Differentially expressed proteins identified in proteomic analysis were annotated as being involved in tumor cell invasion/migration, cell survival/death, proliferation, DNA repair, metabolism and immune response according to their Gene Ontology classifications. On the basis of these annotations, we quantified the representation of differentially expressed proteins in each of these selected categories. Approximately half of all differentially expressed proteins belonged to one of these categories, and of these, approximately 70% were related to metabolism or invasion/migration.