Bortezomib, a modified dipeptidyl boronic acid, is a therapeutic proteasome inhibitors used for the treatment of cancers. It is indicated for the treatment of relapsed multiple myeloma and mantle cell lymphoma. It is capable of inhibiting the mammalian 26S proteasome, which is important in regulating the intracellular concentration of specific proteins to maintain homeostasis within cells. The disruption of 26S proteasome function disrupts normal cellular homeostasis, leading to cytotoxic effect on various kinds of cancer cells.