In contrast to classically activated macrophages that stimulate phagocytosis, inflammation, and host immunity, a prominent population of macrophages in tumor microenvironment undergoes alternative activation to acquire tumor-promoting functions, for example, these macrophages express anti-inflammatory cytokines, such as interleukin-10 (IL-10), and tumor growth factor-β (TGF-β), and arginase-1 that inhibits nitric oxide (NO) production and produces ornithine4–7. Here, ARG1 is linked to neoplasm.