They further revealed that GM-CSF, which is distinctively upregulated in the glioma microenvironment, triggered the secretion of IL-4Rα in myeloid cells resulting in the promotion of IL-13-stimulated Arg-1 secretion as well as T cell suppression in vitro cultured cells as well as cells isolated from glioma-bearing hosts [30]. Here, ARG1 is linked to central nervous system cancer.