Induction of expression of osteopontin (OPN; secreted phosphoprotein) in metastatic, ras-transformed NIH 3T3 cells

Anticancer Res. Jan-Feb 1992;12(1):43-7.

Abstract

We have previously shown that transfection of NIH 3T3 cells with the T24 H-ras oncogene converts the cells to a tumorigenic and metastatic phenotype, in proportion to levels of ras expression. We hypothesize that ras-induced increases in malignancy occur via altered expression of various genes. We have identified OPN (osteopontin; also known as Secreted Phosphoprotein, 2ar, Eta-1, and transformation-associated phosphoprotein) as a ras-induced gene in these cells. We report here that expression of OPN RNA and secretion of OPN protein are increased in a series of ras-transformed NIH 3T3 cells, in proportion to levels of expression of ras. Detection of secreted OPN protein was facilitated by a barium citrate precipitation procedure. Although the function of this protein in tumor cells is not known, OPN contains a conserved GRGDS (glycine-arginine-glycine-aspartic acid-serine) amino acid sequence, which may function as a cell attachment site for this protein. We speculate that increased expression of OPN contributes to the increased malignancy of ras oncogene-transformed NIH 3T3 cells, perhaps by alterations in either adhesive properties or integrin-mediated signal transduction pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • Cell Transformation, Neoplastic / metabolism*
  • Chemical Precipitation
  • Citrates
  • Citric Acid
  • Genes, ras*
  • Mice
  • Neoplasm Metastasis
  • Osteopontin
  • Phosphoproteins / analysis*
  • RNA, Messenger / analysis
  • Sialoglycoproteins / analysis*
  • Sialoglycoproteins / genetics

Substances

  • Citrates
  • Phosphoproteins
  • RNA, Messenger
  • Sialoglycoproteins
  • Spp1 protein, mouse
  • Osteopontin
  • Citric Acid