Statin-induced breast cancer cell death: role of inducible nitric oxide and arginase-dependent pathways.
Statins are widely used cholesterol-lowering drugs that selectively inhibit the enzyme 3-hydroxy-3-methylglutaryl CoA reductase, leading to decreased cholesterol biosynthesis. Emerging data indicate that statins stimulate apoptotic cell death in several types of proliferating tumor cells, including breast cancer cells, which is independent of its cholesterol-lowering property. The objective here was to elucidate the molecular mechanism(s) by which statins induce breast cancer cell death. Fluvastatin and simvastatin (5-10 mumol/L) treatment enhanced the caspase-3-like activity and DNA fragmentation in MCF-7 cells, and significantly inhibited the proliferation of MCF-7 cells but not MCF-10 cells (noncancerous epithelial cells). Statin-induced cytotoxic effects were reversed by mevalonate, an immediate metabolic product of the acetyl CoA/3-hydroxy-3-methylglutaryl CoA reductase reaction. Both simvastatin and fluvastatin enhanced nitric oxide ((.)NO) levels which were inhibited by mevalonate. Statin-induced (.)NO and tumor cell cytotoxicity were inhibited by 1400W, a more specific inhibitor of inducible nitric oxide synthase (iNOS or NOS II). Both fluvastatin and simvastatin increased iNOS mRNA and protein expression. Stimulation of iNOS by statins via inhibition of geranylgeranylation by GGTI-298, but not via inhibition of farnesylation by FTI-277, enhanced the proapoptotic effects of statins in MCF-7 cells. Statin-mediated antiproliferative and proapoptotic effects were exacerbated by sepiapterin, a precursor of tetrahydrobiopterin, an essential cofactor of (.)NO biosynthesis by NOS. We conclude that iNOS-mediated (.)NO is responsible in part for the proapoptotic, tumoricidal, and antiproliferative effects of statins in MCF-7 cells.
Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
Srigiridhar
S
Kotamraju
Carol L
CL
Williams
Carol L
CL
Willams
Balaraman
B
Kalyanaraman
D000924:Anticholesteremic Agents / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001119:Arginase / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D053148:Caspase 3 / Q000378:metabolism; D002448:Cell Adhesion; D002453:Cell Cycle / Q000187:drug effects; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology*; D000077340:Fluvastatin; D006801:Humans; D020287:In Situ Nick-End Labeling; D007211:Indoles / Q000494:pharmacology*; D008798:Mevalonic Acid / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D011106:Polyisoprenyl Phosphates / Q000378:metabolism; D017368:Protein Prenylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*; D019821:Simvastatin / Q000494:pharmacology*
D000924:Anticholesteremic Agents; D000975:Antioxidants; D005229:Fatty Acids, Monounsaturated; D007211:Indoles; D011106:Polyisoprenyl Phosphates; D012333:RNA, Messenger; D009569:Nitric Oxide; D000077340:Fluvastatin; D019821:Simvastatin; D052247:Nitric Oxide Synthase Type II; D053148:Caspase 3; D001119:Arginase; C002963:geranylgeranyl pyrophosphate; D008798:Mevalonic Acid