CXC Chemokine Receptor 4 Pathway Research Articles

The significance of the SDF-1/CXCR4 signaling pathway in the normal development.

Chemokines are chemoattractants that can regulate cell movement and adhesion. SDF-1 [stromal cell-derived factor-1 (SDF-1)] is a homeostatic CXC chemokine. SDF-1 and its receptors [CXC chemokine receptor 4 (CXCR4)] form a signaling pathway that plays critical roles in different pathological and physiological mechanisms, including embryogenesis, wound healing, angiogenesis, tumor growth, and proliferation. Therefore, the current review aimed to summarize the related studies that addressed the molecular signature of the SDF-1/CXCR4 pathway and to explain how this axis is involved in normal events.

Coadministration of Curcumin and Hydromorphone Hydrochloride Alleviates Postoperative Pain in Rats.

This study aimed to explore the effect of curcumin and hydromorphone hydrochloride (HH) cotreatment on postoperative pain in rats. An incision + formaldehyde-induced pain rat model was established. Rats were treated with vehicle, curcumin, HH, or curcumin + HH. Paw mechanical withdrawal threshold and thermal withdrawal latency were measured at 1 d before surgery as well as 1 , 2 h, 1 , 3 , and 7 d after surgery to assess pain sensitivity. The L4-6 region of the spinal cord was collected from each rat at 2 h, 1 , 3 , and 7 d after surgery. Western blot analysis and immunohistochemical staining were carried out to detect the protein expression of pain-related genes. Quantitative real-time PCR and enzyme-linked immunosorbent assay were conducted to measure the expression and production of proinflammatory mediators. Compared with other groups, Curcumin + HH significantly reduced pain sensitivity in the model rats. Mechanistically, curcumin + HH suppressed protein expression of stromal cell-derived factor-1 (SDF-1), CXC chemokine receptor 4 (CXCR4), p-Akt, and c-fos while enhancing protein expression of nerve growth factor (NGF) in the dorsal root ganglia (DRG) of model rats. Curcumin + HH inhibited the expression and production of interleukin 1β (IL-1β), cyclooxygenase-2 (COX-2), tumor necrosis factor α (TNF-α), and p65 nuclear factor kappa B (NF-κB) in the DRG. Coadministration of curcumin and HH alleviates incision + formaldehyde-induced pain in rats, possibly by suppressing the SDF-1/CXCR4 pathway and the production of proinflammatory mediators. Our results provide curcumin and HH cotreatment as a promising therapeutic strategy in the management of postoperative pain.

Targeted blockade of immune mechanisms inhibit B precursor acute lymphoblastic leukemia cell invasion of the central nervous system

SummaryAcute lymphoblastic leukemia (ALL) dissemination to the central nervous system (CNS) is a challenging clinical problem whose underlying mechanisms are poorly understood. Here, we show that primary human ALL samples injected into the femora of immunodeficient mice migrate to the skull and vertebral bone marrow and provoke bone lesions that enable passage into the subarachnoid space. Treatment of leukemia xenografted mice with a biologic antagonist of receptor activator of nuclear factor κB ligand (RANKL) blocks this entry route. In addition to erosion of cranial and vertebral bone, samples from individuals with B-ALL also penetrate the blood-cerebrospinal fluid barrier of recipient mice. Co-administration of C-X-C chemokine receptor 4 (CXCR4) and RANKL antagonists attenuate both identified routes of entry. Our findings suggest that targeted RANKL and CXCR4 pathway inhibitors could attenuate routes of leukemia blast CNS invasion and provide benefit for B-ALL-affected individuals.

Hypermethylation of microRNA-149 activates SDF-1/CXCR4 to promote osteogenic differentiation of mesenchymal stem cells.

MicroRNAs (miRs) involve in osteogenic differentiation and osteogenic potential of mesenchymal stem cells (MSCs). Accordingly, the present study aimed to further uncover role miR-149 plays in osteogenic differentiation of MSCs with the involvement of the stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor-4 (CXCR4) pathway. Initially, the osteogenic differentiation model was induced. Next, the positive expression of STRO-1 in periosteum, alkaline phosphatase (ALP) activity, osteocalcin (OCN) protein content, and the calcium deposition in MSCs were determined. MSCs were treated with DNA methyltransferase inhibitor 5-aza-CdR, SDF-1 neutralizing antibody, or CXCR4 antagonist AMD3100 to investigate their roles in osteogenic differentiation; with the expression of CD44, CD90, CD14, and CD45 detected. Furthermore, the levels of SDF-1 and CXCR4, and the genes related to stemness (Nanog, Oct-4, and Sox-2) were measured to explore the effects of miR-149. The obtained data revealed the upregulation of STRO-1 in the periosteum. miR-149 could specifically bind to SDF-1. Besides, increased miR-149 methylation, higher ALP activity and OCN content, decreased positive rates of CD44 and CD90, and increased positive rates of CD14 and CD45 were found in osteogenic differentiation of MSCs. Subsequently, 5-Aza-CdR treatment reversed the above-mentioned effects. MSCs were finally treated with SDF-1 neutralizing antibody or AMD3100 to decrease Nanog, Oct-4, and Sox-2 expression. Taken together these results, miR-149 hypermethylation has the potential to activate the SDF-1/CXCR4 pathway and further promote osteogenic differentiation of MSCs.

AMD3100 inhibits epithelial-mesenchymal transition, cell invasion, and metastasis in the liver and the lung through blocking the SDF-1α/CXCR4 signaling pathway in prostate cancer.

Stromal cell-derived factor-1 (SDF-1) and CXC chemokine receptor 4 (CXCR4) have been found to be tightly correlated with the progression of prostate cancer (PC). In this study, we investigated the effects of an SDF-1α/CXCR4 inhibitor, AMD3100, on cell progression and metastasis potential of human PC cells. Human PC cell lines (LNCaP, PC3, and DU145) were cultured to detect SDF-1α/CXCR4, which showed higher SDF-1α and CXCR4 expression than the normal human prostate epithelial cell line, RWPE-1. AMD3100 was confirmed to be an inhibitor of SDF-1α, and to detect the effect of SDF-1α/CXCR4 inhibition on PC, PC cells were treated with AMD3100 or/and CXCR4 siRNA. The results suggested that inhibition of the SDF-1α/CXCR4 pathway could promote the E-cadherin level but inhibit the levels of invasion and migration of vimentin, N-cadherin and α5β1 integrin. Finally, tumor formation in nude mice was conducted, and the cell experiment results were verfied. These data show that AMD3100 suppresses epithelial-mesenchymal transition and migration of PC cells by inhibiting the SDF-1α/CXCR4 signaling pathway, which provides a clinical target in the treatment of PC.

NT21MP negatively regulates paclitaxel-resistant cells by targeting miR‑155‑3p and miR‑155-5p via the CXCR4 pathway in breast cancer.

Evidence has shown that microRNAs (miRNAs) are vital in cell growth, migration, and invasion by inhibiting their target genes. A previous study demonstrated that miRNA (miR)-155-3p and miR-155-5p exerted opposite effects on cell proliferation, apoptosis, migration and invasion in breast cancer cell lines. An miRNA microarray was used to show that miR-155-3p was downregulated whereas miR-155-5p was upregulated in paclitaxel-resistant (PR) cells compared with parental breast cancer cells. However, the role of miR-155 in breast cancer cell invasion and metastasis remains to be elucidated. A 21-residue peptide derived from the viral macrophage inflammatory protein II (NT21MP), competes with the ligand of CXC chemokine receptor 4 (CXCR4) and its ligand stromal cell-derived factor-1α, inducing cell apoptosis in breast cancer. The present study aimed to identify the underlying mechanism of action of miR-155-3p/5p and NT21MP in PR breast cancer cells. Quantitative polymerase chain reaction, western blotting, wound-healing, cell cycle and apoptosis assays, and Cell Counting kit-8 assay were used to achieve this goal. The combined overexpression of miR-155-3p with NT21MP decreased the migration and invasion ability and increased the number of apoptotic and arrested cells in the G0/G1 phase transition in vitro. The knockdown of miR-155-5p combined with NT21MP had a similar effect on PR breast cancer cells. Furthermore, the ectopic expression of their target gene myeloid differentiation primary response gene 88 (MYD88) or tumor protein 53-induced nuclear protein 1 (TP53INP1) combined with NT21MP enhanced the sensitivity of the breast cancer cells to paclitaxel. Taken together, these findings suggested that miR-155-3p/5p and their target genes MYD88 and TP53INP1 may serve as novel biomarkers for NT21MP therapy through the CXCR4 pathway for improving sensitivity to paclitaxel in breast cancer.

The Function of SDF-1-CXCR4 Axis in SP Cells-Mediated Protective Role for Renal Ischemia/Reperfusion Injury by SHH/GLI1-ABCG2 Pathway.

Renal ischemia-reperfusion (I/R) injury ranks as the primary cause of acute renal injury with severe morbidity and mortality. Side population (SP) cells have recently drawn increasing attention due to their critical role in injury repair and regeneration. Unfortunately, the underlying mechanism involved in renal I/R remains poorly elucidated. Here, pronounced increases of stromal cell-derived factor-1 (SDF-1) and its receptor CXC chemokine receptor 4 (CXCR4) were substantiated in I/R kidneys from C57BL/6 mice subjected to clamp the bilateral renal pedicles to mimic renal ischemia. Similar up-regulation of them was also determined in SP cells upon simulated ischemia/reperfusion (SI/R). In contrast to non-SP cells, SP cells exhibited higher viability, apoptosis resistance, chemotaxis, and paracrine actions following SI/R treatment, and these were further enhanced after SDF-1 stimulation. Interestingly, blocking CXCR4 signaling with AMD3100 notably ameliorated the above effects. Mechanism analysis corroborated that SDF-1/CXCR4 further induced the expression of ATP-binding cassette transporter ABCG2, an essential element for SP-mediated kidney regeneration after renal I/R injury. Moreover, AMD3100 pretreatment strikingly attenuated ABCG2 elevation in SP cells. Additionally, sonic hedgehog (SHH)-Gli 1 signaling was involved in SDF-1/CXCR4-mediated ABCG2 expression. When SP cells pretreated with AMD3100 were intravenously injected into I/R mice, SP cell-mediated decreases in blood urea nitrogen, serum creatinine, and histological score of kidney were noticeably attenuated, indicating that blocking CXCR4 pathway mitigated the therapeutic function of SP cells in renal I/R injury. Together, this research suggests that SDF-1/CXCR4 axis might act, via Shh-Gli1-ABCG2 signaling, as a positive regulator of SP cell-based therapies for renal I/R by Shh-Gli 1-ABCG2 signaling.

CXCR4/CXCL12/CXCR7 axis is functional in neuroendocrine tumors and signals on mTOR.

ObjectiveTo evaluate the possible crosstalk between C-X-C chemokine receptor 4 (CXCR4)/C-X-C motif chemokine 12 (CXCL12)/C-X-C chemokine receptor 7 (CXCR7) axis with the mammalian target of rapamycin (mTOR) pathway in neuroendocrine tumors (NETs).MethodsSixty-one human NETs were included into the study. CXCR4/CXCL12/CXCR7 axis and mTOR pathway were assessed by qRT-PCR and immunohistochemistry (IHC). The effect of mTOR inhibitor, RAD001, was evaluated on CXCR4 pathway through proliferation and p-Erk and p-AKT induction. Results: CXCR4/CXCL12/CXCR7 axis and p-mTOR were found to be active and correlated with grading, Ki67 index and tumor stage. mTOR pathway activation significantly correlated with poor prognosis. In human NET cells, CXCL12 induced mTOR signalling while AMD3100 (CXCR4-antagonist) impaired it. The mTOR-antagonist, RAD001, impaired the CXCL12-dependent induction of CXCR4 downstream effectors. Combination of AMD3100 and RAD001 potentiate cell growth inhibition.ConclusionsCXCR4/CXCL12/CXCR7 axis is active in NETs and signals on mTOR. CXCR4 might be considered a prognostic factor in NETs. Combined treatment with AMD3100 and RAD001 may provide clinical benefits in NET patients with drug-resistant.

Serum ubiquitin via CXC chemokine receptor 4 triggered cyclooxygenase-1 ubiquitination possibly involved in the pathogenesis of aspirin resistance.

Extracellular ubiquitin (Ub) with platelet aggregation property was found higher in acute myocardial infarction (AMI) patients. Here we detected the platelet functions and serum Ub levels in 250 AMI patients and 50 healthy volunteers before and after aspirin treatment. The influence of serum Ub on platelet functions was determined in vitro. We found that 47 out of 250 AMI patients showed aspirin resistance (AR) and 203 showed aspirin sensitivity (AS). During hospitalization, AR group had higher serum Ub levels than the AS group or the healthy group, and the serum Ub levels was related to the rates of thrombosis events. The patients with higher serum Ub levels showed that the platelets had more ubiquitinated platelets, higher contents of ubiquitinated proteins and ubiquitinated cyclooxygenase-1 (COX-1). The levels of ubiquitinated COX-1 in the platelets was inversely correlated with acetylated COX-1, the separated ubiquitinated COX-1 activity was approximately twofold or fourfold higher than the total COX-1(ubiquitinated COX-1 and COX-1) or COX-1. In vitro, we found that extracellular Ub, via the CXC chemokine receptor 4 (CXCR4) pathway, facilitated COX-1 to be ubiquitined and prevented aspirin to acetylate its target. Platelets had higher levels of ubiquitinated COX-1 showing poor response to aspirin. Such results were not detected in Ub-free serum or ovalbumin incubated platelets. Serum Ub, via the CXCR4 pathway, facilitated COX-1 to be ubiquitined and activated the platelets possibly involved in the pathogenesis of AR.

Bifunctional fused polypeptide inhibits the growth and metastasis of breast cancer.

Breast cancer is the most common cancer and the leading cause of cancer-related death among women worldwide, with urgent need to develop new therapeutics. Targeted therapy is a promising strategy for breast cancer therapy. Stromal-derived factor-1/CXC chemokine receptor 4 (CXCR4) has been implicated in the metastasis of breast cancer, which renders it to be therapeutic target. This study aimed to evaluate the anticancer effect of fused TAT– DV1–BH3 polypeptide, an antagonist of CXCR4, and investigate the underlying mechanism for the cancer cell-killing effect in the treatment of breast cancer in vitro and in vivo. This results in a potent inhibitory effect of fused TAT–DV1–BH3 polypeptide on tumor growth and metastasis in nude mice bearing established MDA-MB-231 tumors. Fused TAT–DV1–BH3 polypeptide inhibited the proliferation of MDA-MB-231 and MCF-7 cells but did not affect that of HEK-293 cells. The fused TAT–DV1–BH3 polypeptide colocalized with mitochondria and exhibited a proapoptotic effect through the regulation of caspase-9 and -3. Furthermore, the fused TAT–DV1–BH3 polypeptide suppressed the migration and invasion of the highly metastatic breast cancer cell line MDA-MB-231 in a concentration-dependent manner. Notably, the DV1-mediated inhibition of the stromal-derived factor-1/CXCR4 pathway contributed to the antimetastasis effect, evident from the reduction in the level of phosphoinositide 3 kinase and matrix metalloproteinase 9 in MDA-MB-231 cells. Collectively, these results indicate that the apoptosis-inducing effect and migration- and invasion-suppressing effect explain the tumor regression and metastasis inhibition in vivo, with the involvement of caspase- and CXCR4-mediated signaling pathway. The data suggest that the fused TAT–DV1–BH3 polypeptide is a promising agent for the treatment of breast cancer, and more studies are warranted to fully elucidate the therapeutic targets and molecular mechanism.

Mechanism of Stromal derived factor on the proliferation and migration of endothelial progenitor cells

Objective To study the possible mechanism of stromal derived factor-1 (SDF-1) on proliferation and migration of endothelial progenitor cells (EPCs) in patients with hypertensive intracerebral hemorrhage,so as to explore the SDF-1/CXC chemokine receptor-4 (CXCR4) axis as a target participate in vascular repairment.Methods The endothelial progenitor cells were isolated from 15 ml peripheral venous blood in male patients with acute cerebral hemorrhage.Six days later,the culture EPCs were stimulated with various concentrations of SDF-1 for 24 h.Then,3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to assess the proliferation of EPCs,and cell migration was analyzed by transwell chamber assay.Furthermore,the expression levels of CXCR4 and α5β1 protein were detected by Western blotting after pretreatment with the chemically synthesized CXCR4-siRNA or anti-α5 β1 antibody.Results SDF-1 dose-dependently increased the proliferation and migration of EPCs in patients with hypertensive cerebral hemorrhage (A:0.57 ± 0.03,P ＜ 0.05) ; further mechanism analysis showed that SDF-1 induced the expression of CXCR4 protein with an about two fold increase (P ＜ 0.05),which was accounted for SDF-1-induced cell proliferation and migration as pretreatment with CXCR4 siRNA significantly abolished EPCs proliferation and migration induced by SDF-1 (A:0.363 ± 0.020).Furthermore,SDF-1 enhanced the expression of α5β1 protein with an about two fold increase by CXCR4 pathway,because preconditioning with CXCR4 siRNA obviously attenuated SDF-1-induced upregulation of α5β1 expression.Further analysis confirmed that pretreatment with α5β1 antibody dramatically inhibited α5β1 expression,concomitant with a significant decrease in EPCs proliferation and migration induced by SDF-1/ CXCR4 (A:0.311 ±0.037,migration cells:25.52 ±5.60).Conclusion SDF-1 dose-dependently increased EPCs proliferation and migration in patients with acute cerebral hemorrhage through CXCR4-mediated α5β1 pathway.Consequently,our findings will clarify a new explanation about how SDF-1 induced EPCs proliferation and migration,and provide a potential target for vascular repair after damage. Key words: Stromal derived factor-1/CXC chemokine receptor-4; Integrin α5β1; Endothelial progenitor cells ; Proliferation; Migration; Hypertensive intracerebral hemorrhage

SDF-1/CXCR4 axis in Tie2-lineage cells including endothelial progenitor cells contributes to bone fracture healing.

CXC chemokine receptor 4 (CXCR4) is a specific receptor for stromal-derived-factor 1 (SDF-1). SDF-1/CXCR4 interaction is reported to play an important role in vascular development. On the other hand, the therapeutic potential of endothelial progenitor cells (EPCs) in fracture healing has been demonstrated with mechanistic insight of vasculogenesis/angiogenesis and osteogenesis enhancement at sites of fracture. The purpose of this study was to investigate the influence of the SDF-1/CXCR4 pathway in Tie2-lineage cells (including EPCs) in bone formation. We created CXCR4 gene conditional knockout mice using the Cre/loxP system and set two groups of mice: Tie2-Cre(ER) CXCR4 knockout mice (CXCR4(-/-) ) and wild-type mice (WT). We report here that in vitro, EPCs derived from of CXCR4(-/-) mouse bone marrow demonstrated severe reduction of migration activity and EPC colony-forming activity when compared with those derived from WT mouse bone marrow. In vivo, radiological and morphological examinations showed fracture healing delayed in the CXCR4(-/-) group and the relative callus area at weeks 2 and 3 was significantly smaller in CXCR4(-/-) group mice. Quantitative analysis of capillary density at perifracture sites also showed a significant decrease in the CXCR4(-/-) group. Especially, CXCR4(-/-) group mice demonstrated significant early reduction of blood flow recovery at fracture sites compared with the WT group in laser Doppler perfusion imaging analysis. Real-time RT-PCR analysis showed that the gene expressions of angiogenic markers (CD31, VE-cadherin, vascular endothelial growth factor [VEGF]) and osteogenic markers (osteocalcin, collagen 1A1, bone morphogenetic protein 2 [BMP2]) were lower in the CXCR4(-/-) group. In the gain-of-function study, the fracture in the SDF-1 intraperitoneally injected WT group healed significantly faster with enough callus formation compared with the SDF-1 injected CXCR4(-/-) group. We demonstrated that an EPC SDF-1/CXCR4 axis plays an important role in bone fracture healing using Tie2-Cre(ER) CXCR4 conditional knockout mice.

Antitumour activity of the recombination polypeptide GST-NT21MP is mediated by inhibition of CXCR4 pathway in breast cancer

Background:CXC chemokine receptor 4 (CXCR4) and its ligand stromal cell-derived factor-1α (SDF-1α, also known as CXCL12) have important roles in promoting tumour growth and metastasis. Therefore, targeting CXCR4 could be a promising strategy for treatment of human cancer.Methods:To achieve this goal, we developed a highly purified recombination polypeptide (GST-NT21MP), which is a synthetic 21-mer peptide antagonist of CXCR4 (NT21MP) derived from the viral macrophage inflammatory protein II by fermentation technology, affinity chromatography and fast protein liquid chromatography. In this study, we used multiple methods such as MTT assay, FACS, invasion assay, RT–PCR and western blot to explore the efficacy and mechanism by which GST-NT21MP inhibits cell growth, migration and invasion of breast cancer in vitro and in vivo.Results:We found that blockade of CXCR4 pathway by GST-NT21MP decreased SDF-1-induced cell growth, adhesion and migration capacities in breast cancer cells. Moreover, GST-NT21MP significantly retarded pulmonary metastasis in vivo. Furthermore, GST-NT21MP-mediated antitumour activity was found to be associated with reduced phosphorylated Src, Akt, FAK and ERK1/2 as well as decreased Bcl-2.Conclusions:Our results suggest that GST-NT21MP could be a potential anticancer agent for the treatment of breast cancer.

CXCR4 pathway associated with family history of melanoma

Genetic predisposition plays a major role in the etiology of melanoma, but known genetic markers only account for a limited fraction of family-history-associated melanoma cases. Expression microarrays have offered the opportunity to identify further genomic profiles correlated with family history of melanoma. We aimed to distinguish mRNA expression signatures between melanoma cases with and without a family history of melanoma. Based on the Nurses' Health Study, family history was defined as having one or more first-degree family members diagnosed with melanoma. Melanoma diagnosis was confirmed by reviewing pathology reports, and tumor blocks were collected by mail from across the USA. Genomic interrogation was accomplished through evaluating expression profiling of formalin-fixed paraffin-embedded tissues from 78 primary cutaneous invasive melanoma cases, on either a 6K or whole-genome (24K) Illumina gene chip. Gene set enrichment analysis was performed for each batch to determine the differentially enriched pathways and key contributing genes. The CXC chemokine receptor 4 (CXCR4) pathway was consistently up-regulated within cases of familial melanoma in both platforms. Leading edge analysis showed four genes from the CXCR4 pathway, including MAPK1, PLCG1, CRK, and PTK2, were among the core members that contributed to the enrichment of this pathway. There was no association between the enrichment of CXCR4 pathway and NRAS, BRAF mutation, or Breslow thickness of the primary melanoma cases. We found that the CXCR4 pathway might constitute a novel susceptibility pathway associated with family history of melanoma in first-degree relatives.

Abstract 1347: CXCR4 pathway associated with family history of melanoma.

Abstract Background & Aims: Inherited genetic variants involved in the etiology of melanoma predispose towards elevated risk of disease, but known allele variants only account for a limited fraction of family history-associated melanoma cases. Hence, there is a need to determine contributing allele variants associated with augmented risk and surrogate biomarkers, which can be used to discern family history-associated melanoma. Methods: Using data from the Nurses’ Health Study cohort, family history was defined as having one or more immediate family members diagnosed with melanoma. Secondary confirmation of melanoma cases were reviewed by pathology reports and tumor blocks collected by mail from across the United States. Genomic interrogation was accomplished through evaluating formalin-fixed paraffin-embedded tissues from 78 primary cutaneous invasive melanoma cases, using expression profiling on either a 6K or whole-genome (24K) Illumina gene chip. Gene Set Enrichment Analysis was performed separately for each batch to determine the differentially enriched pathways and key contributing genes. Results: The CXC chemokine receptor 4 (CXCR4) pathway was consistently up-regulated within cases of familial melanoma in both platforms. Leading edge analysis showed four genes from the CXCR4 pathway, including MAPK1, PLCG1, CRK, and PTK2, were among the core members that contributed to the enrichment of this pathway. There was no association between the enrichment of CXCR4 pathway and NRAS, BRAF status, or Breslow thickness of the primary melanoma cases. Conclusion: We found that the CXCR4 pathway may constitute a novel susceptibility pathway associated with family history of melanoma in first-degree relatives. Citation Format: Wenqing LI, Jiali Han, Hans Widlund, Mick Correll, Yaoyu Wang, John Quackenbush, Martin Mihm, Alvaro Laga Canales, Todd Golub, Yujin Hoshida, David Hunter, George Murphy, Thomas Kupper, Abrar Qureshi. CXCR4 pathway associated with family history of melanoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1347. doi:10.1158/1538-7445.AM2013-1347

Regulatory role of stromal cell-derived factor-1 in bone morphogenetic protein-2-induced chondrogenic differentiation in vitro

Chemokine stromal cell-derived factor-1 (SDF-1) signals via binding to its primary transmembrane receptor, cysteine (C)-X-C chemokine receptor-4 (CXCR4). We previously reported that SDF-1 regulates osteogenic differentiation of mesenchymal stem/progenitor cells (MPCs) induced by bone morphogenetic protein-2 (BMP2). Although BMP2 is also capable of inducing chondrogenic differentiation of MPCs, the involvement of SDF-1 signaling in this function of BMP2 remains unknown. In this study, we aimed to test the role of SDF-1 signaling involved in BMP2-induced chondrogenic differentiation, using ATDC5 chondroprogenitors and mouse bone marrow-derived mesenchymal stromal cells (BMSCs). Our data showed that blocking of the SDF-1/CXCR4 pathway inhibits the differentiation of these cells into the chondrocytic lineages in response to BMP2 stimulation, evidenced by the reduced expression of type II collagen α1 (Col2α1), aggrecan, and type X collagen α1 (Col10α1), markers for chondrogenic differentiation. This effect of blocking SDF-1 signaling on BMP2-chondrogenic differentiation is associated with suppressed Sox9 and Runx2 expression (key transcription factors required for early and late stages of chondrogenic differentiation, respectively) and mediated via inhibiting intracellular Smad and Erk activation. Moreover, we found that addition of exogenous SDF-1 protein synergistically enhances the BMP2-induced chondrogenic differentiation in a dose-dependent manner. Collectively, our results demonstrated a novel role of SDF-1 signaling in regulating BMP2-induced chondrogenic differentiation in vitro. These data provide new insights into molecular mechanisms underlying BMP2-osteo/chondrogenesis, and may lead to the identification of new therapeutic targets and strategies to improve cartilage repair and regeneration in broad orthopaedic situations.

The role of CXCR7 on the adhesion, proliferation and angiogenesis of endothelial progenitor cells

Previous studies confirmed that stromal cell-derived factor 1 (SDF-1) was a principal regulator of retention, migration and mobilization of haematopoietic stem cells and endothelial progenitor cells (EPCs) during steady-state homeostasis and injury. CXC chemokine receptor 4 (CXCR4) has been considered as the unique receptor of SDF-1 and as the only mediator of SDF-1-induced biological effects for many years. However, recent studies found that SDF-1 could bind to not only CXCR4 but also CXC chemokine receptor 7 (CXCR7). The evidence that SDF-1 binds to the CXCR7 raises a concern how to distinguish the potential contribution of the SDF-1/CXCR7 pathway from SDF-1/CXCR4 pathway in all the processes that were previously attributed to SDF-1/CXCR4. In this study, the role of CXCR7 in EPCs was investigated in vitro. RT-PCR, Western blot and flow cytometry assay demonstrate that both CXCR4 and CXCR7 were expressed highly in EPCs. The adhesion of EPCs induced by SDF-1 was inhibited by blocking either CXCR4 or CXCR7 with their antibodies or antagonists. SDF-1 regulated the migration of EPCs via CXCR4 but not CXCR7. However, the transendothelial migration of EPCs was inhibited by either blocking of CXCR4 or CXCR7. Both CXCR7 and CXCR4 are essential for the tube formation of EPCs induced by SDF-1. These results suggested that both CXCR7 and CXCR4 are important for EPCs in response to SDF-1, indicating that CXCR7 may be another potential target molecule for angiogenesis-dependent diseases.