Enhancing the treatment effect on melanoma by heat shock protein 70-peptide complexes purified from human melanoma cell lines

Dendritic cell (DC) vaccines are currently one of the most effective approaches to treat melanoma. The immunogenicity of antigens loaded into DCs determines the treatment effects. Patients treated with autologous antigen-loaded DC vaccines achieve the best therapeutic effects. In China, most melanoma patients cannot access their autologous antigens because of formalin treatment of tumor tissue after surgery. In the present study, we purified heat shock protein 70 (HSP70)-peptide complexes (PCs) from human melanoma cell lines A375, A875, M21, M14, WM-35, and SK-HEL-1. We named the purified product as M-HSP70-PCs, and determined its immunological activities. Autologous HSP70-PCs purified from primary tumor cells of melanoma patients (nine cases) were used as controls. These two kinds of tumor antigenic complexes loaded into DCs were used to stimulate an antitumor response against tumor cells in the corresponding patients. Mature DCs pulsed with M-HSP70-PCs stimulated autologous T cells to secrete the same levels of type I cytokines compared with the autologous HSP70-PCs. Moreover, DCs pulsed with M-HSP70-PCs induced CD8+ T cells with an equal ability to kill melanoma cells from patients compared with autologous HSP70-PCs. Next, we used these PC-pulsed autologous DCs and induced autologous specific CD8+ T cells to treat one patient with melanoma of the nasal skin and lung metastasis. The treatment achieved a good effect after six cycles. These findings provide a new direction for DC-based immunotherapy for melanoma patients who cannot access autologous antigens.