Effects of PS-341 on human pancreatic cancer cells in vitro. Effects of PS-341 on human pancreatic cancer cells in vitro. A, effects on cell growth. Cell lines were incubated with the indicated concentrations of PS-341 for 48 h, and cell viability was measured by MTT reduction as described in “Materials and Methods.” Results of one experiment representative of three independent replicates. B, effects on DNA fragmentation. Cell lines were incubated with the indicated concentrations of PS-341 for 48 h, and DNA fragmentation was measured by propidium iodide staining and FACS analysis as described in “Materials and Methods.” Mean ± SD, n = 3. *, indicates values that were significantly different from untreated controls. C, effects on caspase activity. Cells were incubated for 24 h with 10 μm PS-341 (or 1 μm staurosporine as a positive control). Caspase-3-like activity was measured in cytosolic extracts using a fluorigenic substrate (DEVD-AMC) as described in “Materials and Methods.” Mean ± SD, n = 3. *, P < 0.05 compared with control. D, effects on 20S proteasome activity. Cells were exposed to the indicated concentrations of PS-341 for 30 min, and 20S proteasome activity was measured in cytosolic extracts using a fluorigenic dye (Suc-LLVY-AMC) as described in “Materials and Methods.” Results are representative of two independent experiments. Steffan T. Nawrocki et al. Mol Cancer Ther 2002;1:1243-1253 ©2002 by American Association for Cancer Research