IL-1β secreted by macrophage M2 promotes metastasis of osteosarcoma via NF-κB/miR-181α-5p/RASSF1A/Wnt pathway

BACKGROUND: Ras-associated domain family protein1 isoform A (RASSF1A) was significantly absent in clinical samples and many osteosarcoma (OS) cell lines. Overexpression of RASSF1A could suppress OS metastasis, which may be mediated by tumor-associated macrophages polarized M2 (M2-TAMs). However, the relationship between IL-1β secreted by M2-TAMs and RASSF1A remains unknown. METHODS: The expression levels of M2-TAMs markers CD68 and CD204 were measured by flow cytometry, and arginase-1 (Arg-1) and interleukin-1β (IL-1β) secreted by M2-TAMs were examined by real-time quantitative PCR (RT-qPCR). MTT assay was employed to determine the proliferation of OS cells, while scratch wound healing assay and Transwell assay were used to evaluate their migration and invasion, respectively. The level of miR-181α-5p was measured by RT-qPCR, while the levels of RASSF1A, GSK-3β, p-GSK-3β, β-catenin, MMP-2 and MMP-9 were evaluated by Western blot. The direct binding of miR-181α-5p and RASSF1A was identified using dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. RESULTS: The levels of CD68, CD204, Arg-1 and IL-1β were elevated in M2-TAMs compared with control group. Overexpression of RASSF1A and knockdown of miR-181α-5p could both suppress invasion and migration of OS cells through Wnt pathway. IL-1β secreted by M2-TAMs facilitated the OS metastasis via RASSF1A/Wnt pathway, which could be targeted by miR-181α-5p and affected by nuclear factor-kappa B (NF-κB). CONCLUSIONS: IL-1β secreted by M2-TAMs contributed to OS metastasis, which could be suppressed by knockdown of miR-181α-5p or overexpression of RASSF1A through NF-κB/miR-181α-5p/RASSF1A/Wnt pathway. These findings can guide new target discovery for drug development in OS treatment.