Table 1. IC50 values obtained for each β-subunit.
| Proteasome subunit | AMO-1 | AMO-BTZ | AMO-CFZ | |
|---|---|---|---|---|
| BTZ | ||||
| IC50 (nm) (50% functional proteasome inhibition) | β2c | NA | NA | NA |
| β2i | NA | NA | NA | |
| β1c | 40 | 60 | 50–60 | |
| β1i | 20–25 | 50 | 50–60 | |
| β5c | 25 | 80–90 | 50–60 | |
| β5i | 30 | 80–90 | 50–60 | |
| LD50 (nm) (50% cell viability) | 50 | >1000 | >1000 | |
| CFZ | ||||
| IC50 (nm) (50% functional proteasome inhibition) | β2c | 300 | 220 | >1000 |
| β2i | 180 | 90 | 800 | |
| β1c | >500 | 600 | >1000 | |
| β1i | >250 | 250 | 1000 | |
| β5c | 10 | 50 | 90 | |
| β5i | 10 | 50 | 250 | |
| LD50 (nm) (50% cell viability) | 150 | >1000 | >1000 | |
IC50 values for the inhibition of proteasome β-subunits in AMO-1-sensitive cells and AMO cells adapted to bortezomib (AMO-BTZ) and carfilzomib (AMO-CFZ) during treatment with bortezomib (Btz) and carfilzomib (Cfz), as deferred from subunit-selective activity-based fluorescent labeling, in relation to the LD50 (50% cell viability, determined by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium)). NA, not applicable or >1000 nm indicate no significant effect on the IC50 value up to 1000 nm.