Circulating Myeloid-derived Suppressor Cells Facilitate Invasion of Thyroid Cancer Cells by Repressing miR-486-3p
Li Chen, Li Xiong, Shubing Hong, Jin Li, Zijun Huo, Yan Li, Shuwei Chen, Quan Zhang, Ruiying Zhao, Julian A. Gingold, Xiaonan Zhu, Weiming Lv, Yanbing Li, Shuang Yu, Haipeng Xiao
Abstract
BACKGROUND: Myeloid-derived suppressor cells (MDSCs) have become increasingly recognized as facilitators of tumor development. However, the role of MDSCs in papillary thyroid carcinoma (PTC) progression has not been clearly explored. OBJECTIVE: We aimed to evaluate the levels and function of circulating MDSCs in PTC. METHODS: The proportion of circulating polymorphonuclear (PMN)-MDSCs and mononuclear-MDSCs from patients with PTC or benign thyroid nodules and healthy controls was measured using flow cytometry. For immunosuppressive activity analysis, sorted circulating MDSCs were cocultured with CD3/CD28-costimulated T lymphocytes and the proliferation of T cells was determined. PTC cell lines (TPC-1 and BC-PAP) were cocultured with PMN-MDSCs, and the effects on cell migration, invasion, proliferation, and apoptosis were evaluated. The differential expressed microribonucleic acids (RNAs) and messenger RNAs and their function were also explored in TPC-1 cells cocultured with or without PMN-MDSCs. RESULTS: PMN-MDSCs were increased in peripheral blood mononuclear cells of patients with PTC. Circulating PMN-MDSCs displayed strong T cell suppressive activity. PTC cells demonstrated enhanced invasive capabilities in vitro and in vivo when cocultured with sorted PMN-MDSCs. PMN-MDSCs decreased expression of miR-486-3p and activated nuclear factor kappa B2 (NF-κB2), a direct target of miR-486-3p. Rescue of miR-486-3p diminished the cell migration and invasion induced by PMN-MDSCs. CONCLUSION: Collectively, our work indicates that circulating PMN-MDSCs promote PTC progression. By suppressing miR-486-3p, PMN-MDSCs promote the activity of the NF-κB2 signaling pathway, resulting in accelerated invasion of PTC cells, which may provide new therapeutic strategies for treatment of thyroid cancer.