title: Simvastatin-induced cell cycle arrest through inhibition of STAT3/SKP2 axis and activation of AMPK to promote p27 and p21 accumulation in hepatocellular carcinoma cells.
abstract: Hepatocellular carcinoma (HCC) is characterized by a poor prognosis and is one of the leading causes of cancer-related death worldwide. Simvastatin, an HMG-CoA reductase inhibitor, which decreases cholesterol synthesis by inhibiting mevalonate pathways and is widely used to treat cardiovascular diseases. Simvastatin exhibits anticancer effects against several malignancies. However, the molecular mechanisms underlying the anticancer effects of simvastatin on HCC are still not well understood. In this study, we demonstrated simvastatin-induced G0/G1 arrest by inducing p21 and p27 accumulation in HepG2 and Hep3B cells. Simvastatin also promoted AMP-activated protein kinase (AMPK) activation, which induced p21 upregulation by increasing its transcription. Consistent with this finding, we found genetic silencing of AMPK reduced p21 expression; however, AMPK silencing had no effect on p27 expression in HCC cells. Simvastatin decreased Skp2 expression at the transcriptional level, which resulted in p27 accumulation by preventing proteasomal degradation, an effect mediated by signal transducer and activator of transcription 3 (STAT3) inhibition. Constitutive STAT3 activation maintained high-level Skp2 expression and lower level p27 expression and significantly prevented G0/G1 arrest in simvastatin-treated HCC cells. Mevalonate decreased simvastatin-induced AMPK activation and rescued phospho-STAT3 and Skp2 expression in HCC cells, which resulted in the prevention of G0/G1 arrest through inhibition of p21 and p27 accumulation. Moreover, simvastatin significantly decreased tumor growth in HepG2 xenograft mice. Consistently, we found that simvastatin also increased p21 and p27 expression in tumor sections by reducing Skp2 expression and inducing AMPK activation and STAT3 suppression in the same tumor tissues. Taken together, these findings are demonstrative of the existence of a novel pathway in which simvastatin induces G0/G1 arrest by upregulating p21 and p27 by activating AMPK and inhibiting the STAT3-Skp2 axis, respectively. The results identify novel targets that explain the beneficial anticancer effects of simvastatin treatment on HCC in vitro and in vivo.
authors.affiliation: Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan.|Division of Gastroenterology, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Sin-Ting
authors.initials: ST
authors.lastname: Wang
authors.affiliation: Division of Gastroenterology, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Hsiu J
authors.initials: HJ
authors.lastname: Ho
authors.affiliation: School of Medicine, Fu Jen Catholic University, Taipei, Taiwan.|Institute of Population Health Sciences, National Health Research Institutes, Miaoli, Taiwan.
authors.forename: Jaw-Town
authors.initials: JT
authors.lastname: Lin
authors.affiliation: Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan.|Department of Education and Research, Taichung Veterans General Hospital, Taichung, Taiwan.|Department of Life Sciences and Rong Hsing Research Center for Translational Medicine, National Chung Hsing University, Taichung, Taiwan.
authors.forename: Jeng-Jer
authors.initials: JJ
authors.lastname: Shieh
authors.affiliation: Division of Gastroenterology, Taichung Veterans General Hospital, Taichung, Taiwan.|Department of Life Sciences and Rong Hsing Research Center for Translational Medicine, National Chung Hsing University, Taichung, Taiwan.|Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan.|Department of Public Health and Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan.|National Institute of Cancer Research, National Health Research Institutes, Miaoli, Taiwan.
authors.forename: Chun-Ying
authors.initials: CY
authors.lastname: Wu
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects*; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism*; D016193:G1 Phase / Q000187:drug effects; D057809:HEK293 Cells; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D044786:S-Phase Kinase-Associated Proteins / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D019821:Simvastatin / Q000494:pharmacology*
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D044786:S-Phase Kinase-Associated Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050760:Cyclin-Dependent Kinase Inhibitor p27; D019821:Simvastatin; D055372:AMP-Activated Protein Kinases