CXC Chemokine Receptor 4 Antagonist Research Articles

A Quick Fix?

Autologous cell therapy with bone marrow (BM)—derived proangiogenic cells is a promising new treatment modality to enhance ischemic recovery after myocardial infarction. However, its introduction into the clinical mainstream is hampered by technical challenges with cell procurement, handling, selection, expansion, and application. In this issue of Circulation , Jujo et al1 show that mobilization of endogenous cells by a clinically approved drug inhibiting the CXC-chemokine receptor 4 (CXCR4) improves myocardial recovery after infarction in a mouse model of ischemia/reperfusion. Article see p 63 The key finding of this study is that a single dose of the highly specific and short-acting CXCR4 antagonist AMD3100 (AMD), a bicyclam also known as plerixafor, reduces early infarct size and adverse cardiac remodeling when administered immediately at the time of reperfusion after coronary ligation. Interestingly, experiments in BM chimeric mice revealed that the protective effect of AMD treatment required endothelial nitric oxide synthase (eNOS) expression in BM but not in peripheral tissues because mice reconstituted with eNOS-deficient BM did not benefit from AMD treatment, whereas eNOS-knockout mice reconstituted with wild-type BM showed a reduction in infarct size and fibrosis. AMD treatment increased baseline and ischemic levels of circulating CXCR4+ and Sca-1+/Flk1+ mononuclear cells compared with control injection and enhanced recruitment of Tie2+ BM-derived cells to the ischemic myocardium, whereas levels of Tie2+ cells decreased in BM. AMD treatment also increased BM eNOS expression, possibly by directly increasing eNOS promoter activity, upregulated BM matrix metalloproteinase-9, and enhanced processing of soluble kit ligand, a key hematopoietic growth factor pathway regulated by NO. Notably, although AMD was administered just once after the induction of ischemia, the biological effects on cell mobilization and growth factor pathway regulation were sustained over several days and required eNOS expression in BM cells. CXCR4 mediates retention and mobilization …

CXC-Chemokine Receptor 4 Antagonist AMD3100 Promotes Cardiac Functional Recovery After Ischemia/Reperfusion Injury via Endothelial Nitric Oxide Synthase–Dependent Mechanism

CXC-chemokine receptor 4 (CXCR4) regulates the retention of stem/progenitor cells in the bone marrow (BM), and the CXCR4 antagonist AMD3100 improves recovery from coronary ligation injury by mobilizing stem/progenitor cells from the BM to the peripheral blood. Thus, we investigated whether AMD3100 also improves recovery from ischemia/reperfusion injury, which more closely mimics myocardial infarction in patients, because blood flow is only temporarily obstructed. Mice were treated with single subcutaneous injections of AMD3100 (5 mg/kg) or saline after ischemia/reperfusion injury. Three days later, histological measurements of the ratio of infarct area to area at risk were smaller in AMD3100-treated mice than in mice administered saline, and echocardiographic measurements of left ventricular function were greater in the AMD3100-treated mice at week 4. CXCR4(+) cells were mobilized for just 1 day in both groups, but the mobilization of sca1(+)/flk1(+) cells endured for 7 days in AMD3100-treated mice compared with just 1 day in the saline-treated mice. AMD3100 upregulated BM levels of endothelial nitric oxide synthase (eNOS) and 2 targets of eNOS signaling, matrix metalloproteinase-9 and soluble Kit ligand. Furthermore, the loss of BM eNOS expression abolished the benefit of AMD3100 on sca1(+)/flk1(+) cell mobilization without altering the mobilization of CXCR4(+) cells, and the cardioprotective effects of AMD3100 were retained in eNOS-knockout mice that had been transplanted with BM from wild-type mice but not in wild-type mice with eNOS-knockout BM. AMD3100 prolongs BM progenitor mobilization and improves recovery from ischemia/reperfusion injury, and these benefits appear to occur through a previously unidentified link between AMD3100 and BM eNOS expression.

A Locked, Dimeric CXCL12 Variant Effectively Inhibits Pulmonary Metastasis of CXCR4-Expressing Melanoma Cells Due to Enhanced Serum Stability

The CXC chemokine receptor-4 (CXCR4) plays a critical role in cancer by positively regulating cancer cell metastasis and survival. We previously showed that high concentrations of the CXCR4 ligand, wild-type CXCL12 (wtCXCL12), could inhibit colorectal cancer metastasis in vivo, and we have hypothesized that wtCXCL12 dimerizes at high concentration to become a potent antagonist of CXCR4. To address this hypothesis, we engineered a covalently locked, dimeric variant of CXCL12 (CXCL122). Herein, we show that CXCL122 can not only inhibit implantation of lung metastasis of CXCR4-B16-F10 melanoma cells more effectively than AMD3100, but that CXCL122 also blocks the growth of established pulmonary tumors. To identify a basis for the in vivo efficacy of CXCL122, we conducted Western blot analysis and ELISA analyses, which revealed that CXCL122 was stable for at least 12 hours in serum, whereas wtCXCL12 was quickly degraded. CXCL122 also maintained its antagonist properties in in vitro chemotaxis assays for up to 24 hours in serum, whereas wtCXCL12 was ineffective after 6 hours. Heat-inactivation of serum prolonged the stability and function of wtCXCL12 by more than 6 hours, suggesting enzymatic degradation as a possible mechanism for wtCXCL12 inactivation. In vitro analysis of amino-terminal cleavage by enzymes dipeptidylpeptidase IV (DPPIV/CD26) and matrix metalloproteinase-2 (MMP-2) resulted in 25-fold and 2-fold slower degradation rates, respectively, of CXCL122 compared with wtCXCL12. In summary, our results suggest CXCL122 possesses greater potential as an antimetastatic drug as compared with AMD3100 or wtCXCL12, potentially due to enhanced serum stability in the presence of N-terminal degrading enzymes.

ChemInform Abstract: Peptide and Peptidomimetic Ligands for CXC Chemokine Receptor 4 (CXCR4)

AbstractReview: about 200 refs.

Rational Design of Conformationally Constrained Cyclopentapeptide Antagonists for C-X-C Chemokine Receptor 4 (CXCR4)

In the absence of an experimentally determined binding mode for the cyclopentapeptide CXCR4 antagonists, we have rationally designed conformationally constrained analogues to further probe the small peptide binding pocket of CXCR4. Two different rigidification strategies were employed, both resulting in highly potent ligands (9 and 13). The information provided by this cyclopentapeptide ligand series will be very valuable in the development of novel peptidomimetic CXCR4 antagonists.

Stromal cell-derived factor-1α and macrophage migration-inhibitory factor induce metastatic behavior in CXCR4-expressing colon cancer cells

Metastasis of cancer cells is a major cause of death in cancer patients. The process of cancer metastasis includes the proliferation of primary cancer cells, local invasion, intravasation and cancer cell survival in blood flow, extravasation and attachment to secondary organs and metastatic growth in a new environment. In these mechanisms of cancer metastasis, CXC chemokine receptor 4 (CXCR4) and its ligand play an important role. Stromal cell-derived factor-1α (SDF-1α, also known as CXCL12) is well known as a ligand of CXCR4, and macrophage migration-inhibitory factor (MIF) has recently become known as a ligand of CXCR4. In many types of cancers including breast, pancreatic and colorectal cancer (CRC), CXCR4/SDF-1α has been investigated in metastasis-related cancer behavior, which include cell proliferation, adhesion, migration and invasion. However, CXCR4/MIF has rarely been investigated in the metastatic behavior of colon cancer cells. In this report, the effect of SDF-1α or MIF was studied on cell cycle, cell proliferation, adhesion and migration of the CXCR4-expressing colon cancer cell line SW480. SDF-1α or MIF caused a decrease in the number of cells in G0/G1 phase and an increase in the numbers of cells in S and G2/M phases. In addition, SDF-1α or MIF caused an increase in cell proliferation, cell adhesion to fibronectin and migration. AMD3100, a CXCR4 antagonist, attenuated these effects, which included increased cell proliferation, adhesion and migration due to treatment of CXCR4-expressing colon cancer cells with SDF-1α or MIF. In conclusion, SDF-1α or MIF affects the metastasis-related behaviors of CXCR4-expressing colon cancer cells.

Vein graft neointimal hyperplasia is exacerbated by CXCR4 signaling in vein graft-extrinsic cells

Because vein graft neointimal hyperplasia engenders vein graft failure, and because most vein graft neointimal cells derive from outside the vein graft, we sought to determine whether vein graft neointimal hyperplasia is affected by activity of the CXC chemokine receptor-4 (CXCR4), which is important for bone marrow-derived cell migration. In congenic Cxcr4(-/+) and wild-type (WT) recipient mice, we performed interposition grafting of the common carotid artery with the inferior vena cava (IVC) of either Cxcr4(-/+) or WT mice to create four surgically chimeric groups of mice (n ≥ 5 each), characterized by vein graft donor/recipient: WT/WT; Cxcr4(-/+)/WT; WT/Cxcr4(-/+); and Cxcr4(-/+)/Cxcr4(-/+); vein grafts were harvested 6 weeks postoperatively. The agonist for CXCR4 is expressed by cells in the arterializing vein graft. Vein graft neointimal hyperplasia was reduced by reducing CXCR4 activity in vein graft-extrinsic cells, but not in vein graft-intrinsic cells: the rank order of neointimal hyperplasia was WT/WT ≈ Cxcr4(-/+)/WT > WT/Cxcr4(-/+) ≈ Cxcr4(-/+)/Cxcr4(-/+); CXCR4 deficiency in graft-extrinsic cells reduced neointimal hyperplasia by 39% to 47% (P < .05). Vein graft medial area was equivalent in all grafts except Cxcr4(-/+)/Cxcr4(-/+), in which the medial area was 60% ± 20% greater (P < .05). Vein graft re-endothelialization was indistinguishable among all three vein graft groups. However, the prevalence of medial leukocytes was 40% ± 10% lower in Cxcr4(-/+)/Cxcr4(-/+) than in WT/WT vein grafts (P < .05), and the prevalence of smooth muscle actin-positive cells was 45% ± 20% higher (P < .05). We conclude that CXCR4 contributes to vein graft neointimal hyperplasia through mechanisms that alter homing to the vein graft of graft-extrinsic cells, particularly leukocytes. The utility of autologous vein grafts is severely reduced by neointimal hyperplasia, which accelerates subsequent graft atherosclerosis. Our study demonstrates that vein graft neointimal hyperplasia is aggravated by activity of the cell-surface “CXC” chemokine receptor-4 (CXCR4), which is critical for recruitment of bone marrow-derived cells to sites of inflammation. Our model for CXCR4 deficiency used mice with heterozygous deficiency of Cxcr4. Consequently, our results suggest the possibility that a CXCR4 antagonist--like plerixafor, currently in clinical use--could be applied to vein grafts periadventitially, and perhaps achieve beneficial effects on vein graft neointimal hyperplasia.

Inhibition of Porphyromonas gingivalis‐induced periodontal bone loss by CXCR4 antagonist treatment

Microbial pathogens have evolved mechanisms to proactively manipulate innate immunity, thereby improving their fitness in mammalian hosts. We have previously shown that Porphyromonas gingivalis exploits CXC-chemokine receptor-4 (CXCR4) to instigate a subversive crosstalk with Toll-like receptor 2 that inhibits leukocyte killing of this periodontal pathogen. However, whether CXCR4 plays a role in periodontal disease pathogenesis has not been previously addressed. Here, we hypothesized that CXCR4 is required for P. gingivalis virulence in the periodontium and that treatment with AMD3100, a potent CXCR4 antagonist, would inhibit P. gingivalis-induced periodontitis. Indeed, mice given AMD3100 via osmotic minipumps became resistant to induction of periodontal bone loss following oral inoculation with P. gingivalis. AMD3100 appeared to act in an antimicrobial manner, because mice treated with AMD3100 were protected against P. gingivalis colonization and the associated elevation of the total microbiota counts in the periodontal tissue. Moreover, even when administered 2 weeks after infection, AMD3100 halted the progression of P. gingivalis-induced periodontal bone loss. Therefore, AMD3100 can act in both preventive and therapeutic ways and CXCR4 antagonism could be a promising novel approach to treat human periodontitis.

Paradoxical Downregulation of CXC Chemokine Receptor 4 Induced by Polyphemusin II-Derived Antagonists

CXC chemokine receptor 4 (CXCR4) is a G protein-coupled receptor implicated in cell entry of T-cell line-tropic HIV-1 strains. CXCR4 and its ligand stromal cell derived factor-1 (SDF-1)/CXCL12 play pivotal parts in many physiological processes and pathogenetic conditions (e.g., immune cell-homing and cancer metastasis). We previously developed the potent CXCR4 antagonist T140 from structure-activity relationship studies of the antimicrobial peptide polyphemusin II. T140 and its derivatives have been exploited in biological and biomedical studies for the SDF-1/CXCR4 axis. We investigated receptor localization upon ligand stimulation using fluorescent SDF-1 and T140 derivatives as well as a specific labeling technique for cellular-membrane CXCR4. Fluorescent T140 derivatives induced translocation of CXCR4 into the perinuclear region as observed by treatment with fluorescent SDF-1. T140 derivative-mediated internalization of CXCR4 was also monitored by the coiled-coil tag-probe system. These findings demonstrated that the CXCR4 antagonistic activity and anti-HIV activity of T140 derivatives were derived (at least in part) from antagonist-mediated receptor internalization.

The chemokine CXCL12 and the HIV‐1 envelope protein gp120 regulate spontaneous activity of Cajal–Retzius cells in opposite directions

Activation of the CXC chemokine receptor 4 (CXCR4) in Cajal–Retzius cells by CXC chemokine ligand 12 (CXCL12) is important for controlling their excitability. CXCR4 is also a co-receptor for the glycoprotein 120 (gp120) of the envelope of the human immunodeficiency virus type 1 (HIV-1), and binding of gp120 to CXCR4 may produce pathological effects. In order to study CXCR4-dependent modulation of membrane excitability, we recorded in cell-attached configuration spontaneous action currents from hippocampal stratum lacunosum-moleculare Cajal–Retzius cells of the CXCR4-EGFP mouse. CXCL12 (50 nM) powerfully inhibited firing independently of synaptic transmission, suggesting that CXCR4 regulates an intrinsic conductance. This effect was prevented by conditioning slices with BAPTA-AM (200 μM), and by blockers of the BK calcium-dependent potassium channels (TEA (1 mM), paxilline (10 μM) and iberiotoxin (100 nM)). In contrast, exposure to gp120 (pico- to nanomolar range, alone or in combination with soluble cluster of differentiation 4 (CD4)), enhanced spontaneous firing frequency. This effect was prevented by the CXCR4 antagonist AMD3100 (1 μM) and was absent in EGFP-negative stratum lacunosum-moleculare interneurons. Increased excitability was prevented by treating slices with BAPTA-AM or bumetanide, suggesting that gp120 activates a mechanism that is both calcium- and chloride-dependent. In conclusion, our results demonstrate that CXCL12 and gp120 modulate the excitability of Cajal–Retzius cells in opposite directions. We propose that CXCL12 and gp120 either generate calcium responses of different strength or activate distinct pools of intracellular calcium, leading to agonist-specific responses, mediated by BK channels in the case of CXCL12, and by a chloride-dependent mechanism in the case of gp120.

Development of a Unique Small Molecule Modulator of CXCR4

BackgroundMetastasis, the spread and growth of tumor cells to distant organ sites, represents the most devastating attribute and plays a major role in the morbidity and mortality of cancer. Inflammation is crucial for malignant tumor transformation and survival. Thus, blocking inflammation is expected to serve as an effective cancer treatment. Among anti-inflammation therapies, chemokine modulation is now beginning to emerge from the pipeline. CXC chemokine receptor-4 (CXCR4) and its ligand stromal cell-derived factor-1 (CXCL12) interaction and the resulting cell signaling cascade have emerged as highly relevant targets since they play pleiotropic roles in metastatic progression. The unique function of CXCR4 is to promote the homing of tumor cells to their microenvironment at the distant organ sites.Methodology/Principal FindingsWe describe the actions of N,N′-(1,4-phenylenebis(methylene))dipyrimidin-2-amine (designated MSX-122), a novel small molecule and partial CXCR4 antagonist with properties quite unlike that of any other reported CXCR4 antagonists, which was prepared in a single chemical step using a reductive amination reaction. Its specificity toward CXCR4 was tested in a binding affinity assay and a ligand competition assay using 18F-labeled MSX-122. The potency of the compound was determined in two functional assays, Matrigel invasion assay and cAMP modulation. The therapeutic potential of MSX-122 was evaluated in three different murine models for inflammation including an experimental colitis, carrageenan induced paw edema, and bleomycin induced lung fibrosis and three different animal models for metastasis including breast cancer micrometastasis in lung, head and neck cancer metastasis in lung, and uveal melanoma micrometastasis in liver in which CXCR4 was reported to play crucial roles.Conclusions/SignificanceWe developed a novel small molecule, MSX-122, that is a partial CXCR4 antagonist without mobilizing stem cells, which can be safer for long-term blockade of metastasis than other reported CXCR4 antagonists.

ChemInform Abstract: Drug Discovery Research Targeting the CXC Chemokine Receptor 4 (CXCR4)

AbstractReview: 203 refs.

Peptide and peptidomimetic ligands for CXC chemokine receptor 4 (CXCR4)

The development of novel peptide and peptidomimetic ligands for the CXC chemokine receptor 4 (CXCR4) as therapeutic agents for HIV-1 infection, cancer, and immune system diseases has grown over the last decade. In this perspective article, the design of CXCR4 agonists and antagonists from endogenous stromal cell-derived factor-1 (SDF-1)/CXCL12 and horseshoe crab-derived antimicrobial peptides and their therapeutic and diagnostic applications are described.

Enhanced Homing of HSPCs After Treatment with Prostaglandin E2 (PGE2) May Be An Effect of Transcriptional Regulation of CXC Chemokine Receptor 4 (CXCR4) Through Hypoxia Inducible Factor 1α (HIF1α)

Abstract 918Hematopoietic stem cell (HSC) transplantation is widely used to treat a number of hematological malignancies. However, to be effective, transplanted HSCs must efficiently “home” to their supportive niches within the bone marrow. Limited HSC number and poor function are complications of transplant in some circumstances, and can lead to impaired immune function and bone marrow failure. Enhancing HSC homing is a strategy to improve stem cell transplantation outcomes. We have previously shown that treatment of mouse or human HSCs with 1μM 16–16 dimethyl PGE2 (dmPGE2) ex vivo increases their bone marrow homing efficiency and engraftment, coordinate with an increase in surface CXCR4 expression. The transcription factor Hypoxia Inducible Factor 1α (HIF1α) has been shown to up-regulate CXCR4 in certain cancer models. In addition, PGE2 has been shown to stabilize HIF1α under normoxic conditions. We hypothesized that the effects of PGE2 on CXCR4 expression and homing might result from stabilization of HIF1α and its subsequent transcriptional activity in the transplanted HSCs. Treatment of lineageneg bone marrow cells with 1μM dmPGE2 resulted in a 33 ± 8.6% increase in HIF1α protein levels over vehicle (p<0.05) measured by Western Blot analysis. In addition, treatment of HSC with the hypoxia mimetic dimethyloxallyl glycine (DMOG) also resulted in an increase in CXCR4 cell surface expression in mouse LinnegSca-1posc-kitpos (SKL) cells (11.3 ± 3.9% MFI over vehicle, p<0.05) and human CD34+ umbilical cord blood cells (20.1 ± 3.6% MFI over vehicle), which was comparable to treatment with dmPGE2. This increase in CXCR4 expression translated to a functional increase in SKL migration to SDF-1 (46.7 ± 1.5% migration compared to 35 ± 3.1% migration in vehicle, p<0.05). To determine whether the effects of PGE2 on CXCR4 were due effects on HIF1 transcriptional activity, we employed two mouse hepatoma cell lines (ARNT- and ARNT+). These cells express detectable levels of CXCR4 as well as all four of the PGE2 G-protein coupled receptors (EP1-4). However the ARNT- cell line lacks the HIF nuclear translocator, and thus lacks HIF1 transcriptional activity. While ARNT+ cells showed the characteristic increase in CXCR4 cell surface protein (91.3 ± 28.7%) and mRNA (5.69-fold increase) after treatment with 1μM dmPGE2, ARNT- cells failed to show a similar up-regulation of CXCR4 protein (15 ± 6.1% increase) and mRNA (0.44-fold increase) after PGE2 treatment. These data suggest that HIF1 transcriptional activity is necessary for PGE2-mediated CXCR4 regulation. To determine whether HIF1α stabilization has similar effects on HSC function after transplant, in vivo homing studies were performed. Pulse-treatment of mouse SKL cells with 5μM DMOG ex vivo for 1 hour resulted in a 2.9-fold increase in homing (p<0.005), compared to a 2.5-fold increase for cells treated with dmPGE2. Treatment of donor cells with the CXCR4 antagonist AMD3100 resulted in a statistically significant reduction in SKL homing (74.8 ± 9%, p<0.05), indicating that DMOG’s positive effects on homing are mainly due to CXCR4 up-regulation and are similar to effects seen after dmPGE2 treatment. These data suggest the effects of PGE2 on CXCR4 expression are at least partially due to the stabilization of HIF1α. Due to the importance of HIF1α and its involvement in HSC regulation, PGE2 treatment could also have effects on other pathways associated with the hypoxic response mediated through HIF1α that could be targeted to modulate HSC function. Further studies could potentially identify more specific targets to improve the efficacy of HSCs after transplant. Disclosures:Hoggatt:Fate Therapeutics: Consultancy. Pelus:Fate Therapeutics: Consultancy.

CXCR4 Antagonist AMD3100 Modulates Claudin Expression and Intestinal Barrier Function in Experimental Colitis

Ulcerative colitis is a gastrointestinal disorder characterized by local inflammation and impaired epithelial barrier. Previous studies demonstrated that CXC chemokine receptor 4 (CXCR4) antagonists could reduce colonic inflammation and mucosal damage in dextran sulfate sodium (DSS)-induced colitis. Whether CXCR4 antagonist has action on intestinal barrier and the possible mechanism, is largely undefined. In the present study, the experimental colitis was induced by administration of 5% DSS for 7 days, and CXCR4 antagonist AMD3100 was administered intraperitoneally once daily during the study period. For in vitro study, HT-29/B6 colonic cells were treated with cytokines or AMD3100 for 24 h until assay. DSS-induced colitis was characterized by morphologic changes in mice. In AMD3100-treated mice, epithelial destruction, inflammatory infiltration, and submucosal edema were markedly reduced, and the disease activity index was also significantly decreased. Increased intestinal permeability in DSS-induced colitis was also significantly reduced by AMD3100. The expressions of colonic claudin-1, claudin-3, claudin-5, claudin-7 and claudin-8 were markedly decreased after DSS administration, whereas colonic claudin-2 expression was significantly decreased. Treatment with AMD3100 prevented all these changes. However, AMD3100 had no influence on claudin-3, claudin-5, claudin-7 and claudin-8 expression in HT-29/B6 cells. Cytokines as TNF-α, IL-6, and IFN-γ increased apoptosis and monolayer permeability, inhibited the wound-healing and the claudin-3, claudin-7 and claudin-8 expression in HT-29/B6 cells. We suggest that AMD3100 acted on colonic claudin expression and intestinal barrier function, at least partly, in a cytokine-dependent pathway.

AMD3100 is a potent antagonist at CXCR4R334X, a hyperfunctional mutant chemokine receptor and cause of WHIM syndrome

WHIM is an acronym for a rare immunodeficiency syndrome (OMIM #193670) caused by autosomal dominant mutations truncating the C-terminus of the chemokine receptor CXC chemokine receptor 4 (CXCR4). WHIM mutations may potentiate CXCR4 signalling, suggesting that the United States Food and Drug Administration (FDA)-approved CXCR4 antagonist AnorMED3100 (AMD3100) (also known as Plerixafor) may be beneficial in WHIM syndrome. We have tested this at the preclinical level by comparing Chinese hamster ovary (CHO) and K562 cell lines matched for expression of recombinant wild-type CXCR4 (CXCR4WT) and the most common WHIM variant of CXCR4 (CXCR4R334X), as well as leucocytes from a WHIM patient with the CXCR4R334X mutation versus healthy controls. We found that CXCR4R334X mediated modestly increased signalling (∼2-fold) in all functional assays tested, but strongly resisted ligand-dependent down-regulation. AMD3100 was equipotent and equieffective as an antagonist at CXCR4R334X and CXCR4WT. Together, our data provide further evidence that CXCR4R334X is a gain-of-function mutation, and support clinical evaluation of AMD3100 as mechanism-based treatment in patients with WHIM syndrome.

Small molecule HIV entry inhibitors: Part I. Chemokine receptor antagonists: 2004 – 2010

Introduction: HIV/AIDS is one of the most devastating diseases in the world affecting > 40 million people worldwide. Morbidity and mortality from AIDS are significantly reduced due to the advent of highly active antiretroviral therapy (HAART). Long-term toxicity, emergence of drug resistant HIV strains and drug–drug interactions limit the effectiveness of HAART therapy. Chemokine receptor antagonists can provide drugs with lesser side effects and enhanced anti-HIV activity. Maraviroc, a chemokine co-receptor 5 (CCR5) antagonist from Pfizer, is already in clinical use.Areas covered: This review covers patents and patent applications for small molecule CCR5 and CXC chemokine receptor 4 (CXCR4) antagonists published between 2004 and 2010 and related literature with a focus on recent developments based on lead generation and lead modification. The reader will gain information about the development of small molecule CCR5 and CXCR4 antagonists from the major pharmaceutical and biopharmaceutical companies.Expert opinion: Several small lead molecules (CCR5 and CXCR4 antagonists) have been modified over this period for enhanced therapeutic activity and to obtain drug-like properties. CCR5 antagonists such as TBK-652 and TBK-220 from Tobira Therapeutics, and vicriviroc from Schering Plough showed a lot of promise in the developmental stage.

Differential effects of CXCR4 antagonists on the survival and proliferation of myeloid leukemia cellsin vitro

BackgroundAntagonists of CXC chemokine receptor 4 (CXCR4), including AMD3100, induce peripheral mobilization of hematopoietic stem cells and have been approved for clinical use. We explored whether the CXCR4 antagonists affected the survival and proliferation of myeloid leukemia cells in vitro.MethodsThe effects of CXCR4 antagonists AMD3100 and T140 on the survival and proliferation of myeloid leukemia cell lines (U937, HL-60, MO7e, KG1a, and K562) as well as CD34+ cells obtained from patients with AML and CML were analyzed by flow cytometry by using annexin V and a colorimetric cell proliferation assay.ResultsAMD3100, but not T140, stimulated the proliferation of leukemia cells in vitro in a dose-dependent manner for up to 5 days (~2-fold increase at a concentration of 10-5 M), which was not abrogated by pretreatment of the cells with pertussis toxin, but was attenuated by RNAi knockdown of CXCR7 transcripts. In contrast, AMD3100 induced a marked decrease in the cell numbers after 5-7 days. AMD3100, but not T140, induced phosphorylation of MAPK p44/p42. AMD3100 increased the number and size of leukemia cell colonies and reduced cell apoptosis during the first 5-7 days of incubation, but the phenomena were reversed during the later period of incubation.ConclusionThe effects of CXCR4 antagonists on the proliferation of myeloid leukemia cells are not uniform. AMD3100, but not T140, exerts dual effects, initially enhancing and subsequently inhibiting the survival and proliferation of the cells in vitro.

CXCR4/SDF-1 axis is involved in lymph node metastasis of gastric carcinoma

To investigate the role of CXC chemokine receptor-4 (CXCR4) and stromal cell-derived factor-1 (SDF-1) in lymph node metastasis of gastric carcinoma. In 40 cases of gastric cancer, expression of CXCR4 mRNA in cancer and normal mucous membrane and SDF-1 mRNA in lymph nodes around the stomach was detected using quantitative polymerase chain reaction (PCR) (TaqMan) and immunohistochemistry assay. SGC-7901 and MGC80-3 cancer cells were used to investigate the effect of SDF-1 on cell proliferation and migration. Quantitative reverse transcription PCR and immunohistochemistry revealed that the expression level of CXCR4 in gastric cancer was significantly higher than that in normal mucous membrane (1.6244 ± 1.3801 vs 1.0715 ± 0.5243, P < 0.05). The expression level of CXCR4 mRNA in gastric cancer with lymph node metastasis was also significantly higher than that without lymph node metastasis (0.823 ± 0.551 vs 0.392 ± 0.338, P < 0.05). CXCR4 expression was significantly related to poorly differentiated, high tumor stage and lymph node metastasis. Significant differences in the expression level of SDF-1 mRNA were found between lymph nodes in metastatic gastric cancer and normal nodes (0.5432 ± 0.4907 vs 0.2640 ± 0.2601, P < 0.05). The positive expression of SDF-1 mRNA in lymph nodes of metastatic gastric cancer was consistent with the positive expression of CXCR4 mRNA in gastric cancer (r = 0.776, P < 0.01). Additionally, human gastric cancer cell lines expressed CXCR4 and showed vigorous proliferation and migratory responses to SDF-1. AMD3100 (a specific CXCR4 antagonist) was also found to effectively reduce the migration of gastric cancer cells. The CXCR4/SDF-1 axis is involved in the lymph node metastasis of gastric cancer. CXCR4 is considered as a potential therapeutic target in the treatment of gastric cancer.

The Mood Stabilizers Valproic Acid and Lithium Enhance Mesenchymal Stem Cell Migration via Distinct Mechanisms

Mesenchymal stem cells (MSCs) show high potential for the therapy of several human diseases; however, the effectiveness of MSC transplantation has been hampered by the relatively poor migratory capacity of these cells toward disease target sites. This study investigated whether treatment of MSCs with two mood stabilizers-valproic acid (VPA) and lithium-would enhance cell migration and, if so, to explore the mechanisms underlying their effects. Short-term (3 h) exposure of MSCs to a relatively high concentration (2.5 mM) of VPA markedly increased the transcript and protein levels of CXC chemokine receptor 4 (CXCR4). VPA-induced CXCR4 expression required inhibition of histone deacetylases (HDACs), including the HDAC1 isoform, and involved histone hyperacetylation at the promoter region of the CXCR4 gene. Notably, VPA treatment enhanced stromal cell-derived factor-1α (SDF-1α)-mediated MSC migration, which was completely blocked by AMD3100, a CXCR4 antagonist. Treatment of MSCs with lithium (2.5 mM for 1 day) selectively elevated the transcript and protein levels of matrix metalloproteinase-9 (MMP-9) and its enzymatic activity; these effects were mimicked by inhibition or gene silencing of glycogen synthase kinase-3β (GSK-3β). Lithium treatment also potentiated SDF-1α-dependent MSC migration across the extracellular matrix, which was suppressed by two MMP-9 inhibitors, doxycycline and GM6001. Combining VPA and lithium treatment further increased MSC migration. Overall, VPA and lithium stimulated MSC migration through distinct targets and mediators: HDAC-CXCR4 and GSK-3β-MMP-9, respectively.