Table 1.

Fraction of cells undergoing apoptosis with various apoptosis inhibitors and rATG

Inhibitor Target	zFK-fmk Negative control	zVAD-fmk Pancaspase	Pepstatin A Cathepsin D	Genistein Tyrosine kinases	zFA-fmk Cysteine proteases	E-64d Cathepsins B + D	SB203561 MAP kinase
sBc	97.9 ± 2.7	60.1 ± 3.2*	98.7 ± 2.7	91.9 ± 3.1	82.4 ± 1.6	21.4 ± 0.5*	96.3 ± 1.8
RPMI-8226	97.9 ± 2.7	70.1 ± 11.9*	92.2 ± 3.5	25.3 ± 2.9*	100.7 ± 1.5	89.2 ± 2.8	97.5 ± 2.9
U266	97.7 ± 4.0	64.4 ± 3.4*	47.2 ± 1.8*	97.2 ± 1.8	90.9 ± 4.6	95.2 ± 3.8	101.6 ± 1.8
NCI-H929	100.0 ± 1.5	106.3 ± 0.7	20.9 ± 2.2*	21.9 ± 1.7*	111.8 ± 0.2	110.7 ± 0.6	106.0 ± 0.6
ARH-77	83.9 ± 0.2	82.8 ± 0.2	8.6 ± 0.1*	78.1 ± 0.5	84.5 ± 0.5	82.9 ± 0.1	86.3 ± 0.4
HS-Sultan	88.2 ± 5.3	86.1 ± 2.6	97.2 ± 5.3	80.7 ± 7.1	87.5 ± 7.7	57.2 ± 4.8*	78.2 ± 2.1
MC-CAR	79.2 ± 0.9	83.2 ± 5.1	20.2 ± 3.9*	81.2 ± 7.4	79.6 ± 9.1	89.5 ± 4.1	81.9 ± 6.7
hMC	89.1 ± 4.3	66.4 ± 7.1*	54.1 ± 3.7*	82.1 ± 6.8	88.2 ± 5.0	59.6 ± 5.1*	83.4 ± 7.7

rATG appears to activate both cathepsin- and caspase-mediated cell death pathways in myeloma cell lines and primary myeloma cells (hMCs), as well as tyrosine kinase–dependent apoptosis cascades. Myeloma cell lines were incubated with 250 μg/mL rATG in the presence of various inhibitors of apoptosis and then analyzed for cell death by TOPRO-3 staining. Results are the percentage of apoptotic cells in the test sample divided by the percentage of apoptotic cells in a control sample without any inhibitor. The control substance zFK-fmk was used as a second negative control. Each data point represents a mean of 3 independent experiments and results are means ± 1 SD.

^*Values with more than 20% decrease in rATG-induced cell death