Why do cells release vesicles?

Prokaryotic and eukaryotic cells release vesicles into their environment. To answer the question why eukaryotic cells release vesicles, we may learn from prokaryotes. Bacteria release outer membrane vesicles, resembling microparticles, which act as "multi-purpose carriers". They contain signalling molecules for other bacteria, deliver toxins to host cells and exchange DNA encoding virulence genes between bacteria. Similarly, cell-derived microparticles and exosomes from eukaryotic cells are multi-purpose carriers containing e.g. signalling molecules, cellular waste and functional genetic information. To illustrate our rapidly increasing knowledge on the multiple roles that cellular microparticles and exosomes play in disease progression, we focus on cancer, which is one of the best studied diseases in this aspect. The clinical applications of microparticles and exosomes, including diagnosis, prognosis and therapy, in cancer are discussed.