Induction of the metastatic phenotype by transfection of a benign rat mammary epithelial cell line with the gene for p9Ka, a rat calcium-binding protein, but not with the oncogene EJ-ras-1

Oncogene. 1993 Apr;8(4):999-1008.


The rat mammary epithelial cell line, Rama 37, yields benign, non-metastasizing adenomatous tumours in syngeneic Wistar-Furth rats. Transfection of this line with a drug resistance plasmid containing both the gene for resistance to Geneticin (neo) and the gene for p9Ka (pSV2neo-p9Ka), a rat calcium-binding protein, or with a similar plasmid containing neo and the oncogene EJ-ras-1 (pSV2neo-ras) yields drug-resistant transformants that express high levels of the p9Ka or EJ-ras-1 mRNAs and proteins. These transfected cells all produce tumours when injected at subcutaneous sites with a shorter median latent period than the tumours produced by the parental untransfected Rama 37 cells in syngeneic hosts. Cells transfected with pSV2neo-p9Ka yield a higher incidence of tumours than untransfected Rama 37 cells, many of which metastasize to lungs and/or lymph nodes in syngeneic rats. However, cells transfected with pSV2-neo-ras or pSV2neo plasmid alone yield tumours that fail to metastasize. Immunofluorescent studies suggest an association of p9Ka with the cytoskeleton, as depicted by F-actin staining with the reagent phalloidin. It is suggested that the transfection of copies of the gene for the rat calcium-binding protein p9Ka can enhance the tumorigenic potential and induce the metastatic phenotype in this rat mammary model, whereas transfection of control plasmid DNA or the oncogene EJ-ras-1 fails to induce the metastatic phenotype, although EJ-ras-1 transfectants, like those containing p9Ka, possess increased growth properties in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium-Binding Proteins / genetics*
  • Calcium-Binding Proteins / metabolism
  • Calcium-Binding Proteins / physiology*
  • Cell Line
  • Epithelial Cells
  • Gene Expression
  • Genes
  • Genes, ras*
  • In Vitro Techniques
  • Mammary Glands, Animal / cytology
  • Neoplasm Metastasis*
  • Neoplasms, Experimental / pathology*
  • Neoplasms, Experimental / physiopathology
  • Proto-Oncogene Proteins p21(ras) / genetics*
  • Proto-Oncogene Proteins p21(ras) / metabolism
  • RNA, Messenger / genetics
  • Rats
  • Recombinant Proteins
  • S100 Calcium-Binding Protein A4
  • S100 Proteins*
  • Transfection


  • Calcium-Binding Proteins
  • RNA, Messenger
  • Recombinant Proteins
  • S100 Calcium-Binding Protein A4
  • S100 Proteins
  • S100a4 protein, rat
  • Proto-Oncogene Proteins p21(ras)