Effect of radiation and repeated sub-culturing on the transforming growth factor-β1 signaling pathway in FRTL-5 cells

• Published in: In vivo (Athens) Vol. 29; no. 1; pp. 5 - 15
• Main Authors: Burrell, Cheryl G, Gridley, Daila S, Ortloff, Leticia S, Charles, Shelton M, Green, Lora M
• Format: Journal Article
• Language: English
• Published: Greece 01-01-2015
• Subjects: 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; Transforming growth factor-beta 1 (TGF-β1); sub-culturing; thyroid cells; ionizing radiation
• ISSN: 1791-7549

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.
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.
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).
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.