The maximum tolerated dose (126–150 MIU per day) achieved permanent tumor responses in a small subgroup of patients with melanoma and renal cell carcinoma [15], but was accompanied by massive cytokine release, inflammatory reaction, and vascular leak syndrome consisting of increased loss of intravascular fluid into extravascular spaces caused by interaction of IL-2 with IL-2 receptors on endothelial cells [16], reducing cell adhesion of the endothelia to each other or to the extracellular matrix [17]. The gene discussed is IL2; the disease is melanoma.