Journal Article

Lovastatin inhibits tumor growth and lung metastasis in mouse mammary carcinoma model: a p53-independent mitochondrial-mediated apoptotic mechanism

Masa-Aki Shibata, Yuko Ito, Junji Morimoto and Yoshinori Otsuki

in Carcinogenesis

Volume 25, issue 10, pages 1887-1898
Published in print October 2004 | ISSN: 0143-3334
Published online October 2004 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgh201
Lovastatin inhibits tumor growth and lung metastasis in mouse mammary carcinoma model: a p53-independent mitochondrial-mediated apoptotic mechanism

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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.

Keywords: BrdU, 5-bromo-2′-deoxyuridine; fmk, fluoromethyl ketone; H&E, hematoxylin and eosin; HMG-CoA, hydroxymethylglutaryl-coenzyme A; MMTV, mouse mammary tumor virus; PBS, phosphate-buffered saline; RFU, relative fluorescence units; TEM, transmission electron microscopic; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP-FITC nick end-labeling

Journal Article.  7970 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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