GCP-2/CXCL6 synergizes with other endothelial cell-derived chemokines in neutrophil mobilization and is associated with angiogenesis in gastrointestinal tumors
Introduction
Chemokines (chemotactic cytokines) form a complex family of small, secreted proteins that play an important role in innate and adaptive immunity, homeostatic processes, angiogenesis, and tumorigenesis [1], [2]. During host response against acute infection, the subtle interplay between chemokines and adhesion molecules is needed to selectively attract specific leukocyte subsets, expressing chemokine receptors, to the site of inflammation [3]. In this context, chemokines can synergize with each other or with other inflammatory mediators to enhance leukocyte infiltration in an early phase [4]. At a later stage, chemokines can dampen the inflammatory response when they are processed into receptor antagonists by proteases [5]. In addition to their indispensable role in healing processes, chemokines can become detrimental in pathological situations such as cancer [6], rheumatoid arthritis, multiple sclerosis, and many other diseases [7].
Chemokines are functionally divided into different subsets, each with their specific properties (e.g., inducible versus constitutively produced), but are classified on the basis of their primary structure. For example, granulocyte chemotactic protein-2 (GCP-2/CXCL6) and interleukin-8 (IL-8/CXCL8) are neutrophil chemoattractants that belong to the ELR+CXC chemokine subfamily, possessing one additional amino acid separating the two N-terminally conserved cysteine residues. The presence of the amino acid sequence Glu-Leu-Arg (ELR) roughly divides the CXC chemokine family into angiogenic (ELR+) and angiostatic (ELR−) proteins [8], [9]. GCP-2 exerts its biological activity through the G-protein-coupled CXC receptors CXCR1 and CXCR2. In contrast to the CXC chemokines, CC chemokines possess adjacent N-terminal cysteines and bind to different receptors (CCR).
Gastrointestinal (GI) malignancies are common tumors. Histologically, they are a heterogeneous group of neoplasms. Epithelial malignancies, mainly adenocarcinomas, are the most common type. The prognosis of these malignancies is variable but on the average poor, except when the lesion is detected at an early stage. For the growth and survival of a tumor, angiogenesis, the sprouting of new blood vessels from existing vessels, is an essential process for the supply of oxygen and nutrients [10]. Therefore, inhibition of angiogenesis has become an important target in tumor therapy. In addition to their angiogenic potential, chemokines can attract tumor cells, expressing chemokine receptors, and can thereby facilitate metastasis [11].
GCP-2 has earlier been shown to be produced by mesenchymal cells, including fibroblasts and macrovascular endothelial cells [12] and to display angiogenic properties in the rat corneal micropocket model of neovascularization [8]. Overexpression of the murine GCP-2 analog in human tumor cell allografts resulted in enhanced angiogenesis [13]. Although GCP-2 has thus been shown to be important for angiogenesis in these animal models, the presence and role of GCP-2 in tumor development have not been investigated yet in humans. We report here that GCP-2 is produced by microvascular endothelial cells and induces weak proliferation of these cells. In addition, we demonstrate the in vivo production of GCP-2 by endothelial cells in GI malignancies at sites of neovascularization within the tumor. This suggests that GCP-2 may function as an autocrine growth factor. Alternatively, GCP-2 was found to synergize strongly with the endothelial cell-derived CC chemokine monocyte chemotactic protein-1 (MCP-1/CCL2) to chemoattract neutrophils, which coincides with the infiltration of inflammatory cells into tumors.
Section snippets
Patients and classification of tumors
Biopsy samples were obtained from 22 patients operated for gastrointestinal malignancy (12 female; 10 male; mean age: 63 years; range 24–83 years). Malignancies included three adenocarcinomas of the distal esophagus, three adenocarcinomas and one gastrointestinal stromal tumor (GIST) of the stomach, six adenocarcinomas of the colon, one GIST and one B cell lymphoma of the small intestine, and seven ductal adenocarcinomas of the pancreas. Surgical resection specimens containing the tumor and
Immunohistochemical staining of GCP-2 in human gastrointestinal tumors
To investigate the role of GCP-2 in angiogenic processes involved in tumor progression and metastasis, we determined whether GCP-2 was specifically expressed in surgical specimens of patients who were operated for different types of GI malignancies (three esophagus, four stomach, six colon, two small intestine, and seven pancreas). GCP-2 was expressed by endothelial cells in the stroma of 15/22 tumor biopsies, but was not expressed by endothelial cells in normal tissue from non-involved areas.
Discussion
Blood vessels are essential for the delivery of oxygen and nutrients to different compartments of the body and to discharge waste products. During embryogenesis, endothelial cells are formed from endothelial progenitor cells (vasculogenesis), while in adults new blood vessels originate from the existing vasculature (angiogenesis). Except for the female reproductive cycle, angiogenesis is mostly associated with pathological situations [26]. Therefore, the deprivation of oxygen and nutrients by
Acknowledgments
The technical work of R. Conings, J.-P. Lenaerts, and W. Put was greatly appreciated. We thank the members of the Laboratory of Clinical Immunology of the University of Leuven and the members of the Blood Transfusion Center of Antwerp for providing buffy coats. This work was supported by the Fund for Scientific Research of Flanders (FWO-Vlaanderen), the Concerted Research Actions of the Regional Government of Flanders (GOA), the Interuniversity Attraction Poles Programme-Belgian Science Policy
References (38)
Traffic signals for lymphocyte recirculation and leukocyte emigration: the multistep paradigm
Cell
(1994)- et al.
Regulation of the immune response by the interaction of chemokines and proteases
Adv. Immunol.
(2003) - et al.
Chemokines in cancer
Cytokine Growth Factor Rev.
(2002) - et al.
The functional role of the ELR motif in CXC chemokine-mediated angiogenesis
J. Biol. Chem.
(1995) - et al.
CXC chemokines: the regulatory link between inflammation and angiogenesis
Trends Immunol.
(2004) Angiogenesis as a new target for cancer control
Eur. J. Cancer, Suppl.
(2003)- et al.
The CXC chemokine GCP-2/CXCL6 is predominantly induced in mesenchymal cells by interleukin-1beta and is down-regulated by interferon-gamma: comparison with interleukin-8/CXCL8
Lab. Invest.
(2003) - et al.
Tumor angiogenesis induced by granulocyte chemotactic protein-2 as a countercurrent principle
Am. J. Pathol.
(2001) - et al.
Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the separation of proteins in the range from 1 to 100 kDa
Anal. Biochem.
(1987) - et al.
Isolation of human monocyte chemotactic proteins and study of their producer and responder cells by immunotests and bioassays
Methods Enzymol.
(1997)
Patterns and emerging mechanisms of the angiogenic switch during tumorigenesis
Cell
Angiogenic effects of interleukin 8 (CXCL8) in human intestinal microvascular endothelial cells are mediated by CXCR2
J. Biol. Chem.
Analysis of the role of chemokines in angiogenesis
J. Immunol. Methods
Chemotactic factors, passive invasion and metastasis of cancer cells
Immunol. Today
Chemokines in pathology and medicine
J. Intern. Med.
Chemokines in innate and adaptive host defense: basic chemokines grammar for immune cells
Annu. Rev. Immunol.
The unique property of the CC chemokine regakine-1 to synergize with other plasma-derived inflammatory mediators in neutrophil chemotaxis does not reside in its NH2-terminal structure
Mol. Pharmacol.
Chemokines and disease
Nat. Immunol.
Involvement of chemokine receptors in breast cancer metastasis
Nature
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