In the late 1990s, IL-2 gained further attention as the first immunotherapy demonstrating clinical efficacy against metastatic cancer, as high dose IL-2 was approved by the United States Food & Drug Administration (FDA) for the treatment of metastatic renal cell carcinoma in 1992 and metastatic melanoma in 1998 [3]. This evidence concerns the gene IL2 and metastatic malignant neoplasm.