NOS2 and neoplasm: Although the M1 macrophage population (CD11b+iNOS+ or iNOS+TNF-α+ by IHC) was continuously present in the tumor tissue over the 3-month experiment period (Figure 1D and Supplemental Figure 2A), the colocalization of the CD11b/iNOS signal and the EGFP signal displayed a gradual decrease over time (Figure 1D), indicating impaired macrophage phagocytosis of H358 tumor cells in vivo.