CSF2 and neoplasm: Further study from the same group has shown that MDSCs exposed to IFN-γ, IL-13, and GM-CSF in vitro or MDSCs localized in inflammatory or tumor site in vivo have elevated L-arginine transporter cationic amino acid transporter 2 expression, which parallels the expression of ARG1 and iNOS and is required for optimal suppressive activity of MDSCs (146).