Proteomic profiling of tumor exosomes

Exosomes contain various molecular constituents of their cells of origin, including proteins and nucleic acid material. Exosomes have been isolated from blood, urine, saliva, synovial fluid, breast milk, cerebrospinal fluid, and various other body fluids and are also secreted by most cell types in culture. Although the exosomal protein content varies with the cell of origin, most exosomes contain an evolutionary-conserved common set of protein molecules detected by mass spectrometry. Heat shock proteins, CD63, and tetraspanins are the most prominent evolutionary-conserved proteins in exosomes. Cytoskeleton- and metabolism-related proteins form the pool of other frequently found proteins. Exosomes also contain proteins that are involved in cell signaling pathways, apoptotic pathways, and evasion of metastasis. The existence of these multifaceted proteins in tumor exosomes and its sources, isolation techniques and its association with cancer development, sustenance, and drug resistance is further expanded in different cancer types in this chapter.