Human β-defensin-3 Regulates Tumor-associated Macrophage Trafficking via CCR2

Objectives: To investigate the role of the innate antimicrobial peptide, human β-defensin-3 (hBD-3), in oral tumorigenesis. Methods: The relationship between hBD-3, monocyte chemoattractant protein-1 (MCP-1), tumor-associated macrophages (TAMs), and the chemokine receptor 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. Results: MCP-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. Furthermore, 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-6 (IL-6), IL-8, tumor necrosis factor-α (TNF-α), and CCL18, in macrophages. 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. Conclusions: HBD-3 utilizes CCR2 to regulate monocyte/macrophage trafficking and may act as a tumor cell-produced chemoattractant to recruit TAMs, which in turn promote oral carcinogenesis. 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. Supported by a Scientist Development Grant (#0535088N) from the American Heart Association and the Grant #IRG-91-022-15 from the American Cancer Society (GJ).