Colchicine inhibits CTL-mediated cell death, and high concentrations of grB can overcome Bcl-2 block. (A) CTL-induced tritium release in target cells overexpressing Bcl-2 is dependent on the presence of assembled microtubules. Jneo cells (□) and JBcl-2 cells (■) were preloaded with 3H-thymidine and incubated for 2 hours with CTLs (E/T ratio = 2:1) in the presence or absence of colchicines or paclitaxel. The percentage of specific tritium release, which is an indication of DNA fragmentation, was determined as outlined in “Apoptosis detection systems.” The numbers indicate the average of 3 independent experiments done in triplicate, with the corresponding standard deviation. (B) High concentrations of grB can induce apoptosis of JBcl-2 cells. Jneo cells (□) and JBcl-2 cells (■) were incubated with increasing concentrations of 30 nM, 1300 nM, or 5850 nM grB with AD, then loaded with the caspase indicator zVAD-FITC (left panel) and mitochondrial potential indicator dye (TMRE; right panel). Caspase activation and TMRE loss was determined by flow cytometry. The numbers indicate a representative of 2 independent experiments.
