Preclinical and clinical evaluation of proteasome inhibitor PS-341 for the treatment of cancer.

The proteasome is a multicatalytic protease, present in all eukaryotic cells, that is primarily responsible for intracellular protein degradation. By destroying regulatory proteins or their inhibitors, the proteasome influences many cellular regulatory signals and is thus a potential target for pharmacological agents. The dipeptide boronic acid analogue PS-341 is a potent and selective proteasome inhibitor in clinical trials for a variety of tumor types. In vitro and in vivo (murine xenograft) studies show that PS-341 has activity against a variety of malignancies, including myeloma, chronic lymphocytic leukemia, prostate cancer, pancreatic cancer, breast cancer and colon cancer.