title: Enhancer of zeste homolog 2 (EZH2) promotes progression of cholangiocarcinoma cells by regulating cell cycle and apoptosis.
abstract: BACKGROUND
  Enhancer of zeste homolog 2 (EZH2) is the catalytic subunit of the polycomb repressive complex 2 (PRC2). When present in PRC2, EZH2 catalyzes trimethylation on lysine 27 residue of histone H3, resulting in epigenetic silencing of gene expression and cancer progression. We investigated the expression and function of EZH2 in intrahepatic and extrahepatic cholangiocarcinoma (ICC and ECC).
  
  
  METHODS
  The influence of EZH2 on cell growth and apoptosis was assessed by knockdown experiments. Target gene of EZH2 was searched by quantitative RT-PCR. Clinical significance of EZH2 in 86 cholangiocarcinoma patients (45 ICC and 41 ECC) who underwent curative surgery was examined by immunohistochemistry.
  
  
  RESULTS
  In vitro analysis, knockdown of EZH2 reduced cell growth, induced G1 arrest, and induced apoptosis, as confirmed by Annexin V staining and increased sub-G1 populations in cholangiocarcinoma cell lines. The expression levels of p16 (INK4a) and p27 (KIP1) were remarkably increased by knockdown of EZH2 in these cell lines. In immunohistochemical study, EZH2 upregulation correlated with tumor diameter (p = 0.0103) in ICC, lymph node metastasis (p = 0.0292) in ECC, and Ki67 index in both ICC (p = 0.0364) and ECC (p = 0.0017). In addition, EZH2 expression was correlated with poor prognosis in both ICC (p = 0.0447) and ECC (p = 0.0227).
  
  
  CONCLUSIONS
  The current study demonstrated relationships between EZH2 expression and acceleration of the cell cycle and antiapoptosis, and poor prognosis in cholangiocarcinoma. These results suggest that EZH2 may represent a potential therapeutic target in patients with cholangiocarcinoma.
authors.affiliation: Department of Gastroenterological Surgery, Graduate School of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Okabe
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Sakamoto
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Hayashi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Hashimoto
authors.forename: Naomi
authors.initials: N
authors.lastname: Yokoyama
authors.forename: Keita
authors.initials: K
authors.lastname: Sakamoto
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Kuroki
authors.forename: Kosuke
authors.initials: K
authors.lastname: Mima
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Nitta
authors.forename: Katsunori
authors.initials: K
authors.lastname: Imai
authors.forename: Akira
authors.initials: A
authors.lastname: Chikamoto
authors.forename: Masayuki
authors.initials: M
authors.lastname: Watanabe
authors.forename: Toru
authors.initials: T
authors.lastname: Beppu
authors.forename: Hideo
authors.initials: H
authors.lastname: Baba
mesh_terms: D000368:Aged; D017209:Apoptosis; D001650:Bile Duct Neoplasms / Q000378:metabolism / Q000401:mortality / Q000556:secondary*; D017734:Bile Ducts, Extrahepatic; D001653:Bile Ducts, Intrahepatic; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle; D049109:Cell Proliferation; D018281:Cholangiocarcinoma / Q000378:metabolism / Q000401:mortality / Q000473:pathology*; D018450:Disease Progression; D000071221:Enhancer of Zeste Homolog 2 Protein; D005260:Female; D005434:Flow Cytometry; D005500:Follow-Up Studies; D006801:Humans; D007124:Immunoenzyme Techniques; D008207:Lymphatic Metastasis; D008297:Male; D009367:Neoplasm Staging; D063151:Polycomb Repressive Complex 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011379:Prognosis; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015996:Survival Rate; D014407:Tumor Cells, Cultured
chemical_list: D014408:Biomarkers, Tumor; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2