The sensitivity of primary B-CLL cells to brefeldin A is independent of p53 status or the relative expression of key antiapoptotic proteins. (A) Comparison of BFA-induced apoptosis (active caspase-3 staining) in CLL patient samples with (n = 9) or without (n = 11) p53 (17p) deletion. No statistically significant difference in sensitivity to brefeldin A was observed between the 2 groups (P = .704). Error bars indicate SEM. (B) Lysates were prepared from primary CLL cells and multiple myeloma cell lines U266 and NCI-H929. Equivalent amounts of protein from each sample were subjected to SDS-PAGE electrophoresis. Separated proteins were transferred to nitrocellulose membranes and probed for the antiapoptotic proteins Bcl-X_L, Bcl-2, Mcl-1, and XIAP. Actin was used as a loading control. NR = nonrefractory; R = fludarabine refractory. The percentage of cells positive for active caspase-3 as assessed by flow cytometry after 48 hours of treatment with 100 ng/mL brefeldin A is noted for each sample. Values have been adjusted to exclude spontaneous apoptosis.