Table 1. Treatment of HCT116 cells with b-AP15 and cpdA does not deplete cellular cysteine levels.

Sample	Control	b-AP15	BZ	b-AP15 + cpdA	BZ + cpdA
Cysteine (µmol/g)	0.46±0.11	0.65±0.17	1.35±0.48	0.54±0.18	0.53±0.22

HCT116 cells were treated with 1 µM b-AP15 or 100 nM bortezomib (BZ) for 8 hours Where indicated, cells were pre-treated with 10 µM cpdA for 16 hours prior to b-AP15 or bortezomib treatment. Cells were collected and intracellular cysteine levels measured as described. Data are mean ± SD of three independent experiments.