An Antimicrobial Peptide Regulates Tumor-Associated Macrophage Trafficking via the Chemokine Receptor CCR2, a Model for Tumorigenesis

Abstract

BackgroundTumor-associated macrophages (TAMs) constitute a significant part of infiltrating inflammatory cells that are frequently correlated with progression and poor prognosis of a variety of cancers. Tumor cell-produced human β-defensin-3 (hBD-3) has been associated with TAM trafficking in oral cancer; however, its involvement in tumor-related inflammatory processes remains largely unknown.MethodologyThe relationship between hBD-3, monocyte chemoattractant protein-1 (MCP-1), TAMs, and CCR2 was examined using immunofluorescence microscopy in normal and oral carcinoma in situ biopsy specimens. The ability of hBD-3 to chemoattract host macrophages in vivo using a nude mouse model and analysis of hBD-3 on monocytic cell migration in vitro, applying a cross-desensitization strategy of CCR2 and its pharmacological inhibitor (RS102895), respectively, was also carried out.Conclusions/FindingsMCP-1, the most frequently expressed tumor cell-associated chemokine, was not produced by tumor cells nor correlated with the recruitment of macrophages in oral carcinoma in situ lesions. However, hBD-3 was associated with macrophage recruitment in these lesions and hBD-3-expressing tumorigenic cells induced massive tumor infiltration of host macrophages in nude mice. HBD-3 stimulated the expression of tumor-promoting cytokines, including interleukin-1α (IL-1α), IL-6, IL-8, CCL18, and tumor necrosis factor-α (TNF-α) in macrophages derived from human peripheral blood monocytes. Monocytic cell migration in response to hBD-3 was inhibited by cross-desensitization with MCP-1 and the specific CCR2 inhibitor, RS102895, suggesting that CCR2 mediates monocyte/macrophage migration in response to hBD-3. Collectively, these results indicate that hBD-3 utilizes CCR2 to regulate monocyte/macrophage trafficking and may act as a tumor cell-produced chemoattractant to recruit TAMs. This novel mechanism is the first evidence of an hBD molecule orchestrating an in vivo outcome and demonstrates the importance of the innate immune system in the development of tumors.

Human β defensin‐3 induces chemokines from monocytes and macrophages: diminished activity in cells from HIV‐infected persons

“…To generate macrophages, purified CD14 + cells (purified by negative selection) were incubated with M-CSF for 7 days as previously described. 2 The cells became large and granular by flow cytometric analyses and produced high spontaneous levels of MDC (Fig. 3), consistent with their maturation into macrophages.…”

“…This molecule mediates the killing of microbes, 1 chemotaxis of CCR2 + cells such as monocytes 2 and activation of antigen-presenting cells (monocytes and myeloid dendritic cells 3,4 ). These diverse functions indicate that hBD-3 could play an important role in both innate and adaptive defences.…”

Mouse β-Defensin 14 (Defb14) Promotes Tumor Growth by Inducing Angiogenesis in a CCR6-Dependent Manner

“…Furthermore, it has been shown that several b-defensins recruit monocytes and macrophages, which do not express CCR6 (4,5). Recent studies suggest CCR2 as the responsible receptor for CCR6-independent migration of leukocytes (6,7).…”

Functions of Diverse Myeloid Cells in the Tumor Micro-Environment

“…(Bottazzi et al, 1983;Zachariae et al, 1990) Other chemokines these include : CCL3, CCL4, CCL5, CXCL12 (Balkwill, 2004;Konishi et al, 1996;Schioppa et al, 2003). Nonchemokine chemotactic factors are also important, for instance: urokinase plasminogen activator (uPa) (Zhang et al, 2011), M-CSF, TGF; fibroblast growth factor, FGF; vascular endothelial growth factor, VEGF) (Joyce and Pollard, 2009;Lin et al, 2002;Sica and Bronte, 2007) and antimicrobial peptides (-defensin-3, BD-3) (Jin et al, 2010). Many of these molecules correlate with TAMs infiltration in different types of tumor, while other (eg.…”

“…Many of these molecules correlate with TAMs infiltration in different types of tumor, while other (eg. uPa, BD-3) are specifically associated with certain types of cancer, prostate and gastric cancer respectively (Jin et al, 2010;Zhang et al, 2011).…”