Contribution of proteomics to tumor immunology.

In the postgenome era, the global analysis of gene and protein expression is allowed at RNA and protein level by microarrays and proteomics. The application of these complementary approaches provides new opportunities for tumor immunology investigation. Indeed, applied to the study at the molecular level of the differentiation and maturation of dendritic cells which are the most potent antigen presenting cells, microarray analysis has identified important changes in a large number of genes, whereas the proteomic analysis provided information that could not be obtained at the RNA level, such as the separation of different isoforms and the characterization of post-translational modifications. On the other hand, proteomics allows serological screening of tumor antigens. Indeed, two-dimensional (2-D) polyacrylamide gel electrophoresis allows simultaneously separation several thousand individual proteins from tumor tissue or tumor cell lines. Proteins eliciting humoral response in cancer are identified by 2-D Western blot using cancer patient sera, followed by mass spectrometry analysis and database search. Applied to different types of cancer, the proteome based approach has allowed us to define several tumor antigens. The common occurrence of autoantibodies to certain of these proteins in different cancers may be useful in cancer screening and diagnosis as well as for immunotherapy.