Statins potentiate mitochondrial dysfunction and activation of caspase cascades mediated by UCN-01 in cultured leukemia and myeloma cells as well as in primary AML blasts. (A) U937 cells were exposed for 18 hours to 100 nM UCN-01 (UCN) with or without 20 μM lovastatin (LV), 40 μM fluvastatin (FV), or 30 μM simvastatin (SV) (left panels), and RPMI8226 cells (8226) for 24 hours to 100 nM UCN-01 with or without 10 μM lovastatin (right panels). At the end of the incubation period, expression of cytochrome c, Smac/DIABLO, and AIF in cytosolic fractions (S-100) was evaluated by Western blot analysis as described in “Western blot analysis.” (B) U937 (left panels) and RPMI8226 cells (middle panels) were treated as described in panel A. U266 cells were exposed for 48 hours to 150 nM UCN-01 with or without 10 μM lovastatin (right panels). Cells were then lysed and subjected to Western blot analysis to assess cleavage of caspases and degradation of PARP using the indicated primary antibodies. (C) Blasts from AML patient no. 3 were treated with 150 nM UCN-01 with or without 20 μM lovastatin for 18 hours, after which Western blot analysis was performed to assess PARP degradation. (D) U937 cells were incubated with low concentrations of UCN-01 (50 to 75 nM) with or without lovastatin (2.5 to 5μM) for either 48 hours or 72 hours, after which PARP degradation was monitored by Western blot analysis. For all panels, each lane was loaded with 30 μg protein; blots were subsequently stripped and reprobed for expression of α-tubulin or β-actin to ensure equivalent loading and transfer of protein. The results of a representative experiment are shown; an additional study yielded equivalent results. CF indicates cleavage fragment.