TGF-beta 1 inhibits the cell proliferation stimulated by IGF-I by blocking the tyrosine phosphorylation of 175kDa substrate

Endocr Res. 1996 Aug;22(3):277-87. doi: 10.3109/07435809609030512.


TGF-beta strongly inhibits the mitogenic effect of growth factors such as insulin-like growth-I (IGF-I) on thyroid follicular cells. To study the mechanism of this inhibiting action, the effect of TGF-beta 1 on tyrosine phosphorylation of 175kDa substrate induced by IGF-I was investigated in FRTL-5 thyroid epithelial cells. After treatment with TGF-beta 1, tyrosine phosphorylation of 175kDa protein induced by IGF-I was inhibited in parallel with the degree of the inhibition of cell proliferation. However, TGF-beta 1 had no effect on tyrosine phosphorylation of 120kDa substrate. These results suggest that TGF-beta 1 blocks the mitogenic signal of IGF-I by inhibiting the tyrosine phosphorylation of 175kDa substrate in FRTL-5 cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Division / drug effects*
  • Cell Line
  • Cell Size / drug effects
  • DNA / biosynthesis
  • Insulin-Like Growth Factor I / pharmacology*
  • Phosphorylation / drug effects
  • Phosphotyrosine / analysis
  • Protein-Tyrosine Kinases / antagonists & inhibitors*
  • Rats
  • Thyroid Gland / drug effects
  • Thyroid Gland / metabolism
  • Transforming Growth Factor beta / pharmacology*


  • Transforming Growth Factor beta
  • Phosphotyrosine
  • Insulin-Like Growth Factor I
  • DNA
  • Protein-Tyrosine Kinases