Intracellular proteolysis and tumorigenesis

Intracellular protein breakdown plays a pivotal role in cell biology. This process is involved in the control of essential cellular functions such as progression through the cell cycle, differentiation, apoptosis and the prod uction of antigenic peptides. Thereby, proteolysis influences the organism' s physiology, particularly at the level of organogenesis, morphogenesis, va scularization and the immune response. It is thus not surprising that intra cellular proteolysis impairment contributes to oncogenesis. Recent literatu re has shown that the degradation of various proto-oncogenic and onco-suppr essive proteins is altered in many cancer situations, and that some compone nts of the intracellular proteolytic systems are also proto-oncoproteins or onco-suppressive proteins. The diversity of the proteolytic mechanisms aff ected in tumors can be illustrated through several examples involving the u biquitin/proteasome system, which constitutes the main intracellular protei n destruction pathway.