title: HMG-CoA reductase inhibitors, statins, induce phosphorylation of Mdm2 and attenuate the p53 response to DNA damage.
abstract: 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitors, statins, are widely used cholesterol-lowering drugs and have been shown to have anticancer effects in many models. We have investigated the effect of statins on Mdm2, a p53-specific ubiquitin ligase. It was found that pravastatin induced Mdm2 phosphorylation at Ser166 and at 2A10 antibody-specific epitopes in HepG2 cells, while mRNA levels were unchanged. Furthermore, pravastatin was found to induce phosphorylation of mTOR at Ser2448. Ser166 phosphorylation of Mdm2 was abrogated by an inhibitor of mTOR, rapamycin, but not by the PI3-kinase inhibitors LY294002 and wortmannin. Ser166 phosphorylation of Mdm2 has been associated to active Mdm2 and has been shown to increase its ubiquitin ligase activity and lead to increased p53 degradation. Our data show that statins attenuated the p53 response to DNA damage. Thus, in HepG2 cells pravastatin and simvastatin pretreatment attenuated the p53 response to DNA damage induced by 5-fluorouracil and benzo(a)pyrene. Similar attenuation was induced when p53 stabilization was induced by the inhibitor of nuclear export, leptomycin B. Furthermore, in the DNA-damaged cells, half-lives of Mdm2 and p53 were decreased by statins, indicating a more rapid formation of p53/Mdm2 complexes and facilitated p53 degradation. The induction of p53 responsive genes and apoptosis was attenuated. Mdm2 and p53 were also studied in vivo in rat liver employing immunohistochemistry, and it was found that constitutive Mdm2 expression was changed in livers of pravastatin-treated rats. We also show that the p53 response to a challenging dose of diethylnitrosamine was attenuated in hepatocytes in situ and in primary cultures of hepatocytes by pravastatin pretreatment. Taken together, these data indicate that statins induce an mTOR-dependent Ser166 phosphorylation of Mdm2, and this effect may attenuate the duration and intensity of the p53 response to DNA damage in hepatocytes.
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Gerd
authors.initials: G
authors.lastname: Pääjärvi
authors.forename: Emilie
authors.initials: E
authors.lastname: Roudier
authors.forename: Milita
authors.initials: M
authors.lastname: Crisby
authors.forename: Johan
authors.initials: J
authors.lastname: Högberg
authors.forename: Ulla
authors.initials: U
authors.lastname: Stenius
mesh_terms: D000818:Animals; D017209:Apoptosis; D018797:Cell Cycle Proteins / Q000502:physiology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004249:DNA Damage / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D022781:Hepatocytes; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D020287:In Situ Nick-End Labeling; D007328:Insulin / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008113:Liver Neoplasms; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D017035:Pravastatin / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051736:Proto-Oncogene Proteins c-mdm2; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: C493956:CDKN1A protein, human; C493958:Cdkn1a protein, rat; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004791:Enzyme Inhibitors; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007328:Insulin; D009687:Nuclear Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D012694:Serine; C497206:MDM2 protein, human; C497208:Mdm2 protein, rat; D051736:Proto-Oncogene Proteins c-mdm2; D011494:Protein Kinases; C546842:MTOR protein, human; C546845:mTOR protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D017035:Pravastatin; D020123:Sirolimus