CXCR4/CXCL12与胃癌生物学行为

胃癌是一种常见恶性肿瘤,总体疗效欠佳,尤其发生腹膜转移者,预后较差.近年来,CXCR4及CXCL12在肿瘤研究中已逐渐成为热点;在胃癌研究中已逐渐见相关报道,如在胃癌生长、迁徙、转移和肿瘤新生血管形成等诸方面均起着重要作用.CXCR4受体拮抗剂在胃癌动物模型中的治疗效果也显示了其应用前景.此文综述了CXCR4/CXCL12在胃癌中作用机制,对CXCR4/CXCL12的深入研究将有望使其成为胃癌靶向治疗的特异靶点.     

Dissecting the role of the CXCL12/CXCR4 axis in acute myeloid leukaemia

Acute myeloid leukaemia (AML) is the most common adult acute leukaemia with the lowest survival rate. It is characterised by a build-up of immature myeloid cells anchored in the protective niche of the bone marrow (BM) microenvironment. The CXCL12/CXCR4 axis is central to the pathogenesis of AML as it has fundamental control over AML cell adhesion into the protective BM niche, adaptation to the hypoxic environment, cellular migration and survival. High levels of CXCR4 expression are associated with poor relapse-free and overall survival. The CXCR4 ligand, CXCL12 (SDF-1), is expressed by multiple cells types in the BM, facilitating the adhesion and survival of the malignant clone. Blocking the CXCL12/CXCR4 axis is an attractive therapeutic strategy providing a ‘multi-hit’ therapy that both prevents essential survival signals and releases the AML cells from the BM into the circulation. Once out of the protective niche of the BM they would be more susceptible to destruction by conventional chemotherapeutic drugs. In this review, we disentangle the diverse roles of the CXCL12/CXCR4 axis in AML. We then describe multiple CXCR4 inhibitors, including small molecules, peptides, or monoclonal antibodies, which have been developed to date and their progress in pre-clinical and clinical trials. Finally, the review leads us to the conclusion that there is a need for further investigation into the development of a ‘multi-hit’ therapy that targets several signalling pathways related to AML cell adhesion and maintenance in the BM.     

Disturbed CXCR4/CXCL12 axis in paediatric precursor B‐cell acute lymphoblastic leukaemia

Malignant cells infiltrating the bone marrow (BM) interfere with normal cellular behaviour of supporting cells, thereby creating a malignant niche. We found that CXCR4‐receptor expression was increased in paediatric precursor B‐cell acute lymphoblastic leukaemia (BCP‐ALL) cells compared with normal mononuclear haematopoietic cells (P < 0·0001). Furthermore, high CXCR4‐expression correlated with an unfavourable outcome in BCP‐ALL (5‐year cumulative incidence of relapse ± standard error: 38·4% ± 6·9% in CXCR4‐high versus 12% ± 4·6% in CXCR4‐low expressing cases, P < 0·0001). Interestingly, BM levels of the CXCR4‐ligand (CXCL12) were 2·7‐fold lower (P = 0·005) in diagnostic BCP‐ALL samples compared with non‐leukaemic controls. Induction chemotherapy restored CXCL12 levels to normal. Blocking the CXCR4‐receptor with Plerixafor showed that the lower CXCL12 serum levels at diagnosis could not be explained by consumption by the leukaemic cells, nor did we observe an altered CXCL12‐production capacity of BM‐mesenchymal stromal cells (BM‐MSC) at this time‐point. We rather observed that a very high density of leukaemic cells negatively affected CXCL12‐production by the BM‐MSC while stimulating the secretion levels of granulocyte colony‐stimulating factor (G‐CSF). These results suggest that highly proliferative leukaemic cells are able to down‐regulate secretion of cytokines involved in homing (CXCL12), while simultaneously up‐regulating those involved in haematopoietic mobilization (G‐CSF). Therefore, interference with the CXCR4/CXCL12 axis may be an effective way to mobilize BCP‐ALL cells.     

CXCR4/CXCL12-mediated entrapment of axons at the injury site compromises optic nerve regeneration

Regenerative failure in the mammalian optic nerve is generally attributed to axotomy-induced retinal ganglion cell (RGC) death, an insufficient intrinsic regenerative capacity, and an extrinsic inhibitory environment. Here, we show that a chemoattractive CXCL12/CXCR4-dependent mechanism prevents the extension of growth-stimulated axons into the distal nerve. The chemokine CXCL12 is chemoattractive toward axonal growth cones in an inhibitory environment, and these effects are entirely abolished by the specific knockout of its receptor, CXCR4 (CXCR4^−/−), in cultured regenerating RGCs. Notably, 8% of naïve RGCs express CXCL12 and transport the chemokine along their axons in the nerve. Thus, axotomy causes its release at the injury site. However, most osteopontin-positive α-RGCs, the main neuronal population that survives optic nerve injury, express CXCR4 instead. Thus, CXCL12-mediated attraction prevents growth-stimulated axons from regenerating distally in the nerve, indicated by axons returning to the lesion site. Accordingly, specific depletion of CXCR4 in RGC reduces aberrant axonal growth and enables long-distance regeneration. Likewise, CXCL12 knockout in RGCs fully mimics these CXCR4^−/− effects. Thus, active CXCL12/CXCR4-mediated entrapment of regenerating axons to the injury site contributes to regenerative failure in the optic nerve.

Retinal ganglion cells (RGCs) convey the visual input from the eye through the optic nerve and optic tract into the brain’s target regions. As typical neurons of the central nervous system (CNS), mammalian RGCs lose most of their capability to regrow injured axons after birth (1, 2), leading to an irreversible functional loss after optic nerve damage. To date, regenerative failure has been mainly attributed to three leading causes: 1) axotomy-induced apoptosis of RGCs, 2) the low intrinsic capacity to regrow axons, and 3) the external inhibitory environment with CNS myelin and glial scar proteins (3, 4).One widely used approach to delay axotomy-induced RGC degeneration and activate the intrinsic regenerative capacity of injured axons is inflammatory stimulation (IS) in the eye induced by a lens injury, intravitreal Pam₃Cys, or zymosan injection (5–7). IS leads to the expression and release of CNTF, LIF, and IL-6 from retinal astrocytes and Müller cells (8–10), which directly interact with RGCs and activate neuroprotective/regenerative signaling such as the JAK/STAT3 pathway (8, 9, 11, 12). IS, therefore, enables moderate axon regeneration beyond the lesion site of the optic nerve. Although combinatorial strategies, together with measures overcoming the inhibitory CNS environment synergistically, further improve IS-mediated optic nerve regeneration (13–17), the overall outcome remains mostly unsatisfactory. Thus, additional unknown mechanisms besides neurodegeneration, low intrinsic capacity, and the inhibitory environment might contribute to optic nerve regeneration failure.The chemokine receptor CXCR4, a seven-transmembrane G protein–coupled receptor, is expressed in embryonic and adult neurons (18–20). We have recently shown that this receptor is also expressed in the somata and axons of adult rat RGCs (18). Next to its role as a coreceptor for HIV entry and cancer-cell migration/proliferation (21, 22), CXCR4 is reportedly involved in neurogenesis and axonal pathfinding during the embryonal development of RGCs (20, 23, 24). CXCR4 regulates different signaling pathways upon binding its ligand CXCL12 (also known as stromal cell–derived factor 1, SDF-1), which is part of the chemokine family of chemotactic cytokines in the immune system involved in the attraction of lymphocytes (25, 26). CXCL12 is also reportedly expressed by some CNS neurons, astrocytes, and microglia (19, 27–30). As the CXCR4/CXCL12 axis is highly conserved between different species (31) and involved in axonal pathfinding during embryonal development of RGCs (20, 32), we speculated that CXCR4 expression in adult RGCs might also play a role in the regenerative processes of mature axons.The current study shows that growth-stimulated axons of RGCs are actively attracted and entrapped at the lesion site of the optic nerve by a CXCL12/CXCR4-dependent mechanism. CXCL12 is expressed in a subpopulation of RGCs and axonally transported, implying its release at the injury site. A different RGC subpopulation expressed CXCR4, causing axons in the distal nerve to return to the injury site. Specific depletion of CXCR4 or CXCL12 in RGCs abolished aberrant growth. It enabled long-distance regeneration in the optic nerve, with some axons reaching the optic chiasm 3 wk after injury. Thus, active CXCL12/CXCR4-mediated entrapment markedly compromises axon extension into the distal optic nerve and contributes to regenerative failure in the optic nerve.     

The CXCR4 chemokine receptor in acute and chronic leukaemia: a marrow homing receptor and potential therapeutic target

Chemokine (C-X-C motif) receptor 4 (CXCR4) is essential for homing and maintenance of haematopoietic stem cells in distinct stromal cell niches within the marrow. Chemotactic responsiveness of haematopoietic stem cells is restricted to the ligand for CXCR4, stromal cell-derived factor-1 (SDF-1/CXCL12), which is constitutively secreted by marrow stromal cells. Myeloid and lymphoid leukaemia cells also express CXCR4 that induces leukaemia cell chemotaxis and migration beneath marrow stromal cells. CXCR4 expression levels have a major prognostic impact in acute myeloid leukaemia. There is growing in vitro and in vivo evidence that CXCR4 expression by leukaemia cells allows for homing and their retention within the marrow. As such, leukaemia cells appear to utilise CXCR4 to access niches that are normally restricted to progenitor cells, and thereby reside in a microenvironment that favours their growth and survival. CXCR4- and integrin-mediated contact between leukaemia cells and stromal cells protects leukaemia cells from spontaneous and chemotherapy-induced cell death and therefore may represent a mechanism to explain minimal residual disease and subsequent relapses commonly seen in the treatment of these diseases. This review summarises our current knowledge regarding the importance of CXCR4 in acute and chronic leukaemia, discusses the importance of CXCR4 detection by flow cytometry in the diagnostic workup of leukaemia patients, and introduces the potential role of CXCR4-targeting compounds for the treatment of leukaemia patients.     

Roles of the MEK1/2 and AKT pathways in CXCL12/CXCR4 induced cholangiocarcinoma cell invasion

AIM:To evaluate the expression of C-X-C motif chemokine receptor 4(CXCR4)and its signaling cascades,which were previously identified as a key factor for cancer cell progression and metastasis,in cholangiocarcinoma cell lines.METHODS:The expression of CXCR4 and its signaling cascades were determined in the cholangiocarcinoma cell lines(RMCCA1 and KKU100)by Western blotting.The invasion assays and the detection of actin polymerization were tested in these cholangiocarcinoma cells treated with CXC chemokine ligand-12(CXCL12).RESULTS:Expression of CXCR4 was detected in both cholangiocarcinoma cell lines and activation of CXCR4 with CXCL12 triggered the signaling via the extracellular signal-regulated kinase-1/2(ERK1/2)and phosphoinositide 3-kinase(PI3K)and induction of cholangiocarcinoma cell invasion,and displayed high levels of actin polymerization.Addition of CXCR4 inhibitor(AMD3100)abrogated CXCL12-induced phosphorylation of MEK1/2 and Akt in these cells.Moreover,treatment with MEK1/2 inhibitor(U0126)or PI3K inhibitor(LY294 002)also attenuated the effect of CXCL12-induced cholangiocarcinoma cell invasion.CONCLUSION:These results indicated that the activation of CXCR4 and its signaling pathways(MEK1/2 and Akt)are essential for CXCL12-induced cholangiocarcinoma cell invasion.This rises Implications on a potential role for the inhibition of CXCR4 or its signal cascades in the treatment of cholangiocarcinoma.     

趋化因子受体CXCR7及其配体CXCLl2、CXCLll与非小细胞肺癌关系

趋化因子受体CXCR7及CXCLl2、CXCLll在生物体中发挥重要作用,尤其在肿瘤细胞生长、增殖、侵袭、转移等过程中的作用成为近年来的研究热点之一。本文就CXCR7、CXCLl2、CXCLll的珲馋和生物学特性及其在非小细胞肺癌中的研究进展和意义进行综述。     

胃癌组织中CXCL12、CXCR4的表达及意义

目的 探讨胃癌组织中趋化因子CXCL12及其受体CXCR4蛋白表达与肿瘤浸润、转移的关系.方法 选择胃癌患者50例,取其癌组织和癌旁正常组织标本,应用免疫组化SP方法,检测CXCL12及CXCR4在胃癌组织、正常黏膜及转移淋巴结中的表达情况.结果 与正常黏膜相比,CXCL12和CXCR4在胃癌组织中的表达升高(P＜0.01),胃癌有淋巴结转移者较无淋巴结转移者表达升高(P＜0.01).结论 胃癌组织中CXCL12与CXCR4的高表达与胃癌的浸润及淋巴结转移有关;CXCL12和CXCR4检测可作为判断胃癌预后的一项指标.     

趋化因子CXCL12在缺血性脑卒中的作用及其机制

趋化因子CXCL12及其受体CXCR4参与炎症反应、诱导细胞迁徙和归巢等多种生理和病理过程,且与神经的产生、内分泌及变性等均密切相关。动物实验及临床研究证明,CXCL12及其传导通路在缺血性脑卒中不同时期具有加重损伤及促进功能重建的双重作用,有可能成为预测缺血性脑卒中近期发作及预后的一个新的生物学指标,为脑卒中预防及治疗开创新的途径。     

Characterization of the CXCR4 signaling in pancreatic cancer cells

CXCL12 and its receptor, CXCR4, are emerging as promising targets for modulating growth, angiogenesis, and metastasis in several human cancers. Indeed, blocking the receptor is sufficient to prevent metastasis and angiogenesis in experimental breast cancer xenografts. Recently, the biological effect of the CXCR4 in pancreatic cancer, one of the most deadly neoplastic diseases, has been reported. However, the molecular mechanism by which CXCR4 contributes to these properties is not completely understood. In this paper, we characterize the signaling pathways activated by CXCR4 in pancreatic cancer. We show that after CXCR4 activation, EGFR becomes tyrosine phosphorylated, and the kinase activity of this receptor, together with the activation of MMPs, Src, and PI3-Kinase, is required for CXCR4-mediated ERK activation. Analysis of this cascade in pancreatic cancer cells revealed that the ERK-mediated pathway regulates genes involved in angiogenesis, such as VEGF, CD44, HIF1α, and IL-8. Furthermore, ERK blockage inhibits the migration and tube formation of endothelial cells induced by CXCL12. Considering that inhibitors for several components of this pathway, including CXCR4 itself, are at different stages of clinical trials, this study provides theoretical justification for the clinical testing of these drugs in pancreatic cancer, thus extending the list of potential targets for treating this dismal disease.     

CXCR4 modulates contractility in adult cardiac myocytes

The inflammatory response is critical to the development and progression of heart failure. Chemokines and their receptors are a distinct class of inflammatory modulators that may play a role in mediating myocardial dysfunction in heart failure. Levels of the chemokine CXCL12, also known as stromal cell-derived factor (SDF), and its receptor, CXCR4, are elevated in patients with heart failure, and we undertook this study to determine whether this chemokine system can directly affect cardiac function in the absence of leukocytes. Murine papillary muscles and adult rat cardiac myocytes treated with CXCL12, the only identified ligand of CXCR4, demonstrate blunted inotropic responses to physiologic concentrations of calcium. The negative inotropic effects on cardiac myocytes are accompanied by a proportional diminution of calcium transients. The effects are abrogated by AMD3100, a specific CXCR4 inhibitor. Overexpression of the receptor through adenoviral infection with a CXCR4 construct accentuates the negative inotropic effects of CXCL12 on cardiac myocytes during calcium stimulation. CXCR4 activation also attenuates beta-adrenergic-mediated increases in calcium mobilization and fractional shortening in cardiac myocytes. In electrophysiologic studies, CXCL12 decreases forskolin- and isoproterenol-induced voltage-gated L-type calcium channel activation. These studies demonstrate that activation of CXCR4 results in a direct negative inotropic modulation of cardiac myocyte function. The specific mechanism of action involves alterations of calcium channel activity on the membrane. The presence of functional CXCR4 on cardiac myocytes introduces a new target for treating cardiac dysfunction.     

CXCR4 promotes differentiation of oligodendrocyte progenitors and remyelination

Multiple sclerosis is a neurodegenerative disease characterized by episodes of autoimmune attack of oligodendrocytes leading to demyelination and progressive functional deficits. Because many patients exhibit functional recovery in between demyelinating episodes, understanding mechanisms responsible for repair of damaged myelin is critical for developing therapies that promote remyelination and prevent disease progression. The chemokine CXCL12 is a developmental molecule known to orchestrate the migration, proliferation, and differentiation of neuronal precursor cells within the developing CNS. Although studies suggest a role for CXCL12 in oligodendroglia ontogeny in vitro, no studies have investigated the role of CXCL12 in remyelination in vivo in the adult CNS. Using an experimental murine model of demyelination mediated by the copper chelator cuprizone, we evaluated the expression of CXCL12 and its receptor, CXCR4, within the demyelinating and remyelinating corpus callosum (CC). CXCL12 was significantly up-regulated within activated astrocytes and microglia in the CC during demyelination, as were numbers of CXCR4+NG2+ oligodendrocyte precursor cells (OPCs). Loss of CXCR4 signaling via either pharmacological blockade or in vivo RNA silencing led to decreased OPCs maturation and failure to remyelinate. These data indicate that CXCR4 activation, by promoting the differentiation of OPCs into oligodendrocytes, is critical for remyelination of the injured adult CNS.     

Chemokine receptor CXCR4-prognostic factor for gastrointestinal tumors

To review the implication of CXCR4 for gastrointestinal cancer, a ＂Pubmed＂ analysis was performed in order to evaluate the relevance of CXCR4 and its ligands for gastrointestinal cancers. Search terms applied were ＂cancer, malignoma, esophageal, gastric, colon, colorectal, hepatic, pancreatic, CXCR4, SDF- 1α, and SDF-1β＂. CXCR4 expression correlated with dissemination of diverse gastrointestinal malignomas. The CXCR4 ligand SDF-1α might act as ＂chemorepellent＂ while SDF-1β might act as ＂chemorepellent＂ for CTLs, inducing tumor rejection. The paracrine expression of SDF-1α was furthermore closely associated with neoangiogenesis. CXCR4 and its ligands influence the dissemination, immune rejection, and neoangiogenesis of human gastrointestinal cancers. Inhibition of CXCR4 might be an interesting therapeutic option.     

趋化因子CXCL10(IP-10)/CXCR3在类风湿关节炎发病中的作用及应用前景

类风湿关节炎（RA）是一类以关节炎为主要临床表现的系统性自身免疫性疾病。实验证明,T细胞尤其是CD4~＋T细胞的异常活化及其分泌的细胞因子所形成的网络参与了RA激发和延续。趋化因子在炎症细胞向滑膜组织迁移及活化过程中发挥了关键作用,趋化因子C-X-C配体10/干扰素诱导蛋白-10（CXCL10/IP-10）可与表达在T细胞表面的受体趋化因子C-X-C受体3（CXCR3）结合促进其活化并向CD4~＋Th1细胞方向分化,从而促进炎症反应。研究发现,CXCL10在RA血清及滑膜中表达增高。目前作为RA的一个可能的致病因素,CXCL10/CXCR3在发病机制中的作用越来越受到重视。研究发现,CXCL10抗体及裸DNA疫苗可对RA关节炎有抑制及治疗作用,其可能作为RA治疗新靶点的研究日益增多。     

Potential influence of concomitant chemotherapy on CXCR4 expression in receptor directed endoradiotherapy

JCOG9801, a randomized phase III trial, reported that vincristine, cyclophosphamide, doxorubicin and prednisone (VCAP); doxorubicin, ranimustine and prednisone (AMP); and vindesine, etoposide, carboplatin and prednisone (VECP) (VCAP-AMP-VECP; mLSG15) showed superior clinical outcomes when compared to cyclophosphamide, doxorubicin, vincristine and prednisone every 2 weeks (CHOP-14; mLSG19) in patients with untreated aggressive adult T-cell leukaemia-lymphoma (ATL). To identify patients who require VCAP-AMP-VECP, we conducted a supplementary analysis of JCOG9801. Overall, 105 patients were included and categorized into low- (n = 44), intermediate- (n = 54) and high-risk (n = 7) groups according to the age-adjusted ATL prognostic index (ATL-PI). We excluded the high-risk group due to small numbers of patients. VCAP-AMP-VECP did not show any superior trend for overall survival (OS) in the low-risk group (hazard ratio: 1·04; 95% confidence interval: 0·54–2·04). Better OS was observed in the intermediate-risk group treated with VCAP-AMP-VECP (hazard ratio: 0·65; 95% confidence interval: 0·36–1·19). In the intermediate-risk group, the VCAP-AMP-VECP arm showed higher complete response rates than the CHOP-14 arm (44·0% vs. 13·8%). The VCAP-AMP-VECP arm in both risk groups exhibited grade 4 thrombocytopenia, while grade 4 neutropenia was only observed in the intermediate-risk group. VCAP-AMP-VECP remains suitable for the intermediate-risk group, whereas its benefits appear modest in the low-risk group.     

Synthesis and post-translational modification of the androgen receptor in LNCaP cells

Androgen receptor synthesis and modification were studied in the human LNCaP cell line. Immunoblotting with a specific polyclonal antibody showed that the androgen receptor migrated as a closely spaced 110–112 kDa doublet on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gels. Most of the receptor protein is present in the higher molecular mass form. Pulse labelling experiments with [³⁵S]methionine showed that the androgen receptor is synthesized as a single 110 kDa protein which is rapidly converted to a 112 kDa protein. Alkaline phosphatase treatment of cytosols from [³⁵S]methionine pulse labelled cells caused a gradual elimination of the 112 kDa isoform with a concomitant increase of the 110 kDa isoform. This indicates that the observed 110 to 112 kDa upshift of the newly synthesized androgen receptor reflects receptor phosphorylation. Both isoforms can bind hormone and can undergo a hormone dependent transformation to a tight nuclear binding form, indicating that the 110 to 112 kDa conversion is not an obligatory step for hormone binding or receptor transformation.     

Effects of pharmacological and genetic disruption of CXCR4 chemokine receptor function in B‐cell acute lymphoblastic leukaemia

B cell acute lymphoblastic leukaemia (B‐ALL) cells express high levels of CXCR4 chemokine receptors for homing and retention within the marrow microenvironment. Bone marrow stromal cells (BMSC) secrete CXCL12, the ligand for CXCR4, and protect B‐ALL cells from cytotoxic drugs. Therefore, the therapeutic use of CXCR4 antagonists has been proposed to disrupt cross talk between B‐ALL cells and the protective stroma. Because CXCR4 antagonists can have activating agonistic function, we compared the genetic and pharmacological deletion of CXCR4 in B‐ALL cells, using CRISPR‐Cas9 gene editing and CXCR4 antagonists that are in clinical use (plerixafor, BKT140). Both genetic and pharmacological CXCR4 inhibition significantly reduced B‐ALL cell migration to CXCL12 gradients and beneath BMSC, and restored drug sensitivity to dexamethasone, vincristine and cyclophosphamide. NOD/SCID/IL‐2rγnull mice injected with CXCR4 gene‐deleted B‐ALL cells had significant delay in disease progression and superior survival when compared to control mice injected with CXCR4 wild‐type B‐ALL cells. These findings indicate that anti‐leukaemia activity of CXCR4 antagonists is primarily due to CXCR4 inhibition, rather than agonistic activity, and corroborate that CXCR4 is an important target to overcome stroma‐mediated drug resistance in B‐ALL.