IL2 and metastatic melanoma: After Rosenberg’s seminal discovery showing that injections with T-cell growth factor later named interleukin-2 (IL-2) can shrink tumors in humans (17), IL-2 was approved by the FDA as an immunotherapeutic cytokine monotherapy for the treatment of metastatic kidney cancer in 1991 and later for metastatic melanoma in 1998.