Inflammatory-Associated Macrophage Inhibits Proliferation of Head and Neck Squamous Cell Carcinoma Cell Lines

Macrophage is a potent phagocytic cell in immune defense mechanism. High infiltration of macrophage has been found in head and neck squamous cell carcinoma (HNSCC). However, its role in HNSCC has not elucidated yet. We aimed to study the role of inflammatory-associated macrophage in HNSCC cell proliferation. HNSCC cell lines, HN30 and HN31, were derived from pharynx and lymph node metastatic lesion of a patient, respectively. Phorbol 12-myristate 13-acetate (PMA) was used to drive monocytic cell line (THP-1) to macrophage. Lipopolysaccharide (LPS) of Porphyromonas gingivalis (P. gingivalis) at 1,000 ng/ml was used to activate macrophage for 48 hrs. CD14 and interleukin-6 (IL-6) were selected to be representative markers of monocyte-derived macrophage. Conditioned media of LPS-induced macrophage were collected for TNF-alpha and nitric oxide (NO) determination, indicating inflammatory response of the macrophage. The HNSCC cells were treated with the conditioned medium of activated macrophage. Proliferation of HNSCC cells was measured by MTT assay. The result showed that PMA induced THP-1 cells to macrophage with up-regulation of CD14 and increased production of IL-6. LPS activated classical macrophage polarization by up-regulation of TNF-alpha and NO. Interestingly, the conditioned media of macrophage and LPS–induced classical phenotype macrophage significantly inhibited cell proliferation of HN30 and HN31 compared to their controls (P<0.05). In conclusion, P. gingivalis LPS could induce classical phenotype macrophage. Inflammatory mediators, possibly TNF-alpha and NO secreted from macrophage as well as LPS-treated macrophage inhibit proliferation of primary and metastatic HNSCC cell lines. It implies that macrophages and their classical polarization change due to inflammatory response in HNSCC microenvironment may play role in anti-proliferative effect on the cancer cells.