New strategies to improve tumor cell vaccine therapy

The advantage of using a tumor cell vaccine is that it is rich in multiple tumor-associated antigens. The immune responses to those antigens are elicited by most of current tumor cell vaccines that are transduced with immunostimulatory cytokines or costimulatory molecules. However, the lack of long-lasting and objective tumor regression in clinical trials prompted reevaluation of the immunogenicity of tumor cell vaccines and the molecular basis of the immune responses they induced. New vectors for the genetic modification of tumor cell vaccines to improve immunogenicity have been developed. The identification of negative regulators during vaccination has lead to the discovery of new reagents to specifically target regulatory cells or molecules to improve the efficacy of these vaccines. On the basis of their enhancing effects during the cross-priming of CD8 T cells, toll-like receptor ligands have been used in the modification of tumor cells to improve their immunogenicity. Therefore, the endeavors in developing new tumor cell vaccines not only extend our knowledge about the tumor-reactive immunity but also promise an effective treatment regimen in human cancers.