Selective inhibitor of proteasome's caspase-like sites sensitizes cells to specific inhibition of chymotrypsin-like sites.

Proteasomes degrade most proteins in mammalian cells and are established targets of anticancer drugs. All eukaryotic proteasomes have three types of active sites: chymotrypsin-like, trypsin-like, and caspase-like. Chymotrypsin-like sites are the most important in protein degradation and are the primary target of most proteasome inhibitors.