Regulation of the trafficking of tumour-infiltrating dendritic cells by chemokines

Activation of Wnt/β-catenin signal induces DCs to differentiate into immune tolerant regDCs in septic mice

BACKGROUND

Sepsis is a common complication among patients in intensive care units, and has a high mortality rate, with no effective therapies to date. As immunosuppression has become the research focus of sepsis, the regulatory role of dendritic cells (DCs) in the immune response to sepsis has received attention.

OBJECTIVE

To investigate the role of the Wnt/β-catenin signaling pathway in inducing the differentiation of splenic DCs in mice with sepsis caused by cecal ligation and puncture (CLP).

METHODS

C57bl/6 mice were randomly divided into three groups, namely the sham, 24 h post-CLP, and 72 h post-CLP groups. Levels of regulatory T cells (Tregs) among splenic mononuclear cells, suppressor T cells (TSs), and surface markers, such as major histocompatibility complex class II (MHC-II), co-stimulatory molecules (CD80 and CD86), negative co-stimulatory molecule death-ligand 1 (PD-L1), CC chemokine receptor-5 (CCR5), and CC chemokine receptor-7 (CCR7), were analyzed via flow cytometry for each group of mice post-surgery. CD11c+ DCs were purified from the splenic mononuclear cells of each group, and the expression of β-catenin, Wnt5a, and Wnt3a was detected using RT-PCR and western blotting.Each group of DCs was incubated with LPS-containing culture solution, and the supernatant of the culture solution was collected after 24 hours to detect the level of Tumor necrosis factor-α(TNF-α), interleukin (IL)-6, IL-12, and IL-10.

RESULTS

Compared with that in the sham group, the expression of β-catenin, Wnt5a, and Wnt3a in splenic DCs of the other two groups of mice increased with prolonged CLP exposure (P<0.05). Meanwhile, the proportion of Tregs and TSs increased in the mouse spleens after CLP, and levels of DC surface molecules, such as CCR5, CCR7, CD80, CD86, and MHC-II, decreased to different degrees, whereas those of PD-L1 increased. These results suggested that DCs differentiate towards regulatory DCs (regDCs) after CLP in mice. The results of ELISA showed that the longer the exposure time after CLP, the lower the ability of DCs to secrete TNF-α and IL-12, but the higher the level of IL-10 and IL-6.

CONCLUSION

The Wnt/β-catenin signaling pathway activates and induces regDCs differentiation in the splenic DCs of mice with sepsis and participates in the regulation of immune tolerance in the organism.

Melanoma-infiltrating dendritic cells: Limitations and opportunities of mouse models

The infiltration of melanoma lesions by dendritic cells (DCs) has been suggested to play a tumorigenic role due to the capacity of DCs to induce tumor tolerance and promote angiogenesis as well as metastasis. However, it has also been shown that tumor-infiltrating DCs (TIDCs) induce antitumor responses and hence may be targeted in cost-effective therapeutic approaches to obtain patient-specific DCs that present relevant tumor antigens, without the need for ex vivo DC expansion or tumor antigen identification. Unfortunately, little is known about the composition, nature and function of TIDCs found in human melanoma. The development of mouse melanoma models has greatly contributed to the molecular understanding of melanoma immunology in mice, but many questions on TIDCs remain unanswered. Here, we discuss current knowledge about melanoma TIDCs in various mouse models with regard to their translational potential and clinical relevance.

Dendritic cell trafficking in tumor-bearing mice

Prostate cancer is one of the leading causes of cancer deaths, with no curative treatments once it spreads. Alternative therapies, including immunotherapy, have shown limited efficacy. Dendritic cells (DC) have been widely used in the treatment of various malignancies. DC capture antigens and move to the lymphoid organs where they prime naive T cells. Interaction between DC and T cells are most active in lymph nodes and suppression of DC trafficking to lymph nodes impairs the immune response. In this work, we aimed to study trafficking of DC in vivo via various routes of delivery, to optimize the effectiveness of DC-based therapy. A DC labeling system was developed using 1,1'-dioctadecyltetramethyl indotricarbocyanine Iodine for in vivo fluorescent imaging. DC harvested from C57B/6 mice were matured, labeled, and injected intravenously, subcutaneously, or intratumorally, with or without antigen loading with whole tumor lysate, into C57B/6 mice inoculated with RM-1 murine prostate tumor cells. Signal intensity was measured in vivo and ex vivo. Signal intensity at the tumor site increased over time, suggesting trafficking of DC to the tumor with all modes of injection. Subcutaneous injection showed preferential trafficking to lymph nodes and tumor. Intravenous injection showed trafficking to lungs, intestines, and spleen. Subcutaneous injection of DC pulsed with whole tumor lysate resulted in the highest increase in signal intensity at the tumor site and lymph nodes, suggesting subcutaneous injection of primed DC leads to highest preferential trafficking of DC to the immunocompetent organs.

Radiation, inflammation and the immune response in cancer

Radiation is an important component of cancer treatment with more than half of all patients receive radiotherapy during their cancer experience. While the impact of radiation on tumour morphology is routinely examined in the pre-clinical and clinical setting, the impact of radiation on the tumour microenvironment and more specifically the inflammatory/immune response is less well characterised. Inflammation is a key contributor to short- and long-term cancer eradication, with significant tumour and normal tissue consequences. Therefore, the role of radiation in modulating the inflammatory response is highly topical given the current wave of targeted and immuno-therapeutic treatments for cancer. This review provides a general overview of how radiation modulates the inflammatory and immune response—(i) how radiation induces the inflammatory/immune system, (ii) the cellular changes that take place, (iii) how radiation dose delivery affects the immune response, and (iv) a discussion on research directions to improve patient survival, reduce side effects, improve quality of life, and reduce financial costs in the immediate future. Harnessing the benefits of radiation on the immune response will enhance its maximal therapeutic benefit and reduce radiation-induced toxicity.

Laminarin promotes anti-cancer immunity by the maturation of dendritic cells

This research evaluates the effects of laminarin on the maturation of dendritic cells and on the in vivo activation of anti-cancer immunity. In vivo treatment of C56BL/6 mice with laminarin increased the expression levels of co-stimulatory molecules and the production of pro-inflammatory cytokines in spleen dendritic cells. Laminarin enhanced ovalbumin antigen presentation in spleen dendritic cells and promoted the proliferation of OT-I and OT-II T cells. Laminarin also induced the maturation of dendritic cells in tumor-draining lymph nodes and protected interferon-γ and tumor necrosis factor-α and proliferation of OT-I and OT-II T cells in tumors. The combination treatment of laminarin and ovalbumin inhibited B16-ovallbumin melanoma tumor growth and its liver metastasis by antigen-specific immune activation, including cytotoxic T lymphocyte activation and interferon-γ production. Thus, these data demonstrated the potential of laminarin as a new and useful immune stimulatory molecule for use in cancer immunotherapy.

Ascophyllan functions as an adjuvant to promote anti-cancer effect by dendritic cell activation

Our previous study demonstrated that ascophyllan, a sulfated polysaccharide purified from brown alga, has immune-activating effects. In this study, we evaluated ascophyllan as an adjuvant for its therapeutic and preventive effect on tumor in a mouse melanoma model. Ascophyllan induced migration of DCs to spleen and tumor-draining lymph node (drLN) in a mouse B16 melanoma model. Moreover, ascophyllan induced activation of dendritic cells (DCs), and promoted IFN-γ- and TNF-α-producing Th1 immune responses in tumor-bearing mice. In addition, treatment with a combination of ascophyllan and ovalbumin (OVA) in the tumor-bearing mice promoted proliferation of OVA-specific CD4 and CD8 T cells and migration of those cells into the tumor, consequently inhibiting the tumor growth. Immunization with the combination of ascophyllan and OVA caused enhanced OVA-specific antibody production and memory T cell responses compared to OVA immunization alone, and almost completely prevented B16-OVA tumor growth upon subsequent tumor challenge. Finally, the combination of ascophyllan and OVA prevented B16-OVA tumor invasion and metastasis into the liver. Thus, these results demonstrate that ascophyllan can function as an adjuvant to induce DC activation, antigen specific CTL activation, Th1 immune response and antibody production, and hence may be useful as a therapeutic and preventive tumor vaccine.

Molecular mechanisms involved in dendritic cell dysfunction in cancer

Dendritic cells (DC) play a pivotal role in the tumor microenvironment (TME). As the primary antigen-presenting cells in the tumor, DCs modulate anti-tumor responses by regulating the magnitude and duration of infiltrating cytotoxic T lymphocyte responses. Unfortunately, due to the immunosuppressive nature of the TME, as well as the inherent plasticity of DCs, tumor DCs are often dysfunctional, a phenomenon that contributes to immune evasion. Recent progresses in our understanding of tumor DC biology have revealed potential molecular targets that allow us to improve tumor DC immunogenicity and cancer immunotherapy. Here, we review the molecular mechanisms that drive tumor DC dysfunction. We discuss recent advances in our understanding of tumor DC ontogeny, tumor DC subset heterogeneity, and factors in the tumor microenvironment that affect DC recruitment, differentiation, and function. Finally, we describe potential strategies to optimize tumor DC function in the context of cancer therapy.

T Lymphocyte Inhibition by Tumor-Infiltrating Dendritic Cells Involves Ectonucleotidase CD39 but Not Arginase-1

T lymphocytes activated by dendritic cells (DC) which present tumor antigens play a key role in the antitumor immune response. However, in patients suffering from active cancer, DC are not efficient at initiating and supporting immune responses as they participate to T lymphocyte inhibition. DC in the tumor environment are functionally defective and exhibit a characteristic of immature phenotype, different to that of DC present in nonpathological conditions. The mechanistic bases underlying DC dysfunction in cancer responsible for the modulation of T-cell responses and tumor immune escape are still being investigated. Using two different mouse tumor models, we showed that tumor-infiltrating DC (TIDC) are constitutively immunosuppressive, exhibit a semimature phenotype, and impair responder T lymphocyte proliferation and activation by a mechanism involving CD39 ectoenzyme.

Relationship of dendritic cell density, HMGB1 expression, and tumor-infiltrating lymphocytes in non-small cell lung carcinomas

Lung cancer is the leading cause of cancer death worldwide and non-small cell lung carcinoma (NSCLC) is the most common type of lung carcinomas. In adenocarcinomas, the most frequent histologic type of NSCLC, dendritic cells (DCs) are localized in close contact with tumor cells, and tumor-infiltrating lymphocytes (TILs) are observed in the peritumoral zones. In NSCLC, no studies investigating the density of intratumoral DCs and their impact on the density of TILs have been performed. In addition, the role of the alarmin high-mobility group box1 (HMGB1) in intratumoral DCs recruitment has not been analyzed. In the present study, a total of 82 cases of advanced stages of NSCLC were included. Tissue samples were obtained from biopsies and autopsies. DCs in biopsies or combinations of DCs and NK cells, CD3 T lymphocytes, or CD8 T lymphocytes from autopsy specimens were quantified in high power fields. Also, distribution of HMGB1 in tumor cells was detected. In lung adenocarcinomas, irrespective of subclassification, high densities of infiltrating DCs directly associated to high densities of peritumoral TILs. A 2.5-fold increase in TILs was found in specimens with high densities of infiltrating DCs compared with TILs from adenocarcinomas with low densities of infiltrating DCs. High densities of infiltrating DCs were associated with lung adenocarcinomas expressing cytoplasmic or nuclear-cytoplasmic HMGB1. Our results suggest that in adenocarcinoma patients, HMGB1 produced by tumor cells recruits DCs, which associate to an increase of TILs. Encouraging tumor-DCs-T lymphocytes interactions should improve the quality of life and survival of NSCLC patients.

Role of IL-12p40 in cervical carcinoma

BACKGROUND

Previously, we have shown that low IL-12p40 mRNA expression by cervical cancer cells is associated with a poor survival of cervical cancer patients. As IL-12p40 is both a subcomponent of interleukin (IL)-12 and IL-23, the aim of this study was to elucidate the role of IL-12p40 in cervical cancer.

METHODS

We have measured the expression of IL-23p19 mRNA, IL-12p35 mRNA and IL-12p40 mRNA using mRNA in situ hybridisation. The IL-1 and IL-6 were measured by immunohistochemistry.

RESULTS

As IL-23 is a component of the IL-17/IL-23 pathway, a pathway induced by IL-1 and IL-6 in humans, we have studied IL-1 and IL-6 expression. Only a high number of stromal IL-6-positive cells was shown to associate with poor disease-specific survival. The worst disease-specific survival was associated with a subgroup of patients that displayed a high number of IL-6-positive cells and low IL-12p40 expression (P<0.001). Both a high number of IL-6-positive cells and a high number of IL-6-positive cells, plus low IL-12p40 expression were shown to be clinicopathological parameters independent of lymph node metastasis, parametrial involvement and Sedlis score (P=0.009 and P=0.007, respectively).

CONCLUSION

Our results with IL-6 and IL-12p40 are in accordance with the hypothesis that the IL-17/IL-23 pathway has a suppressive role in cervical cancer.

The role of CXC chemokines and their receptors in the progression and treatment of tumors

Chemokines are a class of functional chemotactic peptides that contribute to a number of tumor-related processes. They are functionally defined as soluble factors that are able to control the directional migration of leukocytes, in particular, during infection and inflammation. It appears, however, that the biological effects mediated by chemokines are far more complex, and virtually all cells, including many tumor cell types, can express chemokines and chemokine receptors. A growing body of evidence indicates that they also contribute to a number of tumor-related processes, such as tumor cell growth, angiogenesis/angiostasis, local invasion, and mediate organ-specific metastases of cancer. The CXC chemokine class is a subfamily of a large family of chemokines. During the occurrence and development of tumor cells, this chemokine class is often accompanied by a series of molecular and biological changes. The CXC chemokine subfamily is closely related to the body's immune response to tumors and biological behaviors of tumors. In this paper, CXC chemokines and their role in the progression and treatment of tumors will be reviewed.

The pros and cons of chemokines in tumor immunology

Innate and adaptive immune cells can intervene during tumor progression at different stages including initiation, angiogenesis, local spreading and distant metastasis formation. The net effect can be favorable or detrimental to tumor development, depending on the composition and activation status of the immune infiltrate. Chemokines can determine the distribution of immune cells in the tumor microenvironment and also affect stroma composition. Here we consider how a complex network of chemokines plays a key role in dictating the fate of a tumor. Although the field is in its infancy, we also highlight how targeting chemokines offers a tool to modulate the tumor environment with the aim of enhancing immune-mediated rejection of cancer.

Chemokines in health and disease

Chemokines and their receptors play a key role in development and homeostasis as well as in the pathogenesis of tumors and autoimmune diseases. Chemokines are involved in the implantation of the early conceptus, the migration of subsets of cells during embryonic development, and the overall growth of the embryo. Chemokines also have an important role in the development and maintenance of innate and adaptive immunity. In addition, they play a significant role in wound healing and angiogenesis. When the physiological role of chemokines is subverted or chronically amplified, disease often follows. Chemokines are involved in the pathobiology of chronic inflammation, tumorigenesis and metastasis, as well as autoimmune diseases. This article reviews the role of chemokines and their receptors in normal and disease processes and the potential for using chemokine antagonists for appropriate targeted therapy.

Angiostatic and chemotactic activities of the CXC chemokine CXCL4L1 (platelet factor-4 variant) are mediated by CXCR3

We investigated possible cellular receptors for the human CXC chemokine platelet factor-4 variant/CXCL4L1, a potent inhibitor of angiogenesis. We found that CXCL4L1 has lower affinity for heparin and chondroitin sulfate-E than platelet factor-4 (CXCL4) and showed that CXCL10 and CXCL4L1 could displace each other on microvascular endothelial cells. Labeled CXCL4L1 also bound to CXCR3A- and CXCR3B-transfectants and was displaced by CXCL4L1, CXCL4, and CXCL10. The CXCL4L1 anti-angiogenic activity was blocked by anti-CXCR3 antibodies (Abs) in the Matrigel and cornea micropocket assays. CXCL4L1 application in CXCR3(-/-) or in wild-type mice treated with neutralizing anti-CXCR3 Abs, resulted in reduced inhibitory activity of CXCL4L1 on tumor growth and vascularization of Lewis lung carcinoma. Furthermore, CXCL4L1 and CXCL4 chemoattracted activated T cells, human natural killer cells, and human immature dendritic cells (DCs). Migration of DCs toward CXCL4 and CXCL4L1 was desensitized by preincubation with CXCL10 and CXCL11, inhibited by pertussis toxin, and neutralized by anti-CXCR3 Abs. Chemotaxis of T cells, natural killer cells, and DCs is likely to contribute to the antitumoral action. However, the in vivo data indicate that the angiostatic property of CXCL4L1 is equally important in retarding tumor growth. Thus, both CXCR3A and CXCR3B are implicated in the chemotactic and vascular effects of CXCL4L1.

Recruitment and differentiation of conventional dendritic cell precursors in tumors

The origin of dendritic cells (DCs) in tumors remains obscure. Recent studies indicate that conventional DCs (cDCs) in lymphoid tissues arise from a distinct population of committed cDC precursors (pre-cDCs) that originate in bone marrow and migrate via blood. In this study, we show that pre-cDCs are precursors for cDCs in tumors. Pre-cDCs from tumors, bone marrow, and spleen exhibit similar morphologic, immunophenotypic, and functional properties. Adoptive transfer studies show that bone marrow pre-cDCs migrate from blood into the tumor where they generate cDCs. The chemokine CCL3, which is markedly upregulated in tumors, promotes pre-cDC recruitment. Both pre-cDCs and their cDC progeny actively proliferate within the tumor. cDCs that arise from pre-cDCs in tumors express lower levels of CD11c and MHC class II as compared with those in spleen; however, there was no difference in their abilities to respond to maturation stimuli or activate Ag-specific lymphocytes in vitro. Our study provides the first evidence supporting a role for pre-cDCs in DC development in tumors and suggests a potential target for cancer immunotherapy.

T cell density and location can influence the prognosis of ovarian cancer

The aims of this study were to examine the significance of CD3+ cells in patients with epithelial ovarian cancer and to determine their influence on the disease in relation to their location within tumours. A 157-core tissue-microarray constructed from primary ovarian cancer patients treated at Nottingham-University-Hospitals (2000-2007) was stained for the T-cell marker CD3. The number of CD3+ cells in direct contact with tumour cells was counted per tumour area. These were considered as "intra-tumoural T-cells (ITTC)". Cores were divided into CD3 'high' or 'low' density tumours. "Stromal T-cells (STC)" were assigned as 'positive' or 'negative'. The study population had a median follow-up time of 36-months (0-75). The number of ITTC counted in tumour cores ranged between 0 and 184/mm(2). 90-tumours-(57%) were found to be in the "low-density" rubric, while 56-(36%) were of a "high-density" T-cell population. STC were found in 118-cores-(75%)-compared to 22-cores-(14%)-negative cores. Higher number of ITTC correlated with lower-grade-(p = 0.045), tumour-type-(p = 0.034), and longer-median-survival-times (57-versus 37-months for high-and low-ITTC densities, respectively, p = 0.038). This relationship was reversed when tumours were infiltrated by CD3+ cells in the stroma, predicting worse-survival (Log-rank-test, p = 0.028). Combining ITTC with STC produced an interesting pattern where the ITTC-low/STC + ve had the worst prognosis (p = 0.003). Infiltration of ovarian cancer by T-cells can influence its prognosis depending on the location of these cells (intra-tumoural-versus-stromal). The former predicts improved survival, while the latter is probably contributing to tumour progression and, in turn, worse survival.

The chemokine system in cancer biology and therapy

Chemokines are a key component of cancer-related inflammation. Chemokines and chemokine receptors are downstream of genetic events that cause neoplastic transformation and are components of chronic inflammatory conditions, which predispose to cancer. Components of the chemokine system affect in a cell autonomous or non-autonomous way multiple pathways of tumor progression, including: leukocyte recruitment and function; cellular senescence; tumor cell proliferation and survival; invasion and metastasis. Available information in preclinical and clinical settings suggests that the chemokine system represents a valuable target for the development of innovative therapeutic strategies.

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.

In vitro induction of a dendritic cell phenotype in primary human acute myelogenous leukemia (AML) blasts alters the chemokine release profile and increases the levels of T cell chemotactic CCL17 and CCL22

Immunotherapy is now considered in acute myelogenous leukemia (AML). A dendritic cell (DC) phenotype can be induced in primary human AML cells by in vitro culture in the presence of various cytokine combinations. The aim was to investigate whether this phenotypic alteration is associated with altered chemokine release. AML cells were cultured according to four protocols that have been characterized in detail for AML-DC induction: (1) granulocyte-macrophage colony-stimulating factor (GM-CSF) + interleukin-4 (IL-4) days 1-14 and tumor necrosis factor-alpha (TNF-alpha) for days 6-14, (2) GM-CSF + IL-4 + TNF-alpha + FMS-like tyrosine kinase 3-ligand (Fl3-L) for 8 days, (3) GM-CSF + IL-4 + TNF-alpha + Flt3-L + stem cell factor (SCF) + transforming growth factor-beta1 (TGF-beta1) for 8 days, and (4) 25 Gy gamma-irradiation combined with culture in the presence of GM-CSF + SCF + IL-3 for 4 days. Significantly increased AML-DC release of CCL17 and CCL22 was observed for protocols 1, 2, and 3, whereas effects on CCL2-5, CXCL8, and CXCL10 differed in all protocols. Neutralization studies using a transwell migration assay demonstrated the increased level of CCL17 and CCL22 release was important for AML-DC chemotaxis of normal T cells. Induction of a dendritic AML cell phenotype is associated with an altered chemokine release profile. Detailed characterization of chemokine release should be included in future studies of AML-DC vaccination.

Melanoma and innate immunity--aActive inflammation or just erroneous attraction? Melanoma as the source of leukocyte-attracting chemokines

Unwanted growth breeds response--in the garden as well as in the tumor microenvironment. Innate immune cells mediate the earliest responses against melanoma or its precursors. However, the actual benefit by those cellular efforts is questionable. Why can early melanoma lesions actually develop in the face of rapid innate responses, and why is neutrophil- and macrophage-attracting chemokine secretion observed in melanoma? A surprisingly similar choice of chemokine receptors and chemokines are present in both innate immune cells and melanoma. Here we focus on analogies and differences between the two. Melanoma cell clusters show active chemokine signalling, with mostly tumor growth-enhancing and leukocyte-attracting effects. However, infiltrating leukocytes have only weak tumoricidal effects. Therefore, the observed leukocyte infiltration in melanoma might be at least in part an epiphenomenon of neoplastic self-stimulation rather than a full-fledged innate anti-tumor immune response.

Organ selectivity in metastasis: regulation by chemokines and their receptors

Cancer metastasis results from a non-random process, in which organ selectivity by the tumor cells is largely determined by factors that are expressed at the remote organs that eventually turn into preferred sites of metastasis formation. These factors support the consecutive steps required for metastasis formation, including tumor cell adhesion to microvessel walls, extravasation into target tissue and migration. Of the different components that regulate organ selectivity, instrumental roles were recently attributed to chemokines and their receptors. The present review presents the rationale standing behind the first studies looking at the potential involvement of chemokine-related components in organ selectivity. Based on these studies and many others that followed, the current paradigm is that chemokines that are expressed at specific organs determine to large extent organ specificity by promoting tumor cell adhesion to microvessel walls, by facilitating processes of extravasation into the target tissue and by inducing tumor cell migration. Moreover, chemokines can possibly support additional steps that are required for "successful" establishment of metastases, such as tumor cell proliferation and survival. The review focuses on the CXCL12-CXCR4 pair as the role model in our current understanding of chemokine involvement in organ selectivity. This review also describes the prominent roles played by CCR7 and its corresponding chemokine ligands (CCL21, CCL19) in lymph node metastasis, and of the CCR10-CCL27 axis in melanoma skin survival and metastasis. Overall, the present discussion describes chemokines as important constituents of the tumor microenvironment at metastatic sites, dictating directionality of chemokine receptor-expressing tumor cells, facilitating their adhesion and extravasation, and eventually contributing to organ selectivity.

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.

Manipulating the chemokine-chemokine receptor network to treat cancer

Chemokines are chemoattractant cytokines that regulate the trafficking and activation of leukocytes and other cell types under a variety of inflammatory and noninflammatory conditions. Over the past few years, studies have increasingly shown that chemokines play an important role in several aspects of tumor progression. Tumor cells express functional chemokine receptors, which can sustain proliferation, angiogenesis, and survival and promote organ-specific localization of distant metastases. Chemokine expression in human malignancies is associated with a leukocyte infiltration favoring the establishment of immune escape mechanisms. A literature review of relevant publications on preclinical testing of cancer therapies based on interference with the cancer chemokine network was performed. The feasibility, potential advantages, and limitations of the clinical translation of the results of such studies in treatment of different tumor types and settings are discussed. The chemokine network is a key player in the establishment of metastases. In the preclinical setting, blocking agents and antibodies directed against CXCR4 prevent metastasis of different cancers. In mouse models, overexpression of selected chemokines causes tumor infiltration by distinct leukocyte subsets, resulting in tumor regression and tumor-specific immunity generation. Researchers have also successfully used chemokines as carriers and/or adjuvants for cancer vaccines. The cancer chemokine network is a multifaceted therapeutic target.

In melanoma changes of immature and mature dendritic cell expression correlate with tumor thickness:an immunohistochemical study

Cells with a dendritic morphology and/or expression of dendritic cell (DC) markers have been repeatedly described in several human tumors, but the distribution and density of melanoma-associated DCs have not yet been reported. The aim of the present study is to analyze the density and topographical distribution of melanoma-associated DCs and their relation with CD3(+), CD4(+) and CD8(+) T lymphocytes in forty cases of cutaneous human melanoma. In melanocytic tumours different pools of DCs were recognised in the epidermis and in the dermis, particularly in intimate relation with lymphocyte clusters inside the melanocytic proliferation, and more often at the edges of tumours. The number of Langerin-positive DCs showed an inverse correlation with tumour depth (correlation coefficient r= -0.59, P=0.0001) and was significantly lower in thick melanomas compared to thin and intermediate ones (P<0.0005). The density of CD83(+) DCs was significantly lower in thick melanomas compared to thin and intermediate ones (P<0.009). A significant correlation was found between the density of the two DCs subsets (r=0.57, p<0.0001). The number of CD3(+) lymphocytes was inversely correlated to the depth of infiltration (r=-0.596, P<0.0001): melanoma cases with II-III Clark level showed a higher T lymphocyte mean density compared to cases with IV-V Clark level (P<0.0001). T lymphocyte density was significantly lower in thick melanomas compared to thin and intermediate melanomas (P<0.0005). In conclusion, our study indicates a progressive loss of DCs and T lymphocytes in the neoplastic progression of melanomas; further identification of the molecular pathways involved in the functional impairment of these immunitary cells may lead to new immunotherapeutic approaches for melanoma patients that would improve the clinical outcome of the patients.

The multifaceted roles of chemokines in malignancy

Tumor development and progression are multifactorial processes, regulated by a large variety of intrinsic and microenvironmental factors. A key role in cancer is played by members of the chemokine superfamily. Chemokines and their receptors are expressed by tumor cells and by host cells, in primary tumors and in specific metastatic loci. The effects of chemokines on tumorigenesis are diverse: While some members of the superfamily significantly support this process, others inhibit fundamental events required for tumor establishment and metastasis. The current review describes the multifaceted roles of chemokines in malignancy, addressing four major aspects of their activities: (1) inducing leukocyte infiltration to tumors and regulating immune functions, with emphasis on tumor-associated macrophages (and the chemokines CCL2, CCL5), T cells (and the chemokines CXCL9, CXCL10) and dendritic cells (and the chemokines CCL19, CCL20, CCL21); (2) directing the homing of tumor cells to specific metastatic sites (the CXCL12-CXCR4 axis); (3) regulating angiogenic processes (mainly the ELR(+)-CXC and non-ELR-CXC chemokines); (4) acting directly on the tumor cells to control their malignancy-related functions. Together, these different chemokine functions establish a net of interactions between the tumor cells and their microenvironment, and partly dictate the fate of the malignancy cascade.

Role of tumor-derived proinflammatory cytokines GM-CSF, TNF-alpha, and IL-12 in the migration and differentiation of antigen-presenting cells in cervical carcinoma

BACKGROUND

Proinflammatory cytokines are important in modifying the activity, differentiation, and migration of antigen-presenting cells and may influence the survival of cancer patients. The study assessed whether GM-CSF, TNF-alpha, and IL-12, produced by cervical cancer cells, are important for the activity, differentiation, and migration of antigen-presenting cells.

METHODS

In 90 patients with cervical carcinoma the number of monocytes/tumor-associated macrophages (TAM), mature dendritic cells (DC), and Langerhans cells (LHC) was determined using immunohistochemistry. An RNA in situ hybridization technique was used to measure the expression level of GM-CSF, TNF-alpha, IL-12p35, and IL-12p40.

RESULTS

TAM were detected intraepithelial as well as in the stroma of the tumor. LHC were only detected intraepithelial and mature DC only in the tumor stroma. The number of TAM correlated positively with the number of mature DC. The expression levels of GM-CSF and TNF-alpha correlated positively with the number of TAM and DC. TNF-alpha showed a negative correlation with the number of LHC. A significant correlation between the expression of functional IL-12 (IL-12p40) and stromal TAM was found. The expression of GM-CSF, TNF-alpha, and IL-12p40 did not correlate significantly with disease-free survival. However, high IL-12p40 expression was associated with a favorable cumulative overall survival.

CONCLUSIONS

The results suggest that GM-CSF as well as TNF-alpha, produced by cervical carcinoma cells, may play a role in the differentiation of monocytes into mature DC. Furthermore, TNF-alpha may influence the migration of LHC from the tumor.

Natural killer cell-dendritic cell crosstalk in the initiation of immune responses

Dendritic cells (DCs) and natural killer (NK) cells play a critical role in early defences against cancer and infections. They specialise in complementary functions, including IL-12 or IFN-alpha/beta secretion and antigen presentation for the former, and IFN-gamma secretion and killing of infected or tumour cells for the latter. Both DCs and NK cells are also sensors of the immune system that have developed different, but partially overlapping, systems to identify pathology associated danger signals. Evidence of NK-DC interaction has accumulated recently. This interaction may lead to NK cell activation, DC activation, or apoptosis depending on the activation status of both cell types. Thus, the outcome of NK-DC crosstalk is likely to influence both innate and adaptive immune responses. This review addresses the molecular mechanisms under-lying the different NK-DC interactions, and their in vivo significance in anti-tumour or antimicrobial immunity. Finally, we discuss the potential clinical implications of this new field.

Tumour-associated macrophages are a distinct M2 polarised population promoting tumour progression: potential targets of anti-cancer therapy

Tumour-associated macrophages (TAM) represent the major inflammatory component of the stroma of many tumours, and can affect different aspects of the neoplastic tissue. Many observations indicate that TAM express several M2-associated pro-tumoural functions, including promotion of angiogenesis, matrix remodelling and suppression of adaptive immunity. The pro-tumoural role of TAM in cancer is further supported by clinical studies that found a correlation between the high macrophage content of tumours and poor patient prognosis. Evidence is presented here supporting the view that TAM represent a unique and distinct M2-skewed myeloid population and are a potential target for anti-cancer therapy.

Melanoma cells interfere with the interaction of dendritic cells with NK/LAK cells

Dendritic cells (DCs) and natural killer (NK) cells are key players at the interface between innate resistance and acquired immunity. NK cells can induce DC maturation, a differentiation process whereby DCs respond to a environmental stimulus and acquire the ability of eliciting adaptive immunity. Conversely, maturing DCs promote NK functions in vivo and in vitro. This interplay has important consequences on the immune response to pathogens and possibly to neoplastic cells. Here, we show that B16 melanoma cells actively modulate the interaction between DCs derived from bone marrow precursors and NK/LAK cells propagated from the spleen of C57BL/6 mice. DCs increased in a dose-dependent manner the ability of NK/LAK cells to kill melanoma cells and to produce cytokines. This activatory cross-talk entailed the production of IL-18 by DCs and of IFN-gamma by NK/LAK cells. Melanoma cells were not a passive target of NK activity; they regulated the outcome of the interaction between DCs and NK/LAK cells, inhibiting the in vitro production of cytokines as effectively as the genetic deletion of IL-18 or IFN-gamma. Interference with the NK/DC interaction possibly represents a mechanism used by growing tumors to evade the immune response.

Natural-killer cells and dendritic cells: "l'union fait la force"

Several recent publications have focused on the newly described interactions between natural-killer (NK) cells and dendritic cells (DCs). Activated NK cells induce DC maturation either directly or in synergy with suboptimal levels of microbial signals. Immature DCs appear susceptible to autologous NK-cell-mediated cytolysis while mature DCs are protected. NK-cell-induced DC activation is dependent on both tumor necrosis factor-alpha (TNF-alpha)/interferon-gamma (IFN-gamma) secretion and a cell-cell contact involving NKp30. In vitro, interleukin-12 (IL-12)/IL-18, IL-15, and IFN-alpha/beta production by activated DCs enhance, in turn, NK-cell IFN-gamma production, proliferation, and cytotoxic potential, respectively. In vivo, NK-cell/DC interactions may occur in lymphoid organs as well as in nonlymphoid tissues, and their consequences are multiple. By inducing DC activation, NK-cell activation induced by tumor cells can indirectly promote antitumoral T-cell responses. Reciprocally, DCs activated through Toll-like receptors (TLRs) induce potent NK-cell activation in antiviral responses. Thus, DCs and NK cells are equipped with complementary sets of receptors that allow the recognition of various pathogenic agents, emphasizing the role of NK-cell/DC crosstalk in the coordination of innate and adaptive immune responses.