title: Integrative array-based approach identifies MZB1 as a frequently methylated putative tumor suppressor in hepatocellular carcinoma.
abstract: OBJECTIVE
  The aim of this study was the identification of novel tumor suppressor genes (TSG) silenced by DNA hypermethylation in hepatocellular carcinoma (HCC).
  
  
  METHODS
  We conducted integrative array-based approach for genome-wide screening of methylation targets using a methylated DNA immunoprecipitation-CpG island microarray and expression array in three universal hepatoma cell lines and normal liver tissue. Through detailed expression and functional analyses using hepatoma cell lines and primary HCC samples, we isolated novel TSGs for HCC.
  
  
  RESULTS
  A total of 642 genes were identified as methylated in three hepatoma cell lines but unmethylated in normal liver tissue, whereas 204 genes on autosomes were identified as genes unexpressed but restored after treatment with 5-aza-2'-deoxycytidine in these cell lines and expressed in normal tissue. Through the integration of results of the two-array analyses and further validation analyses of expression and methylation status in 17 cell lines and 30 primary tumors of hepatoma, we identified MZB1, marginal zone B and B1 cell-specific protein, encoding an endoplasmic reticulum protein, as a putative TSG frequently methylated within its CpG island in hepatoma. Among 162 patients with primary HCC, silencing of MZB1 protein was significantly and independently associated with a worse outcome. Restoration of MZB1 expression in hepatoma cells reduced cell proliferation in vitro and in vivo through G(1)-arrest.
  
  
  CONCLUSIONS
  These results suggest that methylation-mediated silencing of MZB1 expression leads to loss of its tumor-suppressive activity, which may be a factor in the hepatocarcinogenesis, and is a useful prognosticator in HCC.
authors.affiliation: Department of Molecular Cytogenetics, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Matsumura
authors.forename: Issei
authors.initials: I
authors.lastname: Imoto
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Kozaki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsui
authors.forename: Tomoki
authors.initials: T
authors.lastname: Muramatsu
authors.forename: Mayuko
authors.initials: M
authors.lastname: Furuta
authors.forename: Shinji
authors.initials: S
authors.lastname: Tanaka
authors.forename: Michiie
authors.initials: M
authors.lastname: Sakamoto
authors.forename: Shigeki
authors.initials: S
authors.lastname: Arii
authors.forename: Johji
authors.initials: J
authors.lastname: Inazawa
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism / Q000401:mortality; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D016207:Cytokines / Q000235:genetics*; D019175:DNA Methylation; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D055106:Genome-Wide Association Study; D006801:Humans; D053208:Kaplan-Meier Estimate; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000401:mortality; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D020411:Oligonucleotide Array Sequence Analysis; D016016:Proportional Hazards Models; D017422:Sequence Analysis, DNA; D025521:Tumor Suppressor Proteins / Q000235:genetics*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D016207:Cytokines; C434482:MZB1 protein, human; D025521:Tumor Suppressor Proteins