Effect of Radiation and Repeated Sub-Culturing on the Transforming Growth factor-β1 Signaling Pathway in FRTL-5 Cells

In Vivo. Jan-Feb 2015;29(1):5-15.


Background/aim: Fisher rat thyroid cells (FRTL-5) display increased proliferation, reduced follicularization and decreased thyroxin release with repeated sub-culturing. These changes occur earlier and more rapidly following exposure to ionizing radiation. We hypothesized that altered transforming growth factor-β1 (TGF-β1) signaling contributes to these differences.

Materials and methods: Assessments included FRTL-5 cell growth rate and quantification of TGF-β1 ligand and receptors. The levels and activity of Smads2, 3 and 4 were measured by western blotting and the ability of TGF-β1 to regulate cyclin A and plasminogen activator inhibitor type 1 (PAI-1) activity was assessed using transfection assays.

Results: TGF-β1 production increased after radiation but returned to control levels after repeated sub-culturing. There was no difference in TGF-β1 levels between un-irradiated cells at low versus high-passage number. TGF-β1 receptors and basal levels of Smads2, 3 and 4 remained unchanged. However, there were significant changes in cell proliferation, TGF-β1-mediated Smads2 and 3 activation and in TGF-β1's ability to regulate cyclin A and PAI-1 transcription in irradiated and repeatedly sub-cultured cells (p<0.05).

Conclusion: Collectively, these results support the conclusion that alterations in the TGF-β1 pathway contribute to phenotypic changes in FRTL-5 cells as a function of passage number and radiation.

Keywords: Transforming growth factor-beta 1 (TGF-β1); ionizing radiation; sub-culturing; thyroid cells.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cell Culture Techniques
  • Cell Line
  • Cell Proliferation / radiation effects
  • Cells, Cultured
  • Dose-Response Relationship, Radiation
  • Gamma Rays
  • Gene Expression
  • Phosphorylation
  • Radiation Dosage
  • Rats
  • Receptors, Transforming Growth Factor beta / genetics
  • Receptors, Transforming Growth Factor beta / metabolism
  • Signal Transduction / radiation effects*
  • Smad Proteins / metabolism
  • Thyroid Gland / cytology
  • Thyroid Gland / metabolism
  • Thyroid Gland / radiation effects
  • Transforming Growth Factor beta1 / metabolism*


  • Receptors, Transforming Growth Factor beta
  • Smad Proteins
  • Transforming Growth Factor beta1