Fig 2: CEBPB transcriptionally activates S100A8 to promote M2 macrophage polarization. A, Venn diagram of three datasets identifying four common secretory factors: differentially expressed genes from CEBPB-overexpressing 4T07 cells bulk RNA-seq, CEBPB binding peaks in 4T07 cells from anti-CEBPB ChIP-seq, and the profile of mouse secretory proteins. B, CEBPB binding peaks for S100A8 and Cxcl1 from anti-CEBPB ChIP-seq in 4T07 cells. C, ChIP-qPCR showing the CEBPB binding regions in the S100a8 promoter or upstream regions of Cxcl1 of 4T07 and EMT6 cells. D, Relative luciferase activity in CEBPB-overexpressing HEK293T cells with the S100a8 promoter WT or MUT, respectively. E-F, mRNA expression of S100a8 or Cxcl1 in 4T07 cells with CEBPB overexpression (E) or knockdown (F). G, Protein expression of S100A8 in 4T07 cells with or without CEBPB overexpression. H, Representative multiplex immunohistochemistry images of Ki67, CEBPB, and S100A8 staining in a TMA of TNBC patient tumor smaples (n = 80). I, mRNA expression of S100a8 in eGFP-/lo and eGFP+/hi tumor cells sorted from 4T07-TetOn or EMT6-TetOn tumor masses. J-K, Percentages of CD206 (J) and MHCII (K) expressing BMDMs with the addition of rS100A8 (100 or 500 ng/mL) or rCXCL1 (100 or 500 ng/mL) for 48 hours. L-N, Tumor volume (L), image (M) and weight (N) of CEBPB-overexpressing with or without S100A8 knockdown EMT6 allografts in BALB/c mice (n = 5). O-R, Flow cytometry analysis of CD8+ T cells (O), CD11b+ F4/80+ cells (P), CD206 + macrophages (Q), and MHCII+ macrophages (R) infiltrated in tumors developed in (L). n.s., not significant, *, P < 0.05, **, P < 0.01, ***, P < 0.001.