title: Effects of Tiam 1 on invasive capacity of gastric cancer cells in vitro and underlying mechanisms.
abstract: OBJECTIVE
  To investigate changes in the invasive capacity of gastric cancer cells in vitro after expression inhibition of T lymphoma invasion and metastasis inducing factor 1 (Tiam 1) and underlying mechanisms.
  
  
  METHODS
  Using adhesion selection, two subpopulations with high (MH) or low (ML) invasive capacity were separated from the human gastric cancer cell line MKN-45 (M0). Tiam 1 antisense oligodeoxynucleotide (ASODN) was transfected into MH cells with liposomes, and expression of Tiam 1 mRNA and protein was determined by RT-PCR and quantitative cellular-ELISA. Changes in the cytoskeleton, invasive capacity in vitro and expression of ras-related C3 botulinum toxin substrate 1 (Rac 1), integrin β1 and matrix metalloproteinase 2 (MMP 2) between Tiam 1 ASODN transfected MH cells and non-transfected cells were observed by HE staining, cytoskeletal protein staining, scanning electron microscopy, Boyden chamber tests and cyto-immunohistochemistry.
  
  
  RESULTS
  A positive correlation existed between the expression level of Tiam l mRNA or protein and the invasion capacity of gastric cancer cells. After ASODN treatment (0.43 μM for 48 h), Tiam 1 mRNA transcription and protein expression in MH cells were decreased by 80% and 24% respectively (P < 0.05), compared with untreated controls, while invasive capacity in vitro was suppressed by 60% (P < 0.05). Morphologic and ultrastructural observation also showed that ASODN-treated MH cells exhibited smooth surfaces with obviously reduced filopodia and microspikes, which resembled M0 and ML cells. Additionally, cytoskeletal distribution dramatically altered from disorder to regularity with reduced long filament-like structure, projections, pseudopodia on cell surface, and with decreased acitn-bodies in cytoplasm. After Tiam 1 ASODN treatment, the expression of Rac 1 and Integrin β1 in MH cells was not affected (P > 0.05), but that of MMP 2 in MH cells was significantly inhibited compared with untreated cells (P < 0.05).
  
  
  CONCLUSIONS
  Over-expression of Tiam-1 contributes to the invasive phenotype of gastric cancer cells. Inhibition of Tiam 1 expression could impair the invasive capacity of gastric cancer cells through modulating reconstruction of the cytoskeleton and regulating expression of MMP 2.
authors.affiliation: Department of General Surgery, Jinan Military General Hospital, Jinan, China. qingfengyunhe@sina.com
authors.forename: Jin-Ming
authors.initials: JM
authors.lastname: Zhu
authors.forename: Pei-Wu
authors.initials: PW
authors.lastname: Yu
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology*; D000704:Analysis of Variance; D045744:Cell Line, Tumor; D002465:Cell Movement; D003599:Cytoskeleton / Q000235:genetics / Q000473:pathology; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D009361:Neoplasm Invasiveness; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger / Q000378:metabolism; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology*; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; D014162:Transfection; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D019012:Integrin beta1; D016376:Oligonucleotides, Antisense; C107953:RAC1 protein, human; D012333:RNA, Messenger; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; C087334:TIAM1 protein, human; D020778:Matrix Metalloproteinase 2; D020830:rac1 GTP-Binding Protein