[Proteasome inhibitors].

Bortezomib, one of the proteasome inhibitors, has been approved in the United States for multiple myeloma as a second-line chemotherapy. In Japan, bortezomib has been used for for phase I clinical trials for multiple myeloma. As the action mechanism, it has been proposed that bortezomib inhibits NF-kappaB via IkappaB alpha. It also demonstrated positive results for non-Hodgkin's lymphoma and non-small cell lung cancer, but not for colorectal cancer or chronic lymphocytic leukemia. The mechanism of drug resistance has been well analized. Bortezomib is very effective but still induces adverse effects including hypotension especially when there is an overdose. Medical oncologists or hematology/oncologists must exert due caution.