Lovastatin induces apoptosis in plasma cell lines by depletion of intracellular pools of GGPP. (A) RPMI 8226 cells were treated for 4 days with solvent control or lovastatin (30 μM) alone or in combination with mevalonate (meva; 100 μM), GGOH (10 μM), or FOH (10 μM). The percentage of apoptotic cells was examined by using the annexin V assay. The percentages of viable plasma cells (annexin V-/PI-), early apoptotic cells (annexin V+/PI-), and late apoptotic cells (annexin V+/PI+) in each dot plot are indicated in the corresponding quadrants. Results are representative of 3 experiments performed in triplicate. (B) RPMI 8226, L363, XG-1, and U266 cells were treated for 4 days with solvent control or different concentrations of lovastatin (5, 10, 40, 100, or 150 μM) alone (▪) or in combination with mevalonate (100 μM; ○), GGOH (10 μM; •), or FOH (10 μM; □), after which apoptosis was determined using the annexin V assay. Shown is the sum of the percentages of early and late apoptotic cells. Experiments were performed 3 times in triplicate. Data are presented as mean ± SEM.