Figure 3.

Combination of bortezomib and thiostrepton suppresses proteasome activity. (A) Proteasome activity assay showed that lysates from MDA-MB-231 tumors treated with a combination of proteasome inhibitors had decreased ability for proteasome substrate cleavage, compared with that from non-treated and single drug-treated tumors. Values represent averages of 6–8 tumors and error bars depict SEM p values are stated within the figure. (B) Proteasome activity assay showed that bortezomib and thiostrepton inhibit proteasome activities of purified proteasomes to a greater extent when used in combination.