Tumor protection in mice immunized with pcDNA3.1-VNTR. A:Mice were immunized with either pcDNA3.1-VNTR, or the empty vector pcDNA3.1, or PBS, as indicated in the legends, followed by challenge with panc02-MUC1 tumor cells (n = 15 mice/group). Each plasmid was administrated at 100 μg doses. The mean tumor volume of the mice immunized with pcDNA3.1-VNTR was significantly smaller than that in the mice in the other two groups (PBS and pcDNA3.1) (mean ± S.E.M. P < 0.0001). B: Mice were immunized with pcDNA3.1-VNTR, and then challenge with panc02 tumor cells (n = 6). The mean tumor volume in these mice was significantly different from that in mice immunized with pcDNA3.1-VNTR and challenged with panc02-MUC1 (mean ± S.E.M. P < 0.0001).