Cloning and characterizing mutated human stromal cell-derived factor-1 (SDF-1): C-terminal alpha-helix of SDF-1alpha plays a critical role in CXCR4 activation and signaling, but not in CXCR4 binding affinity

TILRR Promotes Migration of Immune Cells Through Induction of Soluble Inflammatory Mediators

TILRR has been identified as an important modulator of inflammatory responses. It is associated with NF-κB activation, and inflammation. Our previous study showed that TILRR significantly increased the expression of many innate immune responsive genes and increased the production of several pro-inflammatory cytokines/chemokines by cervical epithelial cells. In this study, we evaluated the effect of TILRR-induced pro-inflammatory cytokines/chemokines on the migration of immune cells. The effect of culture supernatants of TILRR-overexpressed cervical epithelial cells on the migration of THP-1 monocytes and MOLT-4 T-lymphocytes was evaluated using Transwell assay and a novel microfluidic device. We showed that the culture supernatants of TILRR-overexpressed HeLa cells attracted significantly more THP-1 cells (11–40%, p = 0.0004–0.0373) and MOLT-4 cells (14–17%, p = 0.0010–0.0225) than that of controls. The microfluidic device-recorded image analysis showed that significantly higher amount with longer mean cell migration distance of THP-1 (p < 0.0001–0.0180) and MOLT-4 (p < 0.0001–0.0025) cells was observed toward the supernatants of TILRR-overexpressed cervical epithelial cells compared to that of the controls. Thus, the cytokines/chemokines secreted by the TILRR-overexpressed cervical epithelial cells attracted immune cells, such as monocytes and T cells, and may potentially influence immune cell infiltration in tissues.

GPRASP proteins are critical negative regulators of hematopoietic stem cell transplantation

Hematopoietic stem cell (HSC) transplantation (HSCT) is often exploited to treat hematologic disease. Donor HSCs must survive, proliferate, and differentiate in the damaged environment of the reconstituting niche. Illuminating molecular mechanisms regulating the activity of transplanted HSCs will inform efforts to improve HSCT. Here, we report that G-protein-coupled receptor-associated sorting proteins (GPRASPs) function as negative regulators of HSCT. Silencing of Gprasp1 or Gprasp2 increased the survival, quiescence, migration, niche retention, and hematopoietic repopulating activity of hematopoietic stem and progenitor cells (HSPCs) posttransplant. We further show that GPRASP1 and GPRASP2 promote the degradation of CXCR4, a master regulator of HSC function during transplantation. CXCR4 accumulates in Gprasp-deficient HSPCs, boosting their function posttransplant. Thus, GPRASPs negatively regulate CXCR4 stability in HSCs. Our work reveals GPRASP proteins as negative regulators of HSCT and CXCR4 activity. Disruption of GPRASP/CXCR4 interactions could be exploited in the future to enhance the efficiency of HSCT.

A Novel CXCR4 Targeting Protein SDF-1/54 as an HIV-1 Entry Inhibitor

CXC chemokine receptor 4 (CXCR4) is a co-receptor for HIV-1 entry into target cells. Its natural ligand, the chemokine SDF-1, inhibits viral entry mediated by this receptor. However, the broad expression pattern of CXCR4 and its critical roles in various physiological and pathological processes indicate that the direct application of SDF-1 as an entry inhibitor might have severe consequences. Previously, we constructed an effective SDF-1 mutant, SDF-1/54, by deleting the α-helix of the C-terminal functional region of SDF-1. Of note, SDF-1/54 shows remarkable decreased chemotoxic ability, but maintains a similar binding affinity to CXCR4, suggesting SDF-1/54 might better serve as a CXCR4 inhibitor. Here, we found that SDF-1/54 exhibited potent antiviral activity against various X4 HIV-1 strains, including the infectious clone HIV-1 NL4-3, laboratory-adapted strain HIV-1 IIIB, clinical isolates and even drug-resistant strains. By using time-of-addition assay, non-infectious and infectious cell–cell fusion assay and CXCR4 internalization assay, we demonstrated SDF-1/54 is an HIV-1 entry inhibitor. A combination of SDF-1/54 with several antiretroviral drugs exhibited potent synergistic anti-HIV-1 activity. Moreover, SDF-1/54 was stable and its anti-HIV-1 activity was not significantly affected by the presence of seminal fluid, vaginal fluid simulant and human serum albumin. SDF-1/54 showed limited in vitro cytotoxicity to lymphocytes and vaginal epithelial cells. Based on these findings, SDF-1/54 could have a therapeutic potential as an HIV-1 entry inhibitor.

Human Parvovirus B19 (B19V) Up-regulates CXCR4 Surface Expression of Circulating Angiogenic Cells: Implications for Cardiac Ischemia in B19V Cardiomyopathy

Background

Human parvovirus B19 (B19V) infection and damage of circulating angiogenic cells (CAC) results in dysfunctional endogenous vascular repair (DEVR) with secondary end-organ damage. Trafficking of CAC is regulated by SDF-1α and the respective receptor CXCR4. We thus tested the hypothesis of a deregulated CXCR4/SDF-1α axis in symptomatic B19V-cardiomyopathy.

Methods

CAC were infected in vitro with B19V and transfected with B19V-components. Read-out were: CXCR4-expression and migratory capacity at increasing doses of SDF-1α. In 31 patients with chronic B19V-cardiomyopathy compared to 20 controls read-outs were from blood: migratory capacity, CXCR4 expression on CAC, serum SDF-1α; from cardiac biopsies: SDF-1α mRNA, HIF-1α mRNA, microvascular density, resident cardiac stem cells (CSC), transcardiac gradients of CAC.

Results

In vitro B19V-infected CAC showed up-regulation of surface CXCR4 with increased migratory capacity further enhanced by elevated SDF-1α concentrations. Overexpression of the B19V capsid protein VP2 was associated with this effect. Chronic B19V-cardiomyopathy patients showed increased numbers of ischaemia mobilised CAC but DEVR as well as diminished numbers of CAC after transcardiac passage. Cardiac microvascular density and CSC were significantly reduced in B19V-cardiomyopathy.

Conclusions

We thus conclude that B19V infection has a direct VP2-mediated negative impact on trafficking of CAC in the presence of impaired cardiac regeneration.

Phenotypic Knockout of CXCR4 Expression by a Novel Intrakine Mutant hSDF-1α/54/KDEL Inhibits Breast Cancer Metastasis

Many malignant tumors express high levels of the chemokine receptor CXCR4, and the interaction between CXCR4 and its ligand, SDF-1, promotes migration, invasion, and metastasis of breast cancer cells. Therefore, blocking the interaction between CXCR4 and SDF-1 could alter the tumor's metastatic phenotype and control the development and progression of cancers. We used a cellular phenotypic knockout strategy and developed a novel recombinant gene, AdSDF-1α/54/KDEL, which contains an adenovirus vector, a mutant form of SDF-1 that lacks a C-terminal α-helix, and a KDEL tetrapeptide sequence that promotes retention at the endoplasmic reticulum (ER). We hypothesized that SDF-1α/54/KDEL could efficiently block metastasis of breast cancer cells with less inflammatory side effects than SDF-1α/KDEL. Using the MCF-7 cell line, which expresses a stable, high level of CXCR4, we found that SDF-1α/54/KDEL efficiently becomes localized at the ER of tumor cells, where it specifically binds to newly synthesized CXCR4 and prevents it from reaching the cell surface. Chemotaxis and invasion assays revealed that the cells treated with SDF-1α/54/KDEL failed to migrate toward SDF-1. We also found that SDF-1α/54/KDEL impaired lung metastasis of metastatic breast cancer by decreasing CXCR4 on the cell surface. The novel recombinant gene, SDF-1α/54/KDEL, played an instrumental role in blocking SDF-1/CXCR4-mediated cell migration, and we found that this gene-based strategy for targeting the SDF-1/CXCR4 axis offers a very effective alternative method for preventing metastasis of breast cancer and other cancers expressing high levels of CXCR4.

Cardiac regeneration and diabetes

The prevalence of diabetes continues to increase world-wide and is a leading cause of morbidity, mortality, and rapidly rising health care costs. Although strict glucose control combined with good pharmacological and non-pharmacologic interventions can increase diabetic patient life span, the frequency and mortality of myocardial ischemia and infarction remain drastically increased in diabetic patients. Therefore, more effective therapeutic approaches are urgently needed. Over the past 15 years, cellular repair of the injured adult heart has become the focus of a rapidly expanding broad spectrum of pre-clinical and clinical research. Recent clinical trials have achieved favorable initial endpoints with improvements in cardiac function and clinical symptoms following cellular therapy. Due to the increased risk of cardiac disease, cardiac regeneration may be one strategy to treat patients with diabetic cardiomyopathy and/or myocardial infarction. However, pre-clinical studies suggest that the diabetic myocardium may not be a favorable environment for the transplantation and survival of stem cells due to altered kinetics in cellular homing, survival, and in situ remodeling. Therefore, unique conditions in the diabetic myocardium will require novel solutions in order to increase the efficiency of cellular repair following ischemia and/or infarction. This review briefly summarizes some of the recent advances in cardiac regeneration in non-diabetic conditions and then provides an overview of some of the issues related to diabetes that must be addressed in the coming years.

Improving the design of the agarose spot assay for eukaryotic cell chemotaxis

Migration of cells along gradients of effector molecules, i.e., chemotaxis, is necessary in immune response and is involved in development and cancer metastasis. The experimental assessment of chemotaxis thus is of high interest. The agarose spot assay is a simple tissue culture system used to analyze chemotaxis. Although direction sensing requires gradients to be sufficiently steep, how the chemical gradients developed in this assay change over time, and thus, under what conditions chemotaxis is plausible, has not yet been determined. Here, we use numerical solution of the diffusion equation to determine the chemoattractant gradient produced in the assay. Our analysis shows that, for the usual spot size, the lifetime of the assay is optimized if the chemoattractant concentration in the spot is initially 30 times the dissociation constant of the chemoattractant-receptor bond. This result holds regardless of the properties of the chemoattractant. With this initial concentration, the chemoattractant gradient falls to the minimum threshold for directional sensing at the same time that the concentration drops to the optimal level for detecting gradient direction. If a higher initial chemoattractant concentration is used, the useful lifetime of the assay is likely to be shortened because receptor saturation may decrease the cells' sensitivity to the gradient; lower initial concentrations would result in too little chemoattractant for the cells to detect. Moreover, chemoattractants with higher diffusion coefficients would sustain gradients for less time. Based on previous measurements of the diffusion coefficients of the chemoattractants EGF and CXCL12, we estimate that the assay will produce gradients that cells can sense for a duration of 10 h for EGF and 5 h for CXCL12. These gradient durations are comparable to what can be achieved with the Boyden chamber assay. The analysis presented in this work facilitates determination of suitable parameters for the assay, and can be used to assess whether observed cell motility is likely due to chemotaxis or chemokinesis.

Carboxypeptidase M in apoptosis, adipogenesis and cancer

This review covers carboxypeptidase M (CPM) research that appeared in the literature since 2009. The focus is on aspects that are new or interesting from a clinical perspective. Available research tools are discussed as well as their pitfalls and limitations. Evidence is provided to suggest the potential involvement of CPM in apoptosis, adipogenesis and cancer. This evidence derives from the expression pattern of CPM and its putative substrates in cells and tissues. In recent years CPM emerged as a potential cancer biomarker, in well differentiated liposarcoma where the CPM gene is co-amplified with the oncogene MDM2; and in lung adenocarcinoma where coexpression with EGFR correlates with poor prognosis. The available data call for extended investigation of the function of CPM in tumor cells, tumor-associated macrophages, stromal cells and tumor neovascularisation. Such experiments could be instrumental to validate CPM as a therapeutic target.

Development and application of fluorescent SDF-1 derivatives

Background: SDF-1/CXCR4 signaling plays key roles in directed cell migration under physiological and pathological conditions. To develop agonist-based CXCR4 probes for detection of CXCR4 expression on cell lines and metastatic tumors, SAR analyses of fluorescent SDF-1 derivatives were carried out. Results: Several SDF-1 derivatives with a single fluorescent label were designed and synthesized. Modification of the SDF-1 C-terminus with AlexaFluor® 488 or tetramethylrhodamine provided potent CXCR4 probes. Using a potent probe, a novel binding inhibition assay was established for biological evaluation of potential CXCR4 ligands. Conclusion: SDF-1 derivatives with C-terminal modification exhibit equipotent binding with CXCR4 and an alternative SDF-1 receptor CXCR7 to unlabeled SDF-1. The SDF-1 derivatives are applicable to flow cytometry to detect the receptor expression and identify binding compounds for CXCR4.

CXCL12 and [N33A]CXCL12 in 5637 and HeLa cells: regulating HER1 phosphorylation via calmodulin/calcineurin

In the human neoplastic cell lines 5637 and HeLa, recombinant CXCL12 elicited, as expected, downstream signals via both G-protein-dependent and β-arrestin-dependent pathways responsible for inducing a rapid and a late wave, respectively, of ERK1/2 phosphorylation. In contrast, the structural variant [N33A]CXCL12 triggered no β-arrestin-dependent phosphorylation of ERK1/2, and signaled via G protein-dependent pathways alone. Both CXCL12 and [N33A]CXCL12, however, generated signals that transinhibited HER1 phosphorylation via intracellular pathways. 1) Prestimulation of CXCR4/HER1-positive 5637 or HeLa cells with CXCL12 modified the HB-EGF-dependent activation of HER1 by delaying the peak phosphorylation of tyrosine 1068 or 1173. 2) Prestimulation with the synthetic variant [N33A]CXCL12, while preserving CXCR4-related chemotaxis and CXCR4 internalization, abolished HER1 phosphorylation. 3) In cells knockdown of β-arrestin 2, CXCL12 induced a full inhibition of HER1 like [N33A]CXCL12 in non-silenced cells. 4) HER1 phosphorylation was restored as usual by inhibiting PCK, calmodulin or calcineurin, whereas the inhibition of CaMKII had no discernable effect. We conclude that both recombinant CXCL12 and its structural variant [N33A]CXCL12 may transinhibit HER1 via G-proteins/calmodulin/calcineurin, but [N33A]CXCL12 does not activate β-arrestin-dependent ERK1/2 phosphorylation and retains a stronger inhibitory effect. Therefore, we demonstrated that CXCL12 may influence the magnitude and the persistence of signaling downstream of HER1 in turn involved in the proliferative potential of numerous epithelial cancer. In addition, we recognized that [N33A]CXCL12 activates preferentially G-protein-dependent pathways and is an inhibitor of HER1.

C-terminal clipping of chemokine CCL1/I-309 enhances CCR8-mediated intracellular calcium release and anti-apoptotic activity

Carboxypeptidase M (CPM) targets the basic amino acids arginine and lysine present at the C-terminus of peptides or proteins. CPM is thought to be involved in inflammatory processes. This is corroborated by CPM-mediated trimming and modulation of inflammatory factors, and expression of the protease in inflammatory environments. Since the function of CPM in and beyond inflammation remains mainly undefined, the identification of natural substrates can aid in discovering the (patho)physiological role of CPM. CCL1/I-309, with its three C-terminal basic amino acids, forms a potential natural substrate for CPM. CCL1 plays a role not only in inflammation but also in apoptosis, angiogenesis and tumor biology. Enzymatic processing differently impacts the biological activity of chemokines thereby contributing to the complex regulation of the chemokine system. The aim of the present study was to investigate whether (i) CCL1/I-309 is prone to trimming by CPM, and (ii) the biological activity of CCL1 is altered after C-terminal proteolytic processing. CCL1 was identified as a novel substrate for CPM in vitro using mass spectrometry. C-terminal clipping of CCL1 augmented intracellular calcium release mediated by CCR8 but reduced the binding of CCL1 to CCR8. In line with the higher intracellular calcium release, a pronounced increase of the anti-apoptotic activity of CCL1 was observed in the BW5147 cellular model. CCR8 signaling, CCR8 binding and anti-apoptotic activity were unaffected when CPM was exposed to the carboxypeptidase inhibitor DL-2-mercaptomethyl-3-guanidino-ethylthiopropanoic acid. The results of this study suggest that CPM is a likely candidate for the regulation of biological processes relying on the CCL1-CCR8 system.

Selective labelling of stromal cell-derived factor 1α with carboxyfluorescein to study receptor internalisation

SDF1α plays an important role in the regeneration of injured tissue after ischemia or stroke by inducing the migration of progenitor cells. In order to study the function of this therapeutically relevant chemokine site-specific protein labelling is of great interest. However, modification of SDF1α is complicated because of its complex tertiary structure. Here, we describe the first site-specific fluorescent modification of SDF1α by EPL. We recombinantly expressed SDF1α (1-49) by intein-mediated protein expression. The C-terminal peptide SDF1α (50-68) was synthesised by SPPS and selectively labelled with carboxyfluorescein at Lys(56). In a cell migration assay, M-[K(56)(CF)]SDF1α showed a clear potency to induce chemotaxis of human T-cell leukaemia cells. Microscopic analysis on HEK293 cells transfected with the CXCR4 revealed specific binding of the fluorescent ligand. Furthermore, receptor-induced internalisation of the ligand could be visualised. These results show that site-specific modification of SDF1α yields in a biologically functional molecule that allows the characterisation of CXCR4 production of cells on a molecular level.

The potent anti-HIV activity of CXCL12gamma correlates with efficient CXCR4 binding and internalization

We previously demonstrated that the naturally occurring splice variant stromal cell-derived factor 1gamma/CXCL12gamma is the most potent CXCL12 isoform in blocking X4 HIV-1, with weak chemotactic activity. A conserved BBXB domain (B for basic and X for any residue) located in the N terminus ((24)KHLK(27)) is found in all six isoforms of CXCL12. To determine whether the potent antiviral activity of CXCL12gamma is due to the presence of the extra C-terminal BBXB domains, we mutated each domain individually as well as in combination. Although binding of CXCL12gamma to heparan sulfate proteoglycan (HSPG) was 10-fold higher than that observed with CXCL12alpha, the results did not demonstrate a direct correlation between HSPG binding and the potent antiviral activity. CXCL12gamma mutants lacking the conserved BBXB domain (designated gammaB1) showed increased binding to HSPG but reduced anti-HIV activity. In contrast, the mutants lacking the C-terminal second and/or third BBXB domain but retaining the conserved domain (designated B2, B3, and B23) showed decreased binding to HSPG but increased anti-HIV activity. The B2, B3, and B23 mutants were associated with enhanced CXCR4 binding, receptor internalization, and restored chemotaxis. Internalization of CXCR4 was more potent with CXCL12gamma than with CXCL12alpha and was significantly reduced when the conserved BBXB domain was mutated. We concluded that the observed potent anti-HIV-1 activity of CXCL12gamma is due to increased affinity for CXCR4 and to efficient receptor internalization.

A novel CXCR4 antagonist derived from human SDF-1beta enhances angiogenesis in ischaemic mice

AIMS

The effects on angiogenesis of a novel CXC chemokine receptor 4 (CXCR4) antagonist, SDF-1betaP2G, derived from human stromal cell-derived factor-1beta (SDF-1beta), were examined in a model of hind limb ischaemia in mice.

METHODS AND RESULTS

The antagonistic activities of SDF-1betaP2G against CXCR4 were evaluated in vitro and in vivo and compared with phosphate-buffered saline and AMD3100 (a small bicyclam antagonist of SDF-1). Angiogenesis, muscle regeneration and the expression of pro-angiogenic factors were evaluated in ischaemic gastrocnemius muscles. Distant toxic effects of SDF-1betaP2G were evaluated by inflammatory and apoptotic markers. SDF-1betaP2G induced CXCR4 internalization and competitively inhibited the chemotaxis of SDF-1beta but did not mediate migration, calcium influx, or the phosphorylation of Akt and extracellular signal-regulated kinase in cultured T-lymphoblastic leukaemia cells or H9C2 cells. SDF-1betaP2G enhanced blood flow, angiogenesis, and muscle regeneration in ischaemic hind limbs, and the enhancement was significantly better than that of AMD3100. Markers of angiogenesis and progenitor cell migration, including phosphorylated Akt, vascular endothelial growth factor (VEGF), SDF-1 and CXCR4, were up-regulated by SDF-1betaP2G and co-localized with CD31-positive cells. Neutralization of VEGF with its specific antibody abolished SDF-1betaP2G-induced blood reperfusion and angiogenesis. No apparent inflammatory and apoptotic effects were found in heart, liver, kidneys, and testes after SDF-1betaP2G administration.

CONCLUSION

Our findings indicate that the novel CXCR4 antagonist, SDF-1betaP2G, can efficiently enhance ischaemic angiogenesis, blood flow restoration, and muscle regeneration without apparent adverse effects, most likely through a VEGF-dependent pathway.

SDF-1/54-DCN: a novel recombinant chimera with dual inhibitory effects on proliferation and chemotaxis of tumor cells

Several studies have shown that the interaction of CXC chemokine receptor 4 (CXCR4) with its ligand, stromal cell-derived factor-1alpha (SDF-1alpha) is closely involved in the directional migration of some tumors toward specific organs, which provides a new pathway against cancer metastasis. We previously developed an alpha-helix-defective mutant of SDF-1alpha, SDF-1/54 that displays obvious antagonistic activity to CXCR4. But it is necessary to ensure the targeting of SDF-1/54 to tumors in vivo since many normal tissues also express CXCR4. It is known that most tumor cells highly express epidermal growth factor receptor (EGFR). Meanwhile, decorin (DCN), a specific antagonist of EGFR, can target the tumor cells enriched in EGFR and cause a significant downregulation of EGFR. Hereby, we further generated a fusion construct of SDF-1/54 and DCN to expect to enhance the targeting of SDF-1/54 to tumors by dual blocking effects on CXCR4 and EGFR. This study focused on expression of recombinant chimera SDF-1/54-DCN in Escherichia coli, purification and bioactivity to inhibit the physiological functions mediated by CXCR4 and EGFR respectively in various tumor cell lines in vitro. Results indicated that SDF-1/54-DCN could inhibit both chemotaxis and proliferation of the tumor cells we used, which may be attributed to its blocking to CXCR4 and EGFR. These findings suggest that this strategy to link SDF-1/54 with DCN may be a promising approach to increase the targeting of SDF-1/54 to the tumors coexpressing CXCR4 and EGFR.

Maltose binding protein facilitates high-level expression and functional purification of the chemokines RANTES and SDF-1alpha from Escherichia coli

The chemokines RANTES (regulated on activation, normal T cell expressed and secreted) and SDF-1alpha (stromal cell-derived factor-1alpha) are important regulators of leukocyte trafficking and homing. Chemokines form insoluble inclusion bodies when expressed in Escherichia coli (E. coli), resulting in low yields of soluble protein. We have developed a novel chemokine expression system that generates a high amount of soluble protein and uses a simple purification scheme. We cloned different types of RANTES and SDF-1alpha fused to either maltose binding protein (MBP) or glutathione-S-transferase (GST) and expressed the fusion proteins in E. coli under various conditions. We found that the yield of soluble chemokine is influenced by the type of fusion partner. Fusion to MBP resulted in a higher yield of total and soluble chemokine compared to GST. Under optimized conditions, the yield of soluble MBP-RANTES and MBP-SDF-1alpha was 2.5- and 4.5-fold higher than that of the corresponding GST-fusion protein, respectively. Recombinant chemokine fusion proteins exhibited specific binding activity to chemokine receptors. These results demonstrate that the use of MBP-fusion proteins may provide an approach to generating high yields of soluble and functional chemokines, such as RANTES and SDF-1alpha.

Carboxypeptidase M expressed by human bone marrow cells cleaves the C-terminal lysine of stromal cell-derived factor-1alpha: another player in hematopoietic stem/progenitor cell mobilization?

Carboxypeptidase M (CPM) is a membrane-bound zinc-dependent protease that cleaves C-terminal basic residues, such as arginine or lysine, from peptides/proteins. We examined whether CPM is expressed by hematopoietic and stromal cells and could degrade stromal cell-derived factor (SDF)-1alpha, a potent chemoattractant for hematopoietic stem/progenitor cells (HSPC). We found that (a) CPM transcript is expressed by bone marrow (BM) and mobilized peripheral blood CD34(+) cells, myeloid, erythroid, and megakaryocytic cell progenitors, mononuclear cells (MNC), polymorphonuclear cells (PMN), and stromal cells, including mesenchymal stem cells; and that (b) granulocyte-colony-stimulating factor (G-CSF) significantly increases its expression at the gene and protein levels in MNC and PMN. Moreover, we found that recombinant CPM cleaves full-length SDF-1alpha (1-68) rapidly, removing the C-terminal lysine and yielding des-lys SDF-1alpha (1-67). We demonstrated that such CPM treatment of SDF-1alpha reduced the in vitro chemotaxis of HSPC, which, however, was preserved when the CPM was exposed to the carboxypeptidase inhibitor dl-2-mercaptomethyl-3-guanidino-ethylthiopropanoic acid. Thus, we present evidence that CPM is expressed by cells occurring in the BM microenvironment and that the mobilizing agent G-CSF strongly upregulates it in MNC and PMN. We suggest that cleavage of the C-terminal lysine residue of SDF-1alpha by CPM leads to attenuated chemotactic responses and could facilitate G-CSF-induced mobilization of HSPC from BM to peripheral blood.

The synergistic effects of CXCR4 and EGFR on promoting EGF-mediated metastasis in ovarian cancer cells

CXC chemokine receptor 4 (CXCR4) is a cell surface receptor that has been reported to mediate the metastasis of many solid tumors including ovarian, breast, lung and prostate. The over-expression of the epidermal growth factor receptor (EGFR) is associated with the majority of ovarian cancer and has been implicated in the process of malignant transformation by promoting cell proliferation, survival, and motility. In this research, the result first showed that epidermis growth factor (EGF) enhanced the expression of CXCR4 and the migration of ovarian cancer cells, moreover, both stromal cell derived factor-1alpha (SDF-1alpha) and EGF-induced high matrix metallopeptidase 9 (MMP9) expressions. Molecular analysis indicated that augmented CXCR4 and MMP9 expression was regulated by phosphatidylinositol-3-kinase(PI3K)/Akt signal transduction pathway. These results suggested a possible important "cross-talk" between CXCR4 and EGFR intracellular pathways that might link signals of tumor deteriorated and provided a plausible explanation for the poor overall survival rate of patients whose co-expression of CXCR4 and EGFR was detected in their tissue sections. It enlightened that, compared to the respective inhibition of the EGFR or CXCR4 signaling, the simultaneous inhibition of them might be a more useful therapeutic strategy of cancer.