Abstract: Objective To investigate the expression of NDRG2 in breast cancer and its effect on macrophage polarization and breast cancer proliferation,invasion and migration.Methods Bioinformatics was used to detect the expression of NDRG2 in breast cancer tissues and its relationship with clinically relevant pathological features and prognosis.Knockdown or overexpression NDRG2 to explore the effects of altered NDRG2 expression levels on macrophage polarization and immune status in breast cancer microenvironment.The localization and expression of NDRG2 and macrophage molecular markers in breast cancer tissues were detected by immunofluorescence.A co-culture system of macrophages and breast cancer cells was constructed to observe the effects of changes in NDRG2 levels in macrophages on the proliferation,invasion and migration of breast cancer cells.Results NDRG2 expression was down-regulated in breast cancer tissues and was associated with poor prognosis,NDRG2 deficiency in macrophages promoted macrophages polarized to tumor-promoting phenotype named M2,and up-regulation of NDRG2 promoted macrophages polarized to tumor-inhibiting phenotype named M1,and down-regulation of NDRG2 expression in macrophages in co-culture system could increase breast cancer cell proliferation,invasion and migration,thereby promoting breast cancer progression.Conclusion Down-regulation of NDRG2 expression in macrophages can not only promote the transition of macrophages to tumor-promoting M2,but also enhance the proliferation,invasion and migration of breast cancer cells.

Key words: N-myc downstream-regulated gene 2, macrophage polarization, breast cancer