Figure 6.

Basal accumulation of polyubiquitinated proteins inversely correlates with proteasome activity and with intrinsic resistance of MPM clones to the pro-apoptotic effects of bortezomib. (A) Different levels of polyubiquitin conjugates in MPM cell lines. Quantification of the FK2-dependent fluorescence in MPM cells was performed using Image J software (n ≥ 100 cells in ≥ 16 distinct fields). ***P < 0.001. Inverse correlation between levels of polyubiquitinated proteins in MPM clones and 26S proteasome chymotrypsin- and trypsin-like activities (B) and EC₅₀ values relative to apoptotic sensitivity to bortezomib (C).