Indeed, in clinical treatment, the effect of IL-2 is a bit complex because of its dual functional roles in T cell.65 It can not only promote activation and proliferation of natural killer cells and cytotoxic T cells to destroy tumor cells66 but also enhance regulatory T cell activities to downregulate T cell cytotoxicity.67 Therefore, the chemical synthesis of IL-2 could offer an opportunity to construct site-specific modified IL-2 variants with more focused biofunctions, which may lead to better clinical outcomes in cancer or immunosuppression treatments. This evidence concerns the gene IL2 and cancer.