Comparative analysis of immunosuppressive effects of PEM treated with 4T1-M CM or 4T1-N2 CM. (A) PEMs were treated with 4T1-M or -N2 CM for 48 h, and then cultured in serum-free medium. After 48 h, the supernatant was collected for ELISA. (B) The cells pretreated in the absence or presence of 10 mM NAC were cultured with 4T1-M or -N2 CM for 24 h and were treated with 10 μM DCF-DA for 30 min. Harvested cells were analyzed by flow cytometry. (C) In vitro generated PEM was co-cultured with CFSE-labeled CD3+ T cells at 1:2 (PEM:T) ratio for 72 h. The CD8+ T cell proliferation was measured by flow cytometry. *P < 0.05, **P < 0.01. (D) Model demonstrating the effect of NDRG2 expression in breast cancer on TAM activation. NDRG2 expression in breast cancer cells reduces the expression levels of IL-10, PD-L1 and Fra-1 in TAMs and attenuates the immunosuppressive function of TAMs.