title: Ornithine decarboxylase overexpression in mouse 10T1/2 fibroblasts: cellular transformation and invasion.
abstract: BACKGROUND
  Ornithine decarboxylase (ODC) plays a pivotal role in the synthesis of polyamines, a group of chemical compounds that are essential for cell growth. Recent reports have shown that ODC overexpression may be involved in malignant transformation of immortalized NIH 3T3 cells. We have demonstrated that ODC-overproducing mouse breast cancer cells are more invasive in vitro than control cells. However, little information is available concerning the relationship between ODC overexpression, tumor invasion, and metastasis and the signal transduction pathways involved in ODC-induced transformation and invasion.
  
  
  OBJECTIVE
  Our purpose was twofold: 1) to determine whether ODC overexpression is directly involved in tumor cell invasion and 2) to determine whether ODC overexpression induces mitogen-activated protein (MAP) kinase activities that are associated with cell growth and transformation.
  
  
  METHODS
  We transfected C3H clone 8 mouse 10T1/2 fibroblasts with an expression vector that carries a complementary DNA encoding rat ODC. Neomycin-resistant cells that overproduced ODC (4-6.5 times the control levels) were isolated. The transformed phenotype of these cells was determined by assessing colony formation and anchorage-independent growth in soft agar. The invasiveness of the cells was studied by means of an invasion assay that used Matrigel-coated filters in Boyden chambers. The MAP kinase activity of the cells was assayed by an in-gel kinase assay, using myelin basic protein as the substrate.
  
  
  RESULTS
  Overexpression of ODC induced not only cell transformation and anchorage-independent growth in soft agar but also invasiveness through a Matrigel-coated filter. The ODC-overproducing transfectants showed enhanced MAP kinase activity that paralleled the magnitude of cell invasiveness.
  
  
  CONCLUSIONS
  ODC plays a pivotal role not only in cell transformation but also in cancer cell invasion. ODC overexpression enhanced MAP kinase activity.
  
  
  CONCLUSIONS
  Our results demonstrate a connection between the polyamine/ODC and the MAP kinase signal transduction pathways and suggest that MAP kinase may play a pivotal role in ODC-induced cell transformation and invasion.
authors.affiliation: Department of Physiological Chemistry and Nutrition, Faculty of Medicine, The University of Tokyo, Bunkyo-ku, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kubota
authors.forename: H
authors.initials: H
authors.lastname: Kiyosawa
authors.forename: Y
authors.initials: Y
authors.lastname: Nomura
authors.forename: T
authors.initials: T
authors.lastname: Yamada
authors.forename: Y
authors.initials: Y
authors.lastname: Seyama
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D005260:Female; D005347:Fibroblasts / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic; D008325:Mammary Neoplasms, Experimental / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D051379:Mice; D009361:Neoplasm Invasiveness; D009955:Ornithine Decarboxylase / Q000096:biosynthesis*; D010641:Phenotype; D014162:Transfection; D015854:Up-Regulation
chemical_list: D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009955:Ornithine Decarboxylase