1-induced cell migration with IC50 value of 0.26 nmol/L and inhibited SDF-1/CXCR4-mediated intracellular signaling. LY2510924 exhibited a concentration-dependent inhibition of SDF-1-stimulated phospho-ERK and phospho-Akt in tumor cells. Biochemical and cellular analyses revealed that LY2510924 had no apparent agonist activity. Pharmacokinetic analyses suggested that LY2510924 had acceptable in vivo stability and a pharmacokinetic profile similar to a typical small-molecular inhibitor in preclinical species. LY2510924 showed dose-dependent inhibition of tumor growth in human xenograft models developed with non-Hodgkin lymphoma, renal cell carcinoma, lung, and colon cancer cells that express functional CXCR4. In MDA-MB-231, a breast cancer metastatic model, LY2510924 inhibited tumor metastasis by blocking migration/homing process of tumor cells to the lung and by inhibiting cell proliferation after tumor cell homing. Collectively, the preclinical data support further investigation of LY2510924 in clinical studies for cancer.

Upregulation of stromal cell-derived factor 1 (SDF-1) is associated with macrophage infiltration in renal ischemia-reperfusion injury

Background

Stromal cell-derived factor-1(SDF-1) is a chemotactic and angiogenic factor that mediates the repair of various tissues. As macrophages are important contributors to ischemic kidney injury, we examine the role of SDF-1 in a rodent model of ischemia-reperfusion (I/R) injury.

Methods

Male wild-type (WT) (C57BL/6) mice were subjected to bilateral I/R injury or sham operation in the presence or absence of macrophage depletion (liposomal clodronate [0.2 ml/20–25 g body weight i.p.]). Macrophage accumulation was assessed by immunohistochemistry. Tissue levels of SDF-1 (ELISA) and SDF-1 mRNA expression (real-time PCR) were measured. The cellular location of SDF-1 was assessed using immunohistochemical staining.

Results

Immunofluorescence staining of renal tissue sections confirmed macrophage depletion by liposomal clodronate. SDF-1 production was elevated in response to I/R injury and was significantly increased upon macrophage depletion. SDF-1 positive cells initially appeared initially in the cortex, and subsequently diffused to the outer medulla after I/R injury.

Conclusions

Our study demonstrates that SDF-1 is significantly upregulated during renal I/R. We hypothesize that SDF-1 upregulation may be an important macrophage effector mechanism during I/R injury.

CCR7 regulates cell migration and invasion through MAPKs in metastatic squamous cell carcinoma of head and neck

Migration and invasion of tumor cells are essential prerequisites for the formation of metastasis in malignant diseases. Previously, we have reported that CC chemokine receptor 7 (CCR7) regulates the mobility of squamous cell carcinoma of head and neck (SCCHN) cells through several pathways, such as integrin and cdc42. In this study, we investigated the connection between CCR7 and mitogen-activated protein kinase (MAPK) family members, and their influence on cell invasion and migration in metastatic SCCHN cells. Western blotting, immunostaining and fluorescence microcopy were used to detect the protein expression and distribution of MAPKs, and the Migration assay, Matrigel invasion assay and wound-healing assay to detect the role of MAPKs in CCR7 regulating cell mobility. To analyze the correlation between CCR7 and MAPK activity and clinicopathological factors immunohistochemical staining was emplyed. The results showed stimulation of CCL19 and the activation of CCR7 could induce ERK1/2 and JNK phosphorylation, while it had no efect on p38. After activation, ERK1/2 and JNK promoted E-cadherin low expression and Vimentin high expression. The MAPK pathway not only mediated CCR7 induced cell migration, but also mediated invasion speed. The immunohistochemistry results showed that CCR7 was correlated with the phosphorylation of ERK1/2 and JNK in SCCHN, and these molecules were all associated with lymph node metastasis. Therefore, our study demonstrates that MAPK members (ERK1/2 and JNK) play a key role in CCR7 regulating SCCHN metastasis.

SDF-1 chemokine signalling modulates the apoptotic responses to iron deprivation of clathrin-depleted DT40 cells

We have previously deleted both endogenous copies of the clathrin heavy-chain gene in the chicken pre B-cell-line DT40 and replaced them with clathrin under the control of a tetracycline-regulatable promoter (Tet-Off). The originally derived cell-line DKO-S underwent apoptosis when clathrin expression was repressed. We have also described a cell-line DKO-R derived from DKO-S cells that was less sensitive to clathrin-depletion. Here we show that the restriction of transferrin uptake, resulting in iron deprivation, is responsible for the lethal consequence of clathrin-depletion. We further show that the DKO-R cells have up-regulated an anti-apoptotic survival pathway based on the chemokine SDF-1 and its receptor CXCR4. Our work clarifies several puzzling features of clathrin-depleted DT40 cells and reveals an example of how SDF-1/CXCR4 signalling can abrogate pro-apoptotic pathways and increase cell survival. We propose that the phenomenon described here has implications for the therapeutic approach to a variety of cancers.

Understanding and exploiting 5T4 oncofoetal glycoprotein expression

Oncofoetal antigens are present during foetal development with generally limited expression in the adult but are upregulated in cancer. These molecules can sometimes be used to diagnose or follow treatment of tumours or as a target for different immunotherapies. The 5T4 oncofoetal glycoprotein was identified by searching for shared surface molecules of human trophoblast and cancer cells with the rationale that they may function to allow survival of the foetus as a semi-allograft in the mother or a tumour in its host, potentially influencing growth, invasion or altered immune surveillance of the host. 5T4 tumour selective expression has stimulated the development of 5T4 vaccine, 5T4 antibody targeted-superantigen and 5T4 antibody-drug therapies through preclinical and into clinical studies. It is now apparent that 5T4 expression is a marker of the use (or not) of several cellular pathways relevant to tumour growth and spread. Thus 5T4 expression is mechanistically associated with the directional movement of cells through epithelial mesenchymal transition, facilitation of CXCL12/CXCR4 chemotaxis, blocking of canonical Wnt/beta-catenin while favouring non-canonical pathway signalling. These processes are highly regulated in development and in normal adult tissues but can contribute to the spread of cancer cells. Understanding the differential impact of these pathways marked by 5T4 can potentially improve existing, or aid development of novel cancer treatment strategies.

VEGFR-3 and CXCR4 as predictive markers for treatment with fluorouracil, leucovorin plus either oxaliplatin or cisplatin in patients with advanced esophagogastric cancer: a comparative study of the Arbeitsgemeinschaft Internistische Onkologie (AIO)

BACKGROUND

Combination of fluoropyrimidines and a platinum derivative are currently standards for systemic chemotherapy in advanced adenocarcinoma of the stomach and gastroesophageal junction (GEJ). Nevertheless, individual likelihood for response to these therapeutic regimes remains uncertain. Even more, no predictive markers are available to determine which patients may benefit more from oxaliplatin versus cisplatin or vice versa. The new invasion and stem cell markers VEGFR-3 and CXCR4 have been linked prognostically with more aggressive esophagogastric cancer types. Thus, we aimed to assess correlations of VEGFR-3 and CXCR4 expression levels with clinical outcome in a randomized phase III study of patients with oxaliplatin/leucovorin/5-FU (FLO) versus cisplatin/leucovorin/5-FU (FLP).

METHODS

The patients data examined in this study (n = 72) were from the collective of the FLO vs. FLP phase III AIO trial. Tumour tissues were stained via immunohistochemistry for VEGFR-3 and CXCR4 expression and results were evaluated by two independent, blinded investigators.Outcome parameter: Survival analysis was calculated for patients receiving FLO vs. FLP in relation to VEGFR-3 and CXCR4 expression.

RESULTS

54% and 36% of the examined tumour tissues showed strong positive expression of VEGFR-3 and CXCR4 respectively. No superiority of each regime was detected in terms of overall survival (OS) in the whole population. Patients with strong expression of CXCR4 on their tumour tissues profited more in terms of OS under the treatment of FLP (mOS: 28 vs 15 months, p = 0.05 respectively). Patients with negative VEGFR-3 and CXCR4 expression had a trend to live longer when FLO regime was applied (mOS: 22 vs. 9 months, p = 0.099 and 20 vs. 10 months, p = 0.073 respectively). In an exploratory analysis of patients older than 60 years at diagnosis, we observed a significant benefit in overall survival for VEGFR-3 and CXCR4-positive patients when treated with FLP (p = 0.002, p = 0.021 respectively).

CONCLUSIONS

CXCR4 positive patients profited in terms of OS from FLP, whereas FLO proved to be more effective in CXCR4 and VEGFR-3 negative patients. Our results suggest, despite the limited size of the study, a predictive value of these biomarkers concerning chemotherapy with FLP or FLO in advanced esophagogastric cancer.

Biased and g protein-independent signaling of chemokine receptors

Biased signaling or functional selectivity occurs when a 7TM-receptor preferentially activates one of several available pathways. It can be divided into three distinct forms: ligand bias, receptor bias, and tissue or cell bias, where it is mediated by different ligands (on the same receptor), different receptors (with the same ligand), or different tissues or cells (for the same ligand–receptor pair). Most often biased signaling is differentiated into G protein-dependent and β-arrestin-dependent signaling. Yet, it may also cover signaling differences within these groups. Moreover, it may not be absolute, i.e., full versus no activation. Here we discuss biased signaling in the chemokine system, including the structural basis for biased signaling in chemokine receptors, as well as in class A 7TM receptors in general. This includes overall helical movements and the contributions of micro-switches based on recently published 7TM crystals and molecular dynamics studies. All three forms of biased signaling are abundant in the chemokine system. This challenges our understanding of “classic” redundancy inevitably ascribed to this system, where multiple chemokines bind to the same receptor and where a single chemokine may bind to several receptors – in both cases with the same functional outcome. The ubiquitous biased signaling confers a hitherto unknown specificity to the chemokine system with a complex interaction pattern that is better described as promiscuous with context-defined roles and different functional outcomes in a ligand-, receptor-, or cell/tissue-defined manner. As the low number of successful drug development plans implies, there are great difficulties in targeting chemokine receptors; in particular with regard to receptor antagonists as anti-inflammatory drugs. Un-defined and putative non-selective targeting of the complete cellular signaling system could be the underlying cause of lack of success. Therefore, biased ligands could be the solution.

Genes related to antiviral activity, cell migration, and lysis are differentially expressed in CD4(+) T cells in human t cell leukemia virus type 1-associated myelopathy/tropical spastic paraparesis patients

Human T cell leukemia virus type 1 (HTLV-1) preferentially infects CD4(+) T cells and these cells play a central role in HTLV-1 infection. In this study, we investigated the global gene expression profile of circulating CD4(+) T cells from the distinct clinical status of HTLV-1-infected individuals in regard to TAX expression levels. CD4(+) T cells were isolated from asymptomatic HTLV-1 carrier (HAC) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients in order to identify genes involved in HAM/TSP development using a microarray technique. Hierarchical clustering analysis showed that healthy control (CT) and HTLV-1-infected samples clustered separately. We also observed that the HAC and HAM/TSP groups clustered separately regardless of TAX expression. The gene expression profile of CD4(+) T cells was compared among the CT, HAC, and HAM/TSP groups. The paxillin (Pxn), chemokine (C-X-C motif ) receptor 4 (Cxcr4), interleukin 27 (IL27), and granzyme A (Gzma) genes were differentially expressed between the HAC and HAM/TSP groups, regardless of TAX expression. The perforin 1 (Prf1) and forkhead box P3 (Foxp3) genes were increased in the HAM/TSP group and presented a positive correlation to the expression of TAX and the proviral load (PVL). The frequency of CD4(+)FOXP3(+) regulatory T cells (Treg) was higher in HTLV-1-infected individuals. Foxp3 gene expression was positively correlated with cell lysis-related genes (Gzma, Gzmb, and Prf1). These findings suggest that CD4(+) T cell activity is distinct between the HAC and HAM/TSP groups.

Matrix metalloproteinase 9 (MMP-9) mediated release of MMP-9 resistant stromal cell-derived factor 1α (SDF-1α) from surface modified polymer films

Preparation of smart materials by coatings of established surfaces with biomolecules will lead to the next generation of functionalized biomaterials. Rejection of implants is still a major problem in medical applications but masking the implant material with protein coatings is a promising approach. These layers not only disguise the material but also equip it with a certain biological function. The anti-inflammatory chemokine stromal cell-derived factor 1α (SDF-1α) is well suited to take over this function, because it efficiently attracts stem cells and promotes their differentiation and proliferation. At least the initial stem cell homing requires the formation of a concentration gradient. Thus, a reliable and robust release mechanism of SDF-1α from the material is essential. Several proteases, most notably matrix metalloproteinases, are upregulated during inflammation, which, in principle, can be exploited for a tightly controlled release of SDF-1α. Herein, we present the covalent immobilization of M-[S4V]-SDF-1α on novel biodegradable polymer films, which consist of heterobifunctional poly(ethylene glycol) and oligolactide-based functionalized macromers. A peptidic linker with a trimeric matrix metalloproteinase 9 (MMP-9) cleavage site (MCS) was used as connection and the linkage between the three components was achieved by combination of expressed protein ligation and Cu(I) catalyzed azide/alkyne cycloaddition. The MCS was used for MMP-9 mediated release of M-[S4V]-SDF-1α from the biomaterial and the released SDF-1α derivative was biologically active and induced strong cell migration, which demonstrates the great potential of this system.

Cell migration to CXCL12 requires simultaneous IKKα and IKKβ-dependent NF-κB signaling

CXCL12 and its unique receptor CXCR4, is critical for the homing of a variety of cell lineages during both development and tissue repair. CXCL12 is particularly important for the recruitment of hemato/lymphopoietic cells to their target organs. In conjunction with the damage-associated alarmin molecule HMGB1, CXCL12 mediates immune effector and stem/progenitor cell migration towards damaged tissues for subsequent repair. Previously, we showed that cell migration to HMGB1 simultaneously requires both IKKβ and IKKα-dependent NF-κB activation. IKKβ-mediated activation maintains sufficient expression of HMGB1's receptor RAGE, while IKKα-dependent NF-κB activation ensures continuous production of CXCL12, which complexes with HMGB1 to engage CXCR4. Here using fibroblasts and primary mature macrophages, we show that IKKβ and IKKα are simultaneously essential for cell migration in response to CXCL12 alone. Non-canonical NF-κB pathway subunits RelB and p52 are also both essential for cell migration towards CXCL12, suggesting that IKKα is required to drive non-canonical NF-κB signaling. Flow cytometric analyses of CXCR4 expression show that IKKβ, but not IKKα, is required to maintain a critical threshold level of this CXCL12 receptor. Time-lapse video microscopy experiments in primary MEFs reveal that IKKα is required both for polarization of cells towards a CXCL12 gradient and to establish a basal level of velocity towards CXCL12. In addition, CXCL12 modestly up-regulates IKKα-dependent p52 nuclear translocation and IKKα-dependent expression of the CXCL12 gene. On the basis of our collective results we posit that IKKα is needed to maintain the basal expression of a critical protein co-factor required for cell migration to CXCL12.

The role of CXCR4 in highly malignant human gliomas biology: current knowledge and future directions

Given the extensive histomorphological heterogeneity of high-grade gliomas, in terms of extent of invasiveness, angiogenesis, and necrosis and the poor prognosis for patients despite the advancements made in therapeutic management. The identification of genes associated with these phenotypes will permit a better definition of glioma heterogeneity, which may ultimately lead to better treatment strategies. CXCR4, a cell surface chemokine receptor, is implicated in the growth, invasion, angiogenesis and metastasis in a wide range of malignant tumors, including gliomas. It is overexpressed in glioma cells according to tumor grade and in glioma tumor initiating cells. There have been various reports suggesting that CXCR4 is required for tumor proliferation, invasion, angiogenesis, and modulation of the immune response. It may also serve as a prognostic factor in characterizing subsets of glioblastoma multiforme, as patients with CXCR4-positive gliomas seem to have poorer prognosis after surgery. Aim of this review was to analyze the current literature on biological effects of CXCR4 activity and its role in glioma pathogenesis. A better understanding of CXCR4 pathway in glioma will lead to further investigation of CXCR4 as a novel putative therapeutic target.

CXCR4 Antagonists

The CXC chemokine receptor 4 (CXCR4) is a widely expressed G protein–coupled receptor implicated in several diseases. In cancer, an increased number of surface CXCR4 receptors, in parallel with aberrant signaling, have been reported to influence several aspects of malignancy progression. CXCR4 activation by the specific ligand C-X-C motif chemokine 12 (CXCL12) induces several intracellular signaling pathways that have been selectively related to malignancy depending on the tissue or cell type. We developed a panel of CXCR4 screening assays investigating Gαi-mediated cyclic adenosine monophosphate modulation, β-arrestin recruitment, and receptor internalization. All of the assays were set up in recombinant cells and were used to test four reported CXCR4 antagonists. Consequently, a set of hit compounds, deriving from a screening campaign of a 30,000-small-molecule internal library, was profiled with the different assays. We identified several compounds showing a pathway-selective activity: antagonists on a Gαi-dependent pathway; antagonists on both the β-arrestin and Gαi-dependent pathways, some of which induce receptor internalization; and compounds with an antagonist behavior in all of the readouts. The identified biased antagonists induce different functional states on CXCR4 and preferentially affect specific downstream responses from the activated receptor, thus providing an improved therapeutic profile for correction of CXCR4 abnormal signaling.

Hypoxia differentially regulated CXCR4 and CXCR7 signaling in colon cancer

BACKGROUND

HIF-1α and CXCR4/CXCL12 have crucial roles in the metastatic process of colorectal cancer. Our aim was to study the significance of targeting HIF-1α and the CXCR4/CXCL12 axis in colorectal cancer to prevent the dissemination process in vitro.

METHODS

We investigated CXCR4 and CXCR7 mRNA and protein expression in human colon carcinomas and the modulation of their expression by hypoxia and HIF-1α in colon cancer cell lines. The migration of tumor cells in a Boyden chamber was studied after CXCR4 inhibition with siRNA or the CXCR4/CXCL12 neutraligand, chalcone 4.

RESULTS

Analysis of a cohort of colon polyps and chromosome-unstable carcinomas showed that the expression of CXCR4 and CXCR7 was similar to that of the normal mucosa in the polyps and early-stage carcinomas but significantly increased in late stage carcinomas. Our data demonstrate that hypoxia strongly induced the expression of CXCR4 transcript and protein at the cell membrane, both regulated by HIF-1α, whereas CXCR7 expression was independent of hypoxia. After transient hypoxia, CXCR4 levels remained stable at the cell membrane up to 48 hours. Furthermore, reducing CXCR4 expression impaired CXCL12-induced Akt phosphorylation, whereas Erk activation remained unchanged. In contrast, reducing CXCR7 expression did not affect Akt nor Erk activation. In the presence of CXCR4 or CXCR7 siRNAs, a significant reduction in cell migration occurred (37% and 17%, respectively). Although irinotecan inhibited cell migration by 20% (p <0.001), the irinotecan and chalcone 4 combination further increased inhibition to 40% (p <0.001).

CONCLUSION

We demonstrated, for the first time, that hypoxia upregulated CXCR4 but not CXCR7 expression in tumor cells and that the CXCR4 receptor protein level remains high at the cell membrane when the tumor cells return to normoxia for up to 48 hours. In addition we showed the interest to inhibit the CXCR4 signaling by inhibiting both the HIF-1α and CXCR4/CXCL12 pathway. CXCR4 seems to be a relevant target because it is continuously expressed and functional both in normoxic and hypoxic conditions in tumor cells.

The inhibitory effect of doxycycline on cisplatin-sensitive and -resistant epithelial ovarian cancer

Background

Detecting a new effective and hypotoxic anticancer drug is an emerging new strategy for cancer chemotherapy. Doxycycline (DC) is a kind of antibiotics but also inhibits tumorigenesis.

Methods

MTT and cell invasion assay, flow cytometry, western-blot analysis and nude mice were used to investigate the effects and underlying mechanisms of doxycycline on epithelial ovarian cancer cells.

Results

Doxycycline inhibited the proliferation and invasion of SKOV3 and SKOV3/DDP; induced moderate apoptosis of SKOV3/DDP. CXCR4 expression at both mRNA and protein levels was downregulated in both cell lines when treated with doxycycline. Akt and ERK1/2 were involved in doxycycline effect on cell proliferation of SKOV3 but not of SKOV3/DDP. Akt and EKR1/2 phosphorylation were activated by SDF-1α, which was then inhibited by doxycycline in SKOV3. Pro-caspase-3 expression was significantly higher in SKOV3 than that in SKOV3/DDP which was upregulated when treated with doxycycline. In vivo, doxycycline inhibited peritoneal tumor xenograft and decreased malignant ascites.

Conclusion

Doxycycline not only has an inhibitory effect on ovarian cancer, but also can increase sensitivity to cisplatin. SDF-1α/CXCR4-regulated Akt and ERK 1/2 activations are probably involved in the antitumor effect of doxycycline on SKOV3 cells, while upregulation of pro-caspase-3 may be the main mechanism involved in SKOV3/DDP cells.

The role of SDF-1α-ECM crosstalk in determining neural stem cell fate

The consequences of central nervous system injury are far-reaching and debilitating and, while an endogenous repair response to neural injury has been observed in recent years, the mechanisms behind this response remain unclear. Neural progenitor/stem cell (NPSC) migration to the site of injury from the neural stem cell niches (e.g. subventricular zone and hippocampus) has been observed to be vasophilic in nature. While the chemotactic stimuli directing NPSC homing to injury is not well established, it is thought to be due in part to an increasing gradient of chemotactic cytokines, such as stromal cell-derived factor 1α (SDF-1α). Based on these recent findings, we hypothesize that critical crosstalk between SDF-1α and the extracellular matrix (ECM) drives injury-induced NPSC behavior. In this study, we investigated the effect of SDF-1α and ECM substrates (Matrigel, laminin, and vitronectin) on the migration, differentiation, and proliferation of NPSCs in vitro using standard assays. The results demonstrated that SDF-1α and laminin-based ECM (Matrigel and laminin) significantly and synergistically enhanced NPSC migration and acute neuronal differentiation. These effects were significantly attenuated with the addition of AMD3100 (an antagonist against the SDF-1α receptor, CXCR4). SDF-1α alone significantly increased NPSC proliferation regardless of ECM substrate, however no synergy was observed between SDF-1α and the ECM. These results serve to elucidate the relationship between adhesive and soluble signaling factors of interest and their effect on NPSC behavior following neural injury. Furthermore, these results better inform the next generation of biomaterials aimed at stimulating endogenous neural regeneration for neural injury and neurodegenerative diseases.

Changes in adipose tissue macrophages and T cells during aging

Adipose tissue historically was believed to be an inert tissue, functioning primarily in the storage of energy and thermal homeostasis. However, recent discoveries point toward a critical role for adipocytes in endocrine function as well as immune regulation. Excess body fat, accumulated through aging and/or a calorie-rich diet, is associated with many chronic metabolic and inflammatory diseases. Within the stromal vascular fraction of adipose tissue, macrophages and T cells accumulate with increasing tissue mass, secreting pro- or anti-inflammatory cytokines. In this review we discuss the current understanding of immune cell function in both diet-induced and age-related obesity. In both models of obesity, the classically activated, pro-inflammatory (M1) subtype takes precedence over the alternatively activated, anti-inflammatory (M2) macrophages, causing tissue necrosis and releasing pro-inflammatory cytokines like interleukin-6. Other distinct adipose tissue macrophage subtypes have been identified by surface marker expression and their functions characterized. Adipose tissue T cell recruitment to adipose tissue is also different between aging- and diet-induced obesity. Under both conditions, T cells exhibit restricted T-cell receptor diversity and produce higher levels of pro-inflammatory signals like interferon-γ and granzyme B relative to young or healthy mice. However, numbers of regulatory T cells are dramatically different between the 2 models of obesity. Taken together, these findings suggest models of age- and diet-induced obesity may be more distinct than previously thought, with many questions yet to be resolved in this multidimensional disease.

Constitutively active chemokine CXC receptors

Chemokines are low-molecular-weight, secreted proteins that act as leukocyte-specific chemoattractants. The chemokine family has more than 40 members. Based on the position of two conserved cysteines in the N-terminal domain, chemokines can be divided into the CXC, C, CC, and CX3C subfamilies. The interaction of chemokines with their receptors mediates signaling pathways that play critical roles in cell migration, differentiation, and proliferation. The receptors for chemokines are G protein-coupled receptors (GPCRs), and thus far, seven CXC receptors have been cloned and are designated CXCR1-7. Constitutively active GPCRs are present in several human immune-mediated diseases and in tumors, and they have provided valuable information in understanding the molecular mechanism of GPCR activation. Several constitutively active CXC chemokine receptors include the V6.40A and V6.40N mutants of CXCR1; the D3.49V variant of CXCR2; the N3.35A, N3.35S, and T2.56P mutants of CXCR3; the N3.35 mutation of CXCR4; and the naturally occurring KSHV-GPCR. Here, we review the regulation of CXC chemokine receptor signaling, with a particular focus on the constitutive activation of these receptors and the implications in physiological conditions and in pathogenesis. Understanding the mechanisms behind the constitutive activation of CXC chemokine receptors may aid in pharmaceutical design and the screening of inverse agonists and allosteric modulators for the treatment of autoimmune diseases and cancers.

Functions of the chemokine receptor CXCR4 in the central nervous system and its regulation by μ-opioid receptors

Activation of the G protein-coupled receptor CXCR4 by its chemokine ligand CXCL12 regulates a number of physiopathological functions in the central nervous system, during development as well as later in life. In addition to the more classical roles of the CXCL12/CXCR4 axis in the recruitment of immune cells or migration and proliferation of neural precursor cells, recent studies suggest that CXCR4 signaling also modulates synaptic function and neuronal survival in the mature brain, through direct and indirect effects on neurons and glia. These effects, which include regulation of glutamate receptors and uptake, and of dendritic spine density, can significantly alter the ability of neurons to face excitotoxic insults. Therefore, they are particularly relevant to neurodegenerative diseases featuring alterations of glutamate neurotransmission, such as HIV-associated neurocognitive disorders. Importantly, CXCR4 signaling can be dysregulated by HIV viral proteins, host HIV-induced factors, and opioids. Potential mechanisms of opioid regulation of CXCR4 include heterologous desensitization, transcriptional regulation and changes in receptor expression levels, opioid-chemokine receptor dimer or heteromer formation, and the newly described modulation by the protein ferritin heavy chain-all leading to inhibition of CXCR4 signaling. After reviewing major effects of chemokines and opioids in the CNS, this chapter discusses chemokine-opioid interactions in neuronal and immune cells, focusing on their potential contribution to HIV-associated neurocognitive disorders.

Bioinformatic analysis of HIV-1 entry and pathogenesis

The evolution of human immunodeficiency virus type 1 (HIV-1) with respect to co-receptor utilization has been shown to be relevant to HIV-1 pathogenesis and disease. The CCR5-utilizing (R5) virus has been shown to be important in the very early stages of transmission and highly prevalent during asymptomatic infection and chronic disease. In addition, the R5 virus has been proposed to be involved in neuroinvasion and central nervous system (CNS) disease. In contrast, the CXCR4-utilizing (X4) virus is more prevalent during the course of disease progression and concurrent with the loss of CD4(+) T cells. The dual-tropic virus is able to utilize both co-receptors (CXCR4 and CCR5) and has been thought to represent an intermediate transitional virus that possesses properties of both X4 and R5 viruses that can be encountered at many stages of disease. The use of computational tools and bioinformatic approaches in the prediction of HIV-1 co-receptor usage has been growing in importance with respect to understanding HIV-1 pathogenesis and disease, developing diagnostic tools, and improving the efficacy of therapeutic strategies focused on blocking viral entry. Current strategies have enhanced the sensitivity, specificity, and reproducibility relative to the prediction of co-receptor use; however, these technologies need to be improved with respect to their efficient and accurate use across the HIV-1 subtypes. The most effective approach may center on the combined use of different algorithms involving sequences within and outside of the env-V3 loop. This review focuses on the HIV-1 entry process and on co-receptor utilization, including bioinformatic tools utilized in the prediction of co-receptor usage. It also provides novel preliminary analyses for enabling identification of linkages between amino acids in V3 with other components of the HIV-1 genome and demonstrates that these linkages are different between X4 and R5 viruses.

Mammalian cardiac regeneration after fetal myocardial infarction requires cardiac progenitor cell recruitment

BACKGROUND

In contrast to the adult, fetal sheep consistently regenerate functional myocardium after myocardial infarction. We hypothesize that this regeneration is due to the recruitment of cardiac progenitor cells to the infarct by stromal-derived factor-1α (SDF-1α) and that its competitive inhibition will block the regenerative fetal response.

METHODS

A 20% apical infarct was created in adult and fetal sheep by selective permanent coronary artery ligation. Lentiviral overexpression of mutant SDF-1α competitively inhibited SDF-1α in fetal infarcts. Echocardiography was performed to assess left ventricular function and infarct size. Cardiac progenitor cell recruitment and proliferation was assessed in fetal infarcts at 1 month by immunohistochemistry for nkx2.5 and 5-bromo-2-deoxyuridine.

RESULTS

Competitive inhibition of SDF-1α converted the regenerative fetal response into a reparative response, similar to the adult. SDF-inhibited fetal infarcts demonstrated significant infarct expansion by echocardiography (p < 0.001) and a significant decrease in the number of nkx2.5+ cells repopulating the infarct (p < 0.001).

CONCLUSIONS

The fetal regenerative response to myocardial infarction requires the recruitment of cardiac progenitor cells and is dependent on SDF1α. This novel model of mammalian cardiac regeneration after myocardial infarction provides a powerful tool to better understand cardiac progenitor cell biology and to develop strategies to cardiac regeneration in the adult.

The chemokine CXCL12 generates costimulatory signals in T cells to enhance phosphorylation and clustering of the adaptor protein SLP-76

The CXC chemokine CXCL12 mediates the chemoattraction of T cells and enhances the stimulation of T cells through the T cell receptor (TCR). The adaptor SLP-76 [Src homology 2 (SH2) domain-containing leukocyte protein of 76 kD] has two key tyrosine residues, Tyr(113) and Tyr(128), that mediate signaling downstream of the TCR. We investigated the effect of CXCL12 on SLP-76 phosphorylation and the TCR-dependent formation of SLP-76 microclusters. Although CXCL12 alone failed to induce SLP-76 cluster formation, it enhanced the number, stability, and phosphorylation of SLP-76 microclusters formed in response to stimulation of the TCR by an activating antibody against CD3, a component of the TCR complex. Addition of CXCL12 to anti-CD3-stimulated cells resulted in F-actin polymerization that stabilized SLP-76 microclusters in the cells' periphery at the interface with antibody-coated coverslips and increased the interaction between SLP-76 clusters and those containing ZAP-70, the TCR-associated kinase that phosphorylates SLP-76, as well as increased TCR-dependent gene expression. Costimulation with CXCL12 and anti-CD3 increased the extent of phosphorylation of SLP-76 at Tyr(113) and Tyr(128), but not that of other TCR-proximal components, and mutation of either one of these residues impaired the CXCL12-dependent effect on SLP-76 microcluster formation, F-actin polymerization, and TCR-dependent gene expression. The effects of CXCL12 on SLP-76 microcluster formation were dependent on the coupling of its receptor CXCR4 to G(i)-family G proteins (heterotrimeric guanine nucleotide-binding proteins). Thus, we identified a costimulatory mechanism by which CXCL12 and antigen converge at SLP-76 microcluster formation to enhance T cell responses.

The Activity of CCL18 is Principally Mediated through Interaction with Glycosaminoglycans

The CC chemokine ligand 18 (CCL18) was first identified as a chemoattractant for naïve T cells. It has been reported to recruit T and B lymphocytes, and we show here, natural killer (NK) cells, but with low efficacy. Investigation of its ability to elicit G-protein-coupled signaling showed that it does not involve extracellular signal-regulated kinase (ERK) phosphorylation, and it is not able to induce receptor internalization, as assessed on CCR3. CCL18 has recently been reported to possess activities unrelated to cellular recruitment, but it had no effect on T lymphocyte proliferation. We postulated that a more potent chemoattractant may be produced under inflammatory conditions but only minor truncations were observed, with the major form being the full-length protein. In view of the lack of potent immunomodulatory properties, we wondered if binding to CCL18 by the tick chemokine binding proteins Evasin-1 and -4 was an artifact of the methods used, but complex formation was confirmed by size exclusion chromatography, and abrogation of its binding to, and antagonism of, CCR3. Its receptor has remained elusive since its cloning in 1997, although it has been reported to induce migration of breast cancer cells by signaling through PITPNM3, but we show that this receptor is not expressed on lymphocytes. We have developed a radiolabeled equilibrium competition binding assay and demonstrated that it bound with high affinity to peripheral blood leukocytes (PBLs), but the binding was displaced similarly by both unlabelled CCL18 as well as heparin. Both heparin binding and binding to PBLs are considerably abrogated by mutation of the BBXB motif in the 40s loop suggesting an essential role of the CCL18-glycosaminoglycan interaction.

Effect of a nitric oxide synthase inhibitor and a CXC chemokine receptor-4 antagonist on tumor growth and metastasis in a xenotransplanted mouse model of adenoid cystic carcinoma of the oral floor

Nitric oxide (NO) is related to angiogenesis and tumor progression and chemokine receptor-4 (CXCR4) plays a central role in cell migration in metastasis and dissemination of cancer. The present study evaluated the effectiveness of a NOS inhibitor and a CXCR4 antagonist, given as single agents or in combination, in a xenotransplanted mouse model of adenoid cystic carcinoma (ACC) of the oral floor. A metastatic tumor (ACCIM) derived from a cervical metastatic lesion of human ACC that was transplantable in nude mice was used. ACCIM showed a high frequency of spontaneous metastasis to the lung when transplanted subcutaneously in nude mice. Mice with subcutaneous transplants of ACCIM were subdivided into six groups and intraperitoneally received one of the following treatments daily for 5 weeks: a) PBS (control), b) AMD3100 (CXCR4 antagonist), c) L-NAME (NOS inhibitor), d) 1400W (iNOS inhibitor), e) both AMD3100 and L-NAME (AMD3100+L-NAME) and f) both AMD3100 and 1400W (AMD3100+1400W). Tumor growth was evaluated during treatment and metastasis was assessed at 28 weeks. Single-agent treatment with AMD3100, L-NAME or 1400W inhibited tumor growth by 20.8, 26.5 and 54.5%, respectively. Combined treatment with AMD3100+L-NAME and AMD3100+1400W inhibited tumor growth remarkably by 48.0 and 50.2%, respectively. Immunohistochemical analysis revealed lower expression of CXCR4, iNOS and eNOS in tumor cells treated with AMD3100+L-NAME or AMD3100+1400W compared to control tumor cells and increased numbers of apoptotic tumor cells were demonstrated using the TUNEL method. CXCR4 expression decreased in 1400W-treated tumors using western blot analysis. When the effect of each agent on tumor-induced angiogenesis in tumor stroma was examined histologically, microvessel density was significantly lower in the groups treated with 1400W, AMD3100+L-NAME or AMD3100+1400W compared to the control, AMD3100 and L-NAME groups. Moreover, treatment with AMD3100 or 1400W markedly inhibited lung metastasis. Our results indicated that single-agent treatment with 1400W and combined treatment with AMD3100+L-NAME or AMD3100+1400W induced apoptosis and significantly inhibited tumor-induced angiogenesis and proliferation of ACCIM in vivo. Blockade of CXCR4 and iNOS was suggested to inhibit lung metastases from ACCIM. CXCR4 and iNOS may, thus, be important prognostic factors for long-term survival in ACC.

Plasma membrane signaling in HIV-1 infection

Plasma membrane is a multifunctional structure that acts as the initial barrier against infection by intracellular pathogens. The productive HIV-1 infection depends upon the initial interaction of virus and host plasma membrane. Immune cells such as CD4+ T cells and macrophages contain essential cell surface receptors and molecules such as CD4, CXCR4, CCR5 and lipid raft components that facilitate HIV-1 entry. From plasma membrane HIV-1 activates signaling pathways that prepare the grounds for viral replication. Through viral proteins HIV-1 hijacks host plasma membrane receptors such as Fas, TNFRs and DR4/DR5, which results in immune evasion and apoptosis both in infected and uninfected bystander cells. These events are hallmark in HIV-1 pathogenesis that leads towards AIDS. The interplay between HIV-1 and plasma membrane signaling has much to offer in terms of viral fitness and pathogenicity, and a better understanding of this interplay may lead to development of new therapeutic approaches. This article is part of a Special Issue entitled: Viral Membrane Proteins - Channels for Cellular Networking.

Effects of CXCR4 gene silencing by lentivirus shRNA on proliferation of the EC9706 human esophageal carcinoma cell line

CXCL12/CXCR4 has been studied as an important biomarker for many human malignancies, but studies are limited for esophageal squamous cell carcinoma (ESCC). In this study, an effective RNAi sequence targeting the CXCR4 gene was selected, a lentiviral shRNA vector was constructed to specifically silence CXCR4 expression in the EC9706 ESCC cell line, and the effects of CXCR4 silencing on cell growth in vitro and tumour growth in nude mice were then evaluated. The expression of CXCR4 in EC9706 was significantly downregulated after transfection with a lentiviral shRNA vector. The expression of the apoptosis-related gene Bcl-2 was decreased. In addition, after CXCR4 inhibition, cell growth was considerably inhibited, increased apoptosis in the EC9706 cells was found, the G0/G1 percentage was significantly increased, and the number of cells in S phase was reduced. Moreover, tumour growth in nude mice was inhibited. In conclusion, the downregulation of CXCR4 expression by transfection with a lentiviral shRNA vector in ESCC cells could inhibit tumour proliferation. Our data may provide an avenue for finding new ESCC treatments.

SDF-1α upregulation of MMP-2 is mediated by p38 MAPK signaling in pancreatic cancer cell lines

Pancreatic cancer is highly invasive and is currently the fourth leading cause of cancer death worldwide. CXC chemokine receptor-4 (CXCR4) is a G protein-coupled receptor for CXC chemokine ligand 12/stromal cell-derived factor-1α (SDF-1α), a member of a large family of small, structurally related, heparin-binding chemokine proteins. SDF-1α/CXCR4 plays an important role in tumor growth, invasion, metastasis, and angiogenesis. SDF-1α and CXCR4 are upregulated in many tumors, including pancreatic cancer tissues, and preliminary data indicate that the SDF-1/CXCR4 axis plays an important role in tumor invasion. However, their precise role and the mechanism through which they function remain largely unknown. In this study, analysis of SDF-1α, CXCR4 and MMP-2 expression in pancreatic cancer and adjacent tissue samples from ten patients revealed that all three proteins are overexpressed in human pancreatic cancer. SDF-1α induced MMP-2 and MMP-9 upregulation in PANC-1 and SW-1990 cells, which was associated with increased pancreatic cancer cell proliferation and invasion. Furthermore, SDF-1α induced p38 phosphorylation and p38 inhibition reduced both the level of SDF-1α-stimulated MMP-2 expression and PANC-1 cell invasion. Overall, our results demonstrate that SDF-1α/CXCR4 upregulates MMP-2 expression and induces pancreatic cancer cell invasion in PANC-1 and SW-1990 cell lines by activating p38 MAPK.

The bone marrow microenvironment in waldenstrom macroglobulinemia

Waldenstrom macroglobulinemia (WM) is a low-grade B-cell lymphoproliferative disorder characterized primarily by specific homing and growth of tumor cells within the bone marrow niches. The progressive growth of tumor cells throughout the bone marrow indicates that the tumor cells are capable of homing and adhering to specific niches that allow growth, survival and drug resistance. In this review we highlight the interaction of the tumor cells in WM and the bone marrow microenvironment including bone marrow stromal cells, endothelial cells and mast cells. Migration, adhesion and downstream activation of signaling pathways leads to cell trafficking and cell dissemination in WM. Future therapeutic agents need to target not only the tumor clone, but also its close interaction with the bone marrow microenvironment.

CXCR4 Expression and Treatment with SDF-1α or Plerixafor Modulate Proliferation and Chemosensitivity of Colon Cancer Cells

BACKGROUND

Signaling through stromal cell-derived factor-1α (SDF-1α), strongly secreted by bone marrow stromal cells and the CXC chemokine receptor 4 (CXCR4) exposed on tumor cells has pivotal roles in proliferation, metastasis, and tumor cell "dormancy." Dormancy is associated with cytostatic drug resistance and is probably a property of tumor stem cells and minimal residual disease. Thus, hampering the SDF-1α/CXCR4 cross talk by a CXCR4 antagonist like Plerixafor (AMD3100) should overcome tumor cell dormancy bymobilization of tumor cells from "sanctuary" niches. Our aim was to elucidate the direct effects exerted by SDF-1α and Plerixafor on proliferation, chemosensitivity, and apoptosis of CXCR4-expressing tumor cells.

METHODS

The ability of SDF-1α and Plerixafor to regulate intracellular signaling, proliferation, and invasion was investigated using two colon cancer cell lines (HT-29 and SW480) with either high endogenous or lentiviral expression of CXCR4 compared to their respective low CXCR4-expressing counterparts as a model system. Efficacy of Plerixafor on sensitivity of these cell lines against 5-fluorouracil, irinotecan, or oxaliplatin was determined in a cell viability assay as well as stroma-dependent cytotoxicity and apoptosis assays.

RESULTS

SDF-1α increased proliferation, invasion, and ERK signaling of endogenously and lentivirally CXCR4-expressing cells. Exposure to Plerixafor reduced proliferation, invasion, and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling. Combination of chemotherapy with Plerixafor showed an additive effect on chemosensitivity and apoptosis in CXCR4-overexpressing cells. An SDF-1-secreting feeder layer provideda"protective niche" for CXCR4-overexpressing cells resulting in decreased chemosensitivity.

CONCLUSION

CXCR4-antagonistic therapy mobilizes and additionally sensitizes tumor cells toward cytoreductive chemotherapy.

Current status of chemokines in the adult CNS

Chemokines - chemotactic cytokines - are small secreted proteins that attract and activate immune and non-immune cells in vitro and in vivo. It has been suggested that chemokines and their receptors play a role in the central nervous system (CNS), in addition to their well established role in the immune system. We focus here on three chemokines-CXCL12 (C-X-C motif ligand 12), CCL2 (C-C motif ligand 2), and CX3CL1 (C-X-3C motif ligand 1) - and their principal receptors - CXCR4 (C-X-C motif receptor 4), CCR2 (C-C motif receptor 2) and CX3CR1 (C-X-3C motif receptor 1), respectively. We first introduce the classification of chemokines and their G-protein coupled receptors and the main signaling pathways triggered by receptor activation. We then discuss the cellular distribution of CXCL12/CXCR4, CCL2/CCR2 and CX3CL1/CX3CR1 in adult brain and the neurotransmission and neuromodulation effects controlled by these chemokines in the adult CNS. Changes in the expression of CXCL12, CCL2 and CX3CL1 and their respective receptors are also increasingly being implicated in the pathogenesis of CNS disorders, such as Alzheimer's disease, Parkinson's disease, HIV-associated encephalopathy, stroke and multiple sclerosis, and are therefore plausible targets for future pharmacological intervention. The final section thus discusses the role of these chemokines in these pathophysiological states. In conclusion, the role of these chemokines in cellular communication may make it possible: (i) to identify new pathways of neuron-neuron, glia-glia or neuron-glia communications relevant to both normal brain function and neuroinflammatory and neurodegenerative diseases; (ii) to develop new therapeutic approaches for currently untreatable brain diseases.

The role of CXCL12-CXCR4 signaling pathway in pancreatic development

Chemokine (C-X-C motif) receptor 4 (CXCR4) is the receptor for chemokine (C-X-C motif) ligand 12 (CXCL12, also known as stromal derived factor-1, Sdf1). CXCR4, a protein consisting 352 amino acids, is known to transduce various signals such as cell differentiation, cell survival, cell proliferation, cell chemotaxis and apoptosis [1, 2]. The expression of CXCR4 is observed in embryonic stem cells, blood cells, haematopoietic stem cells, endothelial cells, angioblasts and smooth muscle cells [3-9]. The CXCL12-CXCR4 signaling pathway has very important roles in the embryonic development. Mutant mice for CXCL12 or CXCR4 genes showed lethality due to defects in neurogenesis, angiogenesis, cardiogenesis, myelopoiesis, lymphopoiesis and germ cell development [10-13]. Recently, we reported that CXCL12-CXCR4 signaling pathway has a crucial role in regional specification of the gut endoderm during early development [14]. Here, we would like to focus on the role of CXCL12-CXCR4 signaling pathway in pancreatic development and summarize recent findings of its role in the induction of the pancreatic progenitor cells.

Regulated expression of CXCR4 constitutive active mutants revealed the up-modulated chemotaxis and up-regulation of genes crucial for CXCR4 mediated homing and engraftment of hematopoietic stem/progenitor cells

SDF-1/CXCR4 axis plays a principle role in the homing and engraftment of hematopoietic stem/progenitor cells (HSPCs), a process that defines cells ability to reach and seed recipient bone marrow niche following their intravenous infusion. However, the proper functioning of CXCR4 downstream signaling depends upon consistent optimal expression of both SDF-1 ligand and its receptor CXCR4, which in turn is variable and regulated by several factors. The constitutive active mutants of CXCR4 (N119A and N119S) being able to induce autonomous downstream signaling, overcome the limitation of ligand-receptor interaction for induction of CXCR4 signaling. Therefore, we intended to explore their potential in Chemotaxis; a key cellular process which crucially regulates cells homing to bone marrow. In present study, Tet-on inducible gene expression vector system was used for doxycycline inducible regulated transgene expression of CXCR4 active mutants in hematopoietic stem progenitor cell line K-562. Both of these mutants revealed significantly enhanced Chemotaxis to SDF-1 gradient as compared to wild type. Furthermore, gene expression profiling of these genetically engineered cells as assessed by microarray analysis revealed the up-regulation of group of genes that are known to play a crucial role in CXCR4 mediated cells homing and engraftment. Hence, this study suggest the potential prospects of CXCR4 active mutants in research and development aimed to improve the efficiency of cells in the mechanism of homing and engraftment process.

Umbilical cord blood-derived stromal cells regulate megakaryocytic proliferation and migration through SDF-1/PECAM-1 pathway

We have previously reported that human umbilical cord blood-derived stromal cells (hUCBDSCs) are able to enhance the expansion of CFU-Meg in vitro, particularly promote the megakaryocytic lineage recovery, and effectively protect the survival of irradiated mice. In this study, we demonstrated that hUCBDSCs secreted SDF-1 to stimulate PECAM-1 expression in HEL cells (MK cell line), and consequently promoted the proliferation and migration of HEL cells. On the other hand, SDF-1 knock down in hUCBDSCs or PECAM-1 knock down in HEL cells diminished or abrogated the above effect. In addition, SDF-1/PECAM-1 probably activated PI3K/Akt and MAPK/ERK1/2 pathways. This report for the first time defines a SDF-1/PECAM-1 signaling pathway in the proliferation and migration of MKs, which provides supportive evidence for the clinical applications of hUCBDSCs in the treatment of megakaryocytic injury.

Transfusion of CXCR4-primed endothelial progenitor cells reduces cerebral ischemic damage and promotes repair in db/db diabetic mice

This study investigated the role of stromal cell-derived factor-1α (SDF-1α)/CXC chemokine receptor 4 (CXCR4) axis in brain and endothelial progenitor cells (EPCs), and explored the efficacy of CXCR4 primed EPCs in treating ischemic stroke in diabetes. The db/db diabetic and db/+ mice were used in this study. Levels of plasma SDF-1α and circulating CD34+CXCR4+ cells were measured. Brain SDF-1α and CXCR4 expression were quantified at basal and after middle cerebral artery occlusion (MCAO). In in vitro study, EPCs were transfected with adenovirus carrying null (Ad-null) or CXCR4 (Ad-CXCR4) followed with high glucose (HG) treatment for 4 days. For pathway block experiments, cells were pre-incubated with PI3K inhibitor or nitric oxide synthase (NOS) inhibitor for two hours. The CXCR4 expression, function and apoptosis of EPCs were determined. The p-Akt/Akt and p-eNOS/eNOS expression in EPCs were also measured. In in vivo study, EPCs transfected with Ad-null or Ad-CXCR4 were infused into mice via tail vein. On day 2 and 7, the cerebral blood flow, neurologic deficit score, infarct volume, cerebral microvascular density, angiogenesis and neurogenesis were determined. We found: 1) The levels of plasma SDF-1α and circulating CD34+CXCR4+ cells were decreased in db/db mice; 2) The basal level of SDF-1α and MCAO-induced up-regulation of SDF-1α/CXCR4 axis were reduced in the brain of db/db mice; 3) Ad-CXCR4 transfection increased CXCR4 expression in EPCs and enhanced EPC colonic forming capacity; 4) Ad-CXCR4 transfection prevented EPCs from HG-induced dysfunction (migration and tube formation) and apoptosis via activation of PI3K/Akt/eNOS signal pathway; 4) Ad-CXCR4 transfection enhanced the efficacy of EPC infusion in attenuating infarct volume and promoting angiogenesis and neurogenesis. Our data suggest that Ad-CXCR4 primed EPCs have better therapeutic effects for ischemia stroke in diabetes than unmodified EPCs do.

Suicide gene reveals the myocardial neovascularization role of mesenchymal stem cells overexpressing CXCR4 (MSC(CXCR4))

Background

Our previous studies indicated that MSC^CXCR4 improved cardiac function after myocardial infarction (MI). This study was aimed to investigate the specific role of MSC^CXCR4 in neovascularization of infarcted myocardium using a suicide gene approach.

Methods

MSCs were transduced with either lentivirus-null vector/GFP (MSC^Null as control) or vector encoding for overexpressing CXCR4/GFP. The MSC derived-endothelial cell (EC) differentiation was assessed by a tube formation assay, Dil-ac-LDL uptake, EC marker expression, and VE-cadherin promoter activity assay. Gene expression was analyzed by quantitative RT-PCR or Western blot. The suicide gene approach was under the control of VE-cadherin promoter. In vivo studies: Cell patches containing MSC^Null or MSC^CXCR4 were transduced with suicide gene and implanted into the myocardium of MI rat. Rats received either ganciclovir (GCV) or vehicle after cell implantation. After one month, the cardiac functional changes and neovascularization were assessed by echocardiography, histological analysis, and micro-CT imaging.

Results

The expression of VEGF-A and HIF-1α was significantly higher in MSC^CXCR4 as compared to MSC^Null under hypoxia. Additionally, MSC^CXCR4 enhanced new vessel formation and EC differentiation, as well as STAT3 phosphorylation under hypoxia. STAT3 participated in the transcription of VE-cadherin in MSC^CXCR4 under hypoxia, which was inhibited by WP1066 (a STAT3 inhibitor). In addition, GCV specifically induced death of ECs with suicide gene activation. In vivo studies: MSC^CXCR4 implantation promoted cardiac functional restoration, reduced infarct size, improved cardiac remodeling, and enhanced neovascularization in ischemic heart tissue. New vessels derived from MSC^CXCR4 were observed at the injured heart margins and communicated with native coronary arteries. However, the derived vessel networks were reduced by GCV, reversing improvement of cardiac function.

Conclusion

The transplanted MSC^CXCR4 enhanced neovascularization after MI by boosting release of angiogenic factors and increasing the potential of endothelial differentiation.

Molecular mechanisms underlying adhesion and migration of hematopoietic stem cells

Hematopoietic stem cell transplantation is the most powerful treatment modality for a large number of hematopoietic malignancies, including leukemia. Successful hematopoietic recovery after transplantation depends on homing of hematopoietic stem cells to the bone marrow and subsequent lodging of those cells in specific niches in the bone marrow. Migration of hematopoietic stem cells to the bone marrow is a highly regulated process that requires correct regulation of the expression and activity of various molecules including chemoattractants, selectins and integrins. This review will discuss recent studies that have extended our understanding of the molecular mechanisms underlying adhesion, migration and bone marrow homing of hematopoietic stem cells.

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

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

Expression and function of CXCR4 in human salivary gland cancers

Salivary gland cancers (SGCs) frequently metastasize to cervical lymph nodes and distant organs. Currently, the mechanisms responsible for the metastatic behavior of SGC cells are not fully understood. We previously demonstrated that the stromal cell-derived factor-1 (SDF-1; also known as CXCL12)/CXCR4 system is involved in the establishment of metastasis in oral squamous cell carcinoma. In the present study, we investigated the role of CXCR4 in the metastatic behavior of SGCs. We examined the expression of CXCR4 mRNA and protein in human SGC cell lines by quantitative RT-PCR and western blotting, respectively. The expression of CXCR4 mRNA and protein were frequently upregulated in 5 out of 6 SGC cell lines. Functional CXCR4 expression was demonstrated by the ability of these SGC cell lines to migrate toward an SDF-1 gradient. SDF-1 rapidly activated extracellular signal-regulated kinase (ERK)1/2 in SGC cell lines. Immunohistochemical analysis revealed that CXCR4 protein expression was detected in either the nucleus or cytoplasm of cancer cells in 16 out of 20 tissues of adenoid cystic carcinoma (ACC) and in 4 out of 6 tissues of mucoepidermoid carcinoma, which are representative of SGC. Furthermore, ACC cell lines exhibited dramatic metastasis to the lung following intravenous inoculation, whereas AMD3100, a CXCR4 antagonist, significantly inhibited lung metastasis of the cells, ameliorated body weight loss and improved the survival rate of tumor-bearing nude mice. These results indicate that CXCR4 expression contributes to the metastatic potential of SGCs.

SDF-1α degrades whereas glycoprotein 120 upregulates Bcl-2 interacting mediator of death extralong isoform: implications for the development of T cell memory

After a primary immune response, T cell memory occurs when a subset of Ag-specific T cells resists peripheral selection by acquiring resistance to TCR-induced death. Recent data have implicated Bcl-2 interacting mediator of death (Bim) as an essential mediator of the contraction phase of T cell immunity. In this article, we describe that stromal-derived factor-1α (SDF-1α) ligation of CXCR4 on activated T cells promotes two parallel processes that favor survival, phospho-inactivation of Foxo3A, as well as Bim extralong isoform (Bim(EL)) degradation, both in an Akt- and Erk-dependent manner. Activated primary CD4 T cells treated with SDF-1α therefore become resistant to the proapoptotic effects of TCR ligation or IL-2 deprivation and accumulate cells of a memory phenotype. Unlike SDF-1α, gp120 ligation of CXCR4 has the opposite effect because it causes p38-dependent Bim(EL) upregulation. However, when activated CD4 T cells are treated with both gp120 and SDF-1α, the SDF-1α-driven effects of Bim(EL) degradation and acquired resistance to TCR-induced death predominate. These results provide a novel causal link between SDF-1α-induced chemotaxis, degradation of Bim(EL), and the development of CD4 T cell memory.

JCV agnoprotein-induced reduction in CXCL5/LIX secretion by oligodendrocytes is associated with activation of apoptotic signaling in neurons

An indispensable role for oligodendrocytes in the protection of axon function and promotion of neuronal survival is strongly supported by the finding of progressive neuron/axon degeneration in human neurological diseases that affect oligodendrocytes. Imaging and pathological studies of the CNS have shown the presence of neuroaxonal injury in progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the CNS, resulting from destruction of oligodendrocytes upon productive replication of the pathogenic neurotropic polyomavirus JC. Here, we examined the extracellular factors involved in communication between oligodendrocytes and neurons. Culturing cortical neurons with conditioned medium (CM) from rat CG4 oligodendrocytic cells that express the JCV agnoprotein showed that CXCL5/LIX, which is a chemokine closely related to the human CXCL5/ENA78 and CXCL6/GCP-2 chemokines, is essential for neuronal cell survival. We found that in CM from agnoprotein-producing CG-4 cells level of CXC5/LIX is decreased compared to control cells. We also demonstrated that a reduced expression of CXCL5/LIX by CG4 GFP-Agno cells triggered a cascade of signaling events in cortical neurons. Analysis of mitogen-activated protein kinases (MAPK) and glycogen synthase kinase (GSK3) pathways showed that they are involved in mechanisms of neuronal apoptosis in response to the depletion of CXCL5/LIX signaling. These data suggest that agnoprotein-induced dysregulation of chemokine production by oligodendrocytes may contribute to neuronal/axonal injury in the pathogenesis of PML lesions.

Role of stromal microenvironment in nonpharmacological resistance of CML to imatinib through Lyn/CXCR4 interactions in lipid rafts

We and others have previously demonstrated that p210 Bcr-Abl tyrosine kinase inhibits stromal cell-derived factor-1α/CXCR4 chemokine receptor signaling, contributing to the deficient adhesion of chronic myeloid leukemia (CML) cells to bone marrow stroma. Conversely, exposure of CML cells to a tyrosine kinase inhibitor (TKI) enhances migration of CML cells towards stromal cell layers and promotes non-pharmacological resistance to imatinib. Src-related kinase Lyn is known to interact with CXCL12/CXCR4 signaling and is directly activated by p210 Bcr-Abl. In this study, we demonstrate that TKI treatment promoted CXCR4 redistribution into the lipid raft fraction, in which it co-localized with active phosphorylated form of Lyn (LynTyr396) in CML cells. Lyn inhibition or cholesterol depletion abrogated imatinib-induced migration, and dual Src/Abl kinase inhibitor dasatinib induced fewer CML cells to migrate to the stroma. These findings demonstrate the novel mechanism of microenvironment-mediated resistance through lipid raft modulation, which involves compartmental changes of the multivalent CXCR4 and Lyn complex. We propose that pharmacological targeting of lipid rafts may eliminate bone marrow-resident CML cells through interference with microenvironment-mediated resistance.