title: Somatostatin receptor 1, a novel EBV-associated CpG hypermethylated gene, contributes to the pathogenesis of EBV-associated gastric cancer.
abstract: BACKGROUND
  Somatostatin receptor 1 (SSTR1) was preferentially methylated in Epstein-Barr virus (EBV)-positive gastric cancer using promoter methylation array. We aimed to analyse the epigenetic alteration and biological function of SSTR1 in EBV-associated gastric cancer (EBVaGC).
  
  
  METHODS
  Promoter methylation was examined by combined bisulphite restriction analysis (COBRA) and pyrosequencing. The biological functions of SSTR1 were evaluated by loss- and gain-of-function assays.
  
  
  RESULTS
  Promoter hypermethylation of SSTR1 was detected in EBV-positive gastric cancer cell lines (AGS-EBV) with SSTR1 transcriptional silence, but not in EBV-negative gastric cancer cell lines with SSTR1 expression. Expression level of SSTR1 was restored in AGS-EBV by exposure to demethylating agent. Moreover, methylation level of SSTR1 was significantly higher in EBV-positive primary gastric cancers compared with EBV-negative gastric cancers (P=0.004). Knock-down of SSTR1 in gastric cancer cell lines (AGS and BGC823) increased cell proliferation and colony formation ability, and promoted G1 to S-phase transition, enhanced cell migration and invasive ability. In contrast, ectopic expression of SSTR1 in gastric cancer cell lines (MKN28 and MGC803) significantly suppressed cell growth in culture conditions and reduced tumour size in nude mice. The tumour suppressive effect of SSTR1 was associated with upregulation of cyclin-dependent kinase inhibitors (p16, p15, p27 and p21); downregulation of oncogenes (MYC and MDM2), key cell proliferation and pro-survival regulators (PI3KR1, AKT, BCL-XL and MET); and inhibition of the migration/invasion-related genes (integrins, MMP1 (matrix metallopeptidase 1), PLAUR (plasminogen activator urokinase receptor) and IL8 (interleukin 8)).
  
  
  CONCLUSIONS
  Somatostatin receptor 1 is a novel methylated gene driven by EBV infection in gastric cancer cells and acts as a potential tumour suppressor.
authors.affiliation: Department of Medicine and Therapeutics, Institute of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: J
authors.initials: J
authors.lastname: Zhao
authors.forename: Q
authors.initials: Q
authors.lastname: Liang
authors.forename: K-F
authors.initials: KF
authors.lastname: Cheung
authors.forename: W
authors.initials: W
authors.lastname: Kang
authors.forename: Y
authors.initials: Y
authors.lastname: Dong
authors.forename: R W-M
authors.initials: RW
authors.lastname: Lung
authors.forename: J H-M
authors.initials: JH
authors.lastname: Tong
authors.forename: K-F
authors.initials: KF
authors.lastname: To
authors.forename: J J Y
authors.initials: JJ
authors.lastname: Sung
authors.forename: J
authors.initials: J
authors.lastname: Yu
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002472:Cell Transformation, Viral / Q000235:genetics*; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D020031:Epstein-Barr Virus Infections / Q000150:complications*; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor / Q000502:physiology; D004854:Herpesvirus 4, Human / Q000502:physiology*; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D017481:Receptors, Somatostatin / Q000235:genetics*; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology / Q000821:virology*
chemical_list: D017481:Receptors, Somatostatin; C101130:somatostatin receptor type 1