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FOXO1 controls thyroid cell proliferation in response to TSH and IGF-I and is involved in thyroid tumorigenesis

Miguel A Zaballos1, Pilar Santisteban

  • 1Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, 28029 Madrid, Spain.

Molecular Endocrinology (Baltimore, Md.)
|November 20, 2012
PubMed

Insights

Thyroid-stimulating hormone (TSH) and insulin/IGF-I signaling impact thyroid cell proliferation. Forkhead box O (FoxO)1 acts as a key regulator, with its reduced expression linked to thyroid tumor growth.

Area of Science:

  • Endocrinology
  • Molecular Biology
  • Oncology

Background:

  • Thyroid-stimulating hormone (TSH) and insulin/IGF-I synergistically promote thyroid cell proliferation via cAMP and phosphatidylinositol 3-kinase (PI3K) pathways.
  • The PI3K pathway's activation in thyroid malignancies highlights its significance.
  • Forkhead box O (FoxO)-1, a PI3K target, is crucial for cellular processes including proliferation and apoptosis.

Purpose of the Study:

  • To investigate the role of FoxO1 as an integrator of TSH and IGF-I signaling in thyroid cell proliferation.
  • To determine the expression patterns of FoxO1 in normal and cancerous thyroid tissues.
  • To elucidate the regulatory mechanisms of FoxO1 by TSH and IGF-I and its impact on thyroid cell growth.

Main Methods:

  • Quantitative analysis of FoxO1 mRNA and protein levels in differentiated thyroid cells and tumor cells.
  • Assessment of FoxO1 nuclear exclusion via Akt-dependent signaling pathways.
  • Manipulation of FoxO1 expression in thyroid cells to evaluate its effect on proliferation rates.

Main Results:

  • FoxO1 expression is significantly reduced in thyroid tumor cells compared to differentiated thyroid cells.
  • TSH/cAMP decreases FoxO1 levels through proteasome degradation, while TSH and IGF-I promote nuclear exclusion via Akt.
  • FoxO1 re-expression inhibits tumor cell proliferation, and its interference increases differentiated cell proliferation.

Conclusions:

  • FoxO1 plays a critical role in mediating the proliferative effects of TSH and IGF-I on thyroid cells.
  • Reduced FoxO1 expression is associated with the uncontrolled proliferation observed in thyroid tumors.
  • FoxO1 represents a potential therapeutic target for thyroid cancer treatment.

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