Antibody-directed double suicide gene therapy targeting of MUC1- positive leukemia cells in vitro and in vivo.

Our aim was to specifically transfer the cytosine deaminase (CD) and thymidine kinase (TK) genes into mucin 1 (MUC1)-positive leukemia cells by anti-MUC1 antibody directed infection of replication-defective lentivirus and to evaluate the targeted cytotoxicity of double suicide genes to leukemia. The target gene vector (containing CD and TK) and envelope (containing GFP and anti-MUC1) and packaging plasmids were cotransfected into 293T cells to produce the recombinant lentivirus. Suicide genes in virus-infected leukemia cells (U937, Jurkat, and K562) were detected by western blot. The cytotoxicity and bystander effect in vitro and the therapeutic effect in vivo were detected after treatment with the prodrugs. The results revealed that combined treatment with prodrug 5-fluorocytosine (5-FC) and ganciclovir (GCV) inhibited leukemia cell growth and caused significant bystander effect than treatment with either prodrug alone. TK/GCV treatment alone induced degeneration and cell death while the effect of CD/5-FC alone mainly caused vacuolar degeneration and necrosis. The addictive effects of combinatorial use of GCV and 5-FC mainly induced swelling of the mitochondria followed by necrosis of the leukemia cells. In vivo experiments revealed that both single and combinatorial prodrug treatments could prolong the survival time of leukemic mice. In summary, anti-MUC1 antibody directed lentiviral vector successfully transduced dual suicide genes and exerted targeted cytotoxicity against MUC1 positive leukemia cells. This targeted lentiviral dual suicide gene delivering system provides a promising approach for clinical treatment of leukemia in future.