Effects of Bcl-2 overexpression on flavopiridol-induced mitochondrial depolarization and viability. (A) 697 cell lines with normal (697-Neo) or 10-fold Bcl-2 overexpression (697-Bcl2) were treated with 1.0 μM FP in media with 10% human serum for 6 hours (N = 3). Annexin binding and mitochondrial depolarization were assessed as for CLL patient cells. Results are shown relative to untreated cells at the same time point. Error bars represent plus or minus standard deviation. The difference in FP-mediated annexin binding between 697-Neo and 697-Bcl2 at this time point was significant (*P = .03) as was the difference in mitochondrial depolarization (**P = .01). (B) 697-Neo and 697-Bcl2 cells were treated with FP in media with 10% human serum, or F-ara A in media with 10% fetal bovine serum as a positive control for cytotoxicity prevented by Bcl-2. Viability was assessed at 24 hours by MTT assay. The averages of 4 individual experiments, each run in quadruplicate, are shown relative to the untreated control for each, set at 100%. Error bars represent plus of minus standard deviation.