MMP9 and neoplasm: In our study, co-culture with “educated” or “re-educated” macrophages resulted in different tumorigenicity of 4T1 breast tumor cells: “M2-like” macrophages (E-RAW264.7) increased tumor cell number in the S phase, promoted migration and invasion capabilities of 4T1 cells, and increased MMP-9, MMP-2, VEGF expression.