Lovastatin inhibits tumor growth and lung metastasis in mouse mammary carcinoma model: a p53-independent mitochondrial-mediated apoptotic mechanism.
The effects of lovastatin, a potent inhibitor of hydroxymethylglutaryl-coenzyme A reductase, were studied in a mouse model of metastatic mammary cancer carrying a p53 mutation. Mice bearing mammary tumors, induced by inoculation of syngeneic BALB/c mice with BJMC3879 cells, were treated with lovastatin at 0, 25 and 50 mg/kg three times a week. Tumor volumes were significantly reduced in a dose-dependent manner throughout the 6 week study and were associated with both a decrease in DNA synthesis and an increase in apoptosis. The high dose of lovastatin also inhibited lung metastasis. In a corollary in vitro study, flow cytometric analyses of lovastatin-treated mammary cancer cells additionally showed cell cycle arrest at G1 phase and decreases in S and G2/M phases. Laser scanning cytometric analyses further demonstrated that cancer cells in S and G2/M were particularly susceptible to the effects of lovastatin. Transmission electron microscopic evaluation of TUNEL-confirmed apoptotic bodies in lovastatin-treated mammary carcinoma cells revealed many free 3'-OH ends of DNA in condensed chromatin within fragmented nuclei that occasionally assumed a characteristic half-moon shape. Consistent with initiation of apoptosis, cellular caspase-8, caspase-9 and caspase-3 activities were elevated in lovastatin-treated cells. The mitochondrial membrane potential was also decreased, with subsequent release of cytochrome c. However, lovastatin-induced cell death was significantly reduced by the broad spectrum caspase inhibitor z-VAD-fmk, as well as the caspase-9 inhibitor z-LEHD-fmk and the caspase-3 inhibitor z-DEVD-fmk, but not by the specific caspase-8 inhibitor z-IETD-fmk. Since immunoelectron microscopy showed translocation of Bax to the mitochondria in lovastatin-treated cells, lovastatin-induced apoptosis may, therefore, be ultimately dependent on Bax induction of cytochrome c release. These results suggest that lovastatin may be useful as an adjuvant therapy in breast cancers containing p53 mutations due to its ability to both suppress DNA synthesis and induce p53-independent mitochondria-mediated apoptosis.
Shibata
Masa-Aki
MA
Department of Anatomy and Biology, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki, Osaka 569-8686, Japan. an1014@art.osaka-med.ac.jp
Ito
Yuko
Y
Morimoto
Junji
J
Otsuki
Yoshinori
Y
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005434:Flow Cytometry; D020287:In Situ Nick-End Labeling; D008148:Lovastatin / Q000627:therapeutic use*; D008175:Lung Neoplasms / Q000517:prevention & control* / Q000556:secondary*; D008325:Mammary Neoplasms, Experimental / Q000473:pathology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron; D008928:Mitochondria / Q000187:drug effects*; D009154:Mutation / Q000235:genetics; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein
D000970:Antineoplastic Agents; C494827:Bax protein, mouse; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c; D008148:Lovastatin; D020169:Caspases