Statin-mediated disruption of farnesylation but not geranylation contributes to potentiation of UCN-01–induced apoptosis. (A) U937 cells were incubated for 18 hours with 100 nM UCN-01 (UCN) + 20 μM lovastatin (LV) in either the presence or absence of 10 μM GGPP, 10 μM FPP, or both, after which Western blot analysis was performed to assess the prenylation status of H-Ras and Rap1A as well as phosphorylation of ERK1/2. (B) Alternatively, the percentage of cells exhibiting apoptotic morphology was determined by evaluating Wright-Giemsa–stained cytospin preparations. Veh indicates vehicle. (C) U937 cells were treated for 18 hours with 100 nM UCN-01 in the presence of either 20 μM FTI-277 or 20 μM GGTI-2147, after which Western blot analysis was performed to monitor prenylation of H-Ras and Rap1A as well as phosphorylation of ERK1/2. (D) U937 cells were treated with 100 nM UCN-01 in the presence of the indicated concentrations (0 to 30 μM) of either GGTI-2147or FTI-277 for 18 hours, after which the percentage of apoptotic cells was determined by evaluating Wright-Giemsa–stained cytospin preparations. For panels A and C, each lane was loaded with 30 μg protein; blots were subsequently stripped and reprobed for expression of β-actin to ensure equivalent loading and transfer of protein. To detect changes in phosphorylation status of ERK1/2 under the conditions shown in panel A, 100 μg protein was loaded onto each lane, and total ERK1/2 was monitored in parallel in the same gel. Two additional studies yielded equivalent results. UP indicates unprenylated; P, prenylated. For panels B and D, results represent the means ± SD for 3 separate experiments performed in triplicate. *Significantly lower than values for cells cotreated with UCN-01 + lovastatin in the absence of FPP or FPP/GGPP ([B] *P < .05) and FTI-277 treatment alone ([D] **P < .01).