These MDSCs’ immunosuppressive activity, related to increased arginine metabolism via ARG and iNOS [15, 39], was shown to accompany tumour progression and metastasis [40] and caused profound perturbation in myelopoiesis, including extramedullary myelopoiesis to meet the increased demand for myeloid cell proliferation [41, 42]. This evidence concerns the gene NOS2 and neoplasm.