We observed that 5-FU-resistant gastric cancer cells were more effective than 5-FU-sensitive gastric cancer cells in skewing macrophages to M2 polarization, characterized by up-regulated expression of CD163, CD206, IL-10, Arg-1 and VEGF-A and down-regulated expression of CD86, TNF-α and IL-12. Here, ARG1 is linked to gastric cancer.