Peptide vaccines against cancer.

Much recent progress has been made in the identification of new tumor antigens and their epitopes that may serve as potential cancer vaccines. Many of these have been studied as synthetic peptide vaccines corresponding to epitopes identified as presented by particular common human class I HLA molecules, especially HLAA2.1, the most common human class I molecule. Although a number of strategies for immunization against cancer have been investigated, no strategy targeting a specific antigen has yet proven consistently more clinically effective than synthetic peptides. Peptides have the advantage that they can be easily modified by epitope enhancement to improve binding to the MHC molecule or the T cell receptor, and they can be combined with cytokines, chemokines, and costimulatory molecules to increase vaccine potency and steer the responses toward a desired phenotype, such as CTL or Th1 cells. Peptides can also be coated onto dendritic cells, the ultimate professional antigen presenting cell, to bypass any defect in antigen-presenting cell function or maturation related to the presence of the cancer. Thus, as both research tools and as potential clinical vaccines, synthetic peptides remain at the forefront of research in the vaccine immunotherapy of cancer.