IL6 and neoplasm: Furthermore, the inhibition of arginase activity by GA and CA in the tumor cell microenvironment may reverse the suppression of NO-mediated tumor cytotoxicity and may increase the tumoricidal activity of macrophages and other immune cells by increasing the Th1 cytokine (IL-2, IL-6, IFN-γ) activities and inhibiting tumor cell escape (Figure 7).