Low efficacy of IL-2 therapy in cancer patients is due to the short serum half-life, which requires administration of high doses of IL-2 (600,000 IU/kg; 0.037 mg/kg, every 8 h for a maximum of 14 doses) and consequently, severe toxicity and vascular leak syndrome can occur1,4,16,17. This evidence concerns the gene IL2 and cancer.