NOS2 and neoplasm: Therefore, the anti-tumor effect of PepO in TLR2−/− mice was partly concealed by TLR2 deficiency, while in TLR4−/−mice, although PepO cannot induce TAM (M2) to polarize into iNOS+ M1 like macrophages, PepO significantly inhibited TAM polarizing to the M2 phenotype (Fig. 5A, B), which reduced the tumor promoting effect of the M2 cells and ultimately inhibited tumor growth.