title: Sphingosine induces apoptosis in MKN-28 human gastric cancer cells in an SDK-dependent manner.
abstract: OBJECTIVE
  Evidence has pointed to the role of sphingosine in cellular differentiation, cell growth, and apoptosis. The present study investigated sphingosine-induced apoptosis in human gastric cancer cells.
  
  
  METHODS
  Well differentiated MKN-28 and poorly differentiated MKN-45 human gastric cancer cells were cultured. MTT assay, TUNEL staining, Western blotting, and assay of caspase-3, -8, and -9 activities were carried out in cells transfected with and without the siRNA to silence the protein kinase C (PKC)-δ-targeted gene.
  
  
  RESULTS
  Sphingosine induced apoptosis in MKN-28 cells, with the potential much greater than for MKN-45 cells. Transfection with the siRNA to silence the PKC-δ-targeted gene (PKC-δ siRNA) into MKN-28 cells significantly reduced presence of sphingosine-dependent protein kinase (SDK) in association with reduced PKC-δ expression. Sphingosine-induced apoptosis in MKN-28 cells was prevented by transfecting with the PKC-δ siRNA. Sphingosine promoted SDK production from PKC-δ and increased phosphorylated 14-3-3 protein for MKN-28 cells, but such effects were not found with MKN-45 cells. Moreover, sphingosine perturbed mitochondrial membrane potentials and activated caspase-3 and caspase-9 in MKN-28 cells, which were also inhibited by transfecting with the PKC-δ siRNA.
  
  
  CONCLUSIONS
  The results of the present study indicate that sphingosine induces apoptosis in well differentiated MKN-28 human gastric cancer cells by increasing SDK production from PKC-δ, to phosphorylate 14-3- 3 protein, thereby causing disruption of mitochondrial membrane potentials and activating caspase-9 followed by the effector caspase-3.
authors.affiliation: Division of Bioinformation, Department of Physiology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya Department of Thoracic Oncology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kanno
authors.forename: Takaaki
authors.initials: T
authors.lastname: Nishimoto
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Fujita
authors.forename: Akinobu
authors.initials: A
authors.lastname: Gotoh
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Nishizaki
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D005753:Gastric Mucosa / Q000378:metabolism; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000378:metabolism; D013110:Sphingosine / Q000378:metabolism*; D013270:Stomach / Q000166:cytology / Q000473:pathology; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000473:pathology; D000099157:Sphingosine Kinase
chemical_list: D048948:14-3-3 Proteins; D053148:Caspase 3; D053453:Caspase 9; D017853:Phosphotransferases (Alcohol Group Acceptor); D051745:Protein Kinase C-delta; D013110:Sphingosine; D000099157:Sphingosine Kinase