Figure 7

Targeting HER2 protein to dendritic cells protects mice from a challenge with HER2/neu-expressing mammary tumor cells. (A, B) FVB/N mice were immunized with DEC-HER2 or Ctrl Ig-HER2 with poly IC or poly IC alone or were left untreated. Mice were challenged with one million NT2.5 tumor cells in the mammary fat tissue 10 days after the boost immunization. Tumor growth was monitored by caliper measurement three times a week. Tumor volume (in cubic millimeters) is shown in (A). Survival analysis is shown in (B). Results of three independent experiments (n = 5 per group) are shown. (C, D) To examine the mechanism of tumor protection, CD4⁺, CD8⁺, or both types of T cells were depleted after immunization (before tumor challenge) as described in Materials and methods. Mice were challenged with one million NT2.5 tumor cells, and tumor growth curves are shown in (C). Survival analysis is shown in (D). Results of two independent experiments (n = 10 mice per group) are shown. (E, F) Anti-tumor immunity was determined 14 days after tumor challenge. Splenic CD4⁺ and CD8⁺ cells were purified by magnetic-activated cell sorting isolation. Splenic CD11c⁺ cells were purified from naïve FVB/N mice. CD4⁺ (E) or CD8⁺ (F) T cells were re-stimulated with CD11c⁺ cells pulsed with 1 μg/mL of HIV gag, HER2 peptide pool 5, or neu peptide pool 4 or 10 μg/mL NT2.5 tumor lysate at a T cell/DC ratio of 3:1 for 3 days. IFNγ production was measured by enzyme-linked immunosorbent spot assay. Four mice were in each group; the results of one of two independent experiments are shown. *P < 0.05, **P < 0.01, ***P < 0.001. HER, human epidermal growth factor receptor; IFNγ, interferon-gamma; Ig, immunoglobulin; NS, not statistically significant; PBS, phosphate-buffered saline; poly IC, polyinosinic/polycytidylic acid.