We hypothesized that due to much more effective and faster induction of anti-cancer effects inducible by mismatched IL-2 activated killer cells, elimination of malignant cells could be accomplished within a few days by non-engrafting donor lymphocytes, thus avoiding the need for prior SCT to ensure consistent rejection of mismatched donor lymphocytes after induction of cytotoxicity against the malignant cells for prevention of GVHD. Here, IL2 is linked to cancer.