Induction of cytotoxicity responses. Splenocytes from immunized mice were isolated 7 days after the third immunization. CTLs were from mice immunized with pcDNA3.1-VNTR, pcDNA3.1 or PBS. Panc02-MUC1or panc02 cells were used as targets. The CTLs induced by the pcDNA3.1-VNTR could specifically kill the panc02-MUC1 cells, but not the panc02 cells and it could be blocked by anti-MUC1 antibody VU3C6.