title: Depletion of OLFM4 gene inhibits cell growth and increases sensitization to hydrogen peroxide and tumor necrosis factor-alpha induced-apoptosis in gastric cancer cells.
abstract: BACKGROUND
  Human olfactomedin 4 (OLFM4) gene is a secreted glycoprotein more commonly known as the anti-apoptotic molecule GW112. OLFM4 is found to be frequently up-regulated in many types of human tumors including gastric cancer and it was believed to play significant role in the progression of gastric cancer. Although the function of OLFM4 has been indicated in many studies, recent evidence strongly suggests a cell or tissue type-dependent role of OLFM4 in cell growth and apoptosis. The aim of this study is to examine the role of gastric cancer-specific expression of OLFM4 in cell growth and apoptosis resistance.
  
  
  METHODS
  OLFM4 expression was eliminated by RNA interference in SGC-7901 and MKN45 cells. Cell proliferation, anchorage-independent growth, cell cycle and apoptosis were characterized in vitro. Tumorigenicity was analyzed in vivo. The apoptosis and caspase-3 activation in response to hydrogen peroxide (H2O2) or tumor necrosis factor-alpha (TNF α) were assessed in the presence or absence of caspase inhibitor Z-VAD-fmk.
  
  
  RESULTS
  The elimination of OLFM4 protein by RNA interference in SGC-7901 and MKN45 cells significantly inhibits tumorigenicity both in vitro and in vivo by induction of cell G1 arrest (all P < 0.01). OLFM4 knockdown did not trigger obvious cell apoptosis but increased H2O2 or TNF α-induced apoptosis and caspase-3 activity (all P < 0.01). Treatment of Z-VAD-fmk attenuated caspase-3 activity and significantly reversed the H(2)O(2) or TNF α-induced apoptosis in OLFM4 knockdown cells (all P < 0.01).
  
  
  CONCLUSIONS
  Our study suggests that depletion of OLFM4 significantly inhibits tumorigenicity of the gastric cancer SGC-7901 and MKN45 cells. Blocking OLFM4 expression can sensitize gastric cancer cells to H2O2 or TNF α treatment by increasing caspase-3 dependent apoptosis. A combination strategy based on OLFM4 inhibition and anticancer drugs treatment may provide therapeutic potential in gastric cancer intervention.
authors.affiliation: Center for Clinical Molecular Medicine, Ministry of Education Key Laboratory of Child Development and Disorders, Chongqing International Science and Technology Cooperation Center for Child Development and Disorders, Children's Hospital, Chongqing Medical University, Chongqing 400014, China.
authors.forename: Rui-hua
authors.initials: RH
authors.lastname: Liu
authors.forename: Mei-hua
authors.initials: MH
authors.lastname: Yang
authors.forename: Hua
authors.initials: H
authors.lastname: Xiang
authors.forename: Li-ming
authors.initials: LM
authors.lastname: Bao
authors.forename: Hua-an
authors.initials: HA
authors.lastname: Yang
authors.forename: Li-wen
authors.initials: LW
authors.lastname: Yue
authors.forename: Xue
authors.initials: X
authors.lastname: Jiang
authors.forename: Na
authors.initials: N
authors.lastname: Ang
authors.forename: Li-ya
authors.initials: LY
authors.lastname: Wu
authors.forename: Yi
authors.initials: Y
authors.lastname: Huang
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D016193:G1 Phase / Q000187:drug effects / Q000235:genetics; D017353:Gene Deletion; D016179:Granulocyte Colony-Stimulating Factor / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D016877:Oxidants / Q000494:pharmacology*; D034622:RNA Interference; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; C454127:OLFM4 protein, human; D016877:Oxidants; D014409:Tumor Necrosis Factor-alpha; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D016179:Granulocyte Colony-Stimulating Factor; D006861:Hydrogen Peroxide; D020169:Caspases