Many stimuli have been reported in previous literature, including IFN-γ and GM-CSF, which induce neutrophils to N1 polarization for anti-tumor function, and IL-6, IL-8, CXCL2, and CXCL5, which induce neutrophils to N2 polarization for pro-tumor function (Figure 3B). Here, CSF2 is linked to neoplasm.