The novel structure make LDM effectively remove CD123+ AML stem cells in combination with interleukin 3.

CD123 became a therapeutic target for acute myelocytic leukemia(AML) because of its overexpression only on AML stem cells. It is α subunit of interleukin-3 (multi-CSF, IL3) receptor. Lidamycin(LDM) is a novel antibiotic composed of an apoprotein (LDP) and a chromophore (AE). We cloned, expressed and isolated IL3LDP fusion protein first then assembled with AE in vitro. We found that131/132 amino acids of IL3 were the key factors for IL3 fusion protein stability and I131L/F132L mutation effectively improved the IL3 fusion protein stability. The toxicity of IL3LDM to CD123+ tumor cells was 2-10 times compared to LDM alone and 10000 times compared to ADR. Meanwhile, IL3LDM impaired the colony-forming ability of CD123+ stem-like cells but not to CD123 negative normal cord blood cells. Three drug delivery methods in vivo were adopted: prophylactic treatment and single/multiple-dosing administration. The tumor-free survival extended to 120 d and cancer cell invasion significantly decreased after IL3LDM continuous multiple treated. Moreover, IL3LDM had been shown to modulate apoptosis by arrested cell cycle in G2/M phase. Therefore, IL3LDM is expected to be a new drug for leukemia target therapy.