ARG1 and gastric cancer: Additionally, immunofluorescence staining with F4/80 (a macrophage marker) and iNOS (an M1 polarization marker)/Arg1 (an M2 polarization marker) was used to investigate the impact of SERPINE1 on M2 macrophage infiltration in xenograft tumors, revealing decreased F4/80+Arg1+ cells (M2 TAMs) and increased F4/80+iNOS+ cells (M1 TAMs) in xenograft tumors of GC cells with stably silenced SERPINE1 (Fig. 2H).