Protective and therapeutic immunity elicited by peptide vaccination against CMS5mHEOVA. The immunization protocol was identical to that described in Figure 4 except that CMS5mHEOVA cells were used. Lung weight was measured as an indication of tumor metastasis, and the presence of metastases was checked visually as shown in the photographs. (A) Pre-tumor injection. CMS5mHEOVA tumor cells were challenged after peptide immunization. In mice immunized with OVA_323-339 or HER2_16-30 in conjunction with HER2_63-71, no increase in lung weight was observed compared with the lung weight of age-matched naive mice, indicating complete prevention of metastasis. In mice immunized with HER2_63-71 alone, lung weight increased moderately. (B) Post-tumor injection. Peptide immunization similar to that described in Figure 4B was performed, followed by CMS5mHEOVA tumor inoculation. The results were essentially similar to those described in A. Data represent the mean ± SD of five mice per group in A and B. (C) Post-tumor injection. Survival was monitored up to 90 days after tumor inoculation in mice that received weekly peptide immunization. All mice treated with OVA_323-339 or HER2_16-30 in conjunction with HER2_63-71 were alive at the end of the observation period. A limited prolongation of survival time was observed in mice treated with HER2_63-71 alone.