Induction of protective anti-tumor immunity. Mice (five per group) were immunized with 20 μg of pORF-hFlk-1 LDC, pORF-mFlk-1 LDC, pORF-mcs LDC or GS once a week for 6 weeks. Mice were then challenged subcutaneously with 2 × 105 CT26(A, C) tumor cells, or 8 × 105 4T1 tumor cells(B, D), 1 week after the sixth immunization. There was an apparent difference in tumor volume between human VEGFR-2 LDC-immunized and control groups. Results are expressed as means ± SEM.