Presentation of tumour antigens by dendritic cells and challenges faced

The use of dendritic cells (DCs) for the generation of anti-tumour immunity has been the focus of a vast array of scientific and clinical studies. The ability of DCs to present protein tumour antigens (T-Ags) to CD4(+) and CD8(+) T cells is pivotal to the success of therapeutic cancer vaccines. DC's specialised capacity to cross-present exogenous Ags onto major histocompatibility (MHC) class I molecules for the generation of T-Ag-specific cytotoxic T lymphocytes (CTLs) has made these cells the focal point of vaccine-based immunotherapy of cancer. However, although DC-based strategies can induce T cell responses in cancer patients, recent reviews of clinical studies demonstrate that DC-based approaches have essentially failed to meet their clinical end points. These findings highlight the need to re-evaluate the DC-based vaccine strategies and incorporate recent advancements in DC biology and tumour immunology. The current review considers the issues related to how best to target the Ag-processing pathway of DCs, the role of adjuvants, the appropriate conditioning of the DCs and strategies to overcome tumour-mediated immune escape.