Chemokines and cancer

Chemokine–chemokine receptors in cancer immunotherapy

A surge in interest in the chemokine–chemokine receptor network is probably related to the expanding roles that chemokines have now been identified to play in human biology, particularly immunity. Specific tissue microenvironments express distinct chemokines and both hematopoietic and nonhematopoietic cells have receptor expression profiles that permit the coordinated trafficking and organization of cells within these specific tissues. Since the chemokine network plays critical roles in both the function of the immune system and the progression of cancer, it is an attractive target for therapeutic manipulation. This review will focus on chemokine and chemokine receptor network-related therapeutic interventions that utilize host–tumor interactions particularly involving the immune system.

Chemokine receptor CXCR4 as a therapeutic target for neuroectodermal tumors

Chemokines (chemotactic cytokines) are a family of proteins associated with the trafficking and activation of leukocytes and other cell types in immune surveillance and inflammatory response. Besides their roles in the immune system, they play pleiotropic roles in tumor initiation, promotion, and progression. Chemokines can be classified into four subfamilies of chemokines, CXC, CC, C, or CX3C, based on their number and spacing of conserved cysteine residues near the N-terminus. This CXC subfamily can be further subclassified into two groups, depending on the presence or absence of a tripeptide motif glutamic acid-leucine-arginine (ELR) in the N-terminal domain. ELR(-)CXCL12, which binds to CXCR4 has been frequently implicated in various cancers. Over the past several years, studies have increasingly shown that the CXCR4/CXCL12 axis plays critical roles in tumor progression, such as invasion, angiogenesis, survival, homing to metastatic sites. This review focuses on involvement of CXCR4/CXCL12 interaction in neuroectodermal cancers and their therapeutic potentials. As an attractive therapeutic target of CXCR4/CXCL12 axis for cancer chemotherapy, development history and application of CXCR4 antagonists are described.

Chemokine CXCL12 and its receptor CXCR4 expression are associated with perineural invasion of prostate cancer

Objective

To identify the roles of CXCL12 and CXCR4 and the associated mechanism involved in perineural invasion of prostate cancer.

Methods

The distribution and expression of CXCL12, CXCR4, MMP-2 and MMP-9 in human prostate cancer and in tumor cells invading nerve tissue were studied with immunohistochemical staining. The effects of exogenous CXCL12 and CXCR4 antagonist AMD3100 on PC3 prostate cancer cells invasiveness were assessed in vitro and in vivo.

Results

The expression of CXCL12, CXCR4, MMP-2, and MMP-9 in human prostate cancer were higher than those in hyperplastic prostate tissues (P < 0.05). In vitro CXCL12 could stimulate the PC3 cells invasiveness (P < 0.05) while AMD3100 could inhibit invasiveness. In vivo, the number of nerves around the tumor tissue in the group treated with CXCL12 was significantly higher than that found in the control group (P < 0.05). Both the control group and the CXCL12-treated group had more nerves number near the tumor tissue than it found in the AMD3100-treated group. The positive cell number of CXCL12, CXCR4, MMP-2, MMP-9, and NGF expression ranked from highest to lowest, were the CXCL12-treated, the control, and the AMD3100-treated group(P < 0.05).

Conclusion

CXCL12 and its receptor CXCR4 along with MMP-2 and MMP-9 are related with prostate cancer perineural invasion.

Chemokines in neuroectodermal cancers: the crucial growth signal from the soil

Although chemokines and their receptors were initially identified as regulators of cell trafficking during inflammation and immune response, they have emerged as crucial players in all stages of tumor development, primary growth, migration, angiogenesis, and establishment as metastases in distant target organs. Neuroectodermal tumors regroup neoplasms originating from the embryonic neural crest cells, which display clinical and biological similarities. These tumors are highly malignant and rapidly progressing diseases that disseminate to similar target organs such as bone marrow, bone, liver and lungs. There is increasing evidence that interaction of several chemokine receptors with corresponding chemokine ligands are implicated in the growth and invasive characteristics of these tumors. In this review we summarize the current knowledge on the role of CXCL12 chemokine and its CXCR4 and CXCR7 receptors in the progression and survival of neuroectodermal tumors, with particular emphasis on neuroblastoma, the most typical and enigmatic neuroectodermal childhood tumor.

Moving targets: cell migration inhibitors as new anti-inflammatory therapies

The pharmaceutical industry has targeted various types of molecules to subdue inflammatory diseases. Drugs that disrupt cell migration appear particularly promising in clinical trials and in many animal models of inflammatory disease. Cell migration inhibitors not only interfere with migration of cells to a tissue, but also can affect other necessary processes such as mediator release and angiogenesis. However, the question is whether drugs that target adhesion molecules or chemoattractant receptors will prove superior to drugs that target other molecular types. This review proclaims the virtues of targeting cell migration-related molecules for development of new anti-inflammatory and anti-tumor based drugs. It is likely that cell migration inhibitors will transform the way in which many human inflammatory diseases and cancers are treated.

Expression and regulation of chemokines in mycobacterial infection

Chemokines are the key molecules that recruit immune cells by chemotaxis and act in leukocyte activation during mycobacterial diseases. Currently, tuberculosis is a leading infectious disease affecting millions of people worldwide. The purpose of this review is to describe a series of recent scientific evidence concerning to the protective role of some members of the CC- and the CXC chemokine subfamilies for the control of mycobacterial infection. The discussion will (1) highlight the effectiveness of some chemokines as potent immunoprophylactic tool for controlling the mycobacterial establishment within the host, (2) describe recent work on the relevance of cellular signaling pathways by which mycobacterial antigens mediate chemokine induction, and (3) summarize current progress in the understanding of the potential use of chemokines as potent adjuvants in antimycobacterial immune responses.

Molecular signatures of metastasis in head and neck cancer

BACKGROUND

Metastases are the primary cause of cancer treatment failure and death, yet metastatic mechanisms remain incompletely understood.

METHODS

We studied the molecular basis of head and neck cancer metastasis by transcriptionally profiling 70 samples from 27 patients-matching normal adjacent tissue, primary tumor, and cervical lymph node metastases.

RESULTS

We identified tumor-associated expression signatures common to both primary tumors and metastases. Use of matching metastases revealed an additional 46 dysregulated genes associated solely with head and neck cancer metastasis. However, despite being metastasis-specific in our sample set, these 46 genes are concordant with genes previously discovered in primary tumors that metastasized.

CONCLUSIONS

Although our data and related studies show that most of the metastatic potential appears to be inherent to the primary tumor, they are also consistent with the notion that a limited number of additional clonal changes are necessary to yield the final metastatic cell(s), albeit in a variable temporal order.

Structural basis of CXCR4 sulfotyrosine recognition by the chemokine SDF-1/CXCL12

Stem cell homing and breast cancer metastasis are orchestrated by the chemokine stromal cell-derived factor 1 (SDF-1) and its receptor CXCR4. Here, we report the nuclear magnetic resonance structure of a constitutively dimeric SDF-1 in complex with a CXCR4 fragment that contains three sulfotyrosine residues important for a high-affinity ligand-receptor interaction. CXCR4 bridged the SDF-1 dimer interface so that sulfotyrosines sTyr7 and sTyr12 of CXCR4 occupied positively charged clefts on opposing chemokine subunits. Dimeric SDF-1 induced intracellular Ca2+ mobilization but had no chemotactic activity; instead, it prevented native SDF-1-induced chemotaxis, suggesting that it acted as a potent partial agonist. Our work elucidates the structural basis for sulfotyrosine recognition in the chemokine-receptor interaction and suggests a strategy for CXCR4-targeted drug development.

The chemokine receptor CXCR6 and its ligand CXCL16 are expressed in carcinomas and inhibit proliferation

The chemokine receptor CXCR6 and its ligand CXCL16 are involved in inflammation. Thus far, they were known to be expressed mainly by T cells and macrophages, respectively. However, we detected both in all of 170 human primary mammary carcinomas and at similar levels in all 8 human mammary carcinoma cell lines tested by microarray analysis. Expression was confirmed by reverse transcription-PCR and for the cell lines also by fluorescence-activated cell sorting analysis. CXCR6 and CXCL16 were also detected in several mouse and human mammary, colon, and pancreatic carcinoma cell lines. CXCL16 is a transmembrane protein from which the soluble chemokine can be cleaved off. The transmembrane form is present on the surface of the carcinoma cells. Surprisingly, suppression of either CXCR6 or CXCL16 led to greatly enhanced proliferation in vitro as well as in vivo, indicating that their interaction inhibits proliferation. This notion was verified using inhibitory antibodies and by introduction of CXCL16 into a rare CXCL16-negative cell line. The effect was mediated by the G protein-coupled receptor CXCR6 because it was blocked by the G(i) protein inhibitor pertussis toxin. In contrast, the soluble CXCL16 chemokine enhanced proliferation, and this was also mediated by CXCR6 but not via G(i) protein. It is remarkable that both CXCR6 and CXCL16 are expressed by all mammary carcinomas because cells that lose either acquire a growth advantage and should be selected during tumor progression. This suggests an unknown important role in tumor formation. Proteases, possibly macrophage derived, might convert inhibitory transmembrane CXCL16 into the stimulatory chemokine.

Distinct motifs in the chemokine receptor CCR7 regulate signal transduction, receptor trafficking and chemotaxis

The chemokine receptor CCR7, together with its ligands CCL19 and CCL21, is responsible for the correct homing and trafficking of dendritic cells and lymphocytes to secondary lymphoid tissues. Moreover, cancer cells can utilize CCR7 to metastasize to draining lymph nodes. However, information on CCR7 signaling leading to cell migration or receptor trafficking is sparse. Using novel CCR7 deletion mutants with successive truncations of the intracellular C-terminus and a mutant with impaired G-protein coupling, we identified distinct motifs responsible for various aspects of CCR7 signal transduction. Deleting a Ser/Thr motif at the tip of the intracellular tail of CCR7 resulted in an impaired chemokine-mediated activation of Erk1/2 kinases. Interestingly, deleting an additional adjacent motif restored the ability of CCL19-mediated Erk1/2 phosphorylation, suggesting the presence of a regulatory motif. Both the Ser/Thr and the regulatory motif are dispensable for signaling events leading to cell migration and receptor trafficking. A CCR7 mutant lacking virtually the complete C-terminus readily bound CCL19 and was internalized, but was unable to activate the G protein and to transmit signals required for cell migration, mobilization of [Ca2+]i and Erk1/2 activation. Finally, G-protein coupling was critical for [Ca2+]i mobilization, Erk1/2 phosphorylation and chemotaxis, but not for CCR7 trafficking.

The chemokine receptors CXCR4 and CCR7 are associated with tumor size and pathologic indicators of tumor aggressiveness in papillary thyroid carcinoma

BACKGROUND

Functional chemokine receptors are expressed in many malignant tumors, including papillary thyroid carcinoma (PTC). These receptors promote tumor growth and metastasis in response to endogenous chemokines. The purpose of this study was to examine the expression of two chemokine receptors-CXCR4 and CCR7-in a series of PTCs. We hypothesized that CXCR4 and CCR7 would correlate with indicators of tumor aggressiveness, including tumor size, extrathyroidal extension (ETE), angiolymphatic invasion (ALI), and lymph node metastasis.

METHODS

CXCR4 and CCR7, as well as their specific chemokine ligands (CXCL12 and CCL21, respectively), were assessed in 88 PTCs from 65 patients using a semiquantitative measure of immunohistochemical (IHC) staining intensity for each molecule. Staining intensity was compared with clinicopathologic features including patient age, gender, tumor size, multifocality, ETE, ALI, and lymph node metastasis. Differences in CXCR4 and CCR7 mRNA levels were sought in a subset of tumors using gene microarrays and quantitative RT-PCR. [

STATISTICS

t test, Mann-Whitney U test; P < .05].

RESULTS

High-intensity IHC staining for CXCR4 was associated with larger tumor size (P = .02), while PTCs exhibiting ETE, ALI, or lymph node metastasis showed higher-intensity IHC staining for CCR7 than those without (P = .01, .03, and .01, respectively). CCR7 mRNA levels were also higher in tumors with ALI (P = .04).

CONCLUSION

Expression of CXCR4 and CCR7 by PTCs is associated with indicators of tumor aggressiveness, including tumor size, ETE, ALI, and lymph node metastasis. Further studies are necessary to define the mechanisms underlying this association and to determine its potential prognostic and therapeutic implications.

Overexpression of CXCL16 and its receptor CXCR6/Bonzo promotes growth of human schwannomas

Chemokines and their receptors play a decisive role in tumor progression and metastasis. Here, we describe the expression of the CXCL16-CXCR6-system in human schwannomas of different localization and in malignant peripheral nerve sheath tumors. The transmembrane chemokine CXCL16 and its receptor CXCR6/Bonzo were overexpressed on the mRNA and protein levels in all tumor samples investigated as compared with normal peripheral or 8th cranial nerve tissues. Chromogenic immunostaining and confocal laser microscopy revealed that CXCL16 and CXCR6 were localized mainly on S-100 positive schwannoma cells. Cultured schwannoma cells responded to CXCL16-stimulation by phosphorylation of kinases p42/44 (Erk 2/1) that could be inhibited by the MEK1/2-inhibitor U0126 indicating an involvement of the mitogen-activated protein kinase signal transduction pathway. As a biological response, CXCL16 increased proliferation and induced migration of schwannomas. Hence, CXCL16 appears to be a novel growth factor for schwannomas of different localization.

Chemokine decoy receptor d6 plays a negative role in human breast cancer

Chemokine binding protein D6 is a promiscuous decoy receptor that can inhibit inflammation in vivo; however, the role it plays in cancer is not well known yet. In this study, we showed for the first time that human breast cancer differentially expressed D6 and the expression could be regulated by some cytokines. More importantly, overexpression of D6 in human breast cancer cells inhibits proliferation and invasion in vitro and tumorigenesis and lung metastasis in vivo. This inhibition is associated with decreased chemokines (e.g., CCL2 and CCL5), vessel density, and tumor-associated macrophage infiltration. Furthermore, D6 expression is inversely correlated to lymph node metastasis as well as clinical stages, but positively correlated to disease-free survival rate in cancer patients. Therefore, D6 plays a negative role in the growth and metastasis of breast cancer.

Slit-2 induces a tumor-suppressive effect by regulating beta-catenin in breast cancer cells

SLIT-2 is considered as a candidate tumor suppressor gene, because it is frequently inactivated in various cancers due to hypermethylation of its promoter region and allelic loss. However, the exact mechanism of its tumor-suppressive effect has not been elucidated. Here, we observed that Slit-2-overexpressing breast cancer cells exhibited decreased proliferation and migration capabilities compared with control cells under in vitro conditions. These results were confirmed in vivo in mouse model systems. Mice injected with MCF-7/Slit-2 cells showed a 60-70% reduction in tumor size compared with mice injected with MCF-7/VC cells both in the absence and presence of estrogen. Upon further elucidation, we observed that Slit-2 mediates the tumor-suppressive effect via a coordinated regulation of the beta-catenin and PI3K signaling pathways and by enhancing beta-catenin/E-cadherin-mediated cell-cell adhesion. Our study for the first time reveals that Slit-2-overexpressing breast cancer cells exhibit tumor suppressor capabilities through the novel mechanism of beta-catenin modulation.

Prognostic significance of expression of CCL5/RANTES receptors in patients with gastric cancer

BACKGROUND AND OBJECTIVES

The clinical significance of CCL5 has been reported in several malignancies. In this study, we examined the prognostic impact of serum CCL5 levels and the expression of CCL5 receptors on tumor cells in patients with gastric cancer.

METHODS

Serum CCL5 levels in patients with gastric cancer were measured by enzyme-linked immunoabsorbent assay. Immunohistochemical staining of three chemokine receptors, CCR1, CCR3, and CCR5, which are known as CCL5 receptors, was performed in gastric cancer tissue.

RESULTS

We found that serum CCL5 levels themselves had no impact on survival; however, higher serum CCL5 concentrations were associated with more advanced disease. Eighty-six (41%), 48 (23%), and 60 patients (28%) showed positive expression of CCR1, CCR3, and CCR5, respectively, on gastric cancer cells. Among the patients who underwent curative resection for stages II-IV disease, patients with positive CCR3 expression had significantly lower survival rates compared to those with negative CCR3 expression. Unlike CCR1, positive CCR5 expression was also associated with poorer prognosis. Multivariate analysis revealed that expression of CCR3 and/or CCR5 was an independent prognostic factor.

CONCLUSIONS

Tumor expression of CCR3 and/or CCR5 (receptors for CCL5) is associated with a lower survival rate in patients with gastric cancer.

Procollagen I COOH-terminal fragment induces VEGF-A and CXCR4 expression in breast carcinoma cells

The COOH-terminal fragment of procollagen type I (C3) is produced in tissues with high synthesis of collagen I, such as in breast cancer stroma and in bone. We previously demonstrated that C3 is chemoattractant for breast carcinoma and endothelial cells, and that in tumor cells it induces expression and activation of metalloproteinases (MMP) -2 and -9. Here we demonstrate that C3 induces expression of vascular-endothelial growth factor (VEGF) and of CXCR4, the receptor of the CXCL12/SDF-1 chemokine, in MDA MB 231 breast cancer cells. We show that the changes in gene expression and motility induced by C3 occur in a timely succession and are mediated by multiple and different signaling pathways. C3 induces early phosphorylation of p38/MAPK. Induction of VEGF expression requires continual activity of p38/MAPK and of Protein Kinase C (PKC). Pro-MMP-2 and -9 are induced through a signaling pathway involving G0alpha.i protein, and cell migration requires the activity of a combination of these signaling pathways. Our results suggest that C3 acts as a stromal-derived, cancer-promoting agent active in inducing the migratory phenotype and the survival of cancer cells and determining timely changes in their gene expression that establish conditions promoting tumor angiogenesis and invasion.

Inhibition of Foxo1 protects pancreatic islet beta-cells against fatty acid and endoplasmic reticulum stress-induced apoptosis

OBJECTIVE

beta-Cells are particularly susceptible to fatty acid-induced apoptosis associated with decreased insulin receptor/phosphatidylinositol-3 kinase/Akt signaling and the activation of stress kinases. We examined the mechanism of fatty acid-induced apoptosis of mouse beta-cells especially as related to the role played by endoplasmic reticulum (ER) stress-induced Foxo1 activation and whether decreasing Foxo1 activity could enhance cell survival.

RESEARCH DESIGN AND METHODS

Mouse insulinoma (MIN6) cells were administered with fatty acids, and the role of Foxo1 in mediating effects on signaling pathways and apoptosis was examined by measuring Foxo1 activity and using dominant-negative Foxo1.

RESULTS

Increasing fatty acid concentrations (100-400 micromol/l palmitate or oleate) led to early Jun NH(2)-terminal kinase (JNK) activation that preceded induction of ER stress markers and apoptosis. Foxo1 activity was increased with fatty acid administration and by pharmacological inducers of ER stress, and this increase was prevented by JNK inhibition. Fatty acids induced nuclear localization of Foxo1 at 4 h when Akt activity was increased, indicating that FoxO1 activation was not mediated by JNK inhibition of Akt. In contrast, fatty acid administration for 24 h was associated with decreased insulin signaling. A dominant-negative Foxo1 adenovirus (Adv-DNFoxo) conferred cells with protection from ER stress and fatty acid-mediated apoptosis. Microarray analysis revealed that fatty acid induction of gene expression was in most cases reversed by Adv-DNFoxo, including the proapoptotic transcription factor CHOP (C/EBP [CCAAT/enhancer binding protein] homologous protein).

CONCLUSIONS

Early induction of JNK and Foxo1 activation plays an important role in fatty acid-induced apoptosis. Expressing a dominant-negative allele of Foxo1 reduces expression of apoptotic and ER stress markers and promotes beta-cell survival from fatty acid and ER stress, identifying a potential therapeutic target for preserving beta-cells in type 2 diabetes.

Chemokines and their receptors: drug targets in immunity and inflammation

The chemokine system coordinates leukocyte migration in immunity and inflammation and is implicated in the pathogenesis of many human diseases. Although several successful strategies have been identified to develop drugs targeting chemokines and their receptors, this has not yet resulted in many new therapeutics. This is likely due to a complexity of the chemokine system, which was not initially appreciated, that is characterized by redundancy, pleiotropy, and differences among species. Nevertheless, our understanding of chemokine biology is continuing to grow and several promising drugs are currently being tested in late-stage clinical trials. In this review, we examine the role of chemokines in health and diseases and discuss strategies to target the chemokine system.

Autocrine and paracrine chemokine receptor 7 activation in head and neck cancer: implications for therapy

BACKGROUND

The chemokine receptor 7 (CCR7) mediates survival and invasiveness of metastatic squamous cell carcinoma of the head and neck (SCCHN) to regional lymph nodes. Constitutive prosurvival signaling by the phosphoinositide-3 kinase/Akt pathway has been observed in SCCHN cells independent of epidermal growth factor receptor (EGFR) signaling.

METHODS

Human SCCHN cell lines were treated with agents that block or activate CCR7-mediated signaling, and Akt activation, cell viability in the presence or absence of EGFR inhibition, and cisplatin-induced apoptosis (in the presence or absence of Akt inhibition) were assessed by immunoblotting, the MTT assay, and the detection of annexin V, respectively. Expression and secretion of chemokines by primary tumors, metastatic nodes, and benign nodes of patients with SCCHN were determined by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. The role of paracrine activation of CCR7 on tumor growth was analyzed by comparing the growth of orthotopic tumors derived from B7E3 murine oral carcinoma cells in wild-type BALB/c mice, in paucity of lymphoid T cell (plt, deficient in CCL19 and CCL21 expression) mice, and in plt mice in which the implanted B7E3 cells overexpressed CCR7 (n = 14 mice per group).

RESULTS

In the absence of exogenous ligand treatment, blockade of CCR7 signaling reduced levels of phosphorylated (activated) Akt and decreased SCCHN cell viability by up to 59% (95% confidence interval [CI] = 58.2% to 59.8%), enhancing the effect of EGFR inhibition. CCR7 stimulation protected metastatic SCCHN cells from cisplatin-induced apoptosis in an Akt-dependent manner. Metastatic nodes expressed and secreted higher levels of CCL19 than benign nodes or primary tumors. CCR7-positive murine SCCHN tumors grew more slowly in plt mice than in control BALB/c mice (mean average tumor volume on day 20 = 12.2 and 26.5 mm(3), respectively; difference = 14.3 mm(3), 95% CI = 12.3 to 17.1 mm(3)).

CONCLUSIONS

Secretion of CCL19 and CCL21 by SCCHN cells and by paracrine sources combine to promote activation of CCR7 prosurvival signaling associated with tumor progression and disease relapse. CCR7 and its cognate chemokines may be useful biomarkers of SCCHN progression, and blockade of CCR7-mediated signaling may enhance the efficacy of platinum- and EGFR-based therapies.

Multiple roles of chemokine CXCL12 in the central nervous system: a migration from immunology to neurobiology

Chemotactic cytokines (chemokines) have been traditionally defined as small (10-14kDa) secreted leukocyte chemoattractants. However, chemokines and their cognate receptors are constitutively expressed in the central nervous system (CNS) where immune activities are under stringent control. Why and how the CNS uses the chemokine system to carry out its complex physiological functions has intrigued neurobiologists. Here, we focus on chemokine CXCL12 and its receptor CXCR4 that have been widely characterized in peripheral tissues and delineate their main functions in the CNS. Extensive evidence supports CXCL12 as a key regulator for early development of the CNS. CXCR4 signaling is required for the migration of neuronal precursors, axon guidance/pathfinding and maintenance of neural progenitor cells (NPCs). In the mature CNS, CXCL12 modulates neurotransmission, neurotoxicity and neuroglial interactions. Thus, chemokines represent an inherent system that helps establish and maintain CNS homeostasis. In addition, growing evidence implicates altered expression of CXCL12 and CXCR4 in the pathogenesis of CNS disorders such as HIV-associated encephalopathy, brain tumor, stroke and multiple sclerosis (MS), making them the plausible targets for future pharmacological intervention.

Chemokines and cancer: migration, intracellular signalling and intercellular communication in the microenvironment

Inappropriate chemokine/receptor expression or regulation is linked to many diseases, especially those characterized by an excessive cellular infiltrate, such as rheumatoid arthritis and other inflammatory disorders. There is now overwhelming evidence that chemokines are also involved in the progression of cancer, where they function in several capacities. First, specific chemokine–receptor pairs are involved in tumour metastasis. This is not surprising, in view of their role as chemoattractants in cell migration. Secondly, chemokines help to shape the tumour microenvironment, often in favour of tumour growth and metastasis, by recruitment of leucocytes and activation of pro-inflammatory mediators. Emerging evidence suggests that chemokine receptor signalling also contributes to survival and proliferation, which may be particularly important for metastasized cells to adapt to foreign environments. However, there is considerable diversity and complexity in the chemokine network, both at the chemokine/receptor level and in the downstream signalling pathways they couple into, which may be key to a better understanding of how and why particular chemokines contribute to cancer growth and metastasis. Further investigation into these areas may identify targets that, if inhibited, could render cancer cells more susceptible to chemotherapy.

Chemokines: novel targets for breast cancer metastasis

Recent studies have highlighted the possible involvement of chemokines and their receptors in breast cancer progression and metastasis. Chemokines and their receptors constitute a superfamily of signalling factors whose prognosis value in breast cancer progression remains unclear. We will examine here the expression pattern of chemokines and their receptors in mammary gland physiology and carcinogenesis. The nature of the cells producing chemokines or harboring chemokine receptors appears to be crucial in certain conditions for example, the infiltration of the primary tumor by leukocytes and angiogenesis. In addition, chemokines, their receptors and the interaction with glycosaminoglycan (GAGs) are key players in the homing of cancer cells to distant metastasis sites. Several lines of evidence, including in vitro and in vivo models, suggest that the mechanism of action of chemokines in cancer development involves the modulation of proliferation, apoptosis, invasion, leukocyte recruitment or angiogenesis. Furthermore, we will discuss the regulation of chemokine network in tumor neovascularity by decoy receptors. The reasons accounting for the deregulation of chemokines and chemokine receptors expression in breast cancer are certainly crucial for the comprehension of chemokine role in breast cancer and are in several cases linked to estrogen receptor status. The targeting of chemokines and chemokine receptors by antibodies, small molecule antagonists, viral chemokine binding proteins and heparins appears as promising tracks to develop therapeutic strategies. Thus there is significant interest in developing strategies to antagonize the chemokine function, and an opportunity to interfere with metastasis, the leading cause of death in most patients.

Transcriptional modulation using HDACi depsipeptide promotes immune cell-mediated tumor destruction of murine B16 melanoma

With melanoma, as with many other malignancies, aberrant transcriptional repression is a hallmark of refractory cancer. To restore gene expression, use of a histone deacetylase inhibitor (HDACi) is expected to be effective. Our recent DNA micro-array analysis showed that the HDACi depsipeptide (FK228) significantly enhances gp100 antigen expression. Herein, we demonstrate that depsipeptide promotes tumor-specific T-cell-mediated killing of B16/F10 murine melanoma cells. First, by a quantitative assay of caspase-3/7 activity, a sublethal dose of depsipeptide was determined (ED50: 5 nM), in which p21(Waf1/Cip1) and Fas were sufficiently evoked concomitantly with histone H3 acetylation. Second, the sublethal dose of depsipeptide treatment with either a recombinant Fas ligand or tumor-specific T cells synergistically enhanced apoptotic cell death in B16/F10 cells in vitro. Furthermore, we found that depsipeptide increased levels of perforin in T cells. Finally, in vivo metastatic growth of B16/F10 in the lung was significantly inhibited by a combination of depsipeptide treatment and immune cell adoptive transfer from immunized mice using irradiated B16 cells and gp100-specific (Pmel-1) TCR transgenic mice (P<0.05, vs cell transfer alone). Consequently, employment of a transcriptional modulation strategy using HDACis might prove to be a useful pretreatment for human melanoma immunotherapy.

Matrix metalloproteinase-9 is up-regulated by CCL21/CCR7 interaction via extracellular signal-regulated kinase-1/2 signaling and is involved in CCL21-driven B-cell chronic lymphocytic leukemia cell invasion and migration

B-cell chronic lymphocytic leukemia (B-CLL) progression is frequently accompanied by clinical lymphadenopathy, and the CCL21 chemokine may play an important role in this process. Indeed, CCR7 (the CCL21 receptor), as well as matrix metalloproteinase-9 (MMP-9), are overexpressed in infiltrating B-CLL cells. We have studied whether MMP-9 is regulated by CCL21 and participates in CCL21-dependent migration. CCL21 significantly increased B-CLL MMP-9 production, measured by gelatin zymography. This was inhibited by blocking extracellular signal-regulated kinase-1/2 (ERK1/2) activity or by cell transfection with CCR7-siRNA. Accordingly, CCL21/CCR7 interaction activated the ERK1/2/c-Fos pathway and increased MMP-9 mRNA. CCL21-driven B-CLL cell migration through Matrigel or human umbilical vein endothelial cells (HUVEC) was blocked by anti-CCR7 antibodies, CCR7-siRNA transfection, or the ERK1/2 inhibitor U0126, as well as by anti-MMP-9 antibodies or tissue inhibitor of metalloproteinase 1 (TIMP-1). These results strongly suggest that MMP-9 is involved in B-CLL nodal infiltration and expand the roles of MMP-9 and CCR7 in B-CLL progression. Both molecules could thus constitute therapeutic targets for this disease.

CCR7 signaling inhibits T cell proliferation

CCR7 and its ligands, CCL19 and CCL21, are responsible for directing the migration of T cells and dendritic cells into lymph nodes, where these cells play an important role in the initiation of the immune response. Recently, we have shown that systemic application of CCL19-IgG is able to inhibit the colocalization of T cells and dendritic cells within secondary lymphoid organs, resulting in pronounced immunosuppression with reduced allograft rejection after organ transplantation. In this study, we demonstrate that the application of sustained high concentrations of either soluble or immobilized CCL19 and CCL21 elicits an inhibitory program in T cells. We show that these ligands specifically interfere with cell proliferation and IL-2 secretion of CCR7(+) cells. This could be demonstrated for human and murine T cells and was valid for both CD4(+) and CD8(+) T cells. In contrast, CCL19 had no inhibitory effect on T cells from CCR7 knockout mice, but CCR7(-/-) T cells showed a proliferative response upon TCR-stimulation similar to that of CCL19-treated wild-type cells. Furthermore, the inhibition of proliferation is associated with delayed degradation of the cyclin-dependent kinase (CDK) inhibitor p27(Kip1) and the down-regulation of CDK1. This shows that CCR7 signaling is linked to cell cycle control and that sustained engagement of CCR7, either by high concentrations of soluble ligands or by high density of immobilized ligands, is capable of inducing cell cycle arrest in TCR-stimulated cells. Thus, CCR7, a chemokine receptor that has been demonstrated to play an essential role during activation of the immune response, is also competent to directly inhibit T cell proliferation.

Biological role and potential therapeutic targeting of the chemokine receptor CXCR4 in undifferentiated thyroid cancer

Anaplastic thyroid carcinoma (ATC) is a rare thyroid cancer type with an extremely poor prognosis. Despite appropriate treatment, which includes surgery, radiotherapy, and chemotherapy, this cancer is invariably fatal. CXCR4 is the receptor for the stromal cell-derived factor-1 (SDF-1)/CXCL12 chemokine and it is expressed in a variety of solid tumors, including papillary thyroid carcinoma. Here, we show that ATC cell lines overexpress CXCR4, both at the level of mRNA and protein. Furthermore, we found that CXCR4 was overexpressed in ATC clinical samples, with respect to normal thyroid tissues by real-time PCR and immunohistochemistry. Treatment of ATC cells with SDF-1 induced proliferation and increase in phosphorylation of extracellular signal-regulated kinases and protein kinase B/AKT. These effects were blocked by the specific CXCR4 antagonist AMD3100 and by CXCR4 RNA interference. Moreover, AMD3100 effectively reduced tumor growth in nude mice inoculated with different ATC cells. Thus, we suggest that CXCR4 targeting is a novel potential strategy in the treatment of human ATC.

Level of Toll-like receptor agonist exposure differentially determines chemokine production in humans

Toll-like receptor (TLR) agonists, ubiquitously present in the environment, are key players in activating synthesis of cytokines and chemokines that control normal and pathophysiological processes, including multiple inflammatory diseases. TLR2 and TLR4 respond to bacterial cell wall products. We examined the impact of TLR activation on human immune capacity using stimuli ranging from the low levels seen in most environments to the high concentrations widely used for in vitro studies. Peripheral blood mononuclear cells from 117 healthy children were activated with lipopolysaccharide (TLR4 ligand) or peptidoglycan (TLR2 ligand) over a million-fold range of concentrations. Resulting interleukin-6, CCL2, and CCL22 production were quantified by ELISA. The intensity of cytokine production elicited was linearly related to the intensity of the stimulus up to maximal responses. In marked contrast, chemokine production was not linearly related to agonist concentration. Responses rose with increasing stimulation, and then were markedly reduced (40%-100%, p < 0.0001) in response to the high levels of TLR stimulation most commonly cited. Thus, the levels of TLR4 and TLR2 agonists typically used for in vitro interrogation of immune capacity yield results clearly distinct from those obtained using commonly occurring environmental levels of TLR ligands. These findings demonstrate the importance of utilizing TLR ligands at concentrations more closely mimicking environmental levels when assessing immune capacity.

Low-dose paclitaxel prior to intratumoral dendritic cell vaccine modulates intratumoral cytokine network and lung cancer growth

PURPOSE

The main goal of this study was to provide the "proof-of-principle" that low-dose paclitaxel is able to change the tumor microenvironment and improve the outcome of intratumoral dendritic cell vaccine in a murine lung cancer model.

EXPERIMENTAL DESIGN

We evaluated the antitumor potential and changes in the intratumoral milieu of a combination of low-dose chemotherapy and dendritic cell vaccine in the Lewis lung carcinoma model in vivo.

RESULTS

The low-dose paclitaxel, which induced apoptosis in approximately 10% of tumor cells, was not toxic to bone marrow cells and dendritic cells and stimulated dendritic cell maturation and function in vitro. Although tumor cells inhibited dendritic cell differentiation in vitro, this immunosuppressive effect was abrogated by the pretreatment of tumor cells with low-dose paclitaxel. Based on these data, we next tested whether pretreatment of tumor-bearing mice with low-dose paclitaxel in vivo would improve the antitumor potential of dendritic cell vaccine administered intratumorally. Significant inhibition of tumor growth in mice treated with low-dose paclitaxel plus intratumoral dendritic cell vaccine, associated with increased tumor infiltration by CD4(+) and CD8(+) T cells and elevated tumor-specific IFN-gamma production by draining lymph node cells, was revealed. Using a novel intratumoral microdialysis technique and Luminex technology for collecting and characterizing soluble factors released within the tumor bed for several days in live freely moving animals, we showed that low-dose paclitaxel altered the cytokine network at the tumor site.

CONCLUSIONS

Our data indicate that low-dose chemotherapy before intratumoral delivery of dendritic cells might be associated with beneficial alterations of the intratumoral microenvironment and thus support antitumor immunity.

CXCL14 expression and potential function in pancreatic cancer

CXC chemokines influence angiogenesis, growth, and metastatic potential of pancreatic cancer. Therefore, the expression and potential function of CXCL14, a recently described CXC chemokine, was evaluated. CXCL14 is upregulated in pancreatic cancer tissues compared to chronic pancreatitis and normal pancreas. Immunolocalization revealed a distinct expression of CXCL14 in tubular complexes in chronic pancreatitis and in particular at the invasive front of pancreatic cancer tissues. Stimulation of pancreatic cancer cells with CXCL14 showed no effects on cell viability and on chemosensitivity. However, CXCL14 clearly increased invasiveness of pancreatic cancer cells without affecting MMP-2 and VEGF secretion, whereas CXCL14 influenced NFkB p65 levels. In conclusion, CXCL14 might play a pivotal role in the pathobiology of pancreatic cancer, probably by regulating cancer invasion.

The chemokine network. II. On how polymorphisms and alternative splicing increase the number of molecular species and configure intricate patterns of disease susceptibility

In this second review on chemokines, we focus on the polymorphisms and alternative splicings and on their consequences in disease. Because chemokines are key mediators in the pathogenesis of inflammatory, autoimmune, vascular and neoplastic disorders, a large number of studies attempting to relate particular polymorphisms of chemokines to given diseases have already been conducted, sometimes with contradictory results. Reviewing the published data, it becomes evident that some chemokine genes that are polymorphic have alleles that are found repeatedly, associated with disease of different aetiologies but sharing some aspects of pathogenesis. Among CXC chemokines, single nucleotide polymorphisms (SNPs) in the CXCL8 and CXCL12 genes stand out, as they have alleles associated with many diseases such as asthma and human immunodeficiency virus (HIV), respectively. Of CC chemokines, the stronger associations occur among alleles from SNPs in CCL2 and CCL5 genes and a number of inflammatory conditions. To understand how chemokines contribute to disease it is also necessary to take into account all the isoforms resulting from differential splicing. The first part of this review deals with polymorphisms and the second with the diversity of molecular species derived from each chemokine gene due to alternative splicing phenomena. The number of molecular species and the level of expression of each of them for every chemokine and for each functionally related group of chemokines reaches a complexity that requires new modelling algorithms akin to those proposed in systems biology approaches.

Breast cancer: origins and evolution

Breast cancer is not a single disease, but rather is composed of distinct subtypes associated with different clinical outcomes. Understanding this heterogeneity is key for the development of targeted cancer-preventative and -therapeutic interventions. Current models explaining inter- and intratumoral diversity are the cancer stem cell and the clonal evolution hypotheses. Although tumor initiation and progression are predominantly driven by acquired genetic alterations, recent data implicate a role for microenvironmental and epigenetic changes as well. Comprehensive unbiased studies of tumors and patient populations have significantly advanced our molecular understanding of breast cancer, but translating these findings into clinical practice remains a challenge.

Chemokine receptors in cancer metastasis and cancer cell-derived chemokines in host immune response

The chemotactic cytokines called chemokines are a superfamily of small secreted cytokines that were initially characterized through their ability to prompt the migration of leukocytes. Attention has been focused on the chemokine receptors expressed on cancer cells because cancer cell migration and metastasis show similarities to leukocyte trafficking. CXC chemokine receptor 4 (CXCR4) was first investigated as a chemokine receptor that is associated with lung metastasis of breast cancers. Recently, CXCR4 was reported to be a key molecule in the formation of peritoneal carcinomatosis in gastric cancer. In the present review, we highlight current knowledge about the role of CXCR4 in cancer metastases. In contrast to chemokine receptors expressed on cancer cells, little is known about the roles of cancer cell-derived chemokines. Cancer tissue consists of both cancer cells and various stromal cells, and leukocytes that infiltrate into cancer are of particular importance in cancer progression. Although colorectal cancer invasion is regulated by the chemokine CCL9-induced infiltration of immature myeloid cells into cancer, high-level expression of cancer cell-derived chemokine CXCL16 increases infiltrating CD8(+) and CD4(+) T cells into cancer tissues, and correlates with a good prognosis. We discuss the conflicting biological effects of cancer cell-derived chemokines on cancer progression, using CCL9 and CXCL16 as examples.

Retroviral insertions in the VISION database identify molecular pathways in mouse lymphoid leukemia and lymphoma

AKXD recombinant inbred (RI) strains develop a variety of leukemias and lymphomas due to somatically acquired insertions of retroviral DNA into the genome of hematopoetic cells that can mutate cellular proto-oncogenes and tumor suppressor genes. We generated a new set of tumors from nine AKXD RI strains selected for their propensity to develop B-cell tumors, the most common type of human hematopoietic cancers. We employed a PCR technique called viral insertion site amplification (VISA) to rapidly isolate genomic sequence at the site of provirus insertion. Here we describe 550 VISA sequence tags (VSTs) that identify 74 common insertion sites (CISs), of which 21 have not been identified previously. Several suspected proto-oncogenes and tumor suppressor genes lie near CISs, providing supportive evidence for their roles in cancer. Furthermore, numerous previously uncharacterized genes lie near CISs, providing a pool of candidate disease genes for future research. Pathway analysis of candidate genes identified several signaling pathways as common and powerful routes to blood cancer, including Notch, E-protein, NFκB, and Ras signaling. Misregulation of several Notch signaling genes was confirmed by quantitative RT-PCR. Our data suggest that analyses of insertional mutagenesis on a single genetic background are biased toward the identification of cooperating mutations. This tumor collection represents the most comprehensive study of the genetics of B-cell leukemia and lymphoma development in mice. We have deposited the VST sequences, CISs in a genome viewer, histopathology, and molecular tumor typing data in a public web database called VISION (Viral Insertion Sites Identifying Oncogenes), which is located at http://www.mouse-genome.bcm.tmc.edu/vision.

Cell motility and cytoskeletal regulation in invasion and metastasis

Cell motility and chemotaxis can make important contributions to the metastatic cascade. Cell migration pathways in general play significant roles in a variety of physiological processes that can be "hijacked" by cancer cells. Both growth factors and chemokines provide important chemotactic signals in development and metastasis. Receptor activation, following binding of a growth factor or a chemokine, leads to dynamic morphological changes in the actin cytoskeleton network via a variety of distinct and interconnected pathways, resulting in translocation of the cell up a chemoattractant gradient. Such gradients may be produced by stromal cells in the local microenvironment, including macrophages and fibroblasts. A better understanding of the mechanisms of cell motility and cytoskeletal regulation may provide novel therapeutic strategies that would block metastatic progression, reducing dissemination of tumor cells and increasing patient survival.

Primary adrenal adult T-cell leukemia/lymphoma: a case report and review of the literature

Primary adrenal lymphoma (PAL) is very rare; the majority of cases reported previously were of B-cell origin. We report a rare case of primary adrenal adult T-cell leukemia/lymphoma (primary adrenal ATLL). ATLL is a highly aggressive T-cell type non-Hodgkin's lymphoma and etiologically associated with human T-cell lymphotropic virus 1 (HTLV-1). Most ATLL patients present with leukemia and widespread lymphadenopathy. A 37-year-old Japanese woman presented with back pain in January 2004. Examination showed no peripheral lymphadenopathy, circulating lymphoma cells, hepatosplenomegaly, and skin lesions. Imaging studies demonstrated large adrenal masses bilaterally. Subsequently, she underwent open adrenal biopsy and pathological diagnosis was confirmed as T-cell lymphoma. The serum antibody to HTLV-1 was positive. Southern blot analysis detected monoclonal integration of proviral DNA of HTLV-1 into host genome in the biopsy specimen. The diagnosis of ATLL arising in adrenal glands was established. Despite repeated systemic chemotherapy, the patient died of progressive disease in December 2004. ATLL could primarily involve the adrenal gland and this disease entity should be included in the differential diagnosis of adrenal mass lesions.

Role of chemokines in tumor growth

Chemokines play a paramount role in the tumor progression. Chronic inflammation promotes tumor formation. Both tumor cells and stromal cells elaborate chemokines and cytokines. These act either by autocrine or paracrine mechanisms to sustain tumor cell growth, induce angiogenesis and facilitate evasion of immune surveillance through immunoediting. The chemokine receptor CXCR2 and its ligands promote tumor angiogenesis and leukocyte infiltration into the tumor microenvironment. In harsh acidic and hypoxic microenvironmental conditions tumor cells up-regulate their expression of CXCR4, which equips them to migrate up a gradient of CXCL12 elaborated by carcinoma-associated fibroblasts (CAFs) to a normoxic microenvironment. The CXCL12-CXCR4 axis facilitates metastasis to distant organs and the CCL21-CCR7 chemokine ligand-receptor pair favors metastasis to lymph nodes. These two chemokine ligand-receptor systems are common key mediators of tumor cell metastasis for several malignancies and as such provide key targets for chemotherapy. In this paper, the role of specific chemokines/chemokine receptor interactions in tumor progression, growth and metastasis and the role of chemokine/chemokine receptor interactions in the stromal compartment as related to angiogenesis, metastasis, and immune response to the tumor are reviewed.

CXCR4 chemokine receptor engagement modifies integrin dependent adhesion of renal carcinoma cells

The mechanisms leading to renal cell carcinoma (RCC) metastasis are incompletely understood. Although evidence shows that the chemokine receptor CXCR4 and its ligand CXCL12 may regulate tumor dissemination, their role in RCC is not clearly defined. We examined CXCR4 expression and functionality on RCC cell lines, and explored CXCL12-triggered tumor adhesion to human endothelium (HUVEC) or extracellular matrix proteins. Functional CXCR4 was expressed on A498 tumor cells, enabling them to migrate towards a CXCL12 gradient. CXCR4 engagement by CXCL12 induced elevated cell adhesion to HUVEC, to immobilized fibronectin, laminin or collagen. Anti-CXCR4 antibodies or CXCR4 knock down by siRNA applied prior to CXCL12 stimulation impaired CXCL12-triggered tumor adhesion. However, blocking CXCR4 subsequent to CXCL12 stimulation did not. This pointed to an indirect control of tumor cell adhesion by CXCR4. In fact, CXCR4 engagement by CXCL12 also induced alterations of receptors of the integrin family, notably alpha3, alpha5, beta1 and beta3 subunits, and blocking beta1 integrins with a function-blocking antibody prevented CXCL12-induced A498 adhesion. Focal adhesion kinase (total and activated) and integrin-linked kinase significantly increased in CXCL12-treated A498 cells, accompanied by a distinct up-regulation of ERK1/2, JNK and p38 phosphorylation. Therefore, CXCR4 may be crucial in controlling adhesion of A498 cells via cross talking with integrin receptors. These data show that CXCR4 receptors contribute to RCC dissemination and may provide a novel link between CXCR4 chemokine receptor expression and integrin triggered RCC adhesion to the vascular wall and subendothelial matrix components.

Epigenetic up-regulation of CXCR4 and CXCL12 expression by 17 beta-estradiol and tamoxifen is associated with formation of DNA methyltransferase 3B4 splice variant in Ishikawa endometrial adenocarcinoma cells

Increased risk for the development of endometrial cancer has been associated with unopposed oestrogen exposure, hyperoestrogenic factors, and a history of breast cancer treated long-term with tamoxifen (Tam). Stromal cell-derived factor-1, currently named as CXCL12, is a chemokine that, via binding to CXCR4 receptor, activates several downstream effectors and signalling pathways responsible for proliferation, survival, and migration of cancer cells. We observed that 17beta-estradiol (E2) and tamoxifen (Tam) increase the expression of CXCR4 and CXCL12 transcripts and proteins in oestrogen receptor positive (ER(+)) but not in negative (ER(-)02) Ishikawa endometrial adenocarcinoma (ISH) cell lines. However, the demethylating agent 5-Aza-2'-deoxycytidine profoundly elevated CXCR4 and CXCL12 expression in both ER(+) and ER(-)02 ISH cells. Bisulfite sequencing revealed that E2 and Tam up-regulate expression via demethylation of cytosine in the cytosine-guanosine dinucleotide island of CXCR4 and CXCL12 promoters. We also found that E2 and Tam significantly increased, for several hours, the expression of DNA methyltransferase 3B4 enzymatically inactive splice variant in ER(+) but not in ER(-)02 ISH cells. Our results suggest that E2 and Tam, through their ability for gene-transcription regulation, change the cellular milieu that maintains the hypermethylated stage of CpG islands of CXCR4 and CXCL12 promoters.

Regulation of CXCR4 signaling

The chemokine receptor CXCR4 belongs to the large superfamily of G protein-coupled receptors, and is directly involved in a number of biological processes including organogenesis, hematopoiesis, and immune response. Recent evidence has highlighted the role of CXCR4 in a variety of diseases including HIV, cancer, and WHIM syndrome. Importantly, the involvement of CXCR4 in cancer metastasis and WHIM syndrome appears to be due to dysregulation of the receptor leading to enhanced signaling. Herein we review what is currently known regarding the regulation of CXCR4 and how dysregulation contributes to disease progression.