Immunotherapy with recombinant human interleukin-2 (IL-2) is an attractive treatment option for certain metastatic cancers, as it exerts both stimulatory and regulatory functions on the immune system and is, along with other members of the common γ chain (γc) cytokine family, central to immune homeostasis [4,5]. This evidence concerns the gene IL2 and metastatic malignant neoplasm.