title: Inhibition of GSK 3β activity is associated with excessive EZH2 expression and enhanced tumour invasion in nasopharyngeal carcinoma.
abstract: BACKGROUND
  Enhancer of zeste homolog 2 (EZH2) has been shown to contribute to tumour development and/or progression. However, the signalling pathway underlying the regulation of EZH2 in nasopharyngeal carcinoma (NPC) remains unclear. Since EZH2 contains the putative Glycogen synthase kinase 3 beta (GSK3β) phosphorylation motif ADHWDSKNVSCKNC (591) and may act as a possible substrate of GSK-3β, it is possible that inactivation of GSK3β may lead to excessive EZH2 expression in NPC.
  
  
  METHODS
  We first examined the expression of EZH2 and phosphorylated GSK3β (p-GSK3β) by immunohistochemical staining in NPC samples. Then, we evaluated the interaction of GSK3β and EZH2 using immunoprecipitation and immune blot. Moreover, we determined the effect of inhibition of GSK3β activity on EZH2 expression and tumor invasiveness in NPC cell lines in vitro. Finally, we evaluated the invasive properties of NPC cells after knocking down EZH2 expression with EZH2 siRNA.
  
  
  RESULTS
  We found that expression of EZH2 correlated with phosphorylated GSK3β (p-GSK3β) at Ser 9 (an inactivated form of GSK3β) in human nasopharyngeal carcinoma (NPC) samples. We also provided evidence that GSK3β is able to interact with EZH2 using immunoprecipitation and immune blot. Furthermore, we found that inhibition of GSK3β activity can lead to upregulation of EZH2 in NPC cell lines in vitro, with enhanced local invasiveness. By knocking down EZH2 expression with EZH2 siRNA, we found that these invasive properties were EZH2 dependent.
  
  
  CONCLUSIONS
  Our findings indicate that GSK3β inactivation may account for EZH2 overexpression and subsequent tumour progression, and this mechanism might be a potential target for NPC therapy.
authors.affiliation: Allergy and Cancer Center, Otorhinolarygology Hospital, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
authors.forename: Renqiang
authors.initials: R
authors.lastname: Ma
authors.forename: Yi
authors.initials: Y
authors.lastname: Wei
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Huang
authors.forename: Ran
authors.initials: R
authors.lastname: Fu
authors.forename: Xi
authors.initials: X
authors.lastname: Luo
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Zhu
authors.forename: Wenbin
authors.initials: W
authors.lastname: Lei
authors.forename: Jugao
authors.initials: J
authors.lastname: Fang
authors.forename: Huabin
authors.initials: H
authors.lastname: Li
authors.forename: Weiping
authors.initials: W
authors.lastname: Wen
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000704:Analysis of Variance; D002277:Carcinoma; D000071221:Enhancer of Zeste Homolog 2 Protein; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors* / Q000235:genetics; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000503:physiopathology*; D009361:Neoplasm Invasiveness / Q000503:physiopathology*; D010766:Phosphorylation; D063151:Polycomb Repressive Complex 2 / Q000378:metabolism*; D034622:RNA Interference; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D018709:Statistics, Nonparametric
chemical_list: C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3