Purification and identification of chemokines potentially involved in kidney-specific metastasis by a murine lymphoma variant: induction of migration and NFkappaB activation

[The role of CXC and CC chemokines in patients with uveal melanoma]

Uveal melanoma is a malignant neoplasm with high metastatic potential; its pathogenesis is currently being studied. Chemokines play a key role not only in the inflammatory response, but also in enhancing angiogenesis, tumor invasiveness, increasing proliferative potential and metastasis.

PURPOSE

To study the role of chemokines of classes CXC and CC in blood serum and tear fluid of patients with uveal melanoma.

MATERIAL AND METHODS

The study included 118 people aged 53.7±12.2 years, among them 80 patients with uveal melanoma and 38 healthy donors. Group 1 included 32 patients with small tumors, group 2 (medium-sized tumors) - 26 patients; group 3 (large tumors) was comprised of 22 patients. Chemokines of classes CC (CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β, CCL5/RANTES, CCL11/Eotaxin) and CXC (CXCL1/GRO-α, CXCL8/IL-8, CXCL10/IP-10, CXCL12/SDF-1α) were determined by multiplex analysis of the blood serum and tear fluid. Statistical processing: Student's t-test, Fisher criteria, and Pierson's chi-squared test (χ2), differences were considered significant at p<0.05.

RESULTS

Significantly increased level of chemokines with pro-inflammatory (CCL5/RANTES), proliferative (CXCL10/IP-10) and pro-angiogenic (CXCL12/SDF-1α) effects was found in the blood serum of patients with small-sized uveal melanoma in comparison with healthy donors. Concentration of all studied pro-inflammatory, proliferative, and pro-angiogenic chemokines in the lacrimal fluid was found to be significantly elevated in both the affected and the paired "healthy" eyes in all 3 groups of patients, with the maximum content seen in the large tumor group.

CONCLUSION

The obtained data indicates that early local and systemic immune imbalance can be observed in uveal melanoma, and detection of chemokines can serve as a good reason for developing targeted therapy for small uveal melanoma.

Targeting of HA to chemokine receptors induces strong and cross-reactive T cell responses after DNA vaccination in pigs

Efficient influenza vaccination of pigs can reduce disease burdens for the swine industry, but also represents an important measure for reducing the risk from novel viral reassortments that pose pandemic threats to the human population. Here, we have vaccinated pigs with a DNA vaccine encoding influenza virus hemagglutinin (HA) linked to the chemokine MIP1α that bind chemokine receptors 1, 3, and 5 expressed on antigen presenting cells (APC). Such MIP1α targeting of HA to APC enhanced induction of HA reactive antibodies, particularly IgG2. In addition, the MIP1α- HA vaccine induced strong T cell responses that could cross-react with different influenza subtypes. Thus, the strategy of targeting HA to chemokine receptors could be important for inducing broad protection against antigenically diverse influenza strains in pigs.

Tumor-Associated Macrophages and Dendritic Cells as Prototypic Type II Polarized Myeloid Populations

Environmental signals polarize mononuclear phagocytes which can express different functional programmes. Fully polarized type I and type II (or alternatively activated) macrophages are the extremes of a continuum of functional states. Tumor-derived and T cell-derived cytokines stimulate tumor associated macrophages (TAM) to acquire a polarized type II phenotype. These functionally polarized cells, and similarly oriented or immature dendritic cells present in tumors, play a key role in subversion of adaptive immunity and in inflammatory circuits which promote tumor growth and progression.

Chemokines in homeostasis and diseases

For the past twenty years, chemokines have emerged as a family of critical mediators of cell migration during immune surveillance, development, inflammation and cancer progression. Chemokines bind to seven transmembrane G protein-coupled receptors (GPCRs) that are expressed by a wide variety of cell types and cause conformational changes in trimeric G proteins that trigger the intracellular signaling pathways necessary for cell movement and activation. Although chemokines have evolved to benefit the host, inappropriate regulation or utilization of these small proteins may contribute to or even cause diseases. Therefore, understanding the role of chemokines and their GPCRs in the complex physiological and diseased microenvironment is important for the identification of novel therapeutic targets. This review introduces the functional array and signals of multiple chemokine GPCRs in guiding leukocyte trafficking as well as their roles in homeostasis, inflammation, immune responses and cancer.

Lactobacillus plantarum displaying CCL3 chemokine in fusion with HIV-1 Gag derived antigen causes increased recruitment of T cells

Background

Chemokines are attractive candidates for vaccine adjuvants due to their ability to recruit the immune cells. Lactic acid bacteria (LAB)-based delivery vehicles have potential to be used as a cheap and safe option for vaccination. Chemokine produced on the surface of LAB may potentially enhance the immune response to an antigen and this approach can be considered in development of future mucosal vaccines.

Results

We have constructed strains of Lactobacillusplantarum displaying a chemokine on their surface. L. plantarum was genetically engineered to express and anchor to the surface a protein called CCL3Gag. CCL3Gag is a fusion protein comprising of truncated HIV-1 Gag antigen and the murine chemokine CCL3, also known as MIP-1α. Various surface anchoring strategies were explored: (1) a lipobox-based covalent membrane anchor, (2) sortase-mediated covalent cell wall anchoring, (3) LysM-based non-covalent cell wall anchoring, and (4) an N-terminal signal peptide-based transmembrane anchor. Protein production and correct localization were confirmed using Western blotting, flow cytometry and immunofluorescence microscopy. Using a chemotaxis assay, we demonstrated that CCL3Gag-producing L. plantarum strains are able to recruit immune cells in vitro.

Conclusions

The results show the ability of engineered L. plantarum to produce a functional chemotactic protein immobilized on the bacterial surface. We observed that the activity of surface-displayed CCL3Gag differed depending on the type of anchor used. The chemokine which is a part of the bacteria-based vaccine may increase the recruitment of immune cells and, thereby, enhance the reaction of the immune system to the vaccine.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-015-0360-z) contains supplementary material, which is available to authorized users.

The role of chemoattractant receptors in shaping the tumor microenvironment

Chemoattractant receptors are a family of seven transmembrane G protein coupled receptors (GPCRs) initially found to mediate the chemotaxis and activation of immune cells. During the past decades, the functions of these GPCRs have been discovered to not only regulate leukocyte trafficking and promote immune responses, but also play important roles in homeostasis, development, angiogenesis, and tumor progression. Accumulating evidence indicates that chemoattractant GPCRs and their ligands promote the progression of malignant tumors based on their capacity to orchestrate the infiltration of the tumor microenvironment by immune cells, endothelial cells, fibroblasts, and mesenchymal cells. This facilitates the interaction of tumor cells with host cells, tumor cells with tumor cells, and host cells with host cells to provide a basis for the expansion of established tumors and development of distant metastasis. In addition, many malignant tumors of the nonhematopoietic origin express multiple chemoattractant GPCRs that increase the invasiveness and metastasis of tumor cells. Therefore, GPCRs and their ligands constitute targets for the development of novel antitumor therapeutics.

Monocyte chemoattractant protein-1/CCL2 produced by stromal cells promotes lung metastasis of 4T1 murine breast cancer cells

MCP-1/CCL2 plays an important role in the initiation and progression of cancer. Since tumor cells produce MCP-1, they are considered to be the main source of this chemokine. Here, we examined whether MCP-1 produced by non-tumor cells affects the growth and lung metastasis of 4T1 breast cancer cells by transplanting them into the mammary pad of WT or MCP-1^−/− mice. Primary tumors at the injected site grew similarly in both mice; however, lung metastases were markedly reduced in MCP-1^−/− mice, with significantly longer mouse survival. High levels of MCP-1 mRNA were detected in tumors growing in WT, but not MCP-1^−/− mice. Serum MCP-1 levels were increased in tumor-bearing WT, but not MCP-1^−/− mice. Transplantation of MCP-1^−/− bone marrow cells into WT mice did not alter the incidence of lung metastasis, whereas transplantation of WT bone marrow cells into MCP-1^−/− mice increased lung metastasis. The primary tumors of MCP-1^−/− mice consistently developed necrosis earlier than those of WT mice and showed decreased infiltration by macrophages and reduced angiogenesis. Interestingly, 4T1 cells that metastasized to the lung constitutively expressed elevated levels of MCP-1, and intravenous injection of 4T1 cells producing a high level of MCP-1 resulted in increased tumor foci in the lung of WT and MCP-1^−/− mice. Thus, stromal cell-derived MCP-1 in the primary tumors promotes lung metastasis of 4T1 cells, but tumor cell-derived MCP-1 can also contribute once tumor cells enter the circulation. A greater understanding of the source and role of this chemokine may lead to novel strategies for cancer treatment.

Coexpression of atypical chemokine binders (ACBs) in breast cancer predicts better outcomes

Some evidence suggests that atypical chemokine binders (ACBs) including DARC, D6, and CCX-CKR play an important role in inhibiting invasion and metastasis of cancer cells; however, their expression in breast cancer has not been well characterized. The purpose of this study was to determine the predictive value of ACBs for relapse-free survival and overall survival in breast cancer. The expressions of the three molecules were analyzed immunohistochemically in a total of 558 consecutive breast specimens comprising 12 normal breast tissues, 29 noninvasive (carcinoma in situ), and 517 invasive breast carcinoma and their relationships to clinicopathological features and survival were investigated in invasive breast cancer. Coexpression of ACBs in invasive breast carcinoma (55.9%) was much lower that of noninvasive breast carcinoma (93.1%) and normal breast tissue (100.0%), P = 0.0004, 0.0096, respectively. Their separate stainings in invasive cancer were significantly conversely correlated with lymph node status and tumor stage. In univariate analysis, the three proteins and their coexpression were significantly associated with higher relapse-free survival and overall survival. In multivariate analysis, each of these molecules was favorable for relapse-free survival, but not overall survival. Surprisingly, their coexpression was not only independently prognostic factor for relapse-free survival (RR = 0.182, 95% CI: 0.101-0.327, P < 0.001), but also for overall survival (RR = 0.271, 95% CI: 0.081-0.910, P = 0.035). These findings highlight that the multiple loss of ACBs may occur during the development of tumorigenesis and their coexpression in breast cancer is predictive of favorable outcomes.

Small interfering RNA-mediated CXCR1 or CXCR2 knock-down inhibits melanoma tumor growth and invasion

CXCR1 and CXCR2 are receptors for CXCL-8 and are differentially expressed on melanoma and endothelial cells. In this study, we determined the functional role of these receptors in melanoma progression. We stably knock-down the expression of CXCR1 and/or CXCR2 in A375-SM (SM; high metastatic) human melanoma cells by short-hairpin RNA transfection. Cell proliferation, migration, invasion, ERK phosphorlyation and cytoskeletal rearrangements were carried out in vitro. In vivo growth was evaluated using murine subcutaneous xenograft model. Our data demonstrate that knock-down of CXCR1 and/or CXCR2 expression, inhibited melanoma cell proliferation, survival, migration and invasive potential in vitro. Moreover, we also observed inhibition of ERK phosphorylation and cytoskeltal rearrangement in SM-shCXCR1, SM-shCXCR2 and SM-shCXCR1/2 cells. Furthermore, when SM-shCXCR1 or SM-shCXCR2 cells implanted in nude mice, tumor growth, proliferation and microvessel density was significantly inhibited as compared to SM-control cells. In addition, we observed a significant increase in melanoma cell apoptosis in SM-shCXCR1 and SM-shCXCR2 tumors compared to SM-control tumors. Together, these data demonstrate that CXCR1 and CXCR2 expression play a critical role in human melanoma tumor progression and, functional blockade of CXCR1 and CXCR2 could be potentially used for future therapeutic intervention in malignant melanoma.

CK beta 8/CCL23 induces cell migration via the Gi/Go protein/PLC/PKC delta/NF-kappa B and is involved in inflammatory responses

AIMS

CKbeta8/CCL23 is a CC chemokine and alternative splicing of the CKbeta8 gene produces two mRNAs that encode CKbeta8 and its isoform CKbeta8-1. Although it has been reported that CKbeta8 and CKbeta8-1 are implicated in leukocyte trafficking and development of inflammation, the exact roles of these two chemokines in immune responses and the associated chemotaxis signaling are still obscure.

MAIN METHODS

To understand the mechanism of CKbeta8- and CKbeta8-1-induced chemotaxis signaling, we examined the chemotactic activities of osteogenic sarcoma cells expressing CC chemokine receptor 1 in response to CKbeta8 and CKbeta8-1. We also examined involvement of CKbeta8 and CKbeta8-1 in inflammatory responses by determining the mRNA expression of pro-inflammatory molecules induced by two chemokines and expressions of these chemokines in foam cells.

KEY FINDINGS

Results from a chemotaxis assay using various inhibitors for signaling molecules showed that the chemotaxis signal pathway induced by both CKbeta8 and CKbeta8-1 was mediated via the G(i)/G(o) protein, phospholipase C (PLC) and protein kinase Cdelta (PKCdelta). Treatment with a nuclear factor kappaB (NF-kappaB) inhibitor reduced the chemotactic activities of CKbeta8 and CKbeta8-1, and NF-kappaB was activated in response to CKbeta8 and CKbeta8-1. In addition, CKbeta8 and CKbeta8-1 increased mRNA expression of pro-inflammatory cytokines and adhesion molecules. The mRNA levels of CKbeta8 and CKbeta8-1 were increased in foam cells.

SIGNIFICANCE

These results indicate that both CKbeta8 and CKbeta8-1 transduce the chemotaxis signal through the G(i)/G(o) protein, PLC, PKCdelta, and NF-kappaB, and that CKbeta8 and CKbeta8-1 probably play important roles in inflammatory diseases such as atherosclerosis.

Immunotherapeutic approaches for glioma

The development of effective immunotherapy strategies for glioma requires adequate understanding of the unique immunological microenvironment in the central nervous system (CNS) and CNS tumors. Although the CNS is often considered to be an immunologically privileged site and poses unique challenges for the delivery of effector cells and molecules, recent advances in technology and discoveries in CNS immunology suggest novel mechanisms that may significantly improve the efficacy of immunotherapy against gliomas. In this review, we first summarize recent advances in the CNS and CNS tumor immunology. We address factors that may promote immune escape of gliomas. We also review advances in passive and active immunotherapy strategies for glioma, with an emphasis on lessons learned from recent early-phase clinical trials. We also discuss novel immunotherapy strategies that have been recently tested in non-CNS tumors and show great potential for application to gliomas. Finally, we discuss how each of these promising strategies can be combined to achieve clinical benefit for patients with gliomas.

G-protein coupled chemoattractant receptors and cancer

Chemoattractant receptors are a group of seven transmembrane, G protein coupled receptors (GPCRs). They were initially identified mainly on leukocytes to mediate cell migration in response to pathogen or host-derived chemotactic factors. During the past decade, chemoattractant GPCRs have been discovered not only to mediate leukocyte chemotaxis thus promoting innate and adaptive host immune responses, but also to play essential roles in development, homeostasis, HIV infection, angiogenesis and wound healing. A growing body of evidence further indicates that chemoattractant GPCRs contribute to tumor growth, invasion, angiogenesis/angiostasis and metastasis. The diverse properties of GPCRs in the progression of malignant tumors have attracted intense interest in their potential as novel anti-tumor pharmacological targets.

Receptor "hijacking" by malignant glioma cells: a tactic for tumor progression

Gliomas are the most common and deadly tumors in the central nervous system (CNS). In the course of studying the role of chemoattractant receptors in tumor growth and metastasis, we discovered that highly malignant human glioblastoma and anaplastic astrocytoma specimens were stained positively for the formylpeptide receptor (FPR), which is normally expressed in myeloid cells and accounts for their chemotaxis and activation induced by bacterial peptides. Screening of human glioma cell lines revealed that FPR was expressed selectively in glioma cell lines with a more highly malignant phenotype. FPR expressed in glioblastoma cell lines mediates cell chemotaxis, proliferation and production of an angiogenic factor, vascular endothelial growth factor (VEGF), in response to agonists released by necrotic tumor cells. Furthermore, FPR in glioblastoma cells activates the receptor for epidermal growth factor (EGFR) by increasing the phosphorylation of a selected tyrosine residue in the intracellular tail of EGFR. Thus, FPR hijacked by human glioblastoma cells exploits the function of EGFR to promote rapid tumor progression.

PREFERENTIAL EXPRESSION OF CHEMOKINE RECEPTOR CXCR4 BY HIGHLY MALIGNANT HUMAN GLIOMAS AND ITS ASSOCIATION WITH POOR PATIENT SURVIVAL

OBJECTIVE

CXCR4 is implicated in the growth, metastasis, and angiogenesis of malignant tumors. We investigated the potential role of CXCR4 in human gliomas.

METHODS

The expression of CXCR4 messenger ribonucleic acid and protein by human glioma cell lines was examined by reverse-transcriptase polymerase chain reaction and immunocytochemistry analysis. Tumor cell chemotaxis and production of vascular endothelial growth factor induced by the CXCR4 ligand SDF-1beta were measured. Xenograft models were used for evaluation of glioma cell tumorigenesis. CXCR4 expression by xenografted tumors and primary human glioma specimens were evaluated for CXCR4 protein expression. The relationship between CXCR4 expression and patient survival was analyzed. A synthetic lipoxygenase inhibitor, Nordy, was tested for its effects on glioma cell expression and function of CXCR4, as well as on glioma cell tumorigenicity.

RESULTS

CXCR4 expression correlated directly with the degree of malignancy of the human glioma cell lines and primary tumors. Activation of CXCR4 induced tumor cell chemotaxis and increased production of vascular endothelial growth factor. Glioma cells expressing higher levels of CXCR4 formed more rapidly growing and lethal tumors in nude mice. Primary human glioma specimens expressing CXCR4 contained high-density microvessels. Patients with CXCR4-positive gliomas had poorer prognosis after surgery. The lipoxygenase inhibitor Nordy diminished CXCR4 expression by glioma cell lines in vitro and reduced their tumorigenicity in nude mice.

CONCLUSION

The level of CXCR4 expression seems to correlate with the degree of malignancy of human gliomas and may contribute to their rapid growth.

Tumor-Derived Chemokine MCP-1/CCL2 Is Sufficient for Mediating Tumor Tropism of Adoptively Transferred T Cells

To exert a therapeutic effect, adoptively transferred tumor-specific CTLs must traffic to sites of tumor burden, exit the circulation, and infiltrate the tumor microenvironment. In this study, we examine the ability of adoptively transferred human CTL to traffic to tumors with disparate chemokine secretion profiles independent of tumor Ag recognition. Using a combination of in vivo tumor tropism studies and in vitro biophotonic chemotaxis assays, we observed that cell lines derived from glioma, medulloblastoma, and renal cell carcinoma efficiently chemoattracted ex vivo-expanded primary human T cells. We compared the chemokines secreted by tumor cell lines with high chemotactic activity with those that failed to elicit T cell chemotaxis (Daudi lymphoma, 10HTB neuroblastoma, and A2058 melanoma cells) and found a correlation between tumor-derived production of MCP-1/CCL2 (> or =10 ng/ml) and T cell chemotaxis. Chemokine immunodepletion studies confirmed that tumor-derived MCP-1 elicits effector T cell chemotaxis. Moreover, MCP-1 is sufficient for in vivo T cell tumor tropism as evidenced by the selective accumulation of i.v. administered firefly luciferase-expressing T cells in intracerebral xenografts of tumor transfectants secreting MCP-1. These studies suggest that the capacity of adoptively transferred T cells to home to tumors may be, in part, dictated by the species and amounts of tumor-derived chemokines, in particular MCP-1.

Macrophage inflammatory protein (MIP)1alpha and MIP1beta differentially regulate release of inflammatory cytokines and generation of tumoricidal monocytes in malignancy

The C-C chemokines, macrophage inflammatory protein (MIP)1alpha and MIP1beta are potent chemoattractants for the monocytes, which form an important component of the stroma of tumor tissue and may regulate tumor growth and associated inflammation. We examined the role of MIP1alpha and MIP1beta in inducing the release of inflammatory cytokines and the generation of tumoricidal monocytes from the peripheral blood monocytes (PBM) of healthy women and patients with carcinoma of breast (CaBr). Interleukin-1 (IL-1) and tumor necrosis factor (TNF) alpha release by the PBM was markedly stimulated by MIP1alpha in CaBr patients, but only marginally so in healthy women. In contrast, MIP1beta stimulated the release of these cytokines by the PBM of healthy women, but failed to do so in CaBr patients. MIP1alpha, but not MIP1beta, synergized with LPS in inducing the release of IL-1 from the PBM of both healthy women and CaBr patients. Both MIP1alpha and MIP1beta augmented respiratory bursts in PBM and generated tumoricidal PBM that killed T24 cells, MIP1alpha being more effective in CaBr patients and MIP1beta in healthy women. IFN-gamma co-stimulated and IL-4 suppressed MIP1alpha and beta-induced cytotoxicity in PBM. The synergy of IFN-gamma was more marked with MIP1alpha than with MIP1beta. The differential effects of MIP1alpha and MIP1beta on the PBM of healthy women and CaBr patients co-related with the levels of expression of CCR1 and CCR5 in these monocytes. The expression of CCR5 was higher than that of CCR1 in the PBM of healthy women and the PBM of the CaBr patients showed overexpression of CCR1 and downregulation of CCR5.

The expression of functional chemokine receptor CXCR4 is associated with the metastatic potential of human nasopharyngeal carcinoma

PURPOSE

Chemokine receptors are implicated in metastasis of several malignant tumors. This study was done to evaluate the contribution of chemokine receptors CXCR4 and CCR7 to metastasis of human nasopharyngeal carcinoma.

EXPERIMENTAL DESIGN

Reverse transcription-PCR, immunohistochemistry, and flow cytometry were used to evaluate mRNA and protein expression of CXCR4 and CCR7 in nasopharyngeal carcinoma tumor tissues and cell lines. Chemotaxis assays were used to evaluate the function of CXCR4 in nasopharyngeal carcinoma cells. Antisense CXCR4 was used to inhibit receptor expression and to block metastasis of human nasopharyngeal carcinoma cells in vivo in athymic mice.

RESULTS

CXCR4 protein was detected in tumor cells in 31 of 40 primary human nasopharyngeal carcinoma and in 13 of 15 lymph node metastases. CXCR4 transcripts were detected in eight CXCR4 protein-positive primary nasopharyngeal carcinoma tissues and seven nasopharyngeal carcinoma cell lines tested. On the other hand, the transcripts for CCR7 were detected only in four primary nasopharyngeal carcinoma tissues and in none of the nasopharyngeal carcinoma cell lines. In functional experiments, metastatic nasopharyngeal carcinoma cell lines that expressed high levels of CXCR4 were found to migrate in response to the CXCR4 ligand SDF-1alpha. Transfection of antisense CXCR4 in metastatic nasopharyngeal carcinoma cells inhibited the expression of CXCR4 and SDF-1alpha-induced cell migration in vitro and reduced the capacity of the tumor cells to form metastasis in the lungs and lymph nodes when injected in athymic mice.

CONCLUSION

The expression of functional CXCR4 but not CCR7 is correlated with the metastatic potential of human nasopharyngeal carcinoma cells. Therefore, CXCR4 may be considered as a potential target for the prevention of nasopharyngeal carcinoma metastasis.

Formylpeptide Receptor FPR and the Rapid Growth of Malignant Human Gliomas

BACKGROUND

The formylpeptide receptor (FPR) is a G-protein-coupled receptor (GPCR) that mediates chemotaxis of phagocytic leukocytes induced by bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (fMLF). We previously showed that selected human glioma cell lines also express functional FPR. We therefore investigated the relationship between FPR expression and the biologic behavior of glioma cells.

METHODS

Expression and function of FPR in the human glioblastoma cell line U-87 were examined by reverse transcription-polymerase chain reaction (RT-PCR) and chemotaxis assays, respectively. FPR protein expression was detected in specimens from 33 human primary gliomas by immunohistochemistry. FPR short interfering (si) RNA was used to block FPR expression in U-87 cells. Cell proliferation was assessed by measuring DNA synthesis. Xenograft tumor formation and growth were measured in nude mice. Endogenous FPR agonist activity released by necrotic tumor cells was assessed by measuring FPR activation in an FPR-transfected basophil leukemia cell line and live U-87 cells. Vascular endothelial growth factor (VEGF) mRNA was assessed by RT-PCR, and VEGF protein was assessed by enzyme-linked immunosorbent assay. All statistical tests were two-sided.

RESULTS

FPR was selectively expressed by the highly malignant human glioblastoma cell line U-87 and most primary grade IV glioblastomas multiforme and grade III anaplastic astrocytomas. U-87 cells responded to the FPR agonist fMLF by chemotaxis (i.e., increased motility), increased cell proliferation, and increased production of VEGF protein. FPR siRNA substantially reduced the tumorigenicity of U-87 cells in nude mice (38 days after implantation, mean tumor volume from wild-type U-87 cells = 842 mm3, 95% confidence interval [CI] = 721 to 963 mm3; and from FPR-siRNA transfected U-87 cells = 225 mm3, 95% CI = 194 to 256 mm3; P = .001). Necrotic glioblastoma cells released a factor(s) that activated FPR in live U-87 cells.

CONCLUSIONS

FPR is expressed by highly malignant human glioma cells and appears to mediate motility, growth, and angiogenesis of human glioblastoma by interacting with host-derived agonists. Thus, FPR may represent a molecular target for the development of novel antiglioma therapeutics.

CCR and CC chemokine expression in relation to Flt3 ligand-induced renal dendritic cell mobilization

BACKGROUND

We investigated the expression and function of CC chemokine receptors (CCR) on highly-purified kidney and blood dendritic cells isolated from mice in which dendritic cells were mobilized with fms-like tyrosine 3 kinase ligand (Flt3L).

METHODS

CCR and CC chemokine expression were determined by RNase protection assay or flow cytometry, and dendritic cell migratory responses assayed using Transwell chambers. Chemokine production in renal tissue was detected by immunofluorescence staining. Trafficking of fluorochrome-labeled dendritic cells was monitored in vivo.

RESULTS

Freshly-isolated renal dendritic cells expressed mRNA for CCR1, 2, 5, and 7 and CCR1 and 5 protein. They did not migrate to inducible chemokines--CCL3 [macrophage inflammatory protein (MIP)-1alpha], CCL5 [regulated upon activation, normal T cell expressed and secreted (RANTES)], or CCL20 (MIP-3alpha). Following lipopolysaccharide (LPS) stimulation, the dendritic cells down-regulated CCR1, 2, and 5 expression, up-regulated or sustained signals for CCR7, and migrated to the constitutively expressed ligands CCL19 (MIP-3beta) and CCL21 (secondary lymphoid tissue chemokine). Normal kidneys expressed weak message for CCL2, 3, and 4, with stronger signals for CCL5 and 19. Intrarenal CCL5 production was enhanced by Flt3L administration, in association with marked increases in interstitial CD45+ mononuclear cells. Mobilized blood dendritic cells migrated to CCR2 and CCR5 ligands and trafficked to renal intertubular sites following adoptive (intravenous) transfer. Their migration to the CCR5 ligand MIP-1beta (CCL4) and homing to kidneys of Flt3L-treated recipients were inhibited by CCR5 antagonism.

CONCLUSION

These data implicate specific CCR and their ligands in regulation of the dendritic cell constituency of the kidney. CCR5 antagonism inhibits their directed migration and intrarenal accumulation.

Increased survival, proliferation, and migration in metastatic human pancreatic tumor cells expressing functional CXCR4

In this study, we have evaluated 11 pancreatic tumor cell lines and tumor cells from surgical samples of patients with pancreatic adenocarcinoma for expression of the chemokine receptor CXCR4. Six of 11 cell lines expressed detectable mRNA of CXCR4, with three cell lines (AsPC1, Capan1, and Hs766T) having substantial amounts of transcripts. Expression was higher in lines derived from metastatic lesions compared with those derived from primary tumors. Different inflammatory cytokines did not modify expression, whereas IFN-gamma down-regulated and hypoxia up-regulated CXCR4 transcripts. Transcript expression was associated with surface expression in pancreatic carcinoma cell lines. All surgical carcinoma samples tested expressed higher levels of CXCR4 than normal pancreatic ducts, which were used as reference tissue. The chemokine CXCL12 induced chemotaxis in CXCR4-positive pancreatic carcinoma cell lines, which was inhibited by anti-CXCR4 monoclonal antibody and by the antagonist AMD3100. Transendothelial migration, Matrigel invasion, and activation of matrix metalloproteases were also enhanced by CXCL12. In CXCR4-positive cell lines, CXCL12 stimulated cell proliferation. The cell line Hs766T produces high levels of CXCL12, and addition of the CXCR4 antagonist AMD3100 partially inhibited proliferation, indicating an autocrine loop. Moreover, the addition of exogenous CXCL12 inhibited apoptosis induced by serum starvation. These results indicate that the CXCR4 receptor is frequently expressed in metastatic pancreatic tumor cells. CXCR4 not only stimulates cell motility and invasion but also promotes survival and proliferation. Strategies to target CXCR4 expressed on tumor cells may be of benefit in patients with pancreatic cancer.

Revisiting immunosurveillance and immunostimulation: Implications for cancer immunotherapy

Experimental and clinical experience demonstrates that the resolution of a pathogenic challenge depends not only on the presence or absence of an immune reaction, but also on the initiation of the proper type of immune reaction. The initiation of a non-protective type of immune reaction will not only result in a lack of protection, but may also exacerbate the underlying condition. For example, in cancer, constituents of the immune system have been shown to augment tumor proliferation, angiogenesis, and metastases. This review discusses the duality of the role of the immune system in cancer, from the theories of immunosurveillance and immunostimulation to current studies, which illustrate that the immune system has both a protective role and a tumor-promoting role in neoplasia. The potential of using chemotherapy to inhibit a tumor-promoting immune reaction is also discussed.

Characterisation of SNP haplotype structure in chemokine and chemokine receptor genes using CEPH pedigrees and statistical estimation

Chemokine signals and their cell-surface receptors are important modulators of HIV-1 disease and cancer. To aid future case/control association studies, aim to further characterise the haplotype structure of variation in chemokine and chemokine receptor genes. To perform haplotype analysis in a population-based association study, haplotypes must be determined by estimation, in the absence of family information or laboratory methods to establish phase. Here, test the accuracy of estimates of haplotype frequency and linkage disequilibrium by comparing estimated haplotypes generated with the expectation maximisation (EM) algorithm to haplotypes determined from Centre d'Etude Polymorphisme Humain (CEPH) pedigree data. To do this, they have characterised haplotypes comprising alleles at 11 biallelic loci in four chemokine receptor genes (CCR3, CCR2, CCR5 and CCRL2), which span 150 kb on chromosome 3p21, and haplotyes of nine biallelic loci in six chemokine genes [MCP-1(CCL2), Eotaxin(CCL11), RANTES(CCL5), MPIF-1(CCL23), PARC(CCL18) and MIP-1α(CCL3) ] on chromosome 17q11-12. Forty multi-generation CEPH families, totalling 489 individuals, were genotyped by the TaqMan 5'-nuclease assay. Phased haplotypes and haplotypes estimated from unphased genotypes were compared in 103 grandparents who were assumed to have mated at random.

For the 3p21 single nucleotide polymorphism (SNP) data, haplotypes determined by pedigree analysis and haplotypes generated by the EM algorithm were nearly identical. Linkage disequilibrium, measured by the D' statistic, was nearly maximal across the 150 kb region, with complete disequilibrium maintained at the extremes between CCR3-Y17Y and CCRL2-1243V. D'-values calculated from estimated haplotypes on 3p21 had high concordance with pairwise comparisons between pedigree-phased chromosomes. Conversely, there was less agreement between analyses of haplotype frequencies and linkage disequilibrium using estimated haplotypes when compared with pedigree-phased haplotypes of SNPs on chromosome 17q11-12. These results suggest that, while estimations of haplotype frequency and linkage disequilibrium may be relatively simple in the 3p21 chemokine receptor cluster in population samples, the more complex environment on chromosome 17q11-12 will require a higher resolution haplotype analysis.

Chemokine-protease interactions in cancer

Solid tumour and leukemic cells expressing chemokine receptors, metastasize to chemokine-secreting organs. Chemokines indirectly affect tumour development by attracting immunocompetent cells with pro- or anti-tumoral activities. Various membrane-associated and soluble proteases selectively cleave specific chemokines. Precursor plasma chemokines (CXCL7, CCL14) need to be proteolytically processed to obtain receptor affinity. Angiogenic CXC chemokines (CXCL1, CXCL8) have increased CXCR1/CXCR2 affinity after limited NH2-terminal processing, whereas truncated angiostatic chemokines (CXCL10) show lower CXCR3 affinity without loss of angiostatic potential. NH2-terminally cleaved monocyte chemotactic proteins (CCL2, CCL7, CCL8) have impaired capacity to attract tumour-associated macrophages and function as receptor antagonists for intact CC chemokines. Migration of Th1/CCR5+ and Th2/CCR4+ effector lymphocytes toward CCR5 (CCL5, CCL3L1) and CCR4 (CCL22) ligands is affected by cleavage. Although proteolytical processing of chemokines is well studied in vitro, the direct or indirect effects on tumour invasion and metastasis are only poorly evaluated.

Chemokines in the recruitment and shaping of the leukocyte infiltrate of tumors

Leukocytes, and macrophages in particular, are an important component of the stroma of neoplastic tissues. Tumor-associated macrophages (TAM) have the properties of a polarized M2 population and are a key component of inflammatory circuits which promote tumor growth and progression. Chemokines play a key role in the recruitment and positioning of TAM and dendritic cells in tumors and contribute to shaping their functional properties. Chemokine-recruited and positioned tumor infiltrating leukocytes are a key component of inflammatory circuits which promote tumor progression.

Tumour-associated macrophages as a prototypic type II polarised phagocyte population: role in tumour progression

Macrophages are versatile, plastic cells which respond to micro-environmental signals with distinct functional programmes. In the tumour microenvironment, tumour-associated macrophages (TAM) polarise towards a type II phenotype, oriented to the promotion of tissue remodelling and repair. As polarised type II macrophages, TAM are a key component of the inflammatory circuits that promote tumour progression.

Dipeptidyl peptidase IV activity and/or structure homologues (DASH) and their substrates in cancer

Post-translational modification of proteins is an important regulatory event. Numerous biologically active peptides that play an essential role in cancerogenesis contain an evolutionary conserved proline residue as a proteolytic-processing regulatory element. Proline-specific proteases could therefore be viewed as important "check-points". Limited proteolysis of such peptides may lead to quantitative but, importantly, due to the change of receptor preference, also qualitative changes of their signaling potential. Dipeptidyl peptidase-IV (DPP-IV, EC 3.4.14.5, identical with CD26) was for many years believed to be a unique cell membrane protease cleaving X-Pro dipeptides from the N-terminal end of peptides and proteins. Subsequently, a number of other molecules were discovered, exhibiting various degree of structural homology and DPP-IV-like enzyme activity, capable of cleaving similar set of substrates. These comprise for example, seprase, fibroblast activation protein alpha, DPP6, DPP8, DPP9, attractin, N-acetylated-alpha-linked-acidic dipeptidases I, II and L, quiescent cell proline dipeptidase, thymus-specific serine protease and DPP IV-beta. It is tempting to speculate their potential participation on DPP-IV biological function(s). Disrupted expression and enzymatic activity of "DPP-IV activity and/or structure homologues" (DASH) might corrupt the message carried by their substrates, promoting abnormal cell behavior. Consequently, modulation of particular enzyme activity using e.g. DASH inhibitors, specific antibodies or DASH expression modification may be an attractive therapeutic concept in cancer treatment. This review summarizes recent information on the interactions between DASH members and their substrates with respect to their possible role in cancer biology.

PARC/CCL18 is a plasma CC chemokine with increased levels in childhood acute lymphoblastic leukemia

Chemokines play an important role in leukocyte mobilization, hematopoiesis, and angiogenesis. Tissue-specific expression of particular chemokines also influences tumor growth and metastasis. Here, the CC chemokine pulmonary and activation-regulated chemokine (PARC)/CCL18 was measured in pediatric patients with acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML). Surprisingly, PARC immunoreactivity was consistently detected in plasma from healthy donors. After purification to homogeneity, the presence of intact PARC (1-69) and processed PARC (1-68) in normal human plasma was confirmed by sequence and mass spectrometry analysis. Furthermore, PARC serum levels were significantly increased in children with T-ALL and prepreB-ALL compared to control serum samples, whereas serum levels in AML and preB-ALL patients were not significantly different from controls. In contrast, the hemofiltrate CC chemokine-1 (HCC-1)/CCL14 was not found to be a biomarker in any of these patients' strata, whereas the cytokine interleukin-6 (IL-6) was significantly decreased in AML and prepreB-ALL. Stimulated leukocytic cell lines or lymphoblasts from patients produced IL-8/CXCL8 or macrophage inflammatory protein-1alpha (MIP-1alpha/CCL3) but not PARC, not even after IL-4 or IL-10 treatment. However, PARC was produced by superantigen or IL-4 stimulated monocytes co-cultured with lymphocytes or lymphoblastic cells. Serum PARC levels thus constitute a novel leukemia marker, possibly reflecting tumor/host cell interactions in the circulation.

Contributions of lung tissue extracts to invasion and migration of human hepatocellular carcinoma cells with various metastatic potentials

PURPOSE

The MHCC97 cell line contains two clones with high (MHCC97-H) and low (MHCC97-L) metastatic potentials, for which the pulmonary metastatic rate was 100% vs 40% between the two human hepatocellular carcinoma (HCC) clones. In an effort to elucidate the mechanism of organ-specific metastasis, we studied the effect of lung extracts from C57BL/6 mice on migration and invasion using the MHCC97 cell line.

METHODS

Determination of migration and invasion induced by lung extracts to MHCC97 cell lines was examined by chemoinvasion assay. The organization of cytoskeleton was tested using filamentous actin (F-actin) polymerization assay and flow cytometry. The activity of matrix metalloproteinase (MMPs) was analyzed by zymogram. Fluorescence double staining was employed for MMPs and F-actin colocalization in MHCC97-H cells induced by lung extracts.

RESULTS

The number of cells in response to extracts of lung, liver, kidney, and spleen in MHCC97-H cells was 64+/-10, 6+/-2, 22+/-4, and 3+/-1, respectively. Of the extracts, lung extracts showed significant differences to promote the migratory and invasive ability for MHCC97-H cells( p<0.001). The number of cells in response to lung extracts was threefold higher in MHCC97-H than that of cells in MHCC97-L ( p<0.001). Confocal laser scan microscope of MHCC97-H cells and MHCC97-L cells stimulated with lung extracts revealed pseudopodia formation around the cell front at the indicated time point. With the time increasing, the pseudopodia formation became increasingly more obvious and distinct. Compared with unstimulated cells, analysis of FACS showed a transient 1.9-fold and 1.7-fold increase in F-actin within 30 s in MHCC97-H cells and MHCC97-L cells, respectively. Confocal laser scan microscopy of MHCC97-H cells stimulated in suspension with lung extracts revealed intense F-actin staining in the periphery of the cells and redistribution of F-actin towards a leading edge. After the cells were incubated with lung extracts, not only expressions of active and latent form of MMP-9 were upregulated, but that of latent form of MMP-2 was increased in the MHCC97-H cells and MHCC97-L cells. The levels of latent and active form of MMP-9(18.8+/-1.2, 100.1+/-1.1), and latent form of MMP-2(22.4+/-1.3) were much higher in MHCC97-H cells than those of MHCC97-L cells, which were 7.8+/-0.3, 40.8+/-2.2, and 8.2+/-0.4, respectively. MMP-9 was mainly localized perinuclear pool when the MHCC97-H cells were incubated with serum-free medium. After the cells were stimulated with lung extracts, MMP-9 were expressed and colocalized with F-actin at the front of extending pseudopodia.

CONCLUSIONS

Our results indicate that the expression of matrix metalloproteinase and the pseudopodia formation in MHCC97-H cells may correlate to the metastatic potential; thus, the host environment may contribute to the preferential metastasis of HCC cells to the lung depending on the high level of MMP-9 and migratory ability.

The role of NF-kappaB in the regulation of cell stress responses

Nuclear factor-kappaB (NF-kappaB) is one of the key regulatory molecules in oxidative stress-induced cell activation. NF-kappaB is normally sequestered in the cytoplasm of nonstimulated cells and must translocate into the nucleus to regulate effector gene expression. A family of inhibitory proteins, IKBs, binds to NF-kappaB and masks its nuclear localization signal domain and therefore controls the translocation of NF-kappaB. Exposure of cells to extracellular stimuli that perturb redox balance results in rapid phosphorylation, ubiquitination, and proteolytic degradation of IkappaBs. This process frees NF-kappaB from the NF-KB/IKB complexes and enables NF-kappaB to translocate to the nucleus where it regulates gene transcription. Many effector genes including those encoding cytokines and adhesion molecules are in turn regulated by NF-kappaB. NF-kappaB is also an essential component of ionizing radiation (IR)-triggered signal transduction pathways that can lead to cell death or survival. The purpose of this review is to briefly summarize the recent progress in the studies of the role of reactive oxygen species (ROS), cytokines and ionizing radiation in NF-kappaB activation.

MCP-1 modulates chemotaxis by follicular lymphoma cells

The localization and establishment of follicular lymphoma (FL) cells in distinct anatomic sites probably involves chemokine and adhesion receptors on the neoplastic cells and appropriate chemokines and adhesion receptor ligands in the microenvironment. Several chemokines play an important role in normal B-cell trafficking and differentiation. Monocyte chemoattractant protein-1 (MCP-1) is a C-C chemokine that induces chemotaxis of a variety of lymphoid cells through its receptor CCR2. CCR2 is also expressed on B cells, and MCP-1 induces chemotaxis of normal B cells. In this report, we investigated expression and function of CCR2 on FL cells. We found FL cells as well as the t(14; 18)+ B-cell lymphoma line H2 expressed CCR2. MCP-1 potentiated SDF-1-induced chemotaxis of FL cells and H2 cells, but MCP-1 alone did not induce chemotaxis. The specificity of the effects of MCP-1 and SDF-1 was demonstrated by antibody blocking studies. Because FL cells are generally associated with follicular dendritic cells (FDCs), FDCs may be an important source of chemokines. We found that cultured FDCs produced MCP-1, and this production was enhanced by tumour necrosis factor. These data implicate MCP-1 in the migration and localization of FL cells.

Linoleic acid induces MCP-1 gene expression in human microvascular endothelial cells through an oxidative mechanism

Linoleic acid is a dietary fatty acid that appears to play an important role in activation of the vascular endothelium under a variety of pathological conditions, including development of atherosclerosis or cancer metastasis. Evidence indicates that inflammatory responses may be an underlying cause of endothelial cell pathology induced by linoleic acid. However, the profile of inflammatory mediators and the potential mechanisms involved in inflammatory reactions stimulated by the exposure to linoleic acid are not fully understood. The present study focused on the mechanisms of linoleic acid-induced expression of monocyte chemoattractant protein-1 (MCP-1) gene in human microvascular endothelial cells (HMEC-1). Treatment of HMEC-1 with increasing doses of linoleic acid markedly activated an oxidative stress-responsive transcription factor, nuclear factor-kappaB (NF-kappaB). In addition, exposure to linoleic acid induced a time- and concentration-dependent overexpression of the MCP-1 gene. Increased MCP-1 mRNA levels were observed in HMEC-1 treated with linoleic acid at doses as low as 10 &mgr;M. Linoleic acid-induced overexpression of the MCP-1 gene was associated with a significant elevation of MCP-1 protein levels. Most importantly, preexposure of HMEC-1 to antioxidants, such as pyrrolidine dithiocarbamate (PDTC) or N-acetylcysteine (NAC), attenuated linoleic acid-induced MCP-1 mRNA expression. The obtained results indicate that linoleic acid triggers MCP-1 gene expression in human microvascular endothelial cells through oxidative stress/redox-related mechanisms.

The role of constitutive NF-kappaB activity in PC-3 human prostate cancer cell invasive behavior

The purpose of this study was to determine if increased NF-kappaB activity of highly invasive PC-3 cells contributed to their invasive behavior. Increased NF-kappaB activity has been observed in several malignant tumors and it may have an important role in tumorigenesis, progression and chemotherapy resistance. By serial selection, we obtained invasion variant PC-3 cell sublines. The PC-3 High Invasive cells invade readily through a Matrigel reconstituted basement membrane while PC-3 Low Invasive cells have low baseline invasion activity. In these studies, we discovered that NF-kappaB DNA binding activity was increased in PC-3 High Invasive cells when compared to PC-3 Low Invasive cells by electrophoretic mobility shift assay (EMSA). Gel supershift assays showed a 4-fold increase in p65 containing complexes and a 2.2-fold increase in the p50 containing complexes in the PC-3 High Invasive cells. Luciferase reporter assays showed that NF-kappaB dependent transcription activity was increased 10.2 +/- 2.5-fold in the highly invasive cells (P < 0.002). The PC-3 High Invasive cells showed a constitutive increase in phospho-IkappaB alpha and introduction of the super-repressor IkappaB alpha S32/36A inhibited NF-kappaB activity to 19.2 +/- 2.5 percent of control transfected cells (P < or = 0.001). The IkappaBa super-repressor reduced the basement membrane invasion of PC-3 High Invasive cells from 6.2 +/- 1.1 to 3.8 +/- 0.4 percent (P < 0.002) with no decrease in cell viability or proliferation. These results demonstrate that increased NF-kappaB activity contributed directly to the invasive behavior of PC-3 High Invasive prostate cancer cells.

Urokinase plasminogen activator and plasmin efficiently convert hemofiltrate CC chemokine 1 into its active

We have previously isolated from human hemofiltrate an N-terminally truncated form of the hemofiltrate CC chemokine 1 (HCC-1), and characterized HCC-1[9-74] as a strong agonist of CCR1, CCR5, and to a lower extent CCR3. In this study, we show that conditioned media from human tumor cell lines PC-3 and 143B contain proteolytic activities that convert HCC-1 into the [9-74] form. This activity was fully inhibited by inhibitors of urokinase-type plasminogen activator (uPA), including PA inhibitor-1, an anti-uPA mAb, and amiloride. Pure preparations of uPA processed HCC-1 with high efficiency, without further degrading HCC-1[9-74]. Plasmin could also generate HCC-1[9-74], but degraded the active product as well. The kinetics of HCC-1 cleavage by uPA and plasmin (Michaelis constant, K(m), of 0.76 +/- 0.4 microM for uPA, and 0.096 +/- 0.05 microM for plasmin; catalytic rate constant, k(cat): 3.36 +/- 0.96 s(-1) for uPA and 6 +/- 3.6 s(-1) for plasmin) are fully compatible with a role in vivo. The activation of an abundant inactive precursor into a broad-spectrum chemokine by uPA and plasmin directly links the production of uPA by numerous tumors and their ability to recruit mononuclear leukocytes, without the need for the transcriptional activation of chemokine genes.

Antioxidants inhibit TNFalpha-induced motility and invasion of human osteosarcoma cells: possible involvement of NFkappaB activation

Osteosarcoma is the most frequent malignant bone tumor in children. It is highly invasive, however, the mechanisms behind osteosarcoma cell invasion are as yet still unknown. In the present study, treatment with TNFalpha enhanced the invasiveness of two human osteosarcoma cell lines, OST and MNNG. TNFalpha treatment also induced tumor cell motility, adhesion to laminin, the expression of matrix metalloproteinase 9 (MMP9), and the nuclear translocation of nuclear factor kappaB (NFkappaB) in the osteosarcoma cells. Moreover, antioxidants inhibited TNFalpha-induced osteosarcoma cell invasion, motility and NFkappaB nuclear translocation, but not adhesion to laminin or MMP9 expression. NFkappaB decoy, another NFkappaB inhibitor, also inhibited TNFalpha-induced osteosarcoma cell invasion and motility. Therefore, motility and NFkappaB activation were possibly related to TNFalpha-induced osteosarcoma cell invasion. However, adhesion to laminin or MMP did not demonstrate any correlation with TNFalpha-induced osteosarcoma cell invasion. Although NFkappaB is known to regulate TNFalpha-induced phenotypes, it may influence only motility and invasion, but not the MMP or laminin-mediated adhesion of these osteosarcoma cells.

Inflammation and cancer: back to Virchow?

The response of the body to a cancer is not a unique mechanism but has many parallels with inflammation and wound healing. This article reviews the links between cancer and inflammation and discusses the implications of these links for cancer prevention and treatment. We suggest that the inflammatory cells and cytokines found in tumours are more likely to contribute to tumour growth, progression, and immunosuppression than they are to mount an effective host antitumour response. Moreover cancer susceptibility and severity may be associated with functional polymorphisms of inflammatory cytokine genes, and deletion or inhibition of inflammatory cytokines inhibits development of experimental cancer. If genetic damage is the "match that lights the fire" of cancer, some types of inflammation may provide the "fuel that feeds the flames". Over the past ten years information about the cytokine and chemokine network has led to development of a range of cytokine/chemokine antagonists targeted at inflammatory and allergic diseases. The first of these to enter the clinic, tumour necrosis factor antagonists, have shown encouraging efficacy. In this article we have provided a rationale for the use of cytokine and chemokine blockade, and further investigation of non-steroidal anti-inflammatory drugs, in the chemoprevention and treatment of malignant diseases.

The LD78beta isoform of MIP-1alpha is the most potent CCR5 agonist and HIV-1-inhibiting chemokine

LD78alpha and LD78beta are 2 highly related nonallelic genes that code for different isoforms of the human CC chemokine macrophage inflammatory protein-1alpha (MIP-1alpha). Two molecular forms of natural LD78beta (7.778 and 7.793 kDa) were identified from conditioned media of stimulated peripheral blood mononuclear cells. Although LD78alpha and LD78beta only differ in 3 amino acids, both LD78beta variants were 100-fold more potent chemoattractants for mouse lymphocytes than was LD78alpha. On the contrary, LD78beta was only 2-fold more efficient than LD78alpha in chemoattracting human lymphocytes and monocytes. Using CC chemokine receptor-transfected cells, both molecular forms of LD78beta proved to be much more potent than LD78alpha in inducing an intracellular calcium rise through CCR5. Compared with LD78alpha and RANTES, this preferential binding of LD78beta to CCR5 resulted in a 10- to 50-fold higher potency in inhibiting infection of peripheral blood mononuclear cells by CCR5-using (R5) HIV-1 strains. To date, LD78beta is the most potent chemokine for inhibiting HIV-1 infection, and can be considered as a potentially important drug candidate for the treatment of infection with R5 HIV-1 strains.

Chemokines and their role in tumor growth and metastasis

Chemokines are a superfamily of pro-inflammatory polypeptide cytokines that selectively attract and activate different cell types. Many patho-physiological conditions require the participation of chemokines, including inflammation, infection, tissue injury, allergy, cardiovascular diseases, as well as malignant tumors. Chemokines activate cells through their binding to shared or unique cell surface receptors which belong to the seven-transmembrane, G-protein-coupled Rhodopsin superfamily. The role of chemokines in malignant tumors is complex: while some chemokines may enhance innate or specific host immunity against tumor implantation, others may favor tumor growth and metastasis by promoting tumor cell proliferation, migration or neovascularization in tumor tissue. In this review, the authors summarize some of the recent advances in chemokine research and emphasis is made on the effect of chemokines in tumor growth and metastasis.