Simvastatin induces apoptosis of B-CLL cells by activation of mitochondrial caspase 9.
OBJECTIVE
Chronic lymphocytic leukemia (CLL) is the most common leukemia in the western world. Despite several advances in therapeutic options, the disease remains incurable. Recently, it was repeatedly demonstrated that statins, competitive inhibitors of 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase, have antineoplastic effects. Therefore we aimed to study the effects of simvastatin (Sim) on malignant B cells derived from patients with CLL and mechanisms of action of the drug.


RESULTS
Purified B-CLL cells from 15 patients were cultured either alone or with Sim at concentrations of 10, 50, and 100 microM. Viability, measured by the activity of mitochondrial dehydrogenases, was reduced significantly in the cells treated with Sim at 50 and 100 microM for 24 hours (p<0.005). The level of apoptosis, as measured by annexin binding to exposed phosphatidylserine moieties, increased significantly in the treated cells at concentrations higher than 50 microM for 24 hours (p<0.003). The level of necrosis, as measured by propidium iodide internalization, increased significantly after 24 hours exposure to Sim at 50 microM (p<0.01). The apoptotic cascade was studied by immunoblot analysis of caspases following Sim treatment. These showed cleavage of caspases 9, 8, and 3. Addition of the caspase inhibitor Z-VAD.fmk inhibited caspase 8 and 3 significantly but did not affect caspase 9.


CONCLUSIONS
Exposure of clonal B lymphocytes from patients with CLL to simvastatin decreases viability significantly by the induction of apoptosis. The apoptosis induced by Sim is probably initiated by the mitochondrial caspase 9, which indirectly leads to activation of caspase 3 and 8.
Chapman-Shimshoni
Daphne
D
Oncogenetic Laboratory, Meir Hospital, Kfar-Saba, Israel.
Yuklea
Mona
M
Radnay
Judith
J
Shapiro
Hava
H
Lishner
Michael
M
D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology*; D019821:Simvastatin / Q000494:pharmacology* / Q000627:therapeutic use; D014407:Tumor Cells, Cultured
D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D019821:Simvastatin; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases