Interleukins -2, -12, -15, -18 and -21 have been shown to promote NK cytotoxicity and proliferation in vitro and in vivo [16], with IL-2 approved for use in metastatic renal cell carcinoma and metastatic melanoma [17], and approved as a monotherapy in melanoma treatment [18]. The gene discussed is IL2; the disease is metastatic melanoma.