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The CXCR4/SDF-1 Chemokine Receptor Axis: A New Target Therapeutic for Non-small Cell Lung Cancer

      Abstract

      Chemokines are proinflammatory chemoattractant cytokines that regulate cell trafficking and adhesion. The CXCR4 chemokine receptor and its ligand, stromal cell derived factor (SDF-1), constitute a chemokine/receptor axis that has attracted great interest because of an increasing understanding of its role in cancer, including lung cancer. The CXCR4/SDF-1 complex activates several pathways that mediate chemotaxis, migration and secretion of angiopoietic factors. Neutralization of SDF-1 by anti-SDF-1 or anti-CXCR4 monoclonal antibody in preclinical in vivo studies results in a significant decrease of non-small cell lung cancer metastases. Since anti-SDF-1/CXCR4 strategies have already been developed for use in combating human immunodeficiency virus infections, it is likely that these approaches will be used in clinical trials in non-small cell lung cancer in the very near future.

      Key Words

      Lung cancer has been the leading cause of cancer death worldwide for many decades. Despite this sobering statistic and years of research, treatments that meaningfully change the natural history of lung cancer remain elusive. Because metastatic spread constitutes the primary source of morbidity and mortality, a thorough understanding of the metastatic process is likely to be crucial to developing effective new therapies for lung cancer. Recently, a growing appreciation of the role of chemokines in cancer has unlocked the secrets of some of the molecular pathways underpinning this process, creating an understanding that reflects Paget's “seed and soil hypothesis” and which may lead to new approaches to lung cancer management. This brief review focuses on one such chemokine receptor axis, namely the CXCR4 and SDF-1 axis, and its emerging role in non-small cell lung cancer (NSCLC).
      Chemokines, a class of small (8–14 kDa) proinflammatory chemoattractant cytokines,
      • Zlotnik A
      • Yoshie O
      Chemokines: a new classification system and their role in immunity.
      are the major regulators of cell trafficking and adhesion in the body.
      • Schier AF
      Chemokine signaling: rules of attraction.
      Chemokines bind and activate a subset of seven transmembrane spanning G protein coupled receptors present on the surface of target cells.
      • Murphy PM
      • Baggiolini M
      • Charo IF
      • et al.
      International union of pharmacology. XXII. Nomenclature for chemokine receptors.
      They play a crucial role in the host immune defense system by recruiting specific leukocyte subpopulations to sites of tissue damage and infection, and are highly up-regulated by inflammatory stimuli such as antigens, polyclonal stimulants, cell irritants, and cytokines.
      • Baggiolini M
      • Dewald B
      • Moser B
      Interleukin-8 and related chemotactic cytokines–CXC and CC chemokines.
      • Taub DD
      • Oppenheim JJ
      Chemokines, inflammation and the immune system.
      Chemokines also have a role in dendritic cell maturation, B and T cell development, T cell responses, infection response and angiogenesis. Most intriguing is the accumulating evidence pointing to their role in tumor growth and metastasis.
      • Zlotnik A
      • Yoshie O
      Chemokines: a new classification system and their role in immunity.

      Basic Biology of the CXCR4/SDF-1 Axis

      The CXCR4 chemokine receptor and its ligand, stromal cell derived factor (SDF-1), constitute a chemokine/receptor axis that has attracted great interest partly because CXCR4 is a target for Human Immunodeficiency Virus (HIV) binding and entry into cells,
      • Deng H
      • Liu R
      • Ellmeier W
      • et al.
      Identification of a major co-receptor for primary isolates of HIV-1.
      • Feng Y
      • Broder CC
      • Kennedy PE
      • Berger EA
      HIV-1 entry cofactor: functional cDNA cloning of a seven-transmembrane, G protein-coupled receptor.
      but also because of an increasing understanding of its role in cancer. CXCR4, although initially cloned from leukocytes,
      • Loetscher M
      • Geiser T
      • O'Reilly T
      • Zwahlen R
      • Baggiolini M
      • Moser B
      Cloning of a human seven-transmembrane domain receptor, LESTR, that is highly expressed in leukocytes.
      is now known to be expressed by many cell types and has a role in multiple facets of cellular movement.
      • Rossi D
      • Zlotnik A
      The biology of chemokines and their receptors.
      Its ligand, SDF-1 (also called CXCL12), a member of the alpha family of chemokines,
      • Zlotnik A
      • Yoshie O
      Chemokines: a new classification system and their role in immunity.
      was initially isolated from a bone marrow stromal cell line
      • Nagasawa T
      • Kikutani H
      • Kishimoto T
      Molecular cloning and structure of a pre-B-cell growth-stimulating factor.
      and is a potent lymphocyte chemoattractant.
      • Bleul CC
      • Fuhlbrigge RC
      • Casasnovas JM
      • Aiuti A
      • Springer TA
      A highly efficacious lymphocyte chemoattractant, stromal cell-derived factor 1 (SDF-1).
      However, SDF-1 is also constitutively secreted by fibroblasts in several different organs/tissues including bone marrow, lymph nodes, lung, liver, and muscle.
      • Zou YR
      • Kottmann AH
      • Kuroda M
      • Taniuchi I
      • Littman DR
      Function of the chemokine receptor CXCR4 in haematopoiesis and in cerebellar development.
      • Ratajczak MZ
      • Majka M
      • Kucia M
      • et al.
      Expression of functional CXCR4 by muscle satellite cells and secretion of SDF-1 by muscle-derived fibroblasts is associated with the presence of both muscle progenitors in bone marrow and hematopoietic stem/progenitor cells in muscles.
      During embryogenesis the CXCR4/SDF-1 axis is involved in both hematopoiesis and organogenesis as demonstrated by knock-out studies.
      • Zou YR
      • Kottmann AH
      • Kuroda M
      • Taniuchi I
      • Littman DR
      Function of the chemokine receptor CXCR4 in haematopoiesis and in cerebellar development.
      • Nagasawa T
      • Hirota S
      • Tachibana K
      • et al.
      Defects of B-cell lymphopoiesis and bone-marrow myelopoiesis in mice lacking the CXC chemokine PBSF/SDF-1.
      • Bagri A
      • Gurney T
      • He X
      • et al.
      The chemokine SDF1 regulates migration of dentate granule cells.
      • Lazarini F
      • Tham TN
      • Casanova P
      • Arenzana-Seisdedos F
      • Dubois-Dalcq M
      Role of the alpha-chemokine stromal cell-derived factor (SDF-1) in the developing and mature central nervous system.
      Later, the CXCR4/SDF-1 axis plays a critical role in the homing and retention of hematopoietic/lymphopoietic stem cells, pre T and B lymphocytes in the bone marrow,
      • Ma Q
      • Jones D
      • Springer TA
      The chemokine receptor CXCR4 is required for the retention of B lineage and granulocytic precursors within the bone marrow microenvironment.
      • Aiuti A
      • Webb IJ
      • Bleul C
      • Springer T
      • Gutierrez-Ramos JC
      The chemokine SDF-1 is a chemoattractant for human CD34+ hematopoietic progenitor cells and provides a new mechanism to explain the mobilization of CD34+ progenitors to peripheral blood.
      and the trafficking of these cells to sites of tissue inflammation and damage.
      • Bleul CC
      • Fuhlbrigge RC
      • Casasnovas JM
      • Aiuti A
      • Springer TA
      A highly efficacious lymphocyte chemoattractant, stromal cell-derived factor 1 (SDF-1).
      • Ratajczak MZ
      • Kucia M
      • Reca R
      • Majka M
      • Janowska-Wieczorek A
      • Ratajczak J
      Stem cell plasticity revisited: CXCR4-positive cells expressing mRNA for early muscle, liver and neural cells ‘hide out’ in the bone marrow.
      Both CXCR4 and SDF-1 can be up-regulated under certain conditions, especially in response to hypoxic stimuli. CXCR4
      • Schioppa T
      • Uranchimeg B
      • Saccani A
      • et al.
      Regulation of the chemokine receptor CXCR4 by hypoxia.
      and SDF-1
      • Ceradini DJ
      • Kulkarni AR
      • Callaghan MJ
      • et al.
      Progenitor cell trafficking is regulated by hypoxic gradients through HIF-1 induction of SDF-1.
      gene expression are up-regulated in response to hypoxia inducible factor-1α (HIF-1α) in endothelial cells and in tumor cells in response to both HIF-1α
      • Schioppa T
      • Uranchimeg B
      • Saccani A
      • et al.
      Regulation of the chemokine receptor CXCR4 by hypoxia.
      • Phillips RJ
      • Mestas J
      • Gharaee-Kermani M
      • et al.
      Epidermal growth factor and hypoxia-induced expression of CXC chemokine receptor 4 on non-small cell lung cancer cells is regulated by the phosphatidylinositol 3-kinase/PTEN/AKT/mammalian target of rapamycin signaling pathway and activation of hypoxia inducible factor-1alpha.
      and NF-κB.
      • Helbig G
      • Christopherson II, KW
      • Bhat-Nakshatri P
      • et al.
      NF-kappaB promotes breast cancer cell migration and metastasis by inducing the expression of the chemokine receptor CXCR4.
      Significantly, it has been shown that activated epidermal growth factor receptor also increases the expression of CXCR4 in lung cancer tumor cells.
      • Phillips RJ
      • Mestas J
      • Gharaee-Kermani M
      • et al.
      Epidermal growth factor and hypoxia-induced expression of CXC chemokine receptor 4 on non-small cell lung cancer cells is regulated by the phosphatidylinositol 3-kinase/PTEN/AKT/mammalian target of rapamycin signaling pathway and activation of hypoxia inducible factor-1alpha.
      Although it had been thought that SDF-1 bound exclusively to CXCR4, and CXCR4 had SDF-1 as its only ligand,
      • Horuk R
      Chemokine receptors.
      there is now evidence that SDF-1 may signal through another chemokine receptor, CXCR7/RDC1,
      • Balabanian K
      • Lagane B
      • Infantino S
      • et al.
      The chemokine SDF-1/CXCL12 binds to and signals through the orphan receptor RDC1 in T lymphocytes.
      • Zhu ZB
      • Rivera AA
      • Makhija SK
      • et al.
      Targeting lung cancer using an infectivity enhanced CXCR4-CRAd.
      but its role in cell trafficking and migration remains undefined.
      • Burns JM
      • Summers BC
      • Wang Y
      • et al.
      A novel chemokine receptor for SDF-1 and I-TAC involved in cell survival, cell adhesion, and tumor development.
      • Sierro F
      • Biben C
      • Martínez-Muñoz L
      • et al.
      Disrupted cardiac development but normal hematopoiesis in mice deficient in the second CXCL12/SDF-1 receptor, CXCR7.

      Molecular Pathways Associated with CXCR4/SDF-1 Axis

      Investigations into the mechanisms of CXCR4 activation have demonstrated that SDF-1 bound-CXCR4 acts via Gαi, to activate the phosphoinositol-3-kinase (PI3K)
      • Vicente-Manzanares M
      • Rey M
      • Jones DR
      • et al.
      Involvement of phosphatidylinositol 3-kinase in stromal cell-derived factor-1 alpha-induced lymphocyte polarization and chemotaxis.
      and mitogen activated protein kinase (MAPK)
      • Ganju RK
      • Brubaker SA
      • Meyer J
      • et al.
      The alpha-chemokine, stromal cell-derived factor-1alpha, binds to the transmembrane G-protein-coupled CXCR-4 receptor and activates multiple signal transduction pathways.
      signaling pathways (Figure 1). It has been suggested that the CXCR4/SDF-1 complex is incorporated into lipid rafts, and may associate with members of the Src family of kinases.
      • Zaman SN
      • Resek ME
      • Robbins SM
      Dual acylation and lipid raft association of Src-family protein tyrosine kinases are required for SDF-1/CXCL12-mediated chemotaxis in the Jurkat human T cell lymphoma cell line.
      Activated CXCR4 increases intracellular calcium mobilization and induces phosphorylation of focal adhesion components such as FAK and Pyk2.
      • Phillips RJ
      • Mestas J
      • Gharaee-Kermani M
      • et al.
      Epidermal growth factor and hypoxia-induced expression of CXC chemokine receptor 4 on non-small cell lung cancer cells is regulated by the phosphatidylinositol 3-kinase/PTEN/AKT/mammalian target of rapamycin signaling pathway and activation of hypoxia inducible factor-1alpha.
      • Phillips RJ
      • Burdick MD
      • Lutz M
      • Belperio JA
      • Keane MP
      • Strieter RM
      The stromal derived factor-1/CXCL12-CXC chemokine receptor 4 biological axis in non-small cell lung cancer metastases.
      • Oonakahara K
      • Matsuyama W
      • Higashimoto I
      • Kawabata M
      • Arimura K
      • Osame M
      Stromal-derived factor-1alpha/CXCL12-CXCR 4 axis is involved in the dissemination of NSCLC cells into pleural space.
      • Fernandis AZ
      • Prasad A
      • Band H
      • Klösel R
      • Ganju RK
      Regulation of CXCR4-mediated chemotaxis and chemoinvasion of breast cancer cells.
      The PI3K/AKT and MAPK signal transduction pathways contribute to chemotaxis, cell migration,
      • Ganju RK
      • Brubaker SA
      • Meyer J
      • et al.
      The alpha-chemokine, stromal cell-derived factor-1alpha, binds to the transmembrane G-protein-coupled CXCR-4 receptor and activates multiple signal transduction pathways.
      • Libura J
      • Drukala J
      • Majka M
      • et al.
      CXCR4-SDF-1 signaling is active in rhabdomyosarcoma cells and regulates locomotion, chemotaxis, and adhesion.
      and secretion of various matrix metalloproteinases (MMP's) including MMP-2 and MMP-9,
      • Fernandis AZ
      • Prasad A
      • Band H
      • Klösel R
      • Ganju RK
      Regulation of CXCR4-mediated chemotaxis and chemoinvasion of breast cancer cells.
      • Tang CH
      • Tan TW
      • Fu WM
      • Yang RS
      Involvement of matrix metalloproteinase-9 in stromal cell-derived factor-1/CXCR4 pathway of lung cancer metastasis.
      which are involved in the invasion of cells through the basement membrane.
      • Janowska-Wieczorek A
      • Marquez LA
      • Dobrowsky A
      • Ratajczak MZ
      • Cabuhat ML
      Differential MMP and TIMP production by human marrow and peripheral blood CD34(+) cells in response to chemokines.
      They also induce expression of several cell surface integrins such as VLA-4 and VLA-5
      • Kijowski J
      • Baj-Krzyworzeka M
      • Majka M
      • et al.
      The SDF-1-CXCR4 axis stimulates VEGF secretion and activates integrins but does not affect proliferation and survival in lymphohematopoietic cells.
      • Peled A
      • Kollet O
      • Ponomaryov T
      • et al.
      The chemokine SDF-1 activates the integrins LFA-1, VLA-4, and VLA-5 on immature human CD34(+) cells: role in transendothelial/stromal migration and engraftment of NOD/SCID mice.
      • Huang YC
      • Hsiao YC
      • Chen YJ
      • Wei YY
      • Lai TH
      • Tang CH
      Stromal cell-derived factor-1 enhances motility and integrin up-regulation through CXCR4, ERK and NF-kappaB-dependent pathway in human lung cancer cells.
      and secretion of the angiopoietic factor, VEGF.
      • Liang Z
      • Brooks J
      • Willard M
      • et al.
      CXCR4/CXCL12 axis promotes VEGF-mediated tumor angiogenesis through Akt signaling pathway.
      Furthermore, blocking either the PI3K or MAPK pathway inhibits CXCR4 activated cell migration in a pre B cell line.
      • Ganju RK
      • Brubaker SA
      • Meyer J
      • et al.
      The alpha-chemokine, stromal cell-derived factor-1alpha, binds to the transmembrane G-protein-coupled CXCR-4 receptor and activates multiple signal transduction pathways.
      Ultimately, through these pathways, SDF1-bound CXCR4 can induce cytoskeletal rearrangement, adhesion to endothelial cells, polarized migration of cells to specific organs and the secretion of angiopoietic factors, all important components of the metastatic process.
      • Hillyer P
      • Mordelet E
      • Flynn G
      • Male D
      Chemokines, chemokine receptors and adhesion molecules on different human endothelia: discriminating the tissue-specific functions that affect leucocyte migration.
      • Cho HH
      • Kyoung KM
      • Seo MJ
      • Kim YJ
      • Bae YC
      • Jung JS
      Overexpression of CXCR4 increases migration and proliferation of human adipose tissue stromal cells.
      • Kucia M
      • Reca R
      • Miekus K
      • et al.
      Trafficking of normal stem cells and metastasis of cancer stem cells involve similar mechanisms: pivotal role of the SDF-1-CXCR4 axis.
      • Alsayed Y
      • Ngo H
      • Runnels J
      • et al.
      Mechanisms of regulation of CXCR4/SDF-1 (CXCL12)-dependent migration and homing in multiple myeloma.
      Figure thumbnail gr1
      FIGURE 1Schematic illustrating molecular pathways by which CXCR4 acts. Stromal cell derived factor (SDF-1) bound-CXCR4, possibly after incorporation into lipid rafts, acts via Gαi, to activate the phosphoinositol-3-kinase (PI3K) and mitogen activated protein kinase (MAPK) signaling pathways. Activated CXCR4 increases intracellular calcium mobilization and induces phosphorylation of focal adhesion components such as FAK and Pyk2. The activated signal transduction pathways contribute to chemotaxis, cell migration, and secretion of various matrix metalloproteinases (MMP's) including MMP-2 and MMP-9. Supporting references in brackets.

      CXCR4 and SDF-1 Role in Cancer

      Involvement of the CXCR4/SDF-1 axis in cancer is attractive because it helps explain some of the well described phenomena associated with metastasis. The two key components of metastasis–acquisition of the capability to break away from the primary tumor to become blood or lymph borne and the subsequent ability to home in on its metastatic destination-can both be influenced by the CXCR4/SDF-1 axis. The molecular changes described above confer on the malignant cell a greater ability to migrate and invade,
      • Sutton A
      • Friand V
      • Brulé-Donneger S
      • et al.
      Stromal cell-derived factor-1/chemokine (C-X-C motif) ligand 12 stimulates human hepatoma cell growth, migration, and invasion.
      • Kang H
      • Watkins G
      • Parr C
      • Douglas-Jones A
      • Mansel RE
      • Jiang WG
      Stromal cell derived factor-1: its influence on invasiveness and migration of breast cancer cells in vitro, and its association with prognosis and survival in human breast cancer.
      while the constitutive release by stromal cells from common sites of metastasis such as bone marrow, lung, and liver, can guide the circulating cell to home in on its metastatic destination.
      • Pituch-Noworolska A
      • Majka M
      • Janowska-Wieczorek A
      • et al.
      Circulating CXCR4-positive stem/progenitor cells compete for SDF-1-positive niches in bone marrow, muscle and neural tissues: an alternative hypothesis to stem cell plasticity.
      The role played by the CXCR4/SDF-1 axis in leukocyte trafficking and homing of stem cells
      • Lapidot T
      • Dar A
      • Kollet O
      How do stem cells find their way home?.
      • Wang J
      • Loberg R
      • Taichman RS
      The pivotal role of CXCL12 (SDF-1)/ CXCR4 axis in bone metastasis.
      is likely analogous to organ selective metastasis of cancer stem cells.
      • Geminder H
      • Sagi-Assif O
      • Goldberg L
      • et al.
      A possible role for CXCR4 and its ligand, the CXC chemokine stromal cell-derived factor-1, in the development of bone marrow metastases in neuroblastoma.
      In this model, a cell's metastatic potential will be determined by surface CXCR4 expression while its destiny will be influenced by local SDF-1 secretion at distal sites. As such, the CXCR4/SDF-1 axis can help explain the “nature” underlying metastatic tendency-CXCR4 expression-as well as the “nurture” of that tendency–SDF-1 secretion at metastatic sites.
      The first evidence of a direct role for CXCR4/SDF-1 in tumor metastasis came from a pivotal study by Muller et al.,
      • Muller A
      • Homey B
      • Soto H
      • et al.
      Involvement of chemokine receptors in breast cancer metastasis.
      which demonstrated that the most abundant of the chemokine receptors in breast cancer was CXCR4. Specifically, CXCR4 expression was markedly up-regulated in breast cancer cells compared with normal mammary epithelial cells in which CXCR4 was undetectable. Furthermore, in vivo administration of an anti-CXCR4 monoclonal antibody markedly reduced lung metastasis in a mouse model of breast cancer, providing the first evidence that CXCR4 inhibition may be a useful antimetastatic strategy. Subsequent studies have suggested that the CXCR4/SDF-1 axis plays a role in the metastasis of many types of tumor cells. Retrospective studies in breast,
      • Kang H
      • Watkins G
      • Parr C
      • Douglas-Jones A
      • Mansel RE
      • Jiang WG
      Stromal cell derived factor-1: its influence on invasiveness and migration of breast cancer cells in vitro, and its association with prognosis and survival in human breast cancer.
      especially triple negative breast cancer
      • Holm NT
      • Benjamin LJL
      • Quyen C
      Overexpression of chemokine receptor cxcr4 in cancer specimens predicts outcome in patients with triple-negative breast cancer.
      and other cancers including nasopharyngeal
      • Hu J
      • Deng X
      • Bian X
      • et al.
      The expression of functional chemokine receptor CXCR4 is associated with the metastatic potential of human nasopharyngeal carcinoma.
      and ovarian carcinomas
      • Jiang YP
      • Wu XH
      • Shi B
      • Wu WX
      • Yin GR
      Expression of chemokine CXCL12 and its receptor CXCR4 in human epithelial ovarian cancer: an independent prognostic factor for tumor progression.
      have provided evidence that high expression of the CXCR4 receptor on primary tumor specimens correlates with a poorer clinical outcome. In vitro studies
      • Hu J
      • Deng X
      • Bian X
      • et al.
      The expression of functional chemokine receptor CXCR4 is associated with the metastatic potential of human nasopharyngeal carcinoma.
      • Hart CA
      • Brown M
      • Bagley S
      • Sharrard M
      • Clarke NW
      Invasive characteristics of human prostatic epithelial cells: understanding the metastatic process.
      • Mori T
      • Doi R
      • Koizumi M
      • et al.
      CXCR4 antagonist inhibits stromal cell-derived factor 1-induced migration and invasion of human pancreatic cancer.
      in various tumor cell lines have shown that inhibition of the CXCR4/SDF-1 chemokine axis results in decreased migration and invasion of these cell lines. Lastly, in vivo studies have revealed that inhibition of the CXCR4/SDF-1 axis significantly decreased the amount of metastasis seen in mouse models of breast,
      • Muller A
      • Homey B
      • Soto H
      • et al.
      Involvement of chemokine receptors in breast cancer metastasis.
      • Smith MC
      • Luker KE
      • Garbow JR
      • et al.
      CXCR4 regulates growth of both primary and metastatic breast cancer.
      renal,
      • Pan J
      • Mestas J
      • Burdick MD
      • et al.
      Stromal derived factor-1 (SDF-1/CXCL12) and CXCR4 in renal cell carcinoma metastasis.
      and head and neck cancers.
      • Yoon Y
      • Liang Z
      • Zhang X
      • et al.
      CXC chemokine receptor-4 antagonist blocks both growth of primary tumor and metastasis of head and neck cancer in xenograft mouse models.

      Lung Cancer and the CXCR4/SDF-1 Axis

      Increasing evidence suggests that the CXCR4/SDF-1 chemokine axis also plays a pivotal role in the metastasis of lung cancer, particularly in NSCLC. Firstly, in vitro studies have shown that NSCLC cell lines express high levels of CXCR4 but not SDF-1 and that SDF-1-activated CXCR4 promotes migration and invasion of these cell lines in vitro.
      • Belperio JA
      • Phillips RJ
      • Burdick MD
      • Lutz M
      • Keane M
      • Strieter R
      The SDF-1/CXCL 12/CXCR4 biological axis in non-small cell lung cancer metastases.
      Interruption of this axis by CXCR4 down-regulation via transfection with a CXCR4 antisense nucleotide fragment, or by incubating cells with a CXCR4 neutralizing antibody, significantly decreases migration, invasion, and adhesion of NSCLC cell line cells in vitro.
      • Su L
      • Zhang J
      • Xu H
      • et al.
      Differential expression of CXCR4 is associated with the metastatic potential of human non-small cell lung cancer cells.
      Secondly, in vivo studies using a SCID mouse model of heterotopic or orthotopic xenoengraftment of human NSCLC cells show that preferential sites of lung cancer metastases have significantly higher levels of SDF-1 protein expression than the primary tumor or plasma levels
      • Belperio JA
      • Phillips RJ
      • Burdick MD
      • Lutz M
      • Keane M
      • Strieter R
      The SDF-1/CXCL 12/CXCR4 biological axis in non-small cell lung cancer metastases.
      suggesting that a chemotactic gradient may be established between the site of the primary tumor and metastatic sites. In vivo neutralization of SDF-1 by an anti-SDF-1 or anti-CXCR4 monoclonal antibody resulted in a significant decrease of NSCLC metastases to several organs including the adrenal glands, liver, lung, brain, and bone marrow.
      • Phillips RJ
      • Mestas J
      • Gharaee-Kermani M
      • et al.
      Epidermal growth factor and hypoxia-induced expression of CXC chemokine receptor 4 on non-small cell lung cancer cells is regulated by the phosphatidylinositol 3-kinase/PTEN/AKT/mammalian target of rapamycin signaling pathway and activation of hypoxia inducible factor-1alpha.
      • Belperio JA
      • Phillips RJ
      • Burdick MD
      • Lutz M
      • Keane M
      • Strieter R
      The SDF-1/CXCL 12/CXCR4 biological axis in non-small cell lung cancer metastases.
      Importantly, this is supported by retrospective clinical studies that show a correlation between primary tumor CXCR4 expression and clinical outcome in NSCLC patients. Patients with high CXCR4 expressing tumors seem more prone to metastasis than patients with low expressing tumors.
      • Su L
      • Zhang J
      • Xu H
      • et al.
      Differential expression of CXCR4 is associated with the metastatic potential of human non-small cell lung cancer cells.
      When CXCR4 expression is limited to the nucleus only, this correlation is lost and a better prognosis is seen clearly suggesting that the metastatic potential is conferred by presumed membrane localization of the receptor.
      • Spano JP
      • Andre F
      • Morat L
      • et al.
      Chemokine receptor CXCR4 and early-stage non-small cell lung cancer: pattern of expression and correlation with outcome.
      Taken together, these studies provide a sound rationale for pursuing anti-CXCR4/SDF-1 approaches in clinical trials.

      Anti-CXCR4 Strategies in Clinical Trials

      Given the accumulating evidence supporting a role for the CXCR4/SDF-1 axis in NSCLC it is not surprising that attention is now focusing on it as a therapeutic target. Although disruption of the CXCR4/SDF-1 axis has been explored in HIV treatment, there is a dearth of experience using this approach in the oncology world. Several CXCR4 inhibitors have been tested in preclinical studies to assess their efficacy in preventing the growth and spread of various tumor cell types, but only recently have these agents entered into clinical trials. Two of these deserve a mention. AMD 3100 is a small molecule specific antagonist of the CXCR4 receptor which competitively binds and prevents the interaction of the receptor with SDF-1. A recent clinical trial showed that the administration of AMD 3100 in combination with granulocyte colony-stimulating factor to patients with non-Hodgkin lymphoma or multiple myeloma significantly increased the mobilization of hematopoietic progenitor cells to be used for autologous transplantation.
      • Flomenberg N
      • DiPersio J
      • Calandra G
      Role of CXCR4 chemokine receptor blockade using AMD3100 for mobilization of autologous hematopoietic progenitor cells.
      That this approach can influence the distribution of progenitor cells in vivo is a very significant proof of principle. Another agent, CTCE-9908, a small peptide CXCR4 antagonist, is well tolerated and preliminary evidence from phase I/II clinical trials with 26 patients, including 3 lung cancer patients, indicate that this agent is efficacious in late stage solid tumors.

      Hotte S. Phase I/II study of CTCE-9908, a novel anticancer agent that inhibits CXCR4, in patients with advanced solid cancers. AACR Molecular Therapy Conference. Abstract, 2007.

      To date there are no other published trials of this approach in early or metastatic disease. There have been no trials of anti-CXCR4 or anti-SDF-1 monoclonal antibodies and no trials as yet of CXCR4 antisense approaches.

      CONCLUSION

      Paget's concept of seed and soil implies that a number of factors involving both the “nature” of the malignant cell and the “nurture” provided by the distal environment must collaborate to allow metastasis to occur. Clearly, chemokines and their receptors provide a molecular explanation for this “seed and soil” phenomenon. The increasing evidence supporting a role for the CXCR4/SDF-1 axis in the metastatic evolution of several cancers, and especially NSCLC, provides the rationale for targeted disruption of this axis in future clinical trials. Because of its well-defined role as a portal of entry for the HIV, a number of inhibitors of this axis have already been developed and may be promptly tested in preclinical models and clinical trials. It is very likely that the detailed understanding of the role of the CXCR4/SDF-1 axis in NSCLC will lead to new treatment strategies that may allow us to more meaningfully change the clinical course of this disease in the very near future.

      ACKNOWLEDGMENTS

      We would like to thank Dr. Greg Cairncross, Dr. Don Morris, Dr. Stephen Robbins, and Dr. Shirin Bonni for their careful review of this paper.

      REFERENCES

        • Zlotnik A
        • Yoshie O
        Chemokines: a new classification system and their role in immunity.
        Immunity. 2000; 12: 121-127
        • Schier AF
        Chemokine signaling: rules of attraction.
        Curr Biol. 2003; 13: R192-R194
        • Murphy PM
        • Baggiolini M
        • Charo IF
        • et al.
        International union of pharmacology. XXII. Nomenclature for chemokine receptors.
        Pharmacol Rev. 2000; 52: 145-176
        • Baggiolini M
        • Dewald B
        • Moser B
        Interleukin-8 and related chemotactic cytokines–CXC and CC chemokines.
        Adv Immunol. 1994; 55: 97-179
        • Taub DD
        • Oppenheim JJ
        Chemokines, inflammation and the immune system.
        Ther Immunol. 1994; 1: 229-246
        • Deng H
        • Liu R
        • Ellmeier W
        • et al.
        Identification of a major co-receptor for primary isolates of HIV-1.
        Nature. 1996; 38: 661-666
        • Feng Y
        • Broder CC
        • Kennedy PE
        • Berger EA
        HIV-1 entry cofactor: functional cDNA cloning of a seven-transmembrane, G protein-coupled receptor.
        Science. 1996; 272: 872-877
        • Loetscher M
        • Geiser T
        • O'Reilly T
        • Zwahlen R
        • Baggiolini M
        • Moser B
        Cloning of a human seven-transmembrane domain receptor, LESTR, that is highly expressed in leukocytes.
        J Biol Chem. 1994; 269: 232-237
        • Rossi D
        • Zlotnik A
        The biology of chemokines and their receptors.
        Annu Rev Immunol. 2000; 18: 217-242
        • Nagasawa T
        • Kikutani H
        • Kishimoto T
        Molecular cloning and structure of a pre-B-cell growth-stimulating factor.
        Proc Natl Acad Sci USA. 1994; 91: 2305-2309
        • Bleul CC
        • Fuhlbrigge RC
        • Casasnovas JM
        • Aiuti A
        • Springer TA
        A highly efficacious lymphocyte chemoattractant, stromal cell-derived factor 1 (SDF-1).
        J Exp Med. 1996; 184: 1101-1109
        • Zou YR
        • Kottmann AH
        • Kuroda M
        • Taniuchi I
        • Littman DR
        Function of the chemokine receptor CXCR4 in haematopoiesis and in cerebellar development.
        Nature. 1998; 393: 595-599
        • Ratajczak MZ
        • Majka M
        • Kucia M
        • et al.
        Expression of functional CXCR4 by muscle satellite cells and secretion of SDF-1 by muscle-derived fibroblasts is associated with the presence of both muscle progenitors in bone marrow and hematopoietic stem/progenitor cells in muscles.
        Stem Cells. 2003; 21: 363-371
        • Nagasawa T
        • Hirota S
        • Tachibana K
        • et al.
        Defects of B-cell lymphopoiesis and bone-marrow myelopoiesis in mice lacking the CXC chemokine PBSF/SDF-1.
        Nature. 1996; 382: 635-638
        • Bagri A
        • Gurney T
        • He X
        • et al.
        The chemokine SDF1 regulates migration of dentate granule cells.
        Development. 2002; 129: 4249-4260
        • Lazarini F
        • Tham TN
        • Casanova P
        • Arenzana-Seisdedos F
        • Dubois-Dalcq M
        Role of the alpha-chemokine stromal cell-derived factor (SDF-1) in the developing and mature central nervous system.
        Glia. 2003; 42: 139-148
        • Ma Q
        • Jones D
        • Springer TA
        The chemokine receptor CXCR4 is required for the retention of B lineage and granulocytic precursors within the bone marrow microenvironment.
        Immunity. 1999; 10: 463-471
        • Aiuti A
        • Webb IJ
        • Bleul C
        • Springer T
        • Gutierrez-Ramos JC
        The chemokine SDF-1 is a chemoattractant for human CD34+ hematopoietic progenitor cells and provides a new mechanism to explain the mobilization of CD34+ progenitors to peripheral blood.
        J Exp Med. 1997; 185: 111-120
        • Ratajczak MZ
        • Kucia M
        • Reca R
        • Majka M
        • Janowska-Wieczorek A
        • Ratajczak J
        Stem cell plasticity revisited: CXCR4-positive cells expressing mRNA for early muscle, liver and neural cells ‘hide out’ in the bone marrow.
        Leukemia. 2004; 18: 29-40
        • Schioppa T
        • Uranchimeg B
        • Saccani A
        • et al.
        Regulation of the chemokine receptor CXCR4 by hypoxia.
        J Exp Med. 2003; 198: 1391-1402
        • Ceradini DJ
        • Kulkarni AR
        • Callaghan MJ
        • et al.
        Progenitor cell trafficking is regulated by hypoxic gradients through HIF-1 induction of SDF-1.
        Nat Med. 2004; 10: 858-864
        • Phillips RJ
        • Mestas J
        • Gharaee-Kermani M
        • et al.
        Epidermal growth factor and hypoxia-induced expression of CXC chemokine receptor 4 on non-small cell lung cancer cells is regulated by the phosphatidylinositol 3-kinase/PTEN/AKT/mammalian target of rapamycin signaling pathway and activation of hypoxia inducible factor-1alpha.
        J Biol Chem. 2005; 280: 22473-22481
        • Helbig G
        • Christopherson II, KW
        • Bhat-Nakshatri P
        • et al.
        NF-kappaB promotes breast cancer cell migration and metastasis by inducing the expression of the chemokine receptor CXCR4.
        J Biol Chem. 2003; 278: 21631-21638
        • Horuk R
        Chemokine receptors.
        Cytokine Growth Factor Rev. 2001; 12: 313-335
        • Balabanian K
        • Lagane B
        • Infantino S
        • et al.
        The chemokine SDF-1/CXCL12 binds to and signals through the orphan receptor RDC1 in T lymphocytes.
        J Biol Chem. 2005; 280: 35760-35766
        • Zhu ZB
        • Rivera AA
        • Makhija SK
        • et al.
        Targeting lung cancer using an infectivity enhanced CXCR4-CRAd.
        Lung Cancer. 2007; 55: 145-156
        • Burns JM
        • Summers BC
        • Wang Y
        • et al.
        A novel chemokine receptor for SDF-1 and I-TAC involved in cell survival, cell adhesion, and tumor development.
        J Exp Med. 2006; 203: 2201-2213
        • Sierro F
        • Biben C
        • Martínez-Muñoz L
        • et al.
        Disrupted cardiac development but normal hematopoiesis in mice deficient in the second CXCL12/SDF-1 receptor, CXCR7.
        Proc Natl Acad Sci USA. 2007; 104: 14759-14764
        • Vicente-Manzanares M
        • Rey M
        • Jones DR
        • et al.
        Involvement of phosphatidylinositol 3-kinase in stromal cell-derived factor-1 alpha-induced lymphocyte polarization and chemotaxis.
        J Immunol. 1999; 163: 4001-4012
        • Ganju RK
        • Brubaker SA
        • Meyer J
        • et al.
        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. 1998; 273: 23169-23175
        • Zaman SN
        • Resek ME
        • Robbins SM
        Dual acylation and lipid raft association of Src-family protein tyrosine kinases are required for SDF-1/CXCL12-mediated chemotaxis in the Jurkat human T cell lymphoma cell line.
        J Leukoc Biol. 2008; 84: 1082-1091
        • Phillips RJ
        • Burdick MD
        • Lutz M
        • Belperio JA
        • Keane MP
        • Strieter RM
        The stromal derived factor-1/CXCL12-CXC chemokine receptor 4 biological axis in non-small cell lung cancer metastases.
        Am J Respir Crit Care Med. 2003; 167: 1676-1686
        • Oonakahara K
        • Matsuyama W
        • Higashimoto I
        • Kawabata M
        • Arimura K
        • Osame M
        Stromal-derived factor-1alpha/CXCL12-CXCR 4 axis is involved in the dissemination of NSCLC cells into pleural space.
        Am J Respir Cell Mol Biol. 2004; 30: 671-677
        • Fernandis AZ
        • Prasad A
        • Band H
        • Klösel R
        • Ganju RK
        Regulation of CXCR4-mediated chemotaxis and chemoinvasion of breast cancer cells.
        Oncogene. 2004; 23: 157-167
        • Libura J
        • Drukala J
        • Majka M
        • et al.
        CXCR4-SDF-1 signaling is active in rhabdomyosarcoma cells and regulates locomotion, chemotaxis, and adhesion.
        Blood. 2002; 100: 2597-2606
        • Tang CH
        • Tan TW
        • Fu WM
        • Yang RS
        Involvement of matrix metalloproteinase-9 in stromal cell-derived factor-1/CXCR4 pathway of lung cancer metastasis.
        Carcinogenesis. 2008; 29: 34-43
        • Janowska-Wieczorek A
        • Marquez LA
        • Dobrowsky A
        • Ratajczak MZ
        • Cabuhat ML
        Differential MMP and TIMP production by human marrow and peripheral blood CD34(+) cells in response to chemokines.
        Exp Hematol. 2000; 28: 1274-1285
        • Kijowski J
        • Baj-Krzyworzeka M
        • Majka M
        • et al.
        The SDF-1-CXCR4 axis stimulates VEGF secretion and activates integrins but does not affect proliferation and survival in lymphohematopoietic cells.
        Stem Cells. 2001; 19: 453-466
        • Peled A
        • Kollet O
        • Ponomaryov T
        • et al.
        The chemokine SDF-1 activates the integrins LFA-1, VLA-4, and VLA-5 on immature human CD34(+) cells: role in transendothelial/stromal migration and engraftment of NOD/SCID mice.
        Blood. 2000; 95: 3289-3296
        • Huang YC
        • Hsiao YC
        • Chen YJ
        • Wei YY
        • Lai TH
        • Tang CH
        Stromal cell-derived factor-1 enhances motility and integrin up-regulation through CXCR4, ERK and NF-kappaB-dependent pathway in human lung cancer cells.
        Biochem Pharmacol. 2007; 74: 1702-1712
        • Liang Z
        • Brooks J
        • Willard M
        • et al.
        CXCR4/CXCL12 axis promotes VEGF-mediated tumor angiogenesis through Akt signaling pathway.
        Biochem Biophys Res Commun. 2007; 359: 716-722
        • Hillyer P
        • Mordelet E
        • Flynn G
        • Male D
        Chemokines, chemokine receptors and adhesion molecules on different human endothelia: discriminating the tissue-specific functions that affect leucocyte migration.
        Clin Exp Immunol. 2003; 134: 431-441
        • Cho HH
        • Kyoung KM
        • Seo MJ
        • Kim YJ
        • Bae YC
        • Jung JS
        Overexpression of CXCR4 increases migration and proliferation of human adipose tissue stromal cells.
        Stem Cells Dev. 2006; 15: 853-864
        • Kucia M
        • Reca R
        • Miekus K
        • et al.
        Trafficking of normal stem cells and metastasis of cancer stem cells involve similar mechanisms: pivotal role of the SDF-1-CXCR4 axis.
        Stem Cells. 2005; 23: 879-894
        • Alsayed Y
        • Ngo H
        • Runnels J
        • et al.
        Mechanisms of regulation of CXCR4/SDF-1 (CXCL12)-dependent migration and homing in multiple myeloma.
        Blood. 2007; 109: 2708-2717
        • Sutton A
        • Friand V
        • Brulé-Donneger S
        • et al.
        Stromal cell-derived factor-1/chemokine (C-X-C motif) ligand 12 stimulates human hepatoma cell growth, migration, and invasion.
        Mol Cancer Res. 2007; 5: 21-33
        • Kang H
        • Watkins G
        • Parr C
        • Douglas-Jones A
        • Mansel RE
        • Jiang WG
        Stromal cell derived factor-1: its influence on invasiveness and migration of breast cancer cells in vitro, and its association with prognosis and survival in human breast cancer.
        Breast Cancer Res. 2005; 7: R402-R410
        • Pituch-Noworolska A
        • Majka M
        • Janowska-Wieczorek A
        • et al.
        Circulating CXCR4-positive stem/progenitor cells compete for SDF-1-positive niches in bone marrow, muscle and neural tissues: an alternative hypothesis to stem cell plasticity.
        Folia Histochem Cytobiol. 2003; 41: 13-21
        • Lapidot T
        • Dar A
        • Kollet O
        How do stem cells find their way home?.
        Blood. 2005; 106: 1901-1910
        • Wang J
        • Loberg R
        • Taichman RS
        The pivotal role of CXCL12 (SDF-1)/ CXCR4 axis in bone metastasis.
        Cancer Metastasis Rev. 2006; 25: 573-587
        • Geminder H
        • Sagi-Assif O
        • Goldberg L
        • et al.
        A possible role for CXCR4 and its ligand, the CXC chemokine stromal cell-derived factor-1, in the development of bone marrow metastases in neuroblastoma.
        J Immunol. 2001; 167: 4747-4757
        • Muller A
        • Homey B
        • Soto H
        • et al.
        Involvement of chemokine receptors in breast cancer metastasis.
        Nature. 2001; 410: 50-56
        • Holm NT
        • Benjamin LJL
        • Quyen C
        Overexpression of chemokine receptor cxcr4 in cancer specimens predicts outcome in patients with triple-negative breast cancer.
        J Clin Oncol. 2008; 26 (abstract 11064.)
        • Hu J
        • Deng X
        • Bian X
        • et al.
        The expression of functional chemokine receptor CXCR4 is associated with the metastatic potential of human nasopharyngeal carcinoma.
        Clin Cancer Res. 2005; 11: 4658-4665
        • Jiang YP
        • Wu XH
        • Shi B
        • Wu WX
        • Yin GR
        Expression of chemokine CXCL12 and its receptor CXCR4 in human epithelial ovarian cancer: an independent prognostic factor for tumor progression.
        Gynecol Oncol. 2006; 103: 226-233
        • Hart CA
        • Brown M
        • Bagley S
        • Sharrard M
        • Clarke NW
        Invasive characteristics of human prostatic epithelial cells: understanding the metastatic process.
        Br J Cancer. 2005; 92: 503-512
        • Mori T
        • Doi R
        • Koizumi M
        • et al.
        CXCR4 antagonist inhibits stromal cell-derived factor 1-induced migration and invasion of human pancreatic cancer.
        Mol Cancer Ther. 2004; 3: 29-37
        • Smith MC
        • Luker KE
        • Garbow JR
        • et al.
        CXCR4 regulates growth of both primary and metastatic breast cancer.
        Cancer Res. 2004; 64: 8604-8612
        • Pan J
        • Mestas J
        • Burdick MD
        • et al.
        Stromal derived factor-1 (SDF-1/CXCL12) and CXCR4 in renal cell carcinoma metastasis.
        Mol Cancer. 2006; 5: 56
        • Yoon Y
        • Liang Z
        • Zhang X
        • et al.
        CXC chemokine receptor-4 antagonist blocks both growth of primary tumor and metastasis of head and neck cancer in xenograft mouse models.
        Cancer Res. 2007; 67: 7518-7524
        • Belperio JA
        • Phillips RJ
        • Burdick MD
        • Lutz M
        • Keane M
        • Strieter R
        The SDF-1/CXCL 12/CXCR4 biological axis in non-small cell lung cancer metastases.
        Chest. 2004; 125: 156S
        • Su L
        • Zhang J
        • Xu H
        • et al.
        Differential expression of CXCR4 is associated with the metastatic potential of human non-small cell lung cancer cells.
        Clin Cancer Res. 2005; 11: 8273-8280
        • Spano JP
        • Andre F
        • Morat L
        • et al.
        Chemokine receptor CXCR4 and early-stage non-small cell lung cancer: pattern of expression and correlation with outcome.
        Ann Oncol. 2004; 15: 613-617
        • Flomenberg N
        • DiPersio J
        • Calandra G
        Role of CXCR4 chemokine receptor blockade using AMD3100 for mobilization of autologous hematopoietic progenitor cells.
        Acta Haematol. 2005; 114: 198-205
      1. Hotte S. Phase I/II study of CTCE-9908, a novel anticancer agent that inhibits CXCR4, in patients with advanced solid cancers. AACR Molecular Therapy Conference. Abstract, 2007.