title: Transcriptional and post-translational regulation of Bim is essential for TGF-β and TNF-α-induced apoptosis of gastric cancer cell.
abstract: BACKGROUND
  Tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β) are well known as central signaling molecules in natural antitumor mechanisms. However, some cancer cells are resistant to TNF-α or TGF-β-induced death signaling. Herein, we investigated synergistic activities of TGF-β and TNF-α and molecular mechanisms involved in apoptosis of gastric cancer cells.
  
  
  METHODS
  SNU620, a human gastric carcinoma cell line was tested for cell viability by treatment of TGF-β in combination with TNF-α. Cell apoptosis, proliferation, caspase activation and gene expression were tested using flow cytometry, Western blot, MTT assay, luciferase assay and real-time qRT-PCR analysis. Knockdown of target genes were performed using lentiviral shRNA system.
  
  
  RESULTS
  TGF-β sensitizes SNU620 cells undergoing TNF-α-induced caspase-dependent apoptosis. TNF-α and TGF-β synergistically induced the degradation of poly(ADP-ribose) polymerase (PARP) and caspase cascade activation. We also confirmed that c-Jun NH2-terminal kinase (JNK) and Smad3 play critical roles in the apoptotic pathway. In addition, a pro-apoptotic protein Bim was critical for apoptosis and was regulated by TGF-β and TNF-α at the transcriptional and post-translational levels. Expression of Bim was induced at the transcriptional level by Smad3 while Bim protein stability was maintained by a JNK-mediated pathway.
  
  
  CONCLUSIONS
  By understanding the synergistic activation of TGF-β and TNF-α in apoptosis, we may have a chance to identify good therapeutic approaches for the treatment of cancers that are resistant to death signals.
  
  
  CONCLUSIONS
  Our results indicate that TGF-β and TNF-α act in concert to activate apoptosis in gastric cancer cell through crosstalk between Smad and JNK signaling pathways.
authors.affiliation: Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Incheon, Republic of Korea.
authors.forename: Huyen Trang
authors.initials: HT
authors.lastname: Ha Thi
authors.forename: Hee-Sun
authors.initials: HS
authors.lastname: Lim
authors.forename: Jooyoung
authors.initials: J
authors.lastname: Kim
authors.forename: Young-Mi
authors.initials: YM
authors.lastname: Kim
authors.forename: Hye-Youn
authors.initials: HY
authors.lastname: Kim
authors.forename: Suntaek
authors.initials: S
authors.lastname: Hong
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis* / Q000235:genetics; D000072224:Bcl-2-Like Protein 11; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D055550:Protein Stability / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; C497790:SMAD3 protein, human; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D048031:JNK Mitogen-Activated Protein Kinases; D020169:Caspases