CHEMOKINES AND CANCER: MIGRATION, INTRACELLULAR SIGNALING, AND

M. O'Hayre2, C.L. Salanga2, T.M. Handel1,2, S.J. Allen2

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INTERCELLULAR COMMUNICATION IN THE MICROENVIRONMENT

Skaggs School of Pharmacy and Pharmaceutical Science, University of California, San Diego, La Jolla,

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California 92093-0684 1

To whom correspondence should be addressed (email: [email protected]). 2

ABSTRACT

Inappropriate chemokine/receptor expression or regulation is linked to many diseases, especially those characterized by excessive cellular infiltrate like rheumatoid arthritis and other inflammatory disorders. There is now overwhelming evidence that chemokines are also involved in the progression of cancer,

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functioning in several capacities. Firstly, specific chemokine-receptor pairs are involved in tumor metastasis. This is not surprising due to their role as chemoattractants in cell migration. Secondly, chemokines help to shape the tumor microenvironment, often in favor of tumor growth and metastasis, by recruitment of leukocytes and activation of pro-inflammatory mediators. Emerging evidence

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suggests that chemokine receptor signaling 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 signaling pathways they couple into, which may be key to better understanding how and why particular chemokines contribute to cancer growth and metastasis. Further investigation chemotherapy.

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into these areas may identify targets that if inhibited, could render cancer cells more susceptible to

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Running Title: Chemokines and Cancer

Keywords: Chemokines, Chemokine Receptors, Cancer, Metastasis, Tumor Microenvironment,

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Signaling

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All authors contributed equally

INTRODUCTION Chemokines comprise a superfamily of ~50 human ligands and 20 receptors that are pivotal regulators

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of cell migration [1, 2]. Traditionally, chemokines and their receptors have been divided into four families based on the pattern of cysteine residues in the ligands (CXC, CC, C, and CX3C). They have also been functionally classified as being "homeostatic" or "inflammatory". Homeostatic chemokines are constitutively expressed and control leukocyte navigation during immune surveillance. Inflammatory chemokines, which constitute the vast majority, are inducible and control cell recruitment to sites of

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infection and inflammation [3]. Certain chemokines are also involved in developmental processes such transition from bone marrow resident hematopoietic stem cells through development of T-cell precursors in the thymus, migration into secondary lymphoid organs for immune response initiation, and maturation into circulating memory and effector T-cells, involves sequentially coordinated changes in the profiles of chemokine receptor expression to guide the cells into the appropriate

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microenvironments [5].

Chemokines are 70-130 amino acid soluble proteins that contain 1-3 disulfide bonds, the exceptions being CX3CL1 (fractalkine)1 and CXCL16, which have a chemokine domain tethered to a membrane anchored mucin stalk [6, 7]. Despite variable levels of sequence homology, they adopt a characteristic fold that consists of an N-terminal unstructured domain that is critical for signaling, a three stranded β-

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sheet connected by loops and turns, and a C-terminal helix (Figure 1A). Although they bind their receptors as monomers in the context of cell migration, many chemokines dimerize or form higher order oligomers that appear to be important for localization to glycosaminoglycans on cell surfaces and the extracellular matrix (ECM) [8], and possibly for signaling related to other processes separate from migration [9, 10]. The chemokine receptors are seven transmembrane G protein-coupled receptors

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(GPCRs). As such, they have been best characterized with respect to signaling through heterotrimeric G proteins, primarily involving Gi [11] (Figure 1B). However, there is ample evidence indicating that chemokine receptors also signal through other G protein subtypes or even through non-G-protein

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mediated pathways [12-15]. Furthermore, although the α subunit of G proteins has traditionally been regarded as the major signaling subunit, the βγ subunits are crucial for activation of many chemokine-

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induced pathways. Two of the major pathways activated by Gβγ are Phosphoinositide 3-Kinase gamma (PI3Kγ) and Phospholipase C (PLC), while G∝i proteins mainly inhibit adenylyl cyclase and transduce signals through tyrosine kinases such as Src [11]. 1

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CHEMOKINE NOMENCLATURE: Chemokines are initially referred to as "new nomenclature (old nomenclature)" for example "CX3CL1 (fractalkine)" (where new = CCL#, CXCL#, CL#, or CX3CL#; # represents a number; L refers to ligand). Subsequently, new nomenclature alone (e.g. CX3CL1) will be employed. The nomenclature for the receptors is CCR#, CXCR#, CR#, or CX3CR#, where R refers to receptor. Chemoattractant receptor systems will be referred to as ligand:receptor. For example, the chemoattractant, CXCL12, and its receptor, CXCR4, will be referred to as CXCL12:CXCR4

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as lymphopoiesis, cardiogenesis and development in the CNS [4]. For example, in lymphopoiesis, the

Despite their structural homology and shared ability to induce chemotaxis, different chemokines can elicit other distinct cellular responses [16, 17] and/or activate different pathways to elicit a particular

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response [18, 19]. The signaling and physiological response downstream of receptor activation can also vary depending on chemokine-receptor combination, cell type and pathophysiological state [16, 17]. Figure 2 summarizes the major signaling cascades and functional outcomes of chemokine-receptor activation. It is important to keep in mind that specific subsets or combinations of these pathways can be used to induce the functional response.

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In the past few years, the involvement of chemokines and their receptors in cancer, particularly since metastasis is not a random process of cell migration. On the contrary, it has been known since the early 1900s that cancer cells have a propensity to metastasize to specific organs [23]. Furthermore, metastasis has many features in common with normal cell migration. However, key differences include abnormal chemokine receptor expression, regulation or utilization, often on cells that typically do not

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migrate. Chemokines then provide a physical address for the secondary destination of the tumor cells. The process by which tumors grow and metastasize is complex [24] with many steps required for primary tumor development and establishment of clinically significant secondary tumors (Figure 3). These steps include (i) survival and growth of the primary tumor (ii) detachment of tumor cells from the primary lesion (iii) invasion into vascular or lymphatic vessels (iv) homing and adherence to the

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destination organs and (v) survival, growth and "organogenesis" of the metastasized cells in their new environment [21, 25]. Since alternative environments like bone marrow and lymph node are not naturally compatible with cells from breast for example, cancer cells must both derive and provide signals to favorably shape the tumor microenvironment to become conducive to survival and growth [26-28]. The role of chemokines and their receptors in cancer can thus be divided into three broad

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categories which contribute to one or more of the above processes: providing directional cues for migration/metastasis, shaping the tumor microenvironment, and providing survival and/or growth signals. In this review we describe the role of chemokines and chemokine receptors in each of these

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processes. Table 1 summarizes chemokine receptors and respective ligands involved in cancer and their general mechanism of tumorigenesis. Although their involvement in these three categories is fairly

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well established, the exact mechanisms of action are not well understood and the underlying complexity of the chemokine network makes it difficult to characterize definitively. Consideration of some of these complexities, discussed at the end of this review, may be crucial to elucidating more precise

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mechanisms and thus enable development of better cancer therapeutics. CHEMOKINES IN MIGRATION/METASTASIS OF CANCER CELLS The leading cause of death in cancer patients is from metastasis, the formation of secondary tumors in organs distant from the original tumor. It is not a random process but rather shows bias for particular Licenced copy. Copying is not permitted, except with prior permission and as allowed by law. © 2008 The Authors Journal compilation © 2008 Biochemical Society

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metastasis, has been firmly established [20-22]. The association with metastasis is not unsurprising

tissues, and is ordered, specific and molecularly directed [20, 24]. Breast cancer for example, has a tendency to metastasize to lymph node, bone marrow, lung and liver. When Müller and colleagues

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highlighted the role for chemokines in directing organ-specific metastasis, it became clear that chemokine receptor expression patterns on cancer cells and the localization of the corresponding ligands could provide clues for understanding directional metastasis [20]. It has now been established that several chemokines and their receptors play a role in the metastatic process by directing the migration of receptor-bearing tumor cells to sites of metastases where the ligands are expressed. tumor migration.

The general mechanisms involved in normal cell migration and metastasis are similar. Chemokines cause cell movement by inducing changes in cytoskeletal structure and dynamics. Actin polymerization leads to formation of protrusions (pseudopods) and with the help of integrins, form focal adhesions with the extracellular matrix (ECM) to help propel the cell forward [29]. While multiple pathways contribute to chemokine-induced cell migration, PI3K, FAK (focal adhesion kinase), and the Rho family of GTPases

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(Rho, Rac, Cdc42) are particularly important [30-33]. ERK and PKC signaling, independently or in conjunction with PI3K may also be involved [34-37]. More detail regarding signaling involved in migration is shown in Figure 2.

Altered Chemokine Receptor Expression on Cancer Cells. What then distinguishes normal cells

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from metastatic cancer cells, enabling the cancer cells to migrate when they normally would not? While there are many contributing factors, in numerous types of cancer, the malignant cells exhibit increased or aberrant expression of particular chemokine receptors relative to their normal counterparts, notably CXCR4, CCR7, and CCR10 [22, 25, 38, 39]. In a study of breast cancer, it was demonstrated that CXCR4 was strongly expressed on cancer cells compared to normal breast epithelial tissue, which

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does not express any CXCR4, and that antibodies against CXCR4 blocked metastasis in a mouse model of breast cancer [20]. Since that seminal publication, CXCR4 and its ligand, CXCL12 (SDF-1α) have been implicated in ~23 different types of cancer [38]. At least two other chemokine systems also

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play a direct role in metastatic homing of cancer cells: CCR10 in metastasis to skin where CCL27 (CTACK) is expressed (e.g. melanoma), and CCR7 in lymph node metastasis where CCL21 (SLC) is

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expressed [20, 25, 39, 40]

Many reasons for altered chemokine/receptor expression have been identified. Chemokine receptor expression is regulated both at the transcriptional level and post-transcriptionally through RNA stability,

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translation, and receptor desensitization and internalization [41-47]. The tumor microenvironment, and mutant proteins or altered signaling in the cancer cell itself, can also affect chemokine receptor levels. Conditions present within a tumor, such as hypoxia and a rich cytokine environment including IL-2, can induce the transcription of certain chemokine receptors [41, 44, 45]. For example, hypoxia induces

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These findings make sense because of the parallels one can draw between lymphocyte trafficking and

upregulation of CXCR4 transcription via hypoxia inducible factor 1 (HIF-1) and through transcript stabilization [42, 44]. HIF-1 was also recently found to promote transcription of CCR7, CXCR1, and

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CXCR2 [46, 47]. In renal carcinoma cells, it was demonstrated that mutation of the von Hippel-Lindau (pVHL) tumor suppressor protein, normally responsible for targeting HIF-1 for cell degradation, results in constitutive activation of HIF-1 target genes including CXCR4 [44]. Nuclear factor kappa B (NF-κB) is a key signaling pathway that is often activated in cancer cells and can contribute to the transcription of chemokines (e.g. CXCL1 (Gro-α), CXCL8 (IL-8), and CXCL12), and chemokine receptors, such as

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CXCR1, CXCR2, and CXCR4 [39, 48]. On a post-transcriptional level, changes in receptor translation and desensitization by internalization and degradation provide other mechanisms for regulating shown to be associated with the oncogene, HER2, which may help to protect CXCR4 from ligandinduced ubiquitination and degradation [42].

For more comprehensive reviews on mechanisms associated with chemokine receptor upregulation in

THE TUMOR MICROENVIRONMENT

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cancer, see [22, 43, 49].

A link between inflammation and cancer was observed over 150 years ago when Rudolf Virchow noted that cancers tend to occur at sites of chronic inflammation [50]. Although the relationship between

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cancer and inflammation is complex, epidemiological studies indicate that inflammatory and infectious diseases are often associated with an increased risk of cancer [51]. In many ways, the microenvironment of tumors mimics that of tissues during the height of an inflammatory response to injury [51]. For example, they both contain a large number of cells from both the innate and adaptive immune system, recruited and activated by a complex profile of chemokines, cytokines, growth factors and proteases. However, unlike the organized morphology of normal tissue, and the ultimate resolution

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of the inflammation that occurs during healing, tumors exist in a state of chronic inflammation characterized by the presence of malignant cells, development of an aberrant vascular network and the persistence of inflammatory mediators. Within the tumor microenvironment, chemokines and their

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receptors play roles in modulating angiogenesis, cell recruitment, tumor survival and proliferation, and through these processes, help to define the progression of the cancer. Although this review focuses

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primarily on the pro-tumorigenic roles of chemokines, it should be noted that many chemokines/receptors have anti-tumorigenic effects as expected given their physiological role in protecting the host [52].

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Recruitment of Leukocytes - Tumor-Associated Macrophages and Dendritic Cells. One important link between cancer and inflammation is the recruitment of cells, including neutrophils, macrophages, dendritic cells, eosinophils, mast cells and lymphocytes. Of these, macrophages, known as tumorassociated macrophages (TAMs) [53] represent an important component of solid tumors and may

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chemokine receptor expression. For example, enhanced CXCR4 translation in breast cancer cells was

account for up to half of the tumor mass. They were first observed in tumors in the late 1970s and therefore represent one of the first specific links between the immune system and cancer.

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Macrophages are very heterogeneous and play many roles in the progression of cancer depending upon the nature of their maturation/polarization. Although an oversimplification of their states, designating the two ends of the spectrum as M1 and M2 represents a convenient way to classify macrophage polarization [54]. M1 (classical) macrophage activation by IL-2/IFN-γ and IL-12 is characterized by high levels of antigen presentation, IL-12/IL-23 production and development of a

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polarized type I response, leading to tumor cell cytotoxicity and necrosis. In contrast, M2 polarization is the induction of angiogenic factors, cytokines and proteases. These factors serve to suppress the adaptive immune response and promote angiogenesis, matrix remodeling and tumor growth. A number of excellent reviews have presented evidence that TAMs function as M2 polarized macrophages [28, 53, 54] that promote a permissive environment for tumor growth. The in vivo significance of macrophage recruitment to tumor growth has been studied in a number of models and in clinical

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studies, and generally high numbers of TAMs correlate with enhanced vascularization and growth [51, 56].

Early studies indicated a role for the pro-inflammatory MCP family of proteins, termed ‘tumor-derived chemotactic factors’ in macrophage recruitment to tumor sites [57]. Over the years, the role of CCL2

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(MCP-1) in macrophage recruitment and activation via one of its receptors, CCR2, has been extensively studied [58]. CCL2 is produced by many types of tumors, including breast, pancreas, lung, cervix, ovary, melanomas, sarcomas and glial cell tumors, and by, fibroblasts, endothelial cells and macrophages at the tumor site [28]. CCL2 expression levels correlate with the extent of macrophage recruitment [59] and for a number of cancers, expression levels of CCL2 are also related to prognosis

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[59, 60]. The relationship between chemokines, macrophages and prognosis, is complex and dependent upon the cancer: this has been termed the ‘macrophage balance hypothesis’. For example, the effect of CCL2 upon tumor progression in melanoma cell lines is concentration-dependent; while

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melanoma cell lines transfected with high levels of CCL2 promote tumor rejection, those transfected with lower levels support tumor growth [61]. A recent model for melanoma has directly correlated low

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levels of CCL2 with the presence of M2 macrophages and increased angiogenesis and tumor growth compared to macrophage-depleted melanomas or melanomas expressing no CCL2 at all [62]. Similarly, pancreatic cancer patients with higher circulating levels of CCL2 had higher survival rates

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than those with lower circulating levels [63]. However, higher levels of CCL2 are associated with increased malignancy in models of mammary adenocarcinomas [64, 65]. CCL5 (RANTES) also recruits macrophages to tumors and its increased presence correlates with poor prognosis in breast and cervical cancer patients [66]. A direct link between macrophage recruitment by

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characterized by defective IL-12 production [55] leading to an IL-12low phenotype and is associated with

CCL5 and breast tumor growth was observed using a CCL5 variant that contains an extra methionine at its N-terminus and functions as a receptor antagonist. Mice treated with the antagonist showed a

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reduction in tumor size and vascularization compared to control-treated mice [67]. The ability of CCL5 to induce the monocyte expression of CCL2 may also play an important role in monocyte recruitment and shaping the tumor microenvironment [68].

In total, about twenty chemokines have been detected in neoplastic tissues of various cancers (Table 1). TAMs themselves express chemokine receptors and selected chemokines (e.g. CCL2, CCL17

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(TARC), CCL18 (PARC), CCL20 (MIP-3α) and CCL22 (MDC)), suggesting both autocrine and levels of chemokine receptors such as CCR2 is very low [69] and may be due to the transition of the cells from blood monocytes to tissue macrophages and/or may prevent these cells from migrating out of the tumor microenvironment once they arrive [70].

Dendritic cells (DCs) are attracted to the tumor microenvironment by chemokines [71-74], where they

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are often found at low levels [75]. Like macrophages, DCs comprise a diverse population of cells and are likely to play multiple roles. While a number of tumors contain mature plasmacytoid DCs capable of priming T-cells, those observed in ovarian cancers are thought to function as pro-angiogenic factors, acting through TNF-α and CXCL8 [72]. Thus, DCs are likely to have both anti-tumorigenic (e.g. T-cell

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priming) and pro-tumorigenic (e.g. angiogenesis, immune tolerance) roles in cancer. A number of tumors, including primary cutaneous melanomas, ovarian tumors and breast carcinomas also contain immature DCs [71, 73, 74]. This suggests that factors in the microenvironment may suppress DC cell maturation to dampen their anti-tumorigenic effects. Factors such as IL-6 and M-CSF present in the tumor environment may also prevent DC maturation by switching the differentiation from DC cells to macrophages [76]. Interestingly, differential localization of immature and mature DCs, most

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likely recruited by CCL20, has been observed in breast adenocarcinomas [71]. Immature cells incapable of T-cell priming are present within the tumor, while mature cells are located in the peritumoral areas, interacting in some cases with T-cells. Since the DC-T cell interaction usually only

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occurs in the lymph, it suggests that these cells may be mounting a tumor-specific response.

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The Pro-tumorigenic Effects of other Stromal Cells in the Microenvironment. The complex interplay between cells in the microenvironment has recently been highlighted by the discovery of tumor-promoting fibroblasts in epithelial cancers [77, 78]. Fibroblasts and myofibroblasts often represent a significant portion of stromal cells in carcinomas. Their direct effects upon carcinoma

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growth were highlighted in 1999 when it was demonstrated that stromal fibroblasts from human prostate carcinomas had tumor-stimulating properties [79]. In this study, fibroblasts from cancerous or non-cancerous tissues were isolated, mixed with immortal but non-tumorigenic prostate epithelial cells, and co-cultured or injected into immunodeficient mice. Only fibroblasts isolated from the carcinomas

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paracrine roles for these proteins in the microenvironment. Interestingly, on TAMs, the expression

were able to stimulate tumor growth. These fibroblasts, termed carcinoma-associated fibroblasts (CAFs), include large populations of myofibroblasts that usually play crucial roles in wound repair, and

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serves as another example of the association between inflammation and cancer. The pro-tumorigenic properties of CAFs in mammary carcinomas are partly mediated by CXCL12 [78]. CXCL12 is expressed at high levels by mammary carcinoma CAFs and plays two main roles. Firstly, it directly stimulates tumor growth by binding to and signaling through CXCR4 on tumor cells. Secondly, it recruits endothelial cells (ECs) into tumors, facilitating angiogenesis (see below). However, CAFs

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exhibit complex and heterogeneous expression profiles, and it is not surprising that other CAF-derived

Angiogenesis - Recruitment of Endothelial Cell Precursors. Angiogenesis is the process of forming new blood vessels, and requires production of new endothelial cells (ECs) to form the vessel walls. It is necessary for tumor growth, and cells in the tumor microenvironment release a plethora of smallmolecules and proteins to promote this process [83-87]. Like leukocyte migration, blood vessel

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formation is directional and oriented towards the tumor to increase vascularization and enhance growth [88]. Chemoattractants contribute to this process both by recruiting precursor ECs and by inducing their proliferation.

However, the role of chemokines in angiogenesis is quite variable: some are angiogenic, some have no

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effect on angiogenesis, and others are angiostatic (inhibit angiogenesis). This variability is especially evident within the CXC class of chemokines, as the presence (+) or absence (-) of the ELR motif (GluLeu-Arg) near their N-termini correlates with angiogenic or angiostatic characteristics [89-91]. Furthermore, introduction of the ELR motif into the ELR- chemokine, CXCL9 (MIG), rendered it angiogenic, whereas mutating the ELR motif out of CXCL8 rendered it angiostatic [89]. CXCL12 is the one exception to the ELR correlation within the CXC chemokines as it lacks the ELR motif but is

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angiogenic. However, it is believed to mediate its angiogenic effects in part through the induction of vascular endothelial growth factor (VEGF) [16, 78]. Non-CXC chemokines can also have angiogenic and angiostatic properties that are not explained by

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the ELR motif. For example, CCL1 (I-309), CCL2, CCL11 (Eotaxin), and CX3CL1 can all induce

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angiogenesis, sometimes directly and sometimes through recruitment of other cells such as TAMs, which in turn release growth and angiogenic factors (e.g. VEGF and basic fibroblast growth factor (bFGF)) [92-94]. Other CC chemokines can inhibit angiogenesis, as has been demonstrated for CCL21

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[95].

All of the ELR+ chemokines bind to CXCR2, which is expressed on ECs [96]. Of these, the TAMderived CXCR2 ligand, CXCL8, is thought to play a particularly important role in angiogenesis where it is believed to induce the migration and proliferation of ECs [96]. The signaling pathways involved in

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chemokines (e.g. CCL2, CCL5 and CXCL8) also play roles in tumor growth [80-82].

angiogenesis are essentially the same pathways for inducing cell migration, survival, and proliferation of leukocytes (just specifically in endothelial cells) as discussed elsewhere in the review. Conversely,

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the angiostatic properties of many of the ELR- chemokines are thought to be due to activation of CXCR3B on ECs which results in the inhibition of migration and proliferation [87, 97]. CXCR3B is a splice variant of CXCR3 that is found on ECs, whereas the CXCR3A splice variant is expressed on mononuclear cells. Interestingly, CXCR3B contains 52 extra amino acids at its N-terminus relative to CXCR3A, which may modulate its chemokine binding and signaling properties. In contrast to CXCR3B,

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activation of CXCR3A results in activation of survival and proliferation pathways [97]. This cell-type specific expression of the CXCR3 splice variants provides an explanation for how ELR- chemokines antagonizing these events in ECs in order to inhibit angiogenesis.

Other Contributors to the Microenvironment - MMPs. Matrix metalloproteases (MMPs) present in the tumor microenvironment have been classically associated with processes such as angiogenesis. However, it has become clear that the roles of MMPs are complex and TAM-derived MMPs play both

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tumor-promoting and tumor-suppressing roles [98-100]. Chemokines and MMPs have an interesting interdependent relationship as they control the function of one another. For example, CCL2 induces the expression of MMP-12 by monocytes/macrophages [101], CXCL8 induces MMP-2 and MMP-9 in endothelial cells [102], CCL5 and CXCL12 induce MMP-9 expression in monocytes [103], and CCL2

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and CXCL8 induce MT1-MMP [104]. In melanoma cells, the up-regulation of MMP-2 by CXCL8 is associated with increased tumor growth and metastasis [105], while the up-regulation of MMP-9 by CCL5 is thought to contribute to the progression of breast cancer [106]. Conversely, proteolysis of chemokines within their N-terminal signaling domains by MMPs can modulate their activity; examples include the MCPs (CCL2/7/8), CXCL11 (I-TAC), CXCL8 and CXCL12 [7, 107]. In the case of the MCPs, the cleavage products have impaired activity, and in fact can function as antagonists, while the

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cleavage of the 6 or 7 N-terminal residues of CXCL8 by MMP-9 increases the activity of this chemokine. Truncated CXCL11 failed to attract lymphocytes and was much less potent in inhibiting microvascular EC migration, leading to the concept that the processed form(s) may lead to reduced

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numbers of tumor infiltrating lymphocytes and a more angiogenic environment [107]. Overall, the ability of MMPs to dramatically alter the function of a given chemokine, makes the full significance of their

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presence in the microenvironment difficult to define. Decoy Receptors - Chemokine Receptors that Dampen the Pro-tumorigenic Activities of Chemokines? Recently, it has been suggested that the non-signaling "decoy chemokine receptors",

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DARC and D6, may play a role in the tumor microenvironment by binding and sequestering chemokines, and thereby inhibiting tumor growth [108]. D6 has an altered DRYLAIV motif in the second intracellular loop (DKYLEIV instead of DRYLAIV) and DARC lacks this motif entirely. Consequently, these receptors don't couple with G-proteins and cannot induce cell migration despite their

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can activate the standard chemotaxis and survival/proliferation pathways in mononuclear cells while

promiscuous chemokine binding profiles [109, 110]. Instead, they efficiently internalize their ligands, thus dampening the immune response [111, 110].

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DARC binds to pro-inflammatory chemokines of both the CC and CXC families, including CCL2 and angiogenic chemokines CXCL1 and CXCL8. In vivo models of mice transplanted with non-small cell lung and breast cancer cell lines over-expressing DARC indicated that increased levels of DARC are associated with decreased rates of tumor growth, increased necrosis and decreased metastasis [112, 113]. In breast cancer cells, DARC was thought to be acting, at least in part, by decreasing CCL2 and

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MMP-9 expression levels, and low levels of DARC in human breast cancer samples were also indicated a role for DARC in reducing tumorigenesis and angiogenesis, by removing prostrate-derived angiogenic chemokines from the circulation. The authors made the link between low levels of DARC expression on erythrocytes and increased mortality rates from prostate cancer [114].

D6 binds promiscuously and with high affinity to a number of CC chemokines [108]. It is thought to play

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a role in regulating and resolving inflammatory reactions by acting as a scavenger receptor [115]. D6 deficient mice show exaggerated inflammatory responses compared to wild-type mice in models of skin inflammation, with higher levels of inflammatory chemokines in the draining lymph nodes. With respect to cancer, D6 suppresses the development of chemically induced skin tumors while D6-deficient mice have increased susceptibility to tumor development [116]. Interestingly, D6 binds major TAM-recruiting

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chemokines (CCL2/5/7/8), as well as chemokines postulated to skew inflammatory processes both towards cell-mediated (e.g. CCL3/4) and antibody-mediated (CCL2/11/17/22) responses. Although further studies are needed to explore the role of decoy receptors in anti-tumor strategies, the antitumorigenic properties of both D6 and DARC again highlight the contribution of chemokine-mediated inflammation to cancer.

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In summary, chemokines and their receptors play multiple roles in shaping the tumor microenvironment by their ability to attract leukocytes, particularly TAMs, which promote angiogenesis and activate other pro-tumorigenic enzymes and cytokines. However, in order for tumors to thrive they must also

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circumvent apoptosis and find ways to promote survival and proliferation. It has recently become clear that tumors utilize chemokine-mediated signaling pathways in order to aid their survival, growth and

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proliferation, as discussed in the following section. SIGNALING: SURVIVAL AND PROLIFERATION

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Expression of chemokine receptors on cancer cells may provide the cells with more than a mechanism for migration from the primary tumor to a metastatic site. Receptor signaling may also provide a survival advantage. Chemokine signaling contributes to cancer cell survival in the primary tumor, but it is likely to be of particular importance to metastasized cells. What allows the metastasized cells to "feel at

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correlated with a poor prognosis. Transgenic DARC-deficient mice in models of prostate cancer also

home” in a foreign environment? How are they protected from the immune system? Although these issues involve a multitude of factors, chemokines are likely to be significant contributors. Furthermore,

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their role in survival signaling is not limited to metastatic cancers. Chemokines that serve as migratory signals to control the homing of lymphocytes to protective niches in the bone marrow and lymph nodes may also promote survival of leukemia cells.

The molecular strategies for survival and growth are often the result of utilizing, and sometimes reprogramming, existing physiological pathways [117]. In some cases the survival signals are likely

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related to the role of specific chemokine-receptor pairs such as CXCL12:CXCR4 and CXCL12:CXCR7 signaling may result from redirecting existing migration pathways (Figure 2).

Chemokines in Survival. While cancer cells generally have a strong propensity to survive and resist apoptotic stimuli, extracellular survival signals can aide or even be necessary for the survival of some cancer cells. For example, chronic lymphocytic leukemia cells (CLLs) rapidly die when cultured in vitro [123]. One of the factors

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unless they are co-cultured with stromal cells termed "Nurselike cells"

secreted by Nurselike cells that contributes to the survival of CLLs in vitro, and presumably in vivo, is CXCL12. CXCL12 has been shown to protect CLLs from spontaneous and drug-induced apoptosis [123], while small molecule CXCR4 antagonists sensitize the cells to fludarabine-induced apoptosis

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[124].

In addition to leukemia cells [123], addition of CXCL12 to in vitro cultures of numerous types of CXCR4expressing cancer cells, including pancreatic adenocarcinoma [125], glioma [126], and breast cancer cells [127] results in their prolonged survival and protection from apoptosis when cultured in suboptimal conditions. CXCL12 also promotes in vivo survival of numerous cancer cells. Administration of antagonists of CXCR4 synergized with chemotherapy in cell killing and tumor regression of

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glioblastoma multiforme-derived tumor cells [128] and in a B16 murine model of melanoma [129]. Knockdown of CXCR4 expression through RNAi or its pharmacologic inhibition via AMD3100 in a murine 4T1 breast cancer model also reduced formation of primary tumors and was found to delay and

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reduce the early growth and/or survival of the 4T1 cells in the lung [127]. These data clearly suggest a

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role for CXCL12:CXCR4 in survival and/or proliferation of both primary and metastasized cells. For many years, it was believed that CXCL12:CXCR4 functioned as an exclusive non-redundant pair, but CXCL12 is now known to bind to another chemokine receptor, CXCR7 (formerly the orphan GPCR, RDC-1) [130, 131]. Like CXCR4, CXCR7 plays a vital role in response to CXCL12, in various aspects

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of embryonic development [122, 132]. Recent studies revealed that targeted deletion of CXCR7 results in postnatal death in >95% of the mice, and a different phenotype is observed compared to the CXCR4 knockout mouse, consisting of heart valve defects but normal hematopoietic and neural development [122]. Furthermore, overexpression of CXCR7 is observed in several types of cancers and has been

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in survival and growth during normal development [118-122]. In other cases, survival and proliferation

shown to contribute to cell survival and tumor development, independent of CXCR4 [130, 133]. Small molecule antagonists of CXCR7 interfere with tumor growth in mouse models of several different

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cancers. Overexpression of CXCR7 in the MDA-MB 435 breast cancer cell line, which normally has undetectable levels of CXCR7, resulted in a growth advantage due to increased cell survival in suboptimal growth conditions [130]. Implantation of CXCR7-overexpressing MDA-MB 435 cells induced formation of larger tumors in Severe Combined Immunodeficiency Disease (SCID) mice than vectorcontrol transfected cells, despite the absence of CXCR4. RNAi silencing of CXCR7 in the 4T1 breast

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cancer cells also resulted in reduced tumor size compared to the WT or control RNAi cells. Finally,

Interestingly, in contrast to the activation of CXCR4 by CXCL12, CXCL12 does not induce calcium flux or migration upon engaging CXCR7, indicating that CXCR7 does not signal in the classic chemokine fashion [122, 130]. Many theories have been proposed to explain this phenomenon, including CXCR7 signaling through different pathways, CXCR7 heterodimerization with other receptors, or its function as a non-signaling decoy receptor [122, 134]. It should be noted that CXCR7 also binds CXCL11, but with

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lower affinity. Furthermore, CXCL11 is not necessary for development and is naturally absent in some mouse strains, including the C57BL/6 mouse strain which was used as the background CXCR7 knockout mouse mentioned earlier [133]. The possibility of CXCR7 functioning as a decoy receptor is not unprecedented since D6 and DARC serve such a function. However, this hypothesis seems unlikely

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due to the importance of CXCR7 in development, and the specificity of CXCR7 for CXCL12 and CXCL11 compared to D6 and DARC which bind multiple CC and CXC chemokines [108, 110]. Given the distinct roles of CXCR4 and CXCR7 in developmental processes and their non-identical CXCL12 binding domains [132], it will be interesting to determine the differences between these receptors in terms of their roles in cancer and whether they function independently and/or synergistically.

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Since CXCL12:CXCR4 and CXCL12:CXCR7 are important survival factors in development, it is understandable that they are also prominently involved in cancer cell survival. Yet several other chemokine-receptor pairs also contribute to cancer cell survival (Table 1). For example, the

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CCL27:CCR10 system is known to attract melanoma cells to the skin, but recent studies suggest that these proteins also promote tumor cell survival by helping to circumvent anti-tumor processes and by

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providing protection against apoptosis [40]. Chemokines in Cell Proliferation and Tumor Growth. Cancer cells frequently have growth and proliferative advantages over normal cellular counterparts. As previously discussed, endothelial cell

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proliferation is important for the formation of new blood vessels to vascularize tumors and provide routes for metastasis. In addition to the recruitment of TAMs that secrete factors to promote cell proliferation and tumor growth, chemokines directly activate growth and proliferation pathways in the cancer cells themselves. Aberrant protein expression within the cancer cells, due to oncogenes or

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similar effects of CXCR7 on cell growth/survival were observed in lung cancer cell lines [133].

mutations in tumor suppressors, may then enhance the amplitude and/or duration of the chemokineactivated pathways.

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The ability of some chemokines to induce cell growth and proliferation in the context of cancer is wellestablished. CXCL1, CXCL2, and CXCL3 were originally named Gro/MGSA- α, β, and γ, respectively, for “Growth-related oncogene” or “Melanoma Growth Stimulatory Activity/growth regulated protein” [135]. These closely related chemokines were found to be expressed in approximately 70% of melanomas and function as oncogenes [135, 136]. All three chemokines bind to CXCR2 and cause

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activation of ERK, PI3K, and tyrosine kinases to mediate cell proliferation and migration effects [90, 91, including CXCL12, also frequently signal growth and proliferation [27, 126, 127].

Downstream signaling in survival, growth, and proliferation. There is a fair amount of overlap between survival and proliferation signaling pathways, as is understandable since they often work hand-in-hand. It has been demonstrated that stimulation of numerous cancer cells with CXCL12 and

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other chemokines activates the PI3K-AKT pathway [11, 18, 27, 46, 123, 140] which is well known to promote survival effects [137]. Although not all chemokines that promote AKT (PKB) activation lead to enhanced survival of cells (e.g. under low serum conditions), many do and this pathway seems to be exploited by a variety of cancer cells [141-143].

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Numerous downstream effectors and transcription factors of AKT, ERK1/2, and tyrosine kinase signaling can promote cell survival and proliferation (Figure 2). Chemokine signaling often activates NFκB, which is commonly downstream of AKT but can be activated through other pathways, like Protein Kinase C (PKC) [144]. NF-κB dimerizes and translocates to the nucleus upon activation, where it promotes transcription of various apoptosis inhibitors and cell-cycle promoting genes [145]. Other downstream targets of AKT include procaspase-9 and the pro-apoptotic BCL-2 family member, BAD,

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which are both inhibited upon phosphorylation. The forkhead (FKHR) family of transcription factors, which induce transcription of numerous apoptotic genes, are also inhibited by AKT [146]. AKT-induced activation of MDM2 leading to p53 degradation and inhibition of GSK-3β leading to stabilization of β-

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catenin, also results in downstream inhibition of negative regulators of cell cycle, and activation of cell cycle promoting genes [147]. Furthermore, via inhibition of TSC2, AKT leads to mTOR activation,

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resulting in activation of p70S6K and thus enhanced protein translation of numerous cell growth regulators [137, 148]. ERK1/2 signaling may also contribute to survival through some of these pathways, for example via phosphorylation and inhibition of procaspase-9 and BAD [149, 150].

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Furthermore, ERK1/2 (MAPK) can itself localize to the nucleus and activate transcription factors involved in cell cycle regulation and differentiation, thereby promoting cell proliferation [151]. Other MAPKs, including JNK have also been implicated in chemokine-induced proliferation signaling [152]. Thus, chemokine receptor signaling resulting in activation of transcription factors involved in anti-

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136-139]. However, induction of cell proliferation is not limited to CXCR2 agonists; other chemokines,

apoptotic mechanisms, cell cycle regulation, and growth factor production are yet other mechanisms whereby cancer cells exploit downstream chemokine signaling pathways. These pro-tumorigenic

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pathways are likely to be particularly important for the ability of metastatic tumor cells to thrive in foreign environments. COMPLEXITY OF THE CHEMOKINE SYSTEM

As already discussed, it is clear that certain chemokine-receptor pairs contribute to cancer progression and metastasis, while others are not implicated or even mediate anti-tumorigenic effects [153].

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Particular chemokine-receptor pairs like CXCL12:CXCR4 have a dominant role in metastasis [39], likely However, they cannot always be categorized as “pro-tumorigenic” and “anti-tumorigenic”; although a particular chemokine may exhibit anti-tumorigenic properties in one context, it may still contribute to malignancy in other types of cancers. For example, one of the CCR7 ligands, CCL21, was shown to mediate anti-tumor effects by inhibiting angiogenesis, but it also provides important directional cues for

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metastasis of cancer cells to lymph nodes [20, 95]. Additionally, low levels of some chemokines, like CCL2, may induce pro-tumorigenic properties while higher levels inhibit tumorigenesis. While it is desirable to compartmentalize the roles of chemokines in cancer in fairly defined ways, there are many complexities that should be appreciated. In this section we discuss some of the many possible

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mechanisms that can complicate the picture.

Diversity of Chemokine/Receptor Responses. Due to their structural homology and common chemoattractant-related functions (e.g. migration), the diversity of chemokine signaling may be greatly underappreciated. The sheer number of chemokines and receptors, along with the fact that many chemokines bind the same receptor and many receptors engage multiple chemokines offers the possibility of many outputs. While such promiscuous partnering gives the appearance of redundancy,

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emerging evidence suggests that cross-reactivity amongst ligands and receptors can result in quantitative and qualitative differences in the cellular response [154, 155]. For example, it is clear that ligands of the same receptor can elicit different responses, even when their binding affinities are not too

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dissimilar. Ultimately, this must be due to differences in the ligand induced conformational states and dynamics of the receptors and how they couple into downstream pathways. In an elegant comparative

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study of CCL17 and CCL22, D'Ambrosio and coworkers showed quantitative differences in CCR4mediated signaling [156]. CCL22 was much more effective than CCL17 in the induction of integrin dependent T-cell adhesion, receptor desensitization and internalization. Furthermore, the authors

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showed that although CCL22 is the higher affinity ligand (but only by 2-3 fold), it dissociates more rapidly than CCL17, and they proposed the intriguing hypothesis that the frequency of association/dissociation may be a critical parameter in the activation of certain intracellular signaling pathways. Similarly, CCR7 binds both CCL19 and CCL21 with comparable affinities and demonstrates

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related to their role in homeostasis, development and the fact that the ligand is constitutively expressed.

similar efficacy in inducing chemotaxis and calcium mobilization. However, CCL19, but not CCL21, led to phosphorylation of CCR7 and subsequent β-arrestin-dependent desensitization in the H9 human T

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lymphocyte cell line [157]. The potency and intensity of CCL19-mediated ERK1/2 activation was also higher than that of CCL21-mediated activation [157].

Distinct responses of a particular receptor to different ligands is also evident in the context of cancer, as the CXCR2 ligand CXCL1, but not CXCL8, was able to activate proliferation and tumor growth in prostate cancer cell lines [17]. Similarly, it is clear that the same chemokine binding to different

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receptors can also elicit different functional responses as already discussed for CXCL12 binding to chemokine-receptor pairs will be needed to fully appreciate how subtle shifts in binding affinity, kinetics and ultimately the induced receptor conformation can lead to different outputs, which in turn will be influenced by cell type. In terms of cancer, this means that it may not always be straightforward to assign a role for a particular chemokine or receptor associated with a cancer. It is important to know what the relevant receptor is for an identified ligand, and vice versa, the relevant ligand for the receptor.

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Additionally, while the identification of chemokine/receptor mRNA transcripts is often used as evidence for the roles of particular proteins in cancer, the data may be misleading, as protein levels do not always track with mRNA levels. Furthermore, chemokines can be agonists of some receptors and antagonists of others, so what then is their true function? As an example of this concept the ligands

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CXCL11, CXCL9, and CXCL10 (IP-10) are agonists of CXCR3, but antagonists of CCR3 [158] while CXCR3 may act as a decoy receptor of CCL11 [158]. N-terminal proteolytic processing may also activate or deactivate chemokines or change their specificity and the question is, what is the predominant state in the tumor milieu? Other cell dependent factors discussed below can also alter the response.

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Complexities of Intracellular Signaling Pathways. Signaling downstream of chemokine-receptor activation is also complex and many factors can influence the functional outcome. While complexity contributes to fine-tuning of normal chemokine functions, it may also facilitate the ability of cancer cells

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to adapt various pathways for purposes not normally used in a particular cell type. As discussed above, there is significant overlap between the pathways that are operative in normal chemokine function and

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those that contribute to cancer. Migration, for example, is critical both to classical chemokine function as well as tumor metastasis. PLC, AKT, ERK1/2 and tyrosine kinase pathways (independently and sometimes in conjunction) have all been implicated in migrational responses in normal cells [18, 35,

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146, 159, 160]. However, these same signaling molecules also contribute to survival, growth, and proliferation in cancer. Furthermore, they can be modulated in many ways, in favor of the cancer cell. Paracrine signals from cells in the microenvironment, or autocrine signals can influence receptor activation and/or regulation. This concept is a major reason why it is so difficult to recapitulate in vivo

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CXCR4 versus CXCR7. More quantitative and qualitative analysis of the responses of different

situations with in vitro systems. Other complicating factors include G protein specificity and isoform availability, receptor dimerization, receptor crosstalk, and altered signaling and regulation.

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Receptor crosstalk in particular has been demonstrated to modulate chemokine receptor signaling. For example, epidermal growth factor (EGF) and platelet derived growth factor (PDGF) are established mediators in ovarian cancer growth and metastasis and now there is clear evidence for a role of CXCL12:CXCR4 [161, 162]. Stimulation with CXCL12 in several ovarian cancer cell lines resulted in cell proliferation through CXCR4 and biphasic activation of ERK1/2 and AKT, which decreased upon

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addition of an EGFR specific inhibitor, suggesting cross-talk between CXCR4 and EFGR. In addition, interactions with EGFR and c-Src, [163].

Dimer and higher order oligomerization of GPCRs is also recognized as an important event in the activation and function of many GPCRs [164, 165]. While the relevance of chemokine receptor homoand hetero- dimer formation is still under study [166], it could affect ligand-receptor specificity, the

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activation of downstream signaling pathways, and the duration of the signal in normal or malignant cells. To date, there is evidence suggesting homo-dimerization (CCR2, CCR5, CXCR1, CXCR2, CXCR4, and CXCR7) and heterodimerization (CCR2/CCR5, CCR2/CXCR4, CXCR1/CXCR2 and CXCR7/CXCR4) of several receptors. Since most of these receptors are implicated in cancer,

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dimerization could affect the cancer phenotype.

While cancer cells use much of the same machinery and signaling pathways as normal cells, they do have altered characteristics, such as the expression of oncogenes or mutations in tumor suppressors that can change or exaggerate the response to chemokines. As already mentioned, the mutant pVHL tumor suppressor and the HER2 oncogene contribute to aberrant expression levels of chemokine receptors on cancer cells, thus altering how the cells would normally respond to chemokine signals. In

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addition, such oncogenes or mutant tumor suppressors could potentially have a dramatic effect on chemokine receptor signaling leading to prolonged or enhanced pathway activation, or even activation of unique pathways. For example, mutation of PTEN, a phosphatase that contributes to inactivation of

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AKT, could prolong chemokine-induced AKT activation, thus leading to aberrant activity [167].

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Additionally, although inappropriate expression of particular chemokine receptors is certainly relevant to a variety of cancers, increased receptor levels do not always correlate with enhanced signaling [168]. For example, CXCR4 upregulation was observed on both metastatic and non-metastatic breast cancer cell lines; however, only the metastatic lines expressed functional CXCR4 [168]. Thus, an increase in

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receptor expression may not always translate into enhanced activity. Furthermore, there may be cancers in which receptor expression is unaltered, yet there are significant changes in the functional response and downstream signaling. Chemokine receptor mutations that cause constitutive activation or that impair desensitization could potentially contribute to tumorigenicity [169-171]. While there are

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CXCL8 stimulation of CXCR1 and CXCR2 expressing ovarian cancer cells activates ERK1/2 through

currently no known endogenously expressed chemokine receptors that exhibit these characteristics, the Kaposi’s Sarcoma Herpes virus (KSHV) GPCR is a CXCR2-like receptor that is constitutively active

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and contributes to the pathogenesis of Kaposi’s lesions [169]. Similarly, point mutations yielding constitutive activation of CXCR2 in NIH 3T3 cells resulted in cell transformation and induced proliferation [170].

Further adding to the complexity, many types of cancer cells express multiple chemokine receptors and/or chemokine ligands. CXCR1, CXCR2, CXCR3, CXCR4, CCR7, and CCR10 can all be expressed

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on melanoma cells and potentially contribute to malignancy [172]. Whether these different receptors determined. In a tumor microenvironment there is a milieu of growth factors, cytokines and chemokines that most likely function in concert to shape the growth, survival, and spread of cancer cells. Although it is critical to gain a solid understanding of the individual contributions of each factor to the progression of cancer, they do not function in isolation, and it will also be necessary to consider the global picture in the context of complexities such as receptor crosstalk, altered signaling, and interactions with other cell

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types. CONCLUSIONS

The well-established properties of chemokines in controlling cell migration have made them clear

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candidates for involvement in cancer cell metastasis. However, the contribution of chemokines to other aspects of cancer such as growth, proliferation, angiogenesis, and cell survival are also becoming areas of extensive investigation. Many important questions arise from such multifaceted effects of chemokines:

• Which pathways are activated by chemokines to elicit different responses? •

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• Why are only select chemokines involved in cancer? Why do some chemokines have anti-tumorigenic functions while others clearly contribute to

malignancy?

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• How does the same chemokine mediate different effects in normal cells and in different types

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of cancer cells?

•Are any of the receptors good drug targets for cancer?

Deciphering signaling pathways activated by chemokines in various cancer cells will be critical to

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understanding how chemokines influence disease progression and may reveal potential downstream therapeutic targets and consequences of therapeutic intervention. An interesting paradigm that is emerging in the chemokine field, and may become more relevant in the cancer field in the future, is that of receptor crosstalk, both between other chemokine receptors (e.g.

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contribute independently, redundantly, and/or in a coordinated manner to the disease remains to be

homo/heterodimerization) and between different types of receptors at the cell surface. A number of chemokine receptors have been shown to form homodimers and/or heterodimers, and the complexes

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often show functional differences compared to their respective monomers [173]. In one recent study, the CXCR4 small-molecule antagonist, AMD3100, was used to demonstrate heterodimerization of CCR2/CXCR4 and trans-inhibition of CCR2 [174]. In addition, TAK779, an antagonist of CCR2, CCR5, and CXCR3, was able to inhibit CXCL12 binding to CXCR4 in the context of the heterodimer. Antagonist trans inhibition presents a unique example of the functional consequences of heterodimer

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formation with substantial implications in drug development. From the standpoint of drug development, it also illustrates the importance of understanding the complex network of interactions associated with influence of the microenvironment in experimental setups. ACKNOWLEDGEMENTS

This work was funded by a University of California AIDS Research Program (UARP) fellowship to SJA (TF06-SD-501), an NIH Training Grant in Cellular and Molecular Pharmacology (GM007752) to MO, a

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Ruth L. Kirschstein NIGMS MARC Predoctoral Fellowship (F31) to CLS, and awards from NIH (RO1-

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AI37113), DOD (BC060331), UARP (1D06-SD-206) and the Lymphoma Research Foundation to TMH.

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chemokines and cancer. In doing so, one of the major challenges will be to find ways to recapitulate the

REFERENCES

8

9 10 11 12 13 14 15 16

17

IN T

St

18

19

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7

TPR

6

OS

5

a) P

4

2(

3

e

2

Rossi, D. and Zlotnik, A. (2000) The biology of chemokines and their receptors. Annu. Rev. Immunol. 18, 217-242 Loetscher, P., Moser, B. and Baggiolini, M. (2000) Chemokines and their receptors in lymphocyte traffic and HIV infection. Adv. Immunol. 74, 127-180 Moser, B. and Willimann, K. (2004) Chemokines: role in inflammation and immune surveillance. Ann. Rheum. Dis. 63 Suppl. 2, ii84-ii89 Nagasawa, T., Tachibana, K. and Kishimoto, T. (1998) A novel CXC chemokine PBSF/SDF-1 and its receptor CXCR4: their functions in development, hematopoiesis and HIV infection. Semin. Immunol. 10, 179-185 Moser, B. and Loetscher, P. (2001) Lymphocyte traffic control by chemokines. Nat. Immunol. 2, 123-128 Lau, E. K., Allen, S., Hsu, A. and Handel, T. M. (2004) Chemokine-receptor interactions: GPCRs, glycosaminoglycans and viral chemokine binding proteins. Adv. Protein Chem. 68, 351-391 Allen, S. J., Crown, S. E. and Handel, T. M. (2007) Chemokine: receptor structure, interactions, and antagonism. Annu. Rev. Immunol. 25, 787-820 Proudfoot, A. E. I., Handel, T. M., Johnson, Z., Lau, E. K., Liwang, P., Clark-Lewis, I., Borlat, F., Wells, T. N. C. and Kosco-Vilbois, M. (2003) Glycosaminoglycan binding and oligomerization are essential for the in vivo activity of certain chemokines. Proc. Natl. Acad. Sci. USA 100, 1885-1890 Appay, V., Brown, A., Cribbes, S., Randle, E. and Czaplewski, L. G. (1999) Aggregation of RANTES is responsible for its inflammatory properties. Characterization of nonaggregating, noninflammatory RANTES mutants. J. Biol. Chem. 274, 27505-27512 Murooka, T. T., Wong, M. M., Rahbar, R., Majchrzak-Kita, B., Proudfoot, A. E. and Fish, E. N. (2006) CCL5-CCR5-mediated apoptosis in T cells: Requirement for glycosaminoglycan binding and CCL5 aggregation. J. Biol. Chem. 281, 25184-25194 Thelen, M. (2001) Dancing to the tune of chemokines. Nat. Immunol. 2, 129-134 Molon, B., Gri, G., Bettella, M., Gomez-Mouton, C., Lanzavecchia, A., Martinez, A. C., Manes, S. and Viola, A. (2005) T cell costimulation by chemokine receptors. Nat. Immunol. 6, 465-471 Bacon, K. B., Premack, B. A., Gardner, P. and Schall, T. J. (1995) Activation of dual T cell signaling pathways by the chemokine RANTES. Science 269, 1727-1730 Arai, H. and Charo, I. F. (1996) Differential regulation of G-protein-mediated signaling by chemokine receptors. J. Biol. Chem. 271, 21814-21819 Rodriguez-Frade, J. M., Mellado, M. and Martinez, A. C. (2001) Chemokine receptor dimerization: two are better than one. Trends Immunol. 22, 612-617 Kijowski, J., Baj-Krzyworzeka, M., Majka, M., Reca, R., Marquez, L. A., Christofidou-Solomidou, M., Janowska-Wieczorek, A. and Ratajczak, M. Z. (2001) The SDF-1-CXCR4 axis stimulates VEGF secretion and activates integrins but does not affect proliferation and survival in lymphohematopoietic cells. Stem Cells 19, 453-466 Moore, B. B., Arenberg, D. A., Stoy, K., Morgan, T., Addison, C. L., Morris, S. B., Glass, M., Wilke, C., Xue, Y. Y., Sitterding, S., Kunkel, S. L., Burdick, M. D. and Strieter, R. M. (1999) Distinct CXC chemokines mediate tumorigenicity of prostate cancer cells. Am. J. Pathol. 154, 1503-1512 Ganju, R. K., Brubaker, S. A., Meyer, J., Dutt, P., Yang, Y., Qin, S., Newman, W. and Groopman, J. E. (1998) The alpha-chemokine, stromal cell-derived factor-1alpha, binds to the transmembrane G-protein-coupled CXCR-4 receptor and activates multiple signal transduction pathways. J. Biol. Chem. 273, 23169-23175 Xue, X., Cai, Z., Seitz, G., Kanz, L., Weisel, K. C. and Mohle, R. (2007) Differential effects of G protein coupled receptors on hematopoietic progenitor cell growth depend on their signaling capacities. Ann. N. Y. Acad. Sci. 1106, 180-189

ag

1

27 28 29 30 31 32 33 34 35

39 40

St

41

ag

38

e

2(

36

42

Licenced copy. Copying is not permitted, except with prior permission and as allowed by law. © 2008 The Authors Journal compilation © 2008 Biochemical Society

THIS IS NOT THE FINAL VERSION - see doi:10.1042/BJ20071493

26

IN T

25

TPR

24

OS

21 22 23

Muller, A., Homey, B., Soto, H., Ge, N., Catron, D., Buchanan, M. E., McClanahan, T., Murphy, E., Yuan, W., Wagner, S. N., Barrera, J. L., Mohar, A., Verastegui, E. and Zlotnik, A. (2001) Involvement of chemokine receptors in breast cancer metastasis. Nature 410, 50-56 Zlotnik, A. (2006) Chemokines and cancer. Int. J. Cancer 119, 2026-2029 Balkwill, F. (2004) Cancer and the chemokine network. Nat. Rev. Cancer 4, 540-550 Murphy, P. M. (2001) Chemokines and the molecular basis of cancer metastasis. N. Engl. J. Med. 345, 833-835 Gupta, G. P. and Massague, J. (2006) Cancer metastasis: building a framework. Cell 127, 679695 Murakami, T., Cardones, A. R. and Hwang, S. T. (2004) Chemokine receptors and melanoma metastasis. J. Dermatol. Sci. 36, 71-78 Ben-Baruch, A. (2003) Host microenvironment in breast cancer development: inflammatory cells, cytokines and chemokines in breast cancer progression: reciprocal tumormicroenvironment interactions. Breast Cancer Res. 5, 31-36 Kulbe, H., Levinson, N. R., Balkwill, F. and Wilson, J. L. (2004) The chemokine network in cancer--much more than directing cell movement. Int. J. Dev. Biol. 48, 489-496 Sica, A., Schioppa, T., Mantovani, A. and Allavena, P. (2006) Tumour-associated macrophages are a distinct M2 polarised population promoting tumour progression: potential targets of anticancer therapy. Eur. J. Cancer 42, 717-727 Friedl, P. and Wolf, K. (2003) Tumour-cell invasion and migration: diversity and escape mechanisms. Nat. Rev. Cancer 3, 362-374 Tan, W., Martin, D. and Gutkind, J. S. (2006) The Galpha13-Rho signaling axis is required for SDF-1-induced migration through CXCR4. J. Biol. Chem. 281, 39542-39549 Tanaka, T., Bai, Z., Srinoulprasert, Y., Yang, B. G., Hayasaka, H. and Miyasaka, M. (2005) Chemokines in tumor progression and metastasis. Cancer Sci. 96, 317-322 Li, S., Guan, J. L. and Chien, S. (2005) Biochemistry and biomechanics of cell motility. Annu. Rev. Biomed. Eng 7, 105-150 Zhao, M., Mueller, B. M., Discipio, R. G. and Schraufstatter, I. U. (2007) Akt plays an important role in breast cancer cell chemotaxis to CXCL12. Breast Cancer Res. Treat. In Press Zipin-Roitman, A., Meshel, T., Sagi-Assif, O., Shalmon, B., Avivi, C., Pfeffer, R. M., Witz, I. P. and Ben-Baruch, A. (2007) CXCL10 promotes invasion-related properties in human colorectal carcinoma cells. Cancer Res 67, 3396-3405 Laudanna, C., Mochly-Rosen, D., Liron, T., Constantin, G. and Butcher, E. C. (1998) Evidence of zeta protein kinase C involvement in polymorphonuclear neutrophil integrin-dependent adhesion and chemotaxis. J Biol Chem 273, 30306-30315 Scala, S., Giuliano, P., Ascierto, P. A., Ierano, C., Franco, R., Napolitano, M., Ottaiano, A., Lombardi, M. L., Luongo, M., Simeone, E., Castiglia, D., Mauro, F., De Michele, I., Calemma, R., Botti, G., Caraco, C., Nicoletti, G., Satriano, R. A. and Castello, G. (2006) Human melanoma metastases express functional CXCR4. Clin. Cancer . M., Turner, C. E., Parsons, J. T. and Horwitz, A. F. (2004) FAK-Src signalling through paxillin, ERK and MLCK regulates adhesion disassembly. Nat. Cell Biol. 6, 154-161 Balkwill, F. (2004) The significance of cancer cell expression of the chemokine receptor CXCR4. Semin Cancer Biol 14, 171-179 Kakinuma, T. and Hwang, S. T. (2006) Chemokines, chemokine receptors, and cancer metastasis. J. Leukoc. Biol. 79, 639-51. Murakami, T., Cardones, A. R., Finkelstein, S. E., Restifo, N. P., Klaunberg, B. A., Nestle, F. O., Castillo, S. S., Dennis, P. A. and Hwang, S. T. (2003) Immune evasion by murine melanoma mediated through CC chemokine receptor-10. J. Exp. Med. 198, 1337-1347 Loetscher, P., Seitz, M., Baggiolini, M. and Moser, B. (1996) Interleukin-2 regulates CC chemokine receptor expression and chemotactic responsiveness in T lymphocytes. J. Exp. Med. 184, 569-577 Li, Y. M., Pan, Y., Wei, Y., Cheng, X., Zhou, B. P., Tan, M., Zhou, X., Xia, W., Hortobagyi, G. N., Yu, D. and Hung, M. C. (2004) Upregulation of CXCR4 is essential for HER2-mediated tumor metastasis. Cancer Cell 6, 459-469

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e

44

Busillo, J. M. and Benovic, J. L. (2007) Regulation of CXCR4 signaling. Biochim. Biophys. Acta. 1768, 952-963 Staller, P., Sulitkova, J., Lisztwan, J., Moch, H., Oakeley, E. J. and Krek, W. (2003) Chemokine receptor CXCR4 downregulated by von Hippel-Lindau tumour suppressor pVHL. Nature 425, 307-311 Schioppa, T., Uranchimeg, B., Saccani, A., Biswas, S. K., Doni, A., Rapisarda, A., Bernasconi, S., Saccani, S., Nebuloni, M., Vago, L., Mantovani, A., Melillo, G. and Sica, A. (2003) Regulation of the chemokine receptor CXCR4 by hypoxia. J. Exp. Med. 198, 1391-1402 Maxwell, P. J., Gallagher, R., Seaton, A., Wilson, C., Scullin, P., Pettigrew, J., Stratford, I. J., Williams, K. J., Johnston, P. G. and Waugh, D. J. (2007) HIF-1 and NF-kappaB-mediated upregulation of CXCR1 and CXCR2 expression promotes cell survival in hypoxic prostate cancer cells. Oncogene 26, 7333-45 Wilson, J. L., Burchell, J. and Grimshaw, M. J. (2006) Endothelins induce CCR7 expression by breast tumor cells via endothelin receptor A and hypoxia-inducible factor-1. Cancer Res. 66, 11802-11807 Helbig, G., Christopherson, K. W., Bhat-Naksharti, P., Kumar, S., Kishimoto, H., Miller, K. D., Broxmeyer, H. E. and Nakshatri, H. (2003) NF-kB promotes breast cancer cell migration and metastasis by inducing the expression of the chemokine receptor CXCR4. J. Biol. Chem. 278, 21631-21638 Luker, K. E. and Luker, G. D. (2006) Functions of CXCL12 and CXCR4 in breast cancer. Cancer Lett. 238, 30-41 Balkwill, F. R. and Mantovani, A. (2001) Inflammation and cancer: back to Virchow? Lancet 357, 539-545 Coussens, L. M. and Werb, Z. (2002) Inflammation and cancer. Nature 420, 860-867 Homey, B., Muller, A. and Zlotnik, A. (2002) Chemokines: agents for the immunotherapy of cancer? Nat. Rev. Immunol. 2, 175-184 Mantovani, A., Schioppa, T., Porta, C., Allavena, P. and Sica, A. (2006) Role of tumorassociated macrophages in tumor progression and invasion. Cancer Metastasis Rev. 25, 315322 Mantovani, A., Sozzani, S., Locati, M., Allavena, P. and Sica, A. (2002) Macrophage polarization: tumor-associated macrophages as a paradigm for polarized M2 mononuclear phagocytes. Trends Immunol. 23, 549-555 Sica, A., Saccani, A., Bottazzi, B., Polentarutti, N., Vecchi, A., van Damme, J. and Mantovani, A. (2000) Autocrine production of IL-10 mediates defective IL-12 production and NF-kappa B activation in tumor-associated macrophages. J. Immunol. 164, 762-767 Lin, E. Y. and Pollard, J. W. (2007) Tumor-associated macrophages press the angiogenic switch in breast cancer. Cancer Res. 67, 5064-5066 Graves, D. T., Jiang, Y. L., Williamson, M. J. and Valente, A. J. (1989) Identification of monocyte chemotactic activity produced by malignant cells. Science 245, 1490-1493 Conti, I. and Rollins, B. J. (2004) CCL2 (monocyte chemoattractant protein-1) and cancer. Semin. Cancer Biol. 14, 149-154 Ueno, T., Toi, M., Saji, H., Muta, M., Bando, H., Kuroi, K., Koike, M., Inadera, H. and Matsushima, K. (2000) Significance of macrophage chemoattractant protein-1 in macrophage recruitment, angiogenesis, and survival in human breast cancer. Clin. Cancer Res. 6, 32823289 Saji, H., Koike, M., Yamori, T., Saji, S., Seiki, M., Matsushima, K. and Toi, M. (2001) Significant correlation of monocyte chemoattractant protein-1 expression with neovascularization and progression of breast carcinoma. Cancer 92, 1085-1091 Nesbit, M., Schaider, H., Miller, T. H. and Herlyn, M. (2001) Low-level monocyte chemoattractant protein-1 stimulation of monocytes leads to tumor formation in nontumorigenic melanoma cells. J. Immunol. 166, 6483-6490 Gazzaniga, S., Bravo, A. I., Guglielmotti, A., van Rooijen, N., Maschi, F., Vecchi, A., Mantovani, A., Mordoh, J. and Wainstok, R. (2007) Targeting tumor-associated macrophages and inhibition

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of MCP-1 reduce angiogenesis and tumor growth in a human melanoma xenograft. J Invest Dermatol. 127, 2031-2041 Monti, P., Leone, B. E., Marchesi, F., Balzano, G., Zerbi, A., Scaltrini, F., Pasquali, C., Calori, G., Pessi, F., Sperti, C., Di Carlo, V., Allavena, P. and Piemonti, L. (2003) The CC chemokine MCP-1/CCL2 in pancreatic cancer progression: regulation of expression and potential mechanisms of antimalignant activity. Cancer Res. 63, 7451-7461 Neumark, E., Anavi, R., Witz, I. P. and Ben-Baruch, A. (1999) MCP-1 expression as a potential contributor to the high malignancy phenotype of murine mammary adenocarcinoma cells. Immunol. Lett. 68, 141-146 Neumark, E., Cohn, M. A., Lukanidin, E., Witz, I. P. and Ben-Baruch, A. (2002) Possible coregulation of genes associated with enhanced progression of mammary adenocarcinomas. Immunol. Letts. 82, 111-121 Niwa, Y., Akamatsu, H., Niwa, H., Sumi, H., Ozaki, Y. and Abe, A. (2001) Correlation of tissue and plasma RANTES levels with disease course in patients with breast or cervical cancer. Clin Cancer Res. 7, 285-289 Robinson, S. C., Scott, K. A., Wilson, J. L., Thompson, R. G., Proudfoot, A. E. and Balkwill, F. (2003) A chemokine receptor antagonist inhibits experimental breast tumor growth. Cancer Res. 63, 8360-8365 Locati, M., Deuschle, U., Massardi, M. L., Martinez, F. O., Sironi, M., Sozzani, S., Bartfai, T. and Mantovani, A. (2002) Analysis of the gene expression profile activated by the CC chemokine ligand 5/RANTES and by lipopolysaccharide in human monocytes. J. Immunol. 168, 3557-3562 Sica, A., Saccani, A., Bottazzi, B., Bernasconi, S., Allavena, P., Gaetano, B., Fei, F., LaRosa, G., Scotton, C. J., Balkwill, F. R. and Mantovani, A. (2000) Defective expression of the monocyte chemotactic protein-1 receptor CCR2 in macrophages associated with human ovarian carcinoma. J. Immunol. 164, 733-738 Scotton, C. J., Milliken, D., Wilson, J. L., Raju, S. and Balkwill, F. R. (2001) Analysis of CC chemokine and chemokine receptor expression in solid ovarian tumours. Brit. J. Cancer 8, 891897 Bell, D., Chomarat, P., Broyles, D., Netto, G., Harb, G. M., Lebecque, S., Valladeau, J., Davoust, J., Palucka, K. A. and Banchereau, J. (1999) In breast carcinoma tissue, immature dendritic cells reside within the tumor, whereas mature dendritic cells are located in peritumoral areas. J. Exp. Med. 190, 1417-1426 Curiel, T. J., Cheng, P., Mottram, P., Alvarez, X., Moons, L., Evdemon-Hogan, M., Wei, S., Zou, L., Kryczek, I., Hoyle, G., Lackner, A., Carmeliet, P. and Zou, W. (2004) Dendritic cell subsets differentially regulate angiogenesis in human ovarian cancer. Cancer Res. 64, 5535-5538 Vermi, W., Bonecchi, R., Facchetti, F., Bianchi, D., Sozzani, S., Festa, S., Berenzi, A., Cella, M. and Colonna, M. (2003) Recruitment of immature plasmacytoid dendritic cells (plasmacytoid monocytes) and myeloid dendritic cells in primary cutaneous melanomas. J. Pathol. 200, 255268 Zou, W., Machelon, V., Coulomb-L'Hermin, A., Borvak, J., Nome, F., Isaeva, T., Wei, S., Krzysiek, R., Durand-Gasselin, I., Gordon, A., Pustilnik, T., Curiel, D. T., Galanaud, P., Capron, F., Emilie, D. and Curiel, T. J. (2001) Stromal-derived factor-1 in human tumors recruits and alters the function of plasmacytoid precursor dendritic cells. Nat. Med. 7, 1339-1346 Shurin, M. R., Shurin, G. V., Lokshin, A., Yurkovetsky, Z. R., Gutkin, D. W., Chatta, G., Zhong, H., Han, B. and Ferris, R. L. (2006) Intratumoral cytokines/chemokines/growth factors and tumor infiltrating dendritic cells: friends or enemies? Cancer Metastasis Rev. 25, 333-356 Chomarat, P., Banchereau, J., Davoust, J. and Palucka, A. K. (2000) IL-6 switches the differentiation of monocytes from dendritic cells to macrophages. Nat. Immunol. 1, 510-514 Orimo, A. and Weinberg, R. A. (2006) Stromal fibroblasts in cancer: a novel tumor-promoting cell type. Cell Cycle 5, 1597-1601 Orimo, A., Gupta, P. B., Sgroi, D. C., Arenzana-Seisdedos, F., Delaunay, T., Naeem, R., Carey, V. J., Richardson, A. L. and Weinberg, R. A. (2005) Stromal fibroblasts present in invasive human breast carcinomas promote tumor growth and angiogenesis through elevated SDF1/CXCL12 secretion. Cell 121, 335-348

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Olumi, A. F., Grossfeld, G. D., Hayward, S. W., Carroll, P. R., Tlsty, T. D. and Cunha, G. R. (1999) Carcinoma-associated fibroblasts direct tumor progression of initiated human prostatic epithelium. Cancer Res. 59, 5002-5011 Nazareth, M. R., Broderick, L., Simpson-Abelson, M. R., Kelleher, R. J., Jr., Yokota, S. J. and Bankert, R. B. (2007) Characterization of human lung tumor-associated fibroblasts and their ability to modulate the activation of tumor-associated T cells. J. Immunol. 178, 5552-5562 Mueller, L., Goumas, F. A., Affeldt, M., Sandtner, S., Gehling, U. M., Brilloff, S., Walter, J., Karnatz, N., Lamszus, K., Rogiers, X. and Broering, D. C. (2007) Stromal Fibroblasts in Colorectal Liver Metastases Originate From Resident Fibroblasts and Generate an Inflammatory Microenvironment. Am. J. Pathol. 171,1608-18 Silzle, T., Kreutz, M., Dobler, M. A., Brockhoff, G., Knuechel, R. and Kunz-Schughart, L. A. (2003) Tumor-associated fibroblasts recruit blood monocytes into tumor tissue. Eur. J. Immunol. 33, 1311-1320 Goede, V., Brogelli, L., Ziche, M. and Augustin, H. G. (1999) Induction of inflammatory angiogenesis by monocyte chemoattractant protein-1. Int. J. Cancer 82, 765-770 Koch, A. E., Polverini, P. J., Kunkel, S. L., Harlow, L. A., DiPietro, L. A., Elner, V. M., Elner, S. G. and Strieter, R. M. (1992) Interleukin-8 as a macrophage-derived mediator of angiogenesis. Science 258, 1798-1801 Torisu, H., Ono, M., Kiryu, H., Furue, M., Ohmoto, Y., Nakayama, J., Nishioka, Y., Sone, S. and Kuwano, M. (2000) Macrophage infiltration correlates with tumor stage and angiogenesis in human malignant melanoma: possible involvement of TNFalpha and IL-1alpha. Int. J. Cancer 85, 182-188 Hu, D. E., Hori, Y. and Fan, T. P. (1993) Interleukin-8 stimulates angiogenesis in rats. Inflammation 17, 135-143 Strieter, R. M., Burdick, M. D., Mestas, J., Gomperts, B., Keane, M. P. and Belperio, J. A. (2006) Cancer CXC chemokine networks and tumour angiogenesis. Eur. J. Cancer 42, 768-778 Folkman, J. and Klagsbrun, M. (1987) Angiogenic factors. Science 235, 442-447 Strieter, R. M., Polverini, P. J., Kunkel, S. L., Arenberg, D. A., Burdick, M. D., Kasper, J., Dzuiba, J., Van Damme, J., Walz, A., Marriott, D. and et al. (1995) The functional role of the ELR motif in CXC chemokine-mediated angiogenesis. J. Biol. Chem. 270, 27348-27357 Dhawan, P. and Richmond, A. (2002) Role of CXCL1 in tumorigenesis of melanoma. Journal of Leukocyte Biology 72, 9-18 Schadendorf, D., Moller, A., Algermissen, B., Worm, M., Sticherling, M. and Czarnetzki, B. M. (1993) IL-8 produced by human malignant melanoma cells in vitro is an essential autocrine growth factor. J. Immunol. 151, 2667-2675 Salcedo, R., Young, H. A., Ponce, M. L., Ward, J. M., Kleinman, H. K., Murphy, W. J. and Oppenheim, J. J. (2001) Eotaxin (CCL11) induces in vivo angiogenic responses by human CCR3+ endothelial cells. J. Immunol. 166, 7571-7578 Lee, S. J., Namkoong, S., Kim, Y. M., Kim, C. K., Lee, H., Ha, K. S., Chung, H. T. and Kwon, Y. G. (2006) Fractalkine stimulates angiogenesis by activating the Raf-1/MEK/ERK- and PI3K/Akt/eNOS-dependent signal pathways. Am. J. Physiol. Heart Circ. Physiol. 291, H28362846 Bernardini, G., Spinetti, G., Ribatti, D., Camarda, G., Morbidelli, L., Ziche, M., Santoni, A., Capogrossi, M. C. and Napolitano, M. (2000) I-309 binds to and activates endothelial cell functions and acts as an angiogenic molecule in vivo. Blood 96, 4039-4045 Vicari, A. P., Ait-Yahia, S., Chemin, K., Mueller, A., Zlotnik, A. and Caux, C. (2000) Antitumor effects of the mouse chemokine 6Ckine/SLC through angiostatic and immunological mechanisms. J. Immunol. 165, 1992-2000 Addison, C. L., Daniel, T. O., Burdick, M. D., Liu, H., Ehlert, J. E., Xue, Y. Y., Buechi, L., Walz, A., Richmond, A. and Strieter, R. M. (2000) The CXC chemokine receptor 2, CXCR2, is the putative receptor for ELR+ CXC chemokine-induced angiogenic activity. J. Immunol. 165, 52695277 Lasagni, L., Francalanci, M., Annunziato, F., Lazzeri, E., Giannini, S., Cosmi, L., Sagrinati, C., Mazzinghi, B., Orlando, C., Maggi, E., Marra, F., Romagnani, S., Serio, M. and Romagnani, P.

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(2003) An alternatively spliced variant of CXCR3 mediates the inhibition of endothelial cell growth induced by IP-10, Mig, and I-TAC, and acts as functional receptor for platelet factor 4. J. Exp. Med. 197, 1537-1549 Jodele, S., Blavier, L., Yoon, J. M. and DeClerck, Y. A. (2006) Modifying the soil to affect the seed: role of stromal-derived matrix metalloproteinases in cancer progression. Cancer Metastasis Rev. 25, 35-43 Giraudo, E., Inoue, M. and Hanahan, D. (2004) An amino-bisphosphonate targets MMP-9expressing macrophages and angiogenesis to impair cervical carcinogenesis. J. Clin. Invest. 114, 623-633 Comerford, I. and Nibbs, R. J. (2005) Post-translational control of chemokines: a role for decoy receptors? Immunol. Lett. 96, 163-174 Wu, L., Fan, J., Matsumoto, S. and Watanabe, T. (2000) Induction and regulation of matrix metalloproteinase-12 by cytokines and CD40 signaling in monocyte/macrophages. Biochem. Biophys. Res. Commun. 269, 808-815 Li, A., Dubey, S., Varney, M. L., Dave, B. J. and Singh, R. K. (2003) IL-8 directly enhanced endothelial cell survival, proliferation, and matrix metalloproteinases production and regulated angiogenesis. J. Immunol. 170, 3369-3376 Klier, C. M., Nelson, E. L., Cohen, C. D., Horuk, R., Schlondorff, D. and Nelson, P. J. (2001) Chemokine-Induced secretion of gelatinase B in primary human monocytes. Biol. Chem. 382, 1405-1410 Galvez, B. G., Genis, L., Matias-Roman, S., Oblander, S. A., Tryggvason, K., Apte, S. S. and Arroyo, A. G. (2005) Membrane type 1-matrix metalloproteinase is regulated by chemokines monocyte-chemoattractant protein-1/CCL2 and interleukin-8/CXCL8 in endothelial cells during angiogenesis. J. Biol. Chem. 280, 1292-1298 Luca, M., Huang, S., Gershenwald, J. E., Singh, R. K., Reich, R. and Bar-Eli, M. (1997) Expression of interleukin-8 by human melanoma cells up-regulates MMP-2 activity and increases tumor growth and metastasis. Am J Pathol 151, 1105-1113 Azenshtein, E., Luboshits, G., Shina, S., Neumark, E., Shahbazian, D., Weil, M., Wigler, N., Keydar, I. and Ben-Baruch, A. (2002) The CC chemokine RANTES in breast carcinoma progression: regulation of expression and potential mechanisms of promalignant activity. Cancer Res. 62, 1093-1102 Proost, P., Mortier, A., Loos, T., Vandercappellen, J., Gouwy, M., Ronsse, I., Schutyser, E., Put, W., Parmentier, M., Struyf, S. and Van Damme, J. (2007) Proteolytic processing of CXCL11 by CD13/aminopeptidase N impairs CXCR3 and CXCR7 binding and signaling and reduces lymphocyte and endothelial cell migration. Blood 110, 37-44 Mantovani, A., Bonecchi, R. and Locati, M. (2006) Tuning inflammation and immunity by chemokine sequestration: decoys and more. Nat Rev Immunol 6, 907-918 Graham, G. J. and McKimmie, C. S. (2006) Chemokine scavenging by D6: a movable feast? Trends Immunol. Locati, M., Torre, Y. M., Galliera, E., Bonecchi, R., Bodduluri, H., Vago, G., Vecchi, A. and Mantovani, A. (2005) Silent chemoattractant receptors: D6 as a decoy and scavenger receptor for inflammatory CC chemokines. Cytokine Growth Factor Rev 16, 679-686 Rot, A. (2005) Contribution of Duffy antigen to chemokine function. Cytokine Growth Factor Rev. 16, 687-694 Wang, J., Ou, Z. L., Hou, Y. F., Luo, J. M., Shen, Z. Z., Ding, J. and Shao, Z. M. (2006) Enhanced expression of Duffy antigen receptor for chemokines by breast cancer cells attenuates growth and metastasis potential. Oncogene 25, 7201-7211 Addison, C. L., Belperio, J. A., Burdick, M. D. and Strieter, R. M. (2004) Overexpression of the duffy antigen receptor for chemokines (DARC) by NSCLC tumor cells results in increased tumor necrosis. BMC Cancer 4, 28 Shen, H., Schuster, R., Stringer, K. F., Waltz, S. E. and Lentsch, A. B. (2006) The Duffy antigen/receptor for chemokines (DARC) regulates prostate tumor growth. Faseb J. 20, 59-64 Martinez de la Torre, Y., Locati, M., Buracchi, C., Dupor, J., Cook, D. N., Bonecchi, R., Nebuloni, M., Rukavina, D., Vago, L., Vecchi, A., Lira, S. A. and Mantovani, A. (2005) Increased

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inflammation in mice deficient for the chemokine decoy receptor D6. Eur. J. Immunol. 35, 13421346 Nibbs, R. J., Gilchrist, D. S., King, V., Ferra, A., Forrow, S., Hunter, K. D. and Graham, G. J. (2007) The atypical chemokine receptor D6 suppresses the development of chemically induced skin tumors. J. Clin. Invest. 117, 1884-1892 Hendrix, M. J., Seftor, E. A., Seftor, R. E., Kasemeier-Kulesa, J., Kulesa, P. M. and Postovit, L. M. (2007) Reprogramming metastatic tumour cells with embryonic microenvironments. Nat. Rev. Cancer 7, 246-255 Stumm, R. K., Zhou, C., Ara, T., Lazarini, F., Dubois-Dalcq, M., Nagasawa, T., Hollt, V. and Schulz, S. (2003) CXCR4 regulates interneuron migration in the developing neocortex. J. Neurosci. 23, 5123-5130 Ma, Q., Jones, D., Borghesani, P. R., Segal, R. A., Nagasawa, T., Kishimoto, T., Bronson, R. T. and Springer, T. A. (1998) Impaired B-lymphopoiesis, myelopoiesis, and derailed cerebellar neuron migration in CXCR4- and SDF-1-deficient mice. Proc. Natl. Acad. Sci. U S A 95, 94489453 Zou, Y. R., Kottmann, A. H., Kuroda, M., Taniuchi, I. and Littman, D. R. (1998) Function of the chemokine receptor CXCR4 in haematopoiesis and in cerebellar development. Nature 393, 595599 Nagasawa, T., Hirota, S., Tachibana, K., Takakura, N., Nishikawa, S., Kitamura, Y., Yoshida, N., Kikutani, H. and Kishimoto, T. (1996) Defects of B-cell lymphopoiesis and bone-marrow myelopoiesis in mice lacking the CXC chemokine PBSF/SDF-1. Nature 382, 635-638 Sierro, F., Biben, C., Martinez-Munoz, L., Mellado, M., Ransohoff, R. M., Li, M., Woehl, B., Leung, H., Groom, J., Batten, M., Harvey, R. P., Martinez, A. C., Mackay, C. R. and Mackay, F. (2007) Disrupted cardiac development but normal hematopoiesis in mice deficient in the second CXCL12/SDF-1 receptor, CXCR7. Proc. Natl. Acad. Sci. U S A 104, 14759-14764 Nishio, M., Endo, T., Tsukada, N., Ohata, J., Kitada, S., Reed, J. C., Zvaifler, N. J. and Kipps, T. J. (2005) Nurselike cells express BAFF and APRIL, which can promote survival of chronic lymphocytic leukemia cells via a paracrine pathway distinct from that of SDF-1alpha. Blood 106, 1012-1020 Burger, M., Hartmann, T., Krome, M., Rawluk, J., Tamamura, H., Fujii, N., Kipps, T. J. and Burger, J. A. (2005) Small peptide inhibitors of the CXCR4 chemokine receptor (CD184) antagonize the activation, migration, and antiapoptotic responses of CXCL12 in chronic lymphocytic leukemia B cells. Blood 106, 1824-1830 Marchesi, F., Monti, P., Leone, B. E., Zerbi, A., Vecchi, A., Piemonti, L., Mantovani, A. and Allavena, P. (2004) Increased survival, proliferation, and migration in metastatic human pancreatic tumor cells expressing functional CXCR4. Cancer Res. 64, 8420-8427 Zhou, Y., Larsen, P. H., Hao, C. and Yong, V. W. (2002) CXCR4 is a major chemokine receptor on glioma cells and mediates their survival. J. Biol. Chem. 277, 49481-49487 Smith, M. C., Luker, K. E., Garbow, J. R., Prior, J. L., Jackson, E., Piwnica-Worms, D. and Luker, G. D. (2004) CXCR4 regulates growth of both primary and metastatic breast cancer. Cancer Res. 64, 8604-8612 Redjal, N., Chan, J. A., Segal, R. A. and Kung, A. L. (2006) CXCR4 inhibition synergizes with cytotoxic chemotherapy in gliomas. Clin. Cancer Res. 12, 6765-6771 Lee, C. H., Kakinuma, T., Wang, J., Zhang, H., Palmer, D. C., Restifo, N. P. and Hwang, S. T. (2006) Sensitization of B16 tumor cells with a CXCR4 antagonist increases the efficacy of immunotherapy for established lung metastases. Mol. Cancer Ther. 5, 2592-2599 Burns, J. M., Summers, B. C., Wang, Y., Melikian, A., Berahovich, R., Miao, Z., Penfold, M. E., Sunshine, M. J., Littman, D. R., Kuo, C. J., Wei, K., McMaster, B. E., Wright, K., Howard, M. C. and Schall, T. J. (2006) A novel chemokine receptor for SDF-1 and I-TAC involved in cell survival, cell adhesion, and tumor development. J Exp. Med. 203, 2201-2213 Balabanian, K., Lagane, B., Infantino, S., Chow, K. Y., Harriague, J., Moepps, B., ArenzanaSeisdedos, F., Thelen, M. and Bachelerie, F. (2005) The chemokine SDF-1/CXCL12 binds to and signals through the orphan receptor RDC1 in T lymphocytes. J. Biol. Chem. 280, 3576035766

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Dambly-Chaudiere, C., Cubedo, N. and Ghysen, A. (2007) Control of cell migration in the development of the posterior lateral line: antagonistic interactions between the chemokine receptors CXCR4 and CXCR7/RDC1. BMC Dev. Biol. 7, 23 Miao, Z., Luker, K. E., Summers, B. C., Berahovich, R., Bhojani, M. S., Rehemtulla, A., Kleer, C. G., Essner, J. J., Nasevicius, A., Luker, G. D., Howard, M. C. and Schall, T. J. (2007) CXCR7 (RDC1) promotes breast and lung tumor growth in vivo and is expressed on tumor-associated vasculature. Proc. Natl. Acad. Sci. U S A 104, 15735-15740 Perlin, J. R. and Talbot, W. S. (2007) Signals on the move: chemokine receptors and organogenesis in zebrafish. Sci STKE 2007, pe45 Wang, D., Yang, W., Du, J., Devalaraja, M. N., Liang, P., Matsumoto, K., Tsubakimoto, K., Endo, T. and Richmond, A. (2000) MGSA/GRO-mediated melanocyte transformation involves induction of Ras expression. Oncogene 19, 4647-4659 Luan, J., Shattuck-Brandt, R., Haghnegahdar, H., Owen, J. D., Strieter, R., Burdick, M., Nirodi, C., Beauchamp, D., Johnson, K. N. and Richmond, A. (1997) Mechanism and biological significance of constitutive expression of MGSA/GRO chemokines in malignant melanoma tumor progression. J. Leukoc. Biol. 62, 588-597 Vivanco, I. and Sawyers, C. L. (2002) The phosphatidylinositol 3-Kinase AKT pathway in human cancer. Nat. Rev. Cancer 2, 489-501 Brew, R., Erikson, J. S., West, D. C., Kinsella, A. R., Slavin, J. and Christmas, S. E. (2000) Interleukin-8 as an autocrine growth factor for human colon carcinoma cells in vitro. Cytokine 12, 78-85 Miyamoto, M., Shimizu, Y., Okada, K., Kashii, Y., Higuchi, K. and Watanabe, A. (1998) Effect of interleukin-8 on production of tumor-associated substances and autocrine growth of human liver and pancreatic cancer cells. Cancer Immunol. Immunother. 47, 47-57 Curnock, A. P., Logan, M. K. and Ward, S. G. (2002) Chemokine signalling: pivoting around multiple phosphoinositide 3-kinases. Immunology 105, 125-136 Brand, S., Dambacher, J., Beigel, F., Olszak, T., Diebold, J., Otte, J.-M., Goeke, B. and Eichhorst, S. T. (2005) CXCR4 and CXCL12 are inversely expressed in colorectal cancer cells and modulate cancer cell migration, invasion and MMP-9 activation. Expt. Cell. Res. 310, 117130 Burger, J. A. and Kipps, T. J. (2006) CXCR4: a key receptor in the crosstalk between tumor cells and their microenvironment. Blood 107, 1761-1767 Fujita, N. and Tsuruo, T. (2003) Survival-signaling pathway as a promising target for cancer chemotherapy. Cancer Chemother. Pharmacol. 52 Suppl 1, S24-28 Ye, R. D. (2001) Regulation of nuclear factor kappaB activation by G-protein-coupled receptors. J. Leukoc. Biol. 70, 839-848 Karin, M. (2006) Nuclear factor-kappaB in cancer development and progression. Nature 441, 431-436 Lee, B. C., Lee, T. H., Avraham, S. and Avraham, H. K. (2004) Involvement of the chemokine receptor CXCR4 and its ligand stromal cell-derived factor 1alpha in breast cancer cell migration through human brain microvascular endothelial cells. Mol. Cancer Res. 2, 327-338 Diehl, J. A., Cheng, M., Roussel, M. F. and Sherr, C. J. (1998) Glycogen synthase kinase-3beta regulates cyclin D1 proteolysis and subcellular localization. Genes Dev. 12, 3499-3511 Shaw, R. J. and Cantley, L. C. (2006) Ras, PI(3)K and mTOR signalling controls tumour cell growth. Nature 441, 424-430 Allan, L. A., Morrice, N., Brady, S., Magee, G., Pathak, S. and Clarke, P. R. (2003) Inhibition of caspase-9 through phosphorylation at Thr 125 by ERK MAPK. Nat. Cell Biol. 5, 647-654 Bonni, A., Brunet, A., West, A. E., Datta, S. R., Takasu, M. A. and Greenberg, M. E. (1999) Cell survival promoted by the Ras-MAPK signaling pathway by transcription-dependent and independent mechanisms. Science 286, 1358-1362 Kyriakis, J. M. (2000) MAP kinases and the regulation of nuclear receptors (2000) Sci. STKE 48, PE1 Sutton, A., Friand, V., Brule-Donneger, S., Chaigneau, T., Ziol, M., Sainte-Catherine, O., Poire, A., Saffar, L., Kraemer, M., Vassy, J., Nahon, P., Salzmann, J. L., Gattegno, L. and Charnaux,

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N. (2007) Stromal cell-derived factor-1/chemokine (C-X-C motif) ligand 12 stimulates human hepatoma cell growth, migration, and invasion. Mol. Cancer Res. 5, 21-33 Rollins, B. J. (2006) Inflammatory chemokines in cancer growth and progression. Eur. J. Cancer 42, 760-767 Mantovani, A. (1999) The chemokine system: redundancy for robust outputs. Immunol. Today 20, 254-257 Devalaraja, M. N. and Richmond, A. (1999) Multiple chemotactic factors: fine control or redundancy? Trends Pharmacol. Sci. 20, 151-156 D'Ambrosio, D., Albanesi, C., Lang, R., Girolomoni, G., Sinigaglia, F. and Laudanna, C. (2002) Quantitative differences in chemokine receptor engagement generate diversity in integrindependent lymphocyte adhesion. J. Immunol. 169, 2303-2312 Kohout, T. A., Nicholas, S. L., Perry, S. J., Reinhart, G., Junger, S. and Struthers, R. S. (2004) Differential desensitization, receptor phosphorylation, beta-arrestin recruitment, and ERK1/2 activation by the two endogenous ligands for the CC chemokine receptor 7. J. Biol. Chem. 279, 23214-23222 Loetscher, P., Pellegrino, A., Gong, J. H., Mattioli, I., Loetscher, M., Bardi, G., Baggiolini, M. and Clark-Lewis, I. (2001) The ligands of CXC chemokine receptor 3, I-TAC, Mig, and IP10, are natural antagonists for CCR3. J. Biol. Chem. 276, 2986-2991 Fernandis, A. Z., Cherla, R. P. and Ganju, R. K. (2003) Differential regulation of CXCR4mediated T-cell chemotaxis and mitogen-activated protein kinase activation by the membrane tyrosine phosphatase, CD45. J. Biol. Chem. 278, 9536-9543 Weiss-Haljiti, C., Pasquali, C., Ji, H., Gillieron, C., Chabert, C., Curchod, M. L., Hirsch, E., Ridley, A. J., van Huijsduijnen, R. H., Camps, M. and Rommel, C. (2004) Involvement of phosphoinositide 3-kinase gamma, Rac, and PAK signaling in chemokine-induced macrophage migration. J. Biol. Chem. 279, 43273-43284 Porcile, C., Bajetto, A., Barbieri, F., Barbero, S., Bonavia, R., Biglieri, M., Pirani, P., Florio, T. and Schettini, G. (2005) Stromal cell-derived factor-1alpha (SDF-1alpha/CXCL12) stimulates ovarian cancer cell growth through the EGF receptor transactivation. Exp. Cell Res. 308, 241253 Scotton, C. J., Wilson, J. L., Scott, K., Stamp, G., Wilbanks, G. D., Fricker, S., Bridger, G. and Balkwill, F. R. (2002) Multiple actions of the chemokine CXCL12 on epithelial tumor cells in human ovarian cancer. Cancer Res. 62, 5930-5938 Venkatakrishnan, G., Salgia, R. and Groopman, J. E. (2000) Chemokine receptors CXCR-1/2 activate mitogen-activated protein kinase via the epidermal growth factor receptor in ovarian cancer cells. J. Biol. Chem. 275, 6868-6875 Terrillon, S. and Bouvier, M. (2004) Roles of G-protein-coupled receptor dimerization. EMBO Rep. 5, 30-34 Milligan, G. (2004) G protein-coupled receptor dimerization: function and ligand pharmacology. Mol. Pharmacol. 66, 1-7 Springael, J. Y., Urizar, E. and Parmentier, M. (2005) Dimerization of chemokine receptors and its functional consequences. Cytokine Growth Factor Rev. 16, 611-623 Fox, J. A., Ung, K., Tanlimco, S. G. and Jirik, F. R. (2002) Disruption of a single Pten allele augments the chemotactic response of B lymphocytes to stromal cell-derived factor-1. J. Immunol. 169, 49-54 Holland, J. D., Kochetkova, M., Akekawatchai, C., Dottore, M., Lopez, A. and McColl, S. R. (2006) Differential functional activation of chemokine receptor CXCR4 is mediated by G proteins in breast cancer cells. Cancer Res. 66, 4117-4124 Arvanitakis, L., Geras-Raaka, E., Varma, A., Gershengorn, M. C. and Cesarman, E. (1997) Human herpesvirus KSHV encodes a constitutively active G-protein-coupled receptor linked to cell proliferation. Nature 385, 347-350 Burger, M., Burger, J. A., Hoch, R. C., Oades, Z., Takamori, H. and Schraufstatter, I. U. (1999) Point mutation causing constitutive signaling of CXCR2 leads to transforming activity similar to Kaposi's sarcoma herpesvirus-G protein-coupled receptor. J. Immunol. 163, 2017-2022

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Yang, T.-Y., Chen, S.-C., Leach, M. W., Manfra, D., Homey, B., Wiekowski, M., Sullivan, L., Jehn, C.-H., Narula, S. K., Chensue, S. W. and Lira, S. A. (2000) Transgenic expression of the chemokine receptor encoded by human herpesvirus 8 induces an angioproliferative disease resembling Kaposi's sarcoma. J. Exp. Med. 191, 445-453 Slettenaar, V. I. and Wilson, J. L. (2006) The chemokine network: a target in cancer biology? Adv. Drug Deliv. Rev. 58, 962-974 Springael, J. Y., Le Minh, P. N., Urizar, E., Costagliola, S., Vassart, G. and Parmentier, M. (2006) Allosteric modulation of binding properties between units of chemokine receptor homoand hetero-oligomers. Mol. Pharmacol. 69, 1652-1661 Sohy, D., Parmentier, M. and Springael, J. Y. (2007) Allosteric trans-inhibition by specific antagonists in CCR2/CXCR4 heterodimers. J. Biol. Chem. 282, 30062-9 Yuan, A., Chen, J. J., Yao, P. L. and Yang, P. C. (2005) The role of interleukin-8 in cancer cells and microenvironment interaction. Front. Biosci. 10, 853-865 Zhu, Y. M., Bagstaff, S. M. and Woll, P. J. (2006) Production and upregulation of granulocyte chemotactic protein-2/CXCL6 by IL-1beta and hypoxia in small cell lung cancer. Br. J. Cancer 94, 1936-1941 Varney, M. L., Li, A., Dave, B. J., Bucana, C. D., Johansson, S. L. and Singh, R. K. (2003) Expression of CXCR1 and CXCR2 receptors in malignant melanoma with different metastatic potential and their role in interleukin-8 (CXCL-8)-mediated modulation of metastatic phenotype. Clin. Exp. Metastasis 20, 723-731 Wente, M. N., Keane, M. P., Burdick, M. D., Friess, H., Buchler, M. W., Ceyhan, G. O., Reber, H. A., Strieter, R. M. and Hines, O. J. (2006) Blockade of the chemokine receptor CXCR2 inhibits pancreatic cancer cell-induced angiogenesis. Cancer Lett. 241, 221-227 Robledo, M. M., Bartolome, R. A., Longo, N., Rodriguez-Frade, J. M., Mellado, M., Longo, I., van Muijen, G. N., Sanchez-Mateos, P. and Teixido, J. (2001) Expression of functional chemokine receptors CXCR3 and CXCR4 on human melanoma cells. J. Biol. Chem. 276, 45098-45105 Berencsi, K., Meropol, N. J., Hoffman, J. P., Sigurdson, E., Giles, L., Rani, P., Somasundaram, R., Zhang, T., Kalabis, J., Caputo, L., Furth, E., Swoboda, R., Marincola, F. and Herlyn, D. (2007) Colon carcinoma cells induce CXCL11-dependent migration of CXCR3-expressing cytotoxic T lymphocytes in organotypic culture. Cancer Immunol. Immunother. 56, 359-370 Burkle, A., Niedermeier, M., Schmitt-Graff, A., Wierda, W. G., Keating, M. J. and Burger, J. A. (2007) Overexpression of the CXCR5 chemokine receptor, and its ligand, CXCL13 in B cell chronic lymphocytic leukemia. Blood 110, 3316-25. Lopez-Giral, S., Quintana, N. E., Cabrerizo, M., Alfonso-Perez, M., Sala-Valdes, M., De Soria, V. G., Fernandez-Ranada, J. M., Fernandez-Ruiz, E. and Munoz, C. (2004) Chemokine receptors that mediate B cell homing to secondary lymphoid tissues are highly expressed in B cell chronic lymphocytic leukemia and non-Hodgkin lymphomas with widespread nodular dissemination. J. Leukoc. Biol. 76, 462-471 Meijer, J., Zeelenberg, I. S., Sipos, B. and Roos, E. (2006) The CXCR5 Chemokine Receptor Is Expressed by Carcinoma Cells and Promotes Growth of Colon Carcinoma in the Liver. Cancer Res. 66, 9576-9582 Luboshits, G., Shina, S., Kaplan, O., Engelberg, S., Nass, D., Lifshitz-Mercer, B., Chaitchik, S., Keydar, I. and Ben-Baruch, A. (1999) Elevated expression of the CC chemokine regulated on activation, normal T cell expressed and secreted (RANTES) in advanced breast carcinoma. Cancer Res. 59, 4681-4687 Mrowietz, U., Schwenk, U., Maune, S., Bartels, J., Kupper, M., Fichtner, I., Schroder, J. M. and Schadendorf, D. (1999) The chemokine RANTES is secreted by human melanoma cells and is associated with enhanced tumour formation in nude mice. Br. J. Cancer 79, 1025-1031 Arenberg, D. A., Keane, M. P., DiGiovine, B., Kunkel, S. L., Strom, S. R., Burdick, M. D., Iannettoni, M. D. and Strieter, R. M. (2000) Macrophage infiltration in human non-small-cell lung cancer: the role of CC chemokines. Cancer Immunol. Immunother. 49, 63-70 Vaday, G. G., Peehl, D. M., Kadam, P. A. and Lawrence, D. M. (2006) Expression of CCL5 (RANTES) and CCR5 in prostate cancer. Prostate 66, 124-134

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Menu, E., De Leenheer, E., De Raeve, H., Coulton, L., Imanishi, T., Miyashita, K., Van Valckenborgh, E., Van Riet, I., Van Camp, B., Horuk, R., Croucher, P. and Vanderkerken, K. (2006) Role of CCR1 and CCR5 in homing and growth of multiple myeloma and in the development of osteolytic lesions: a study in the 5TMM model. Clin. Exp. Metastasis 23, 291300 Wu, X., Fan, J., Wang, X., Zhou, J., Qiu, S., Yu, Y., Liu, Y. and Tang, Z. (2007) Downregulation of CCR1 inhibits human hepatocellular carcinoma cell invasion. Biochem. Biophys. Res. Commun. 355, 866-871 Liang, Y., Bollen, A. W. and Gupta, N. (2007) CC chemokine receptor-2A is frequently overexpressed in glioblastoma. J. Neurooncol. In press. Lu, Y., Cai, Z., Xiao, G., Liu, Y., Keller, E. T., Yao, Z. and Zhang, J. (2007) CCR2 expression correlates with prostate cancer progression. J. Cell. Biochem. 101, 676-685 Vande Broek, I., Asosingh, K., Vanderkerken, K., Straetmans, N., Van Camp, B. and Van Riet, I. (2003) Chemokine receptor CCR2 is expressed by human multiple myeloma cells and mediates migration to bone marrow stromal cell-produced monocyte chemotactic proteins MCP-1, -2 and -3. Br. J. Cancer 88, 855-862 Harasawa, H., Yamada, Y., Hieshima, K., Jin, Z., Nakayama, T., Yoshie, O., Shimizu, K., Hasegawa, H., Hayashi, T., Imaizumi, Y., Ikeda, S., Soda, H., Atogami, S., Takasaki, Y., Tsukasaki, K., Tomonaga, M., Murata, K., Sugahara, K., Tsuruda, K. and Kamihira, S. (2006) Survey of chemokine receptor expression reveals frequent co-expression of skin-homing CCR4 and CCR10 in adult T-cell leukemia/lymphoma. Leuk. Lymphoma 47, 2163-2173 Ishida, T., Ishii, T., Inagaki, A., Yano, H., Kusumoto, S., Ri, M., Komatsu, H., Iida, S., Inagaki, H. and Ueda, R. (2006) The CCR4 as a novel-specific molecular target for immunotherapy in Hodgkin lymphoma. Leukemia 20, 2162-2168 Ishida, T., Utsunomiya, A., Iida, S., Inagaki, H., Takatsuka, Y., Kusumoto, S., Takeuchi, G., Shimizu, S., Ito, M., Komatsu, H., Wakita, A., Eimoto, T., Matsushima, K. and Ueda, R. (2003) Clinical significance of CCR4 expression in adult T-cell leukemia/lymphoma: its close association with skin involvement and unfavorable outcome. Clin. Cancer Res. 9, 3625-3634 Jones, D., O'Hara, C., Kraus, M. D., Perez-Atayde, A. R., Shahsafaei, A., Wu, L. and Dorfman, D. M. (2000) Expression pattern of T-cell-associated chemokine receptors and their chemokines correlates with specific subtypes of T-cell non-Hodgkin lymphoma. Blood 96, 685-690 Robinson, S. C., Scott, K. A., Wilson, J. L., Thompson, R. G., Proudfoot, A. E. and Balkwill, F. R. (2003) A chemokine receptor antagonist inhibits experimental breast tumor growth. Cancer Res. 63, 8360-8365 Manes, S., Mira, E., Colomer, R., Montero, S., Real, L. M., Gomez-Mouton, C., JimenezBaranda, S., Garzon, A., Lacalle, R. A., Harshman, K., Ruiz, A. and Martinez, A. C. (2003) CCR5 expression influences the progression of human breast cancer in a p53-dependent manner. J. Exp. Med. 198, 1381-1389 Rubie, C., Frick, V. O., Wagner, M., Weber, C., Kruse, B., Kempf, K., Konig, J., Rau, B. and Schilling, M. (2006) Chemokine expression in hepatocellular carcinoma versus colorectal liver metastases. World J. Gastroenterol. 12, 6627-6633 Till, K. J., Lin, K., Zuzel, M. and Cawley, J. C. (2002) The chemokine receptor CCR7 and alpha4 integrin are important for migration of chronic lymphocytic leukemia cells into lymph nodes. Blood 99, 2977-2984 Hwang, S. T. (2004) Chemokine receptors in melanoma: CCR9 has a potential role in metastasis to the small bowel. J. Invest. Dermatol. 122, xiv-xv Singh, S., Singh, U. P., Stiles, J. K., Grizzle, W. E. and Lillard, J. W., Jr. (2004) Expression and functional role of CCR9 in prostate cancer cell migration and invasion. Clin. Cancer Res. 10, 8743-8750 Notohamiprodjo, M., Segerer, S., Huss, R., Hildebrandt, B., Soler, D., Djafarzadeh, R., Buck, W., Nelson, P. J. and von Luettichau, I. (2005) CCR10 is expressed in cutaneous T-cell lymphoma. Int. J. Cancer 115, 641-647

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Shulby, S. A., Dolloff, N. G., Stearns, M. E., Meucci, O. and Fatatis, A. (2004) CX3CR1fractalkine expression regulates cellular mechanisms involved in adhesion, migration, and survival of human prostate cancer cells. Cancer Res. 64, 4693-4698 Clore, G. M., Appella, E., Yamada, M., Matsushima, K. and Gronenborn, A. M. (1990) Threedimensional structure of interleukin 8 in solution. Biochemistry 29, 1689-1696 Schwartz, T. W., Frimurer, T. M., Holst, B., Rosenkilde, M. M. and Elling, C. E. (2006) Molecular mechanism of 7TM receptor activation--a global toggle switch model. Annu. Rev. Pharmacol. Toxicol. 46, 481-519 Reiter, E. and Lefkowitz, R. J. (2006) GRKs and beta-arrestins: roles in receptor silencing, trafficking and signaling. Trends Endocrinol. Metab. 17, 159-165 Lefkowitz, R. J. and Whalen, E. J. (2004) beta-arrestins: traffic cops of cell signaling. Curr. Opin. Cell Biol. 16, 162-168 Lefkowitz, R. J. and Shenoy, S. K. (2005) Transduction of receptor signals by beta-arrestins. Science 308, 512-517 Sanchez-Madrid, F. and del Pozo, M. A. (1999) Leukocyte polarization in cell migration and immune interactions. Embo J. 18, 501-511 Cancelas, J. A., Jansen, M. and Williams, D. A. (2006) The role of chemokine activation of Rac GTPases in hematopoietic stem cell marrow homing, retention, and peripheral mobilization. Exp. Hematol. 34, 976-985

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Table 1: Cancer Promoting Properties of Chemokines and their Receptors.

CXCL1, 2, 3, 5, 6, 7, 8

CXCR3

*CXCL9, 10, 11

D

Invasion & metastasis, survival, proliferation

CXCR4

CXCL12

D&I

CXCR5

CXCL13

D

Angiogenesis, invasion & metastasis, growth & proliferation, survival, DC recruitment, MMP-9 expression Invasion & metastasis, growth & proliferation

CXCR7

CXCL12

D

CCR1

*CCL3, 4, 5, 7, 16, 23

D&I

CCR2

*CCL2, 7, 8, 12

CCR3

*CCL5, 7, 11, 24, 26

CCR4

CCL2, 3, 5, 17, 22

D&I

CCR5

*CCL3, 4, 5, 8

D&I

TAM recruitment, polarization, invasion & metastasis, growth, MMP-19 expression (CCL5)

Ref.

Angiogenesis (ELR+), invasion & metastasis, growth & proliferation, survival, MMP2/9/MT1-MMP expression (CXCL8)

Colorectal, lung, melanoma, pancreatic, prostate, renal cell

[46, 90, 96, 101, 102, 104, 138, 172, 175178] [21, 34, 179, 180] [38, 103, 142, 162] [181183]

TAM & DC recruitment, polarization, invasion & metastasis, angiogenesis, MMP9/19 expression (CCL5)

Breast, cervical, HCC, lung, MM, prostate, T-cell leukemia

OS

Growth, survival

Carcinomas (pancreatic, colon, head & neck), CLL, lymphomas Breast, lung

TAM & fibroblast recruitment, polarization, invasion & metastasis, angiogenesis, MMP12/MT1-MMP expression (CCL2)

Breast, glioma, lung, melanoma, MM, prostate

D&I

TAM & eosinophil recruitment, invasion & metastasis, angiogenesis, MMP-19 expression (CCL5) TAM & T cell recruitment, invasion & metastasis

Breast, cervical, CTCL, melanoma, renal cell

CCR6

CCL20

D&I

CCR7

CCL19, 21

D

DC recruitment, invasion & metastasis proliferation, Invasion & metastasis, survival

CCR9

CCL25

D

Invasion & metastasis, survival

St

Colorectal, melanoma, leukemias 23 types

D&I

2(

e

Types of Cancer

ATLL, CTCL, Hodgkin’s lymphoma, ovarian Breast, cervical, lung, MM, pancreatic, prostate

Breast, colorectal, HCC Breast, CLL, colorectal, gastric, head & neck, lung, melanoma Melanoma, prostate

Licenced copy. Copying is not permitted, except with prior permission and as allowed by law. © 2008 The Authors Journal compilation © 2008 Biochemical Society

[130, 133] [22, 6668, 103, 106, 184189] [59-61, 101, 104, 186, 187, 190192] [66, 68, 106, 184, 185] [72, 193196] [66, 68, 106, 184188, 197, 198] [71, 199] [20, 21, 200] [201, 202]

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CXCR1/2

ag

Tumorigenic Properties

a) P

Direct (D)/ Indirect (I) effects D&I

IN T

Ligands

TPR

Chemokine Receptor

CCL27

D

Invasion & metastasis, growth, survival

ATLL, CTCL, melanoma

CX3CR1

*CX3CL1

D

Invasion & metastasis, survival

Prostate

[40, 193, 201, 203] [172, 204]

IN T

CCR10

FIGURE LEGENDS

Figure 1. Molecular Events in the Classical Activation of a Chemokine GPCR Involving G Proteins. A. Structure of the IL-8 monomer (PDB ID 1IL8) [205]. The N-terminal signaling domain is highlighted; this region of the ligand is postulated to insert into the helical bundle of the receptor. It also contains the ELR motif in a subset of angiogenic CXC chemokines (discussed in the text), and in many

OS

chemokines is subject to proteolytic processing which modulates their activity. Additional receptor binding determinants are distributed along the rest of protein on the face shown, particularly the loop following the N-terminus. B. Receptor Activation. When a chemokine agonist binds to the extracellular side of its receptor, it stabilizes the receptor into a conformation that activates heterotrimeric G proteins

a) P

inside the cell by exposing important motifs such as the DRY box [206]. The G proteins have 3 subunits: α, β and γ. The Gα subunit interacts directly with the GPCR C-terminal domain, intracellular loops two and three, and with the G-protein β subunit, which forms a tight complex with the γ subunit. In the inactive state, the Gα subunit binds GDP. Upon ligand binding and activation of the GPCR, GDP dissociates from Gα. GDP is then replaced by GTP, Gα-GTP dissociates from the receptor and from Gβγ, and both of these complexes subsequently activate a variety of downstream effectors that

2(

ultimately lead to the physiological response. Refraction to continued stimuli involves receptor desensitization and internalization by agonist dependent phosphorylation of the C-terminal tail of the GPCR by G-protein receptor kinases (GRKs) [207]. Receptor phosphorylation subsequently promotes

e

binding of arrestins, which sterically block further interaction with G proteins and mediate receptor internalization through clathrin coated pits [208]. Endocytosis of a GPCR can lead to either lysosomal

ag

degradation or recycling back to the cell surface and resensitization. In addition to their involvement in internalization, β-arrestins can function as signal transducers by activating pathways such as AKT,

St

PI3K, MAPK, and NF-κB, which lead to a variety of cellular responses [209] (see Figure 2). Figure 2. Chemokine-Receptor Signaling in Migration and Survival/Proliferation. One of the first events of cell migration involves cell polarization in response to a chemoattractant whereby some receptors and signaling molecules localize toward the source of the chemoattractant, termed the

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TPR

Only chemokines/receptors with pro-tumorigenic roles in cancer are listed. However, some of these chemokines/receptors are known to also mediate anti-tumorigenic effects depending on the context and these are indicated by the asterisk (*). Some of the chemokine receptors are directly expressed on cancer cells (D), while others function indirectly (I) by recruiting TAMs, DCs, or other non-malignant cells that can contribute to the tumor microenvironment. Abbreviations: dendritic cell (DC), tumor associated macrophage (TAM), chronic lymphocytic leukemia (CLL), cutaneous T cell lymphoma (CTCL), adult T cell leukemia/lymphoma (ATLL), Hepatocellular carcinoma (HCC), multiple myeloma (MM).

leading edge, while other molecules distribute away at the trailing edge [210]. This process occurs via chemokine:receptor signaling through the class IB PI3Kγ, which activates Rac and subsequently PAK

IN T

(p21 activated kinase). Protrusion of the leading edge to move in the direction of the chemoattractant is mediated by actin polymerization and focal adhesions activated as chemokines bind to their receptors. Gi-dependent signaling through PI3K and various protein tyrosine kinases induces the activation of AKT, Rac, and Cdc42, which lead to downstream F-actin polymerization [31, 32, 211]. At the trailing edge, activation of ROCK downstream of Rho is responsible for actomyosin contraction at the rear so

TPR

the cell can progress forward [30, 32]. Calcium release and PKC activation downstream of PLC can also play important roles in mediating adhesion events [146]. Activation of FAK, pyk2 (proline-rich process. FAK activation is important in establishing focal adhesions and activating other molecules involved in cell movement, such as p130cas, crk and paxillin [37]. Integrin receptors that interact with ECM to mediate cell adhesion, and secreted proteases such as matrix metalloproteases (MMPs) that can aid in migration by degrading the ECM [24], can also be activated downstream of chemokine

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signaling.

As described in more detail in the section on signaling, some chemokines, in normal function or in the context of cancer, also activate a variety of survival and proliferation pathways. Anti-apoptotic/survival signaling, transcription of growth and proliferation related genes, and transcription of MMPs involved in

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migration and remodeling the mircroenvironment are all transduced downstream from AKT, ERK, PKC, and tyrosine kinase (e.g. Src) activation. GRK phosphorylation of the C-terminus of chemokine receptors allows β-arrestin to bind, leading to receptor desensitization and internalization. However, βarrestin binding also leads to the activation of several proteins including Src, MAPK (ERK, p38, JNK) and PI3K. Clearly, there is a large degree of overlap between the upstream signaling molecules

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underlying these various processes, as these pathways are able to elicit a broad spectrum of effects. Note that solid lines indicate direct activation or inhibition of the downstream molecule while dashed lines indicate indirect activation.

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Figure 3. Illustration of the Various Steps in Cancer Growth and Metastasis where Chemokines and Receptors Play a Role. In the primary lesion, tumor cells (dark blue), are supported by a network

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of cells in the microenvironment including fibroblasts (light blue), DCs (green) and TAMs (yellow). Chemokines produced by the tumor cells serve to recruit ECs thereby promoting angiogenesis. They also recruit leukocytes that produce other cytokines, growth factors and MMPs that enhance growth,

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proliferation, and angiogenesis. Fibroblasts also produce angiogenic and survival/growth promoting chemokines. Metastasis of cells is facilitated by upregulation of particular chemokine receptors (like CXCR4) on the tumor cells, which enables them to migrate to secondary tissues where the ligands are expressed. Similar to the primary site, paracrine and autocrine chemokine/cytokine signaling amongst

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tyrosine kinase 2 or FAK related tyrosine kinase), and other tyrosine kinases are also important in this

cells within the microenvironment may be especially important for survival and growth of the

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e Licenced copy. Copying is not permitted, except with prior permission and as allowed by law. © 2008 The Authors Journal compilation © 2008 Biochemical Society

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metastasized cells.

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Licenced copy. Copying is not permitted, except with prior permission and as allowed by law. © 2008 The Authors Journal compilation © 2008 Biochemical Society

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IN T TPR OS a) P 2( e ag St Figure 1b

Licenced copy. Copying is not permitted, except with prior permission and as allowed by law. © 2008 The Authors Journal compilation © 2008 Biochemical Society

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IN T TPR OS a) P 2( e ag St Figure 2

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IN T TPR OS a) P 2( e ag St Figure 3

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