Targeting the proteasome as a therapeutic strategy against haematological malignancies.

The ubiquitin-proteasome pathway is responsible for the vast majority of regulated eukaryotic intracellular proteolysis. Inhibition of the proteasome induces beneficial antitumour effects by blocking cell-cycle progression, inducing apoptosis and suppressing angiogenesis. Bortezomib is the first proteasome inhibitor to reach the clinical arena, where Phase I - III trials verified its activity against relapsed/refractory multiple myeloma. Testing is ongoing to determine bortezomib's role in front-line therapy of this plasma cell dyscrasia, as well as in non-Hodgkin's lymphoma, in which encouraging single-agent activity has been seen. Proteasome inhibition is also a rational strategy to overcome chemoresistance and induce chemosensitisation. Combinations of bortezomib and other agents have enhanced efficacy, and additional studies are probing the activity of several regimens in lymphoid and myeloid malignancies. The current state of knowledge about the activity of bortezomib, both alone and in combination with standard chemotherapeutics, as part of the emerging armamentarium against haematological malignancies is reviewed.