Dendritic cells pulsed with HER-2/neu-derived peptides can induce specific T-cell responses in patients with gastric cancer.

PURPOSE We have previously reported (K. Kono et al., Int. J. Cancer, 78: 202-208, 1998) that HER-2/neu-derived peptides are naturally processed as tumor-associated antigens recognized by tumor-specific, human leukocyte antigen (HLA)-A2-restricted CTLs in gastric cancer. In the present study, we described a Phase-1 vaccination trial in gastric cancer patients using dendritic cells (DCs) pulsed with the immunodominant HER-2/neu(p369) peptides. EXPERIMENTAL DESIGN Nine enrolled patients, who had HER-2/neu-overexpressing tumors and who were HLA-A2 positive, received four vaccinations by DCs pulsed with HER-2(p369) peptide at 2-week intervals intradermally. RESULTS There were no serious adverse effects noted in the immunized patients. Peripheral blood mononuclear cells, preimmunization and after the fourth immunization, were cultured with autologous, HER-2(p369)-pulsed antigen-presenting cells for 12 days. Thereafter, peptide specificity was evaluated by IFN-gamma secretion assay from cultured T cells against T2 cells pulsed with HER-2(p369) peptide. HER-2/neu peptide-specific recognition could be demonstrated in six of nine patients after immunization, whereas there was no HER-2/neu peptide-specific recognition before immunization. The peptide-specific CTL lines isolated from two of the patients could also lyse a HER2/neu-transfected cell line. Furthermore, a peptide-specific delayed-type hypersensitivity response occurred in three of nine patients. One of the patients underwent a partial clinical response concurrent with a decrease of tumor marker. Another patient demonstrated a stabilization of disease status for a period of 3 months. CONCLUSIONS Taken together, tumor vaccination therapy with DCs pulsed with HER-2/neu-peptides may be a potential candidate for the novel treatment of gastric cancer patients.