MMP9 and neoplasm: Previous studies indicated that neutrophil polarization influences the role they play in the tumor microenvironment [26], so we then determined the phenotypes of the neutrophils, with results indicating that markers of N2-type neutrophils, such as Mmp9 and S100a8/9 were increased, whereas N1 markers Ccl3, Fas and Cxcl3 were decreased in the neutrophils of MMTV-PyVT mice (Figure 3d,e).