A new purification method for enhancing the immunogenicity of heat shock protein 70-peptide complexes

When purified from a tumor, certain heat shock protein 70 (HSP70)-peptidecomplexes (PCs) can function as effective vaccines against the tumor from whichthe complexes were isolated. The immunogenic mechanisms of HSP70 preparationsimply that tumor-derived HSP70-PCs exhibit antigens associated with antigen-presentingcells such as dendritic cells (DCs), inducing antigen-specific cytotoxic CD8+T cells. However, some important membrane-resident tumor-associated peptides,such as the HER-2/neu (c-erbB2) oncogenic protein, cannot be purified from HSP70by traditional methods. In the present study, a new approach for the purificationof HSP70-PCs from HER-2-overexpressing breast cancer cells was established. Thedetergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) wasused to obtain more effectual tumor peptides. The new purified product was namedHSP70-HER-2-PC, and its immunological activities were determined. Traditionallypurified HSP70-PCs (without CHAPS) and recombinant human HSP70-HER-2 protein complexes(recombined in vitro) were used as controls. These three HSP70-associated tumorantigenic complex pulsed dendritic cells (DCs) were used to stimulate an antitumorresponse. The mature DCs pulsed with HSP70-HER-2-PCs stimulated autologous T cellsto secrete higher levels of type I cytokine compared to the two control groups.Moreover, DCs pulsed with HSP70-HER-2-PCs induced the most specific CD8+ T cellsthat specifically killed the same tumor cells. These findings provide a basisfor new approaches in enhancing HSP70-based immunotherapy for HER-2-associatedor other membrane antigenic peptide-related cancers.