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.

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