CXCL7-induced macrophage infiltration in lung tumor is independent of CXCR2 expression CXCL7-induced macrophage chemotaxis in LLC tumors Nese Unver a,⇑ , Gunes Esendagli a , Guldal Yilmaz b , Dicle Guc a a Department of Basic Oncology, Cancer Institute, Hacettepe University, Ankara, Turkey b Department of Pathology, Faculty of Medicine, Gazi University, Ankara, Turkey article info Article history: Received 4 January 2015 Received in revised form 20 July 2015 Accepted 21 July 2015 Available online xxxx Keywords: Neutrophil Macrophage CXCL7 Lung cancer LLC abstract Chemokines play diverse roles in modulating the immune response during tumor development. Levels of CXC chemokine ligand 7 (CXCL7) protein vary during tumorigenesis, and the evidence suggests that this chemokine serves as a novel biomarker of early-stage lung cancer. We investigated the effect of CXCL7 gene expression on the infiltration of myeloid cells into the tumor microenvironment in Lewis lung car- cinoma (LLC). Tumors established from LLC cells overexpressing CXCL7 (CXCL7-LLC tumors) increased the infiltration of CD206 + M2 macrophages at the early stages of tumorigenesis. This infiltration was inde- pendent of CXCR2 expression on either tumor cells or macrophages. CXCL7-LLC tumors developed faster than control-LLC tumors (IRES-LLC tumor) did. The extent of CD4 + T cell, CD8 + T cell, and natural killer T cell infiltration was similar between the two tumor groups. Our findings suggest that CXCL7 attracts macrophages especially at the tumor site and may accelerate lung tumor development in the early stages. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Chemokines and their related receptors have become critical modulators of tumor immunity. In lung cancer, most studies focus on CXCL1, CXCL5, and CXCL8 chemokines. Information about the relationship between cancer and CXCL7 is limited. However, CXCL7 has been identified as a biomarker in lung cancer and advanced myelodysplastic syndrome [1,2]. Therefore, both solid and hematologic tumors have been associated with CXCL7. Chemokine ligand 7 (CXCL7) is one member of the ELR + CXCL family of chemokines. ELR + sequences (glutamic acid–leucine–argi nine) in CXCL chemokines promote tumorigenesis and invasion in part due to their angiogenic potency [3]. These effects are mediated through the G-protein-coupled receptors CXCR1 and CXCR2. The best example of an ELR + CXCL chemokine is CXCL8, and its angio- genic and tumorigenic effects are well documented [3,4]. ELR + CXCL chemokines are produced by inflammatory cells, endothelial cells, and tumor cells of different origins [5]. Enzyme cleavage of CXCL7 results in several different isoforms, including the parent molecule platelet basic protein (PBP), connective tissue-activating peptide III (CTAP-III), and neutrophil-activating peptide 2 (NAP-2). The different isoforms have distinct biological roles, and NAP-2 is the only CXCL7 variant that displays chemotactic activity, especially on neutrophils [4]. Receptors of the CXCL7 chemokine, CXCR1 and CXCR2, are expressed on neutrophils, endothelial cells, macrophages and tumor cells [6–10]. The co-expression of chemokine and chemo- kine receptors in the same cell is controversial because this auto- crine pathway may drive both senescence [8] and tumor development [6]. Although the expression of CXCR may be benefi- cial by forcing the senescence at the early stage of tumorigenesis, CXCR expression may accelerate tumor growth through the activa- tion of the ERK signaling pathway during the late stages [11]. The upregulation of CXCR2 has been reported both in senescent cells in cell culture and in preneoplastic lesions in vivo. High levels of CXCR2 transcript in lung carcinoid and low levels of CXCR2 expres- sion in head and neck tumor with upregulation of most CXCR2 ligands have also been reported [12,13]. The recruitment and activation of tumor-associated macro- phages in the tumor microenvironment are considered crucial steps in tumor progression. In contrast to classically activated http://dx.doi.org/10.1016/j.cyto.2015.07.018 1043-4666/Ó 2015 Elsevier Ltd. All rights reserved. Abbreviations: CXCL7, CXC chemokine ligand 7; LLC, Lewis lung carcinoma; IRES, internal ribosome entry site; CD, cluster of differentiation; CXCR2, CXC receptor 2. ⇑ Corresponding author at: Department of Clinical Cancer Prevention Research, Unit 1013, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, United States. E-mail address: NUnver@mdanderson.org (N. Unver). Cytokine xxx (2015) xxx–xxx Contents lists available at ScienceDirect Cytokine journal homepage: www.journals.elsevier.com/cytokine Please cite this article in press as: N. Unver et al., CXCL7-induced macrophage infiltration in lung tumor is independent of CXCR2 expression, Cytokine (2015), http://dx.doi.org/10.1016/j.cyto.2015.07.018