Studies have shown that antitumor effect of BTZ on MCL cells is primarily exerted by increasing the proapoptotic protein Noxa; however, the accumulation of antiapoptotic protein Mcl-1 induced by inhibition of intracellular proteasome activity via BTZ weakens the antitumor effect of the drug 20–23. The gene discussed is PMAIP1; the disease is mantle cell lymphoma.