Myeloid-derived suppressor cells (MDSCs) and activated tumor-associated macrophages express ARG1, which consumes arginine to form a microenvironment that is not conducive to T cells, resulting in tumor immunosuppression (Rodriguez et al., 2017; Sawa-Wejksza and Kandefer-Szerszen, 2018). The gene discussed is ARG1; the disease is neoplasm.