Stromal Cell-derived Factor-1 Receptor Research Articles

Decreasing Intracellular Superoxide Corrects Defective Ischemia-induced New Vessel Formation in Diabetic Mice

Tissue ischemia promotes vasculogenesis through chemokine-induced recruitment of bone marrow-derived endothelial progenitor cells (EPCs). Diabetes significantly impairs this process. Because hyperglycemia increases reactive oxygen species in a number of cell types, and because many of the defects responsible for impaired vasculogenesis involve HIF1-regulated genes, we hypothesized that HIF1 function is impaired in diabetes because of reactive oxygen species-induced modification of HIF1alpha by the glyoxalase 1 (GLO1) substrate methylglyoxal. Decreasing superoxide in diabetic mice by either transgenic expression of manganese superoxide dismutase or by administration of an superoxide dismutase mimetic corrected post-ischemic defects in neovascularization, oxygen delivery, and chemokine expression, and normalized tissue survival. In hypoxic fibroblasts cultured in high glucose, overexpression of GLO1 prevented reduced expression of both the EPC mobilizing chemokine stromal cell-derived factor-1 (SDF-1) and of vascular epidermal growth factor, which modulates growth and differentiation of recruited EPCs. In hypoxic EPCs cultured in high glucose, overexpression of GLO1 prevented reduced expression of both the SDF-1 receptor CXCR4, and endothelial nitric-oxide synthase, an enzyme essential for EPC mobilization. HIF1alpha modification by methylglyoxal reduced heterodimer formation and HIF1alpha binding to all relevant promoters. These results provide a basis for the rational design of new therapeutics to normalize impaired ischemia-induced vasculogenesis in patients with diabetes.

A Novel Bone Morphogenetic Protein Signaling in Heterotypic Cell Interactions in Prostate Cancer

We examined the effect of the extracellular bone morphogenetic protein (BMP) 2 and 7, which are up-regulated in the prostate adenocarcinomas of the conditional Pten deletion mouse model, on primary cultures of cancer-associated fibroblasts (CAF) derived from these tumors. In the CAF, we show that BMP2 or BMP7, but not transforming growth factor beta-1, can strikingly stimulate secretion of stromal cell-derived factor-1 (SDF-1), also known as CXCL12. The CAF cells express type I and type II BMP receptors as well as the receptor for SDF-1, CXCR4. SDF-1 activation is associated with BMP-induced Smad phosphorylation, and the stimulatory effect is blocked by BMP antagonist, noggin. The findings that BMP treatment can increase SDF-1 pre-mRNA levels in a time-dependent manner and actinomycin D treatment can abolish stimulatory effect of BMP suggest a transcriptional modulation of SDF-1 by BMP signaling. Using a human microvascular endothelial cell line, we show that SDF-1 present in the conditioned medium from the stimulated CAF can significantly induce tube formation, an effect relating to angiogenic function. Furthermore, we found that BMP2 can also protect the CAF from serum starvation-induced apoptosis independent of SDF-1, implying that BMP may induce other factors to sustain the survival of these cells. In short, this report establishes a novel BMP-SDF-1 axis in the prostate tumor along with a new prosurvival effect of BMP that when considered together with our previously described oncogenic properties of BMP indicate a circuitry for heterotypic cell interactions potentially critical in prostate cancer.

Stromal Cell-Derived Factor-1 Promotes Myeloma Cell Growth in Both Autocrine and Paracrine Manners

������������������������������������������������������������������������������������������������������������������������������ ������������������������������������������������������������������������������������������ Background: The question as to whether stromal cell-derived factor-1 (SDF-1) stimulated myeloma cell growth has been controversial. We explored the possibility that SDF-1 may function as an autocrine growth factor of myeloma cells. Methods: CD138+ primary bone marrow myeloma cells and myeloma cell lines (RPMI8226, U266, and ARH77) were used. Chemotaxis in response to SDF-1 of the cells was analyzed using TranswellsTM . Cell proliferation was measured by a colorimetric assay. SDF-1 mRNA expression was analyzed by RT-PCR (reverse-transcription-polymerase chain reaction). SDF-1 and interleukin-6 (IL-6) receptor expression as well as signaling molecule phosphorylation levels, were examined using Western blot analysis. Concentrations of SDF-1 in the cell culture supernatants were measured by ELISA assay. Results: SDF-1 alone had no discernible effect on the proliferation of CD138+ primary myeloma cells or myeloma cell lines. In contrast, SDF-1 significantly enhanced IL-6-induced proliferation of these cells. SDF-1 up-regulated the expression of IL-6 receptor and enhanced phosphorylation of AKT in an additive manner with IL-6. Co-culture of the myeloma cells with umbilical vein endothelial cells over-expressing the SDF-1 gene revealed that SDF-1 played an important role in not only the migration of the cells underneath the stromal cells but also the proliferation of the cells in contact with stromal cells. All the myeloma cell lines expressed SDF-1 mRNA, and SDF-1 was detected in the culture supernatants of the cells. The G protein-coupled receptor inhibitor, pertussis toxin, inhibited the proliferation of these cells in suspension cultures. Conclusion: SDF-1, most likely in concert with IL-6, enhanced the proliferation of myeloma cells in a both paracrine and autocrine manner. (Korean J Hematol 2008;43:127-137.)

Hypoxia inhibits the SDF-1-dependent migration of human leukemic cell line HL-60 via blocking of Akt activation

Hypoxia is known to regulate the expression of genes involved in the migration of various cell types. Although many studies have shown that hypoxia increases cell migration, it still remains unclear whether hypoxia could modulate the stromal cell derived factor-1 (SDF-1)-dependent migration of leukemic cell. Herein, we demonstrated that the SDF-1-dependent migration of HL-60, was reduced under hypoxia with no comparable decrease of CXC-type chemokine receptor CXCR4, a cognate receptor for SDF-1. Furthermore, we showed that migration toward SDF-1 was reduced by inactivation of either serine/threonine kinase Akt or extracellular signal regulated kinase Erk, which was confirmed by selective pathway inhibitor LY294002 and PD98059. In our results, phosphorylation of Erk was increased under hypoxia, but phosphorylation of Akt was attenuated on the contrary. These results led us to conclusion that hypoxia could inhibit the SDF-1-dependent migration of HL-60 via blocking of Akt activation.

Involvement of matrix metalloproteinase-9 in stromal cell-derived factor-1/CXCR4 pathway of lung cancer metastasis

Lung caner cells have a striking tendency to metastasize to bone. The chemokine stromal cell-derived factor-1 (SDF-1) is constitutively secreted by osteoblasts and bone marrow stromal cells and plays a key role for homing of hematopoietic cells to the bone marrow. Reverse transcriptase-polymerase chain reaction and flow cytometry studies demonstrated SDF-1 receptor (CXCR4) messenger RNA (mRNA) and surface expression of CXCR4 in lung cancer cell lines, especially higher in those with high invasiveness (A549) as compared with lower level in H928 cells and H1299 cells. SDF-1, osteoblast-conditioned medium (OBCM) and stromal cell-conditioned medium all induced the invasiveness of lung cancer cells. Matrix metalloproteinase (MMP)-9 small interfering RNA inhibited the SDF-1alpha- or OBCM-induced MMP-9 expression and thereby significantly inhibited the SDF-1alpha- or OBCM-induced cell invasion. Furthermore, mitogen-activated protein kinase kinase inhibitor PD98059 suppressed SDF-1alpha-induced MMP-9 mRNA expression. Transient transfection with dominant-negative extracellular signal-regulated kinase (ERK) mutant also showed that the ERK-signaling pathway was involved in SDF-1alpha-induced MMP-9 expression. Moreover, nuclear factor-kappaB (NF-kappaB) decoy oligodeoxynucleotide suppressed the MMP-9 promoter activity enhanced by SDF-1alpha. Both mitogen-activated protein kinase kinase inhibitor and ERK mutant also antagonized SDF-1alpha-induced NF-kappaB-driven luciferase promoter activity. Taken together, our results indicated that bone marrow-derived-SDF-1alpha enhances the invasiveness of lung cancer cells by increasing MMP-9 expression through the CXCR4/ERK/NF-kappaB signal transduction pathway.

Signals on the Move: Chemokine Receptors and Organogenesis in Zebrafish

The chemokine SDF1 (stromal cell-derived factor 1) directs cell migration in many different contexts, ranging from embryogenesis to inflammation. SDF1a is the guidance cue for the zebrafish lateral line primordium, a tissue that moves along the flank of the embryo and deposits cells that form mechanosensory organs. The SDF1a receptor CXCR4b acts in cells at the leading edge of the primordium to direct its migration. Two new studies show that a second SDF1 receptor, CXCR7, is required only in the trailing cells of the primordium, and they explore how these two receptors orchestrate migration of the primordium. CXCR4b and CXCR7 are expressed in complementary domains, possibly through mutual repression in which each receptor inhibits expression of the other. These studies illustrate how the entire primordium can respond to a single signal, yet generate cell type-specific responses by using different receptors.

Insulin-like growth factor 1 enhances the migratory capacity of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are attractive candidates for cell based therapies. However, the mechanisms responsible for stem cell migration and homing after transplantation remain unknown. It has been shown that insulin-like growth factor-1 (IGF-1) induces proliferation and migration of some cell types, but its effects on stem cells have not been investigated. We isolated and cultured MSC from rat bone marrow, and found that IGF-1 increased the expression levels of the chemokine receptor CXCR4 (receptor for stromal cell-derived factor-1, SDF-1). Moreover, IGF-1 markedly increased the migratory response of MSC to SDF-1. The IGF-1-induced increase in MSC migration in response to SDF-1 was attenuated by PI3 kinase inhibitor (LY294002 and wortmannin) but not by mitogen-activated protein/ERK kinase inhibitor PD98059. Our data indicate that IGF-1 increases MSC migratory responses via CXCR4 chemokine receptor signaling which is PI3/Akt dependent. These findings provide a new paradigm for biological effects of IGF-1 on MSC and have implications for the development of novel stem cell therapeutic strategies.

Therapeutic Benefit of Bone Marrow Stromal Cells Administered 1 Month after Stroke

Bone marrow stromal cells (BMSCs) facilitate functional recovery in rats after stroke when administered acutely (1 day) or subacutely (7 days). In this study, we postponed the time of cell transplantation to 1 month after stroke. Female retired breeder rats were subjected to 2 h of middle cerebral artery occlusion (MCAo). Male BMSCs (3 x 10(6)) or phosphate-buffered saline were administered intravenously, and the animals were killed 3 months later. An additional population of nontreated rats was killed at 1 month after MCAo. Significant recovery of behavior was found in BMSC-treated rats beginning at 1 month after cell injection in the modified neurologic severity score test and the adhesive-removal test compared with control animals (P<0.05). In situ hybridization showed that BMSCs survived and preferentially localized to the ipsilateral hemisphere. Double staining revealed that approximately 13% and 6% Y-chromosome-positive cells expressed the astrocyte marker, glial fibrillary acidic protein, and the neuronal marker, microtubule-associated protein-2, respectively. In addition, BMSC treatment reduced scar thickness, and increased the number of proliferating cells and oligodendrocyte precursor cells along the subventricular zone in the ipsilateral hemisphere. Expression of the chemokine stromal-cell-derived factor-1 (SDF-1) was significantly increased along the ischemic boundary zone compared with the corresponding areas in the contralateral hemisphere at 1 month and 4 months (P<0.01) after stroke. The SDF-1 receptor, CXC-chemokine receptor-4 (CXCR4), was expressed in BMSCs both in vitro and in vivo. Our data show that the time window of BMSC therapy is at least 1 month after stroke; the interaction of SDF-1/CXCR4 may contribute to the trafficking of transplanted BMSCs.

Hypoxia-inducible factor 1 and VEGF upregulate CXCR4 in glioblastoma: implications for angiogenesis and glioma cell invasion

Hypoxia and hypoxia-inducible factor-1 (HIF-1) play a critical role in glioblastoma multiforme (GBMs). CXCR4 is involved in angiogenesis and is upregulated by HIF-1alpha. CXCR4 is a chemokine receptor for stromal cell-derived factor-1 (SDF-1)alpha, also known as CXCL12. We hypothesized that CXCR4 would be upregulated by hypoxia in GBMs. First, we investigated the expression of HIF-1alpha and CXCR4 in GBMs. CXCR4 was consistently found colocalized with HIF-1alpha expression in pseudopalisading glioma cells around areas of necrosis. In addition, angiogenic tumor vessels were strongly positive for CXCR4. Next, we tested the in vitro effect of hypoxia and vascular endothelial growth factor (VEGF) on the expression of CXCR4 in glioma cell lines and in human brain microvascular endothelial cells (HBMECs). Exposure to hypoxia induced significant expression of CXCR4 and HIF-1alpha in glioma cells, whereas treatment with exogenous VEGF increased CXCR4 expression in HBMECs. We also transfected U87MG glioma cells with an HIF-1alpha construct and observed that CXCR4 was upregulated in these cells even in normoxic conditions. We then used a lentivirus-mediated shRNA expression vector directed against HIF-1alpha. When exposed to hypoxia, infected cells failed to show HIF-1alpha and CXCR4 upregulation. We performed migration assays under normoxic and hypoxic conditions in the presence or absence of AMD3100, a CXCR4 inhibitor. There was a significant increase in the migration of U87MG and LN308 glioma cells in hypoxic conditions, which was inhibited in the presence of AMD3100. These studies demonstrate the critical role played by hypoxia and CXCR4 in glioma cell migration. Based on these studies, we suggest that hypoxia regulates CXCR4 in GBMs at two levels. First, through HIF-1alpha in the pseudopalisading tumor cells themselves and, secondly, by the VEGF-stimulated angiogenic response in HBMECs. We believe this knowledge may lead to a potentially important two-pronged therapy against GBM progression using chemotherapy targeting CXCR4.

The surface adhesion molecule CXCR4 stimulates mesenchymal stem cell migration to stromal cell-derived factor-1 in vitro but does not decrease apoptosis under serum deprivation

Bone marrow mesenchymal stem cells (MSCs) can be used for myocardial repair following myocardial infarction. Increased expression of stromal cell-derived factor-1 (SDF-1) by an ischemic myocardium attracts CXCR4+ stem cells toward it. CXCR4, the receptor for SDF-1, is important in the migration, homing, and survival of hematopoietic stem cells. Although low levels of CXCR4 expression were found in minor subpopulations of cultured MSCs, most MSCs do not express CXCR4. To optimize the migration and survival of human MSCs, we expressed the CXCR4 gene in these cells using retroviral transduction. We isolated and cultured MSCs from healthy volunteers and transduced them with a retroviral vector containing either CXCR4 and green fluorescent protein (GFP; CXCR4/GFP vector) or GFP alone (control vector). Flow cytometry confirmed successful transduction and GFP and CXCR4 expression. We used a transwell migration system to study MSC migration to SDF-1. We used Annexin V and propidium iodide stains to assess cell survival before and after the survival challenge. Flow cytometry showed that, on average, 83.4+/-17.7% of transduced MSCs expressed CXCR4. Compared with control MSCs, MSCs transduced with CXCR4 showed significantly more migration toward SDF-1, threefold greater at 3 h and more than fivefold greater at 6 h. Mesenchymal stem cells transduced with CXCR4 showed no significant difference in survival under normal to serum-deprived growth conditions. Mesenchymal stem cells can be efficiently transduced to express CXCR4, and transduced MSCs migrate rapidly toward SDF-1. CXCR4 expression does not render survival advantage to MSCs under serum-deprived conditions.

A Stromal Cell Derived Factor 1 (SDF-1) Agonist Stimulates Neutrophil Mobilization in Normal Humans after Subcutaneous Injection.

Abstract Stromal cell-derived factor-1 (SDF-1) is a well known key signaling molecule in the proliferation, homing, engraftment and expansion of hematopoietic stem cells and leukocytes. CTCE-0214, a peptide produced by rational drug design, is an analog of SDF-1 and agonist of the SDF-1 receptor, CXCR4. In vitro and in vivo models have shown that CTCE-0214 mobilized blood and progenitor cells and enhanced the survival and expansion of cord blood cells (Letters in Drug Design and Discovery.1:126, 2004; Exp Hematol.32:470, 2004; Exp Hematol.32:300, 2004; Stem Cells. In press). In this first phase I clinical trial of CTCE-0214, the safety and tolerability of single doses of CTCE-0214 given subcutaneously to healthy subjects as well as the pharmacokinetic profile and the pharmacodynamic effects were studied. The randomized, double-blinded, placebo-controlled dose-escalation trial enrolled 24 subjects in six dose-escalation groups. Four healthy human subjects in each cohort received either CTCE-0214 or Placebo, randomized in a 3:1 ratio. The starting dose for CTCE-0214 was 0.2 mg/kg. Successive dose cohorts received 0.5 mg/kg, 0.8 mg/kg, 1.5 mg/kg, 2.0 mg/kg, and 3.0 mg/kg. CTCE-0214 was shown to be safe with no serious adverse events reported in any of the dose levels studied. The most common drug related adverse events were injection site pain and erythema which were transient and resolved without intervention. The severity of injection site pain appeared to have an association with the overall quantity of study drug administered. Moderate or severe pain was reported only in subjects who received at least 80 mg of CTCE-0214 per syringe. Dilution across more than one syringe appeared to be effective in reducing injection site pain. Pharmacokinetic analysis of CTCE-0214 plasma concentrations showed that Tmax was reached at 0.25 hours post-administration for all CTCE-0214 treated cohorts. The apparent terminal elimination half-life (t1/2) values were estimated to be 0.41 to 0.32 hours. CTCE-0214 administration was associated with significant dose-dependent increases in total white blood cell and neutrophil counts in treated subjects, peaking at around 6 hours post-injection. In the 3.0 mg/kg arm, the mean difference in neutrophil count from baseline was more than three times the corresponding figure in the Placebo arm. The same trend was apparent in the 2.0 and 1.5 mg/kg arms with a greater than two times and two times increases, respectively. These results suggest that SDF-1 agonists may potentially be used in patients with low neutrophil count receiving chemotherapy with or without the use of G-CSF. The potential for CTCE-0214 to mobilize neutrophils and other blood cells merits serious consideration.

Genetic manipulation of stromal cell-derived factor-1 attests the pivotal role of the autocrine SDF-1-CXCR4 pathway in the aggressiveness of breast cancer cells

Stromal cell-derived factor-1 (SDF-1), via its receptor CXCR4, has been implicated in metastasis of cancer, including breast cancer. Exogenous SDF-1 is known to regulate locomotion, chemotaxis and adhesion. The knowledge regarding the effect of autocrine SDF-1 on breast cancer cells is not available. The current study evaluated the effects of SDF-1 on the biological behaviour of breast cancer cells by genetically modifying the expression of SDF-1 in breast cancer cells. Two human breast cancer cell lines (MDA-MB-231 and MDA-MB-435s) and a human fetal lung fibroblast cell line (MRC5) were used. The expression of SDF-1 and the SDF-1 receptor, CXCR4 in the cell lines were studied. Expression cassettes of human SDF-1 and hammerhead ribozyme transgenes specifically targeting human SDF-1 were constructed and used to over-express SDF-1 or to knockout the expression of SDF-1 in cancer cells, respectively. Invasiveness, migration and growth of the genetically modified cells were assessed. SDF-1 was expressed in wild-type human breast cancer cell line MDA-MB-435s and fibroblast cell line MRC5, but not in MDA-MB-231 cell line. In contrast, CXCR4 expression was observed in all three cell lines tested. The ability of invasion and migration was significantly reduced in SDF-1 knockout MDA-MB-435s cells, compared with wild-type and vector control cells (p<0.01). On the other hand, SDF-1 transfected MDA-MB-231epsilonSDF1+/+ cells that stably expressed SDF-1 showed a different behaviour from MDA-MB-231SDF1+/- (plasmid control) and wild-type MDA-MB-231 cells, both being SDF-1 negative. MDA-MB-231epsilonSDF1+/+ cells displayed a higher degree of invasiveness and migration, compared with wild-type and MDA-MB-231SDF+/- cells (p<0.01). Furthermore, SDF1-knockout MDA-MB-435s cells showed a slower growth rate over a 7-day period compared with the respective control and wild-type MDA-MB-435s cells. In contrast, the growth of the SDF-1 transfected MDA-MB-231SDF1+/+ cells was markedly enhanced when compared with wild-type and vector control cells. Breast cancer cell lines, when equipped with the autocrine SDF-1-CXCR4 signal pathway, display aggressive behaviour, including an increase in invasiveness, migration together with faster growth. SDF-1, together with its receptor CXCR4 may provide important information for predicting the aggressive nature and constitute important therapeutic targets in human breast cancer.

The elevated level of CXCR4 is correlated with nodal metastasis of human breast cancer

CXCR4, the receptor for stromal cell-derived factor-1(SDF-1), belongs to the chemokine receptor family and has been shown to play an important role in regulating the directional migration of breast cancer cells to sites of metastasis. In the present study, we evaluated the expression of CXCR4 and its association with pathological features and clinical outcome in human breast cancer. Expression of CXCR4 in eight breast cancer cell lines and breast cancer tissues was investigated using conventional PCR. Levels of CXCR4 transcript and protein were examined in human breast cancer tissues (n=120) and corresponding normal tissues (n=32) using real-time quantitative PCR and immunohistochemistry, respectively. The level of CXCR4 expression was analyzed against tumour types, grade, nodal status, recurrence, metastasis, and survival over a median 120 month follow-up period. The expression of CXCR4 was detected in all breast cancer cell lines examined, as well as in breast cancer tissues and breast normal tissues. Breast cancer tissues highly expressed CXCR4 compared with corresponding normal tissues (P=0.029). The level of CXCR4 expression showed a significant difference between node-positive group and node-negative group (19+/-13 vs. 49.7+/-9, respectively, P=0.03). The level of CXCR4 expression was marginal, yet statistically insignificant, higher in tumours from patients with metastatic disease compared with those who remained disease free. No correlation was seen between levels of CXCR4 and the overall survival, although at higher levels of CXCR4 linked to shorter disease free survival (113.0 vs. 136.7 months in patients with low CXCR4, P=0.14, Cox proportional test). The level of CXCR4 expression is significantly correlated with lymph node metastasis. The elevated levels of CXCR4 suggest that the patient has high possibility of lymph node metastasis. CXCR4 may be a useful prognostic indicator and a potential therapeutic target in cancer therapies in patients with breast cancer.

Circulating CD26 Is Negatively Associated with Inflammation in Human and Experimental Arthritis

Dipeptidyl peptidase IV (DPPIV, CD26), a protease-cleaving N-terminal X-Pro dipeptide from selected proteins including some chemokines, is expressed both as a soluble form in plasma and on the cell surface of various immune and nonimmune cell types. To gain insights into the pathophysiological role of CD26 in arthritis, we explored DPPIV/CD26 expression during murine antigen-induced arthritis (AIA), an experimental model of arthritis. AIA induction led to reduced plasma DPPIV activity. In CD26-deficient mice, the severity of AIA was increased as assessed by enhanced technetium uptake and by increased histological parameters of inflammation (synovial thickness and exudate). We demonstrated that CD26 controls the in vivo half-life of the intact active form of the proinflammatory chemokine stromal cell-derived factor-1 (SDF-1). CD26-deficient mice exhibited increased levels of circulating active SDF-1, associated with increased numbers of SDF-1 receptor (CXCR4)-positive cells infiltrating arthritic joints. In a clinical study, plasma levels of DPPIV/CD26 from rheumatoid arthritis patients were significantly decreased when compared to those from osteoarthritis patients and inversely correlate with C-reactive protein levels. In conclusion, decreased circulating CD26 levels in arthritis may influence CD26-mediated regulation of the chemotactic SDF-1/CXCR4 axis.

Plasma Levels of SDF-1 and Expression of SDF-1 Receptor on Multiply Myeloma Cells of Human Multiply Myeloma.

Abstract Multiple myeloma(MM) is a monoclonal expansion of malignant cells with a plasmablast-plasma cell morphology that is almost exclusively localized to the bone marrow, except at the final stages of disease, when they proliferate in the extramedullary area. The mechanisms of the selective homing of MM cells to the bone marrow compartment are poorly understood. The chemokine stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 contribute to stem cell homing and play a role in trafficking of leukemic cells. In this study we have investigated expression and biological behavior of SDF-1/CXCR4 in MM-derived cell lines and primary MM cells. FACS and RT-PCR analysis was used to study the expression of CXCR4 and ICAM-1(CD54) on the surface of MM cells from 4 IL-6 dependant cell lines (XG1,XG2,XG6 and XG7) and 25 freshly isolated tumor samples from patients with diagnosed MM. Mononuclear cells were purified by positive selection of magnetical and FACS sorting. Chemotaxis assay through transwell bore polycaronate and ELISA assay were employed to monitor the SDF-1, IL-6, and sICAM-1 levels. We found that[circ1]Fresh MM cells and MM cell lines expressed various levels of functional CXCR4 ranging from 23.1% to 77.7%,which was correlated with the in vitro migration ability of MM cells[(23.2±1.08)%, P&lt;0.01]; [circ2]SDF-1 levels in the bone marrow(BM) of MM patients were significantly higher than the those of healthy persons (3489.23±651.63)pg/ml, (2818.57±597.79)pg/ml, P&lt;0.05; but plasma levels of SDF-1 in peripheral blood of MM patients were lower than those of healthy persons[(1973±133)pg/ml, (2334.857±574.92), P=0.062]; [circ3]Plasma levels of PCL(4097.14±680.71) were significantly higher than those of healthy persons, P&lt;0.01. The results firstly demonstrated abnormal expression of SDF-1 and its receptor CXCR4 on Human MM cells, which is closely correlated with the migration of MM cells. Furthermore, we discovered that SDF-1 could up-regulate the expression of ICAM-1 on MM cells; the plasma level of soluble ICAM-1 was correlated with the expression of CXCR4 on MM cells. These findings suggested that SDF-1/CXCR4 axis play a key role on the trafficking of MM cells via mediating the effect of adhesion molecules. Moreover, we observed higher plasma levels of IL-6 in PB of 60% MM patients compared with those of healthy individuals. Finally, the levels of IL-6 were closely correlated with SDF-1 levels (γ=0.8, P&lt;0.01), These data indicated that in the IL-6-dependent myeloma cell lines or fresh myeloma samples and myeloma cell growth triggered by SDF-1 maybe due to up-regulation of autocrine and paracrine IL-6 by myeloma cells and stromal cells in BM. The results suggested that the expression of CXCR4 have an essential role in the proliferation and migration of myeloma cells in patients with multiple myeloma.In conclusion, MM cells expressed various levels of functional CXCR4, which were correlated with the migration ability of MM cells in vitro; SDF-1/CXCR4 axis plays a key role in the trafficking of MM cells via mediating the effect of adhesion molecules; The plasma levels of IL-6 closely correlated with SDF-1 plasma levels, myeloma cell growth triggered by SDF-1 may be due to up-regulation of autocrine and paracrine IL-6 by myeloma cells and stromal cells in BM. All these suggested that the expression of CXCR4 play an essential role in the proliferation and migration of myeloma cells in patients with multiple myeloma.

Intracellular Localization and Constitutive Endocytosis of CXCR4 in Human CD34+Hematopoietic Progenitor Cells

CXCR4, the stromal cell-derived factor-1 receptor, plays an important role in the migration of hematopoietic progenitor/stem cells. The surface and cytoplasmic expression of CXCR4 on human hematopoietic CD34(+) cells was investigated. We show that its surface expression is low, whereas a large part of CXCR4 protein is sequestered intracellularly. Using confocal microscopy, we demonstrated that CXCR4 is colocalized with EEA-1, Rab5, Rab4, and Rab11, which are localized in early and recycling endosomes. No significant colocalization of CXCR4 with lysosomal markers CD63 and Lamp-1 was detected. Using antibody feeding experiments, we report a role for CXCR4 constitutive endocytosis in subcellular localization in stably transduced UT7-CXCR4-GFP and CD34(+) cells. Agonist-independent endocytosis of CXCR4 occurs through clathrin-coated vesicles. These data implicate a constitutive endocytosis in the regulation of CXCR4 membrane expression and suggest that constitutive endocytosis may be involved in the regulation of trafficking the human hematopoietic progenitor/stem cells to and in the bone marrow microenvironment.

Recruitment of osteoclast precursors by stromal cell derived factor-1 (SDF-1) in giant cell tumor of bone

Giant cell tumor (GCT) of bone is a unique bone lesion that is characterized by an excessive number of multinucleated osteoclasts. GCT consists of neoplastic stromal cells, multinucleated osteoclasts and their precursors, thus serving as a naturally occurring human disease model for the study of osteoclastogenesis. It still remains unclear how stromal cells of GCT recruit osteoclast precursors. In the present study, we characterized the cellular components of GCT and confirmed the presence of CD14(+)-monocytes/CD68(+)-macrophages and CD34(+)-hematopoetic stem cells that express CXCR4, a specific receptor for SDF-1; SDF-1 gene expression and presence of SDF-1 protein were confirmed by real time RT-PCR, in situ hybridization, and immunohistochemistry in the GCT tissue and cultured cells. SDF-1 was present at 25-50 ng/ml in the conditioned media from the GCT cultures, which is in the range of physiological chemotactic concentration. Migration of osteoclast precursors was 2.5-fold higher in response to GCT conditioned media compared to the control media; and migration was inhibited by an average of 36% with anti-SDF-1 neutralizing antibody or competing recombinant SDF-1. These results suggest that SDF-1 is one of the significant chemoattractant factors involved in the recruitment of hematopoietic osteoclast precursor cells during tumor-induced osteoclastogenesis.

Investigation of CXCR4 in squamous cell carcinoma of the tongue

Cancer metastasis is not a random process and different cancer types have favorite metastatic sites. Recent studies on metastasis have focused on chemoattraction, particularly on the role of chemokines. Therefore, in this study we investigated whether CXCR4 (receptor for stromal cell-derived factor-1) is expressed in squamous cell carcinoma of the tongue. For this purpose, immunohistochemical staining was performed on 26 sections obtained from 23 patients (15 patients having tongue tumor without lymph node metastasis and eight patients having lymph node metastasis). All tumor cells expressed CXCR4, whereas normal mucosa of the tongue had no or faint expression CXCR4. Metastatic tumor cells in lymph nodes had stronger expression than primary tongue tumor cells. Our data raises the possibility that CXCR4 could be involved in lymph node metastasis of oral squamous cell carcinoma.

HGF, SDF-1, and MMP-9 are involved in stress-induced human CD34+ stem cell recruitment to the liver.

Hematopoietic stem cells rarely contribute to hepatic regeneration, however, the mechanisms governing their homing to the liver, which is a crucial first step, are poorly understood. The chemokine stromal cell-derived factor-1 (SDF-1), which attracts human and murine progenitors, is expressed by liver bile duct epithelium. Neutralization of the SDF-1 receptor CXCR4 abolished homing and engraftment of the murine liver by human CD34+ hematopoietic progenitors, while local injection of human SDF-1 increased their homing. Engrafted human cells were localized in clusters surrounding the bile ducts, in close proximity to SDF-1-expressing epithelial cells, and differentiated into albumin-producing cells. Irradiation or inflammation increased SDF-1 levels and hepatic injury induced MMP-9 activity, leading to both increased CXCR4 expression and SDF-1-mediated recruitment of hematopoietic progenitors to the liver. Unexpectedly, HGF, which is increased following liver injury, promoted protrusion formation, CXCR4 upregulation, and SDF-1-mediated directional migration by human CD34+ progenitors, and synergized with stem cell factor. Thus, stress-induced signals, such as increased expression of SDF-1, MMP-9, and HGF, recruit human CD34+ progenitors with hematopoietic and/or hepatic-like potential to the liver of NOD/SCID mice. Our results suggest the potential of hematopoietic CD34+/CXCR4+cells to respond to stress signals from nonhematopoietic injured organs as an important mechanism for tissue targeting and repair.

New insights into the actions of bisphosphonate zoledronic acid in breast cancer cells by dual RhoA-dependent and -independent effects.

Zoledronic acid (ZOL) is a nitrogen-containing bisphosphonate and its use in reducing osteoporosis and cancer-induced osteolysis is increasing. Recent findings indicated that ZOL has a direct effect on cancer cells. In this study, the effect of ZOL was examined on the aggressive MDA-MB-231 breast cancer cell line. ZOL induces an important inhibition of cell invasion at low concentrations (1 μM). This is not explained by modifications of proteases involved in cell invasiveness (matrix metalloproteinases and urokinase-type plasminogen activator), but by a disorganisation of actin cytoskeleton due to RhoA inhibition related to its defective prenylation as it was reversed by geranylgeraniol (GGOH) and mimicked by the Rho selective inhibitor C3 exoenzyme. In addition, ZOL inhibits the chemotactic effect induced by stromal cell-derived factor 1(SDF-1), a chemokine greatly involved in cancer metastasis to bone. This effect is related to both reduction of cell motility induced by RhoA inhibition and to a decreased expression of CXCR-4, the SDF-1 receptor. Finally, ZOL reduces Cox-2 expression and, consequently, the secretion of prostaglandins E2 (PGE2) in a RhoA-independent manner. This inhibition could contribute to bone protection in breast cancers because PGE2 stimulates osteoclast-mediated bone resorption. In summary, new insights in the mechanism of ZOL action on aggressive breast cancer cells are demonstrated and could explain its beneficial action in both the reduction of osteolysis and prevention of metastasis.