Dendritic cell-based cancer vaccination: quo vadis?

Dendritic cells (DCs) play a central role in the initiation and regulation of primary immune responses. DCs loaded with tumor-associated antigens induce anti-tumoral cytotoxic T cells in vitro and in vivo. However, clinical trials using ex vivo-generated DCs have failed to demonstrate clinical efficacy. This review summarizes recent advances in concepts and techniques that are providing new impulses to DC-based cancer vaccination. Improvements in protocols for ex vivo-generation of DCs, innovations in immunomonitoring, strategies to overcome tumor-induced immunosuppression and insights into the mutual beneficial effects of vaccines and chemotherapy are all considered. Furthermore, we highlight novel developments in cell-free vaccines targeting DCs in vivo.