title: A Novel Role of Silibinin as a Putative Epigenetic Modulator in Human Prostate Carcinoma.
abstract: Silibinin, extracted from milk thistle (Silybum marianumL.), has exhibited considerable preclinical activity against prostate carcinoma. Its antitumor and chemopreventive activities have been associated with diverse effects on cell cycle, apoptosis, and receptor-dependent mitogenic signaling pathways. Here we hypothesized that silibinin's pleiotropic effects may reflect its interference with epigenetic mechanisms in human prostate cancer cells. More specifically, we have demonstrated that silibinin reduces gene expression levels of the Polycomb Repressive Complex 2 (PRC2) members Enhancer of Zeste Homolog 2 (EZH2), Suppressor of Zeste Homolog 12 (SUZ12), and Embryonic Ectoderm Development (EED) in DU145 and PC3 human prostate cancer cells, as evidenced by Real Time Polymerase Chain Reaction (RT-PCR). Furthermore immunoblot and immunofluorescence analysis revealed that silibinin-mediated reduction of EZH2 levels was accompanied by an increase in trimethylation of histone H3 on lysine (Κ)-27 residue (H3K27me3) levels and that such response was, in part, dependent on decreased expression levels of phosphorylated Akt (ser473) (pAkt) and phosphorylated EZH2 (ser21) (pEZH2). Additionally silibinin exerted other epigenetic effects involving an increase in total DNA methyltransferase (DNMT) activity while it decreased histone deacetylases 1-2 (HDACs1-2) expression levels. We conclude that silibinin induces epigenetic alterations in human prostate cancer cells, suggesting that subsequent disruptions of central processes in chromatin conformation may account for some of its diverse anticancer effects.
authors.affiliation: Department of Molecular Biology and Genetics, Democritus University of Thrace, University Campus, Dragana, 68100 Alexandroupolis, Greece. i.anestopoulos@yahoo.com.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Anestopoulos
authors.affiliation: Department of Molecular Biology and Genetics, Democritus University of Thrace, University Campus, Dragana, 68100 Alexandroupolis, Greece. aristidis.sfakianos@postgrad.manchester.ac.uk.
authors.forename: Aristeidis P
authors.initials: AP
authors.lastname: Sfakianos
authors.affiliation: Redox Biology Center, School of Veterinary Medicine & Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE 68583, USA. rodrigo.franco@unl.edu.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Franco
authors.affiliation: Department of Molecular Biology and Genetics, Democritus University of Thrace, University Campus, Dragana, 68100 Alexandroupolis, Greece. achlichl@mbg.duth.gr.
authors.forename: Katerina
authors.initials: K
authors.lastname: Chlichlia
authors.affiliation: Department of Applied Sciences, Northumbria University, Newcastle Upon Tyne NE1 8ST, UK. m.panagiotidis@northumbria.ac.uk.
authors.forename: Mihalis I
authors.initials: MI
authors.lastname: Panayiotidis
authors.affiliation: Department of Pharmaceutical Sciences, College of Science & Technology, Biomanufacturing Research Institute and Technology Enterprise (BRITE), North Carolina Central University, Durham, NC 27707, USA. davidjkroll@gmail.com.
authors.forename: David J
authors.initials: DJ
authors.lastname: Kroll
authors.affiliation: Department of Molecular Biology and Genetics, Democritus University of Thrace, University Campus, Dragana, 68100 Alexandroupolis, Greece. apappa@mbg.duth.gr.
authors.forename: Aglaia
authors.initials: A
authors.lastname: Pappa
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004248:DNA (Cytosine-5-)-Methyltransferases; D000071221:Enhancer of Zeste Homolog 2 Protein / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D056284:Histone Deacetylase 1 / Q000096:biosynthesis; D056464:Histone Deacetylase 2 / Q000096:biosynthesis; D006657:Histones / Q000378:metabolism; D006801:Humans; D008297:Male; D008745:Methylation / Q000187:drug effects; D009363:Neoplasm Proteins; D010766:Phosphorylation / Q000187:drug effects; D063151:Polycomb Repressive Complex 2 / Q000096:biosynthesis* / Q000235:genetics; D011471:Prostatic Neoplasms / Q000188:drug therapy*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D000077385:Silybin; D012838:Silymarin / Q000494:pharmacology*; D014157:Transcription Factors
chemical_list: D000970:Antineoplastic Agents; D000975:Antioxidants; C491488:EED protein, human; D006657:Histones; D009363:Neoplasm Proteins; C430461:SUZ12 protein, human; D012838:Silymarin; D014157:Transcription Factors; D000077385:Silybin; D004248:DNA (Cytosine-5-)-Methyltransferases; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2; D051057:Proto-Oncogene Proteins c-akt; C110550:HDAC1 protein, human; C533423:HDAC2 protein, human; D056284:Histone Deacetylase 1; D056464:Histone Deacetylase 2
keywords: DNMT; EZH2; H3K27me3; HDAC; PRC2; epigenetics; histone methylation; prostate cancer; silibinin