Role of interleukin-8 secreted from human oral squamous cell carcinoma cell lines

Interleukin-8 (IL-8) is an important cytokine involved in tumor growth and angiogenesis in a variety of malignancies. Furthermore, matrix metalloptoteinases (MMPs) also play important roles in the invasion and metastasis of carcinomas including oral squamous cell carcinoma (OSCC). We studied whether IL-8 and MMPs participate in tumorigenesis and metastasis of OSCC. First, we investigated the gene and protein expressions of IL-8 and IL-8 receptor (IL-8R), and the effect of IL-8 on proliferation, migration and invasion of OSCC. Second, we thus also investigated the effect of IL-8 on MMP release in OSCC cells. OSCC cell lines NA and HSC-4 constitutively expressed IL-8 mRNA and secreted its protein in vitro. The production of IL-8 was significantly enhanced by the addition of tumor necrosis factor (TNF)-alpha and IL-beta, but not interferon (IFN)-gamma, granulocyte-macrophage colony-stimulating factor (GM-CSF) or IL-2. Flow cytometric analysis revealed the constitutive expression of both receptors of IL-8, IL-8RA and IL-8RB, in OSCC cell lines. The expression of IL-8 receptors in HSC-4 cells was stronger than that in NA cells. The intensity of IL-8RA expression was stronger than that of IL-8RB expression in each cell line. The expression of IL-8 receptors was not altered by the addition of cytokines such as TNF-alpha and IL-1beta. The conditioned medium containing IL-8 from OSCC cell lines induced migration and invasion of OSCC cells, but did not change cell proliferation. The differences in migrational and invasive ability between NA cells and HSC-4 cells were correlated with the expression intensity of IL-8 receptors in each cell line. Neutralizing antibodies to IL-8, IL-8RA and IL-8RB partially inhibited the chemotactic activity induced by conditioned medium. The expression of MMP-2, -7 and -9 was detected in culture supernatants from these OSCC cell lines. The expressions of MMP-7 protein and mRNA were enhanced by the addition of rIL-8, but that of other MMPs was not observed in a similar manner. These results suggest that IL-8 secreted from OSCC may contribute to the invasion of OSCC through the regulation of MMP-7 expression.