Figure 1.

Immunotherapeutic approaches. Biological response modifiers are compounds which can specifically enhance the immune response, either by directly stimulating the immune system and/or by the direct induction of tumor cell apoptosis. These compounds can activate the anti-tumor immune response via the direct stimulation of pro-inflammatory immune cells or via the inhibition of detrimental suppressive immune cells like Tregs or myeloid-derived suppressor cells. Monoclonal antibodies bind specifically to one epitope and their application as potential immunotherapeutic agents has received a lot of attention recently. The development of antibodies which bind to co-inhibitory molecules activated during T-cell activation has led to the possibility to prevent T-cell inhibitory mechanisms and therefore enhance the anti-tumor immune response (29). Monoclonal antibodies targeting tumor growth related antigens (like EGFR) may diminish tumor growth by blockade of this receptor. On the other hand the IgG side of the antibody may cause immune-activation and tumor cell destruction in an immune related way. Monoclonal antibodies can also scavenge immunomodulatory proteins like VEGF. Peptide or tumor cell vaccines are designed to deliver tumor antigens to APCs, which can subsequently induce a tumor specific immune response by the adaptive immune system. These vaccines can consist of tumor specific antigens or can be composed of manipulated tumor cells. Cellular immunotherapy includes the adoptive transfer of autologous or allogeneic activated immune cells. The goal of this approach is to induce a tumor-specific immune response via the infusion of, e.g., tumor-antigen loaded dendritic cells or specifically activated T-cells.