Proteomic analysis of exosomes derived from human lymphoma cells

BACKGROUND Exosomes secreted by tumor cells contain specific antigens that may have immunotherapeutic purposes. The aim of this study was to characterize the proteomic content of lymphoma cell-derived exosomes (LCEXs). METHODS In this study, exosomes derived from Raji cells (EXO(Raji)) were purified and proteins of EXO(Raji) were separated by one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis. Protein bands were identified by mass spectrometry. The protein components of EXO(Raji) were analyzed using shotgun technology, and the function proteins of EXO(Raji) were defined and described using the Gene Ontology (GO) database and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. RESULTS A total of 197 proteins were identified in EXO(Raji); 139 proteins were also identified in Raji cells, showing an overlap of 70.56% of the total proteins in EXO(Raji). Interestingly, the remaining 58 proteins were unique to EXO(Raji). The GO database and KEGG were used to define and describe the function of proteins. The data showed that some important proteins involved in antigen procession and presentation as well as cell migration and adhesion were also identified in EXO(Raji), such as MHC-I and II, HSC70, HSP90, and ICMA-1. CONCLUSIONS LCEXs express a discrete set of proteins involved in antigen presentation and cell migration and adhesion, suggesting that LCEXs play an important role in the regulation of immunity and interaction between lymphoma cells and their microenvironment. LCEXs harbor most of the proteins of lymphoma cells and could be one of the sources of lymphoma-associated antigens for immunotherapeutic purposes.