hetIL-15 is then transported to the cell surface and, on proteolytic cleavage of IL-15Rα, released as bioactive soluble heterodimeric molecule.35 36 38–40 hetIL-15 produced from human HEK293 cells is well tolerated and bioactive in both mice41 and rhesus macaques.42 43 Therapeutic efficacy of hetIL-15 and molecules composed of parts of IL-15 and IL-15Rα has been shown in preclinical cancer models,40 44–48 and several molecules similar to hetIL-15 are currently being evaluated in cancer immunotherapy clinical trials (NCT02452268 and49 50). This evidence concerns the gene IL15 and cancer.