Tumor necrosis factor-α, interleukin-8 and interleukin-6 are involved in vascular endothelial cell capillary tube and network formation induced by tumor-associated macrophages

AIM: The goal of this study is to investigate the involvement of inflammatory cytoki-nes produced by tumor-associated macrophages in promoting tumor angiogenesis. METHODS: To study the angiogenic effect of tumor-associated macrophages (TAMs), we overlaid human umbilical vein endothelial cells on top of Matrigel contain-ing MCF-7 breast cancer cells with or without macrophages and investigated the out-come of endothelial cell capillary tube and network formation. We also determined the levels of interleukin (IL)-1β, IL-6, IL-8, IL-10, IL-12p70, tumor necrosis factor-α (TNF-α), and vascular endothelial growth factor (VEGF) in the media of MCF-7 breast cancer cells co-cultivated with or without macrophages. Furthermore, anti-IL-8 receptor an-tagonizing antibody, IL-6 or TNF-α soluble receptor, and inhibitors against NF-κB, MEK, p38MAPK, and JNK, respectively, were used to determine which signal transduc-tion pathways are involved in TAMs-induced angiogenic activity. RESULTS: The Matrigel mixed with MCF-7 cells and macrophages was more efficient than 100 ng/ml of VEGF to induce vascular endothelial cell tube and network forma-tion. The expression of IL-6, IL-8 and TNF-α were significantly enhanced by co-cultivation of MCF-7 cells with macrophages. The promotion of capillary tube and network formation by TAMs was inhibited either with anti-IL-8 receptor antagonizing antibody or with IL-6 or TNF-α soluble receptor, suggesting that IL-8, TNF-α and IL-6 indeed participated in TAMs-induced angiogenesis. In addition, TAMs-induced angio-genic activity could also be attenuated by the presence of inhibitors against NF-κB, ERK, and p38MAPK signaling pathways. CONCLUSION: IL-8, TNF-α and IL-6 were involved in TAMs-associated angiogenesis via NF-κB, ERK, and p38MAPK-dependent signaling pathways