According to the two-phase hypothesis of MDSC accumulation in cancer, granulocyte macrophage-colony stimulating factor (GM-CSF) and granulocyte-colony stimulating factor (G-CSF) belong to the first signals that drive the expansion of early MDSCs, whereas interleukin 6 (IL6) belongs to the second signals that mediate the acquisition of the immunosuppressive activity [2,4]. Here, CSF3 is linked to cancer.