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Early gene expression changes preceding thyroid hormone-induced involution of a thyrotrope tumor
William M Wood1, Virginia D Sarapura, Janet M Dowding
1Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. Wiliam.Wood@uchsc.edu
Endocrinology
|January 18, 2002
Summary
Thyroid hormone (TH) treatment shrinks thyrotropic tumors by altering gene expression. Key growth factors, receptors, and cell cycle genes are downregulated, while apoptosis-related genes are upregulated, leading to tumor growth arrest.
Area of Science:
- Endocrinology
- Molecular Biology
- Oncology
Background:
- Thyroid hormone (TH) is known to induce regression of thyrotropic tumors in hypothyroid models.
- Understanding the molecular mechanisms underlying this tumor shrinkage is crucial for therapeutic development.
Purpose of the Study:
- To investigate the early gene expression changes in thyrotropic tumors following thyroid hormone (TH) treatment.
- To identify specific genes and pathways involved in TH-induced tumor growth arrest and apoptosis.
Main Methods:
- Gene expression profiling using microarrays and Northern analysis.
- Assessment of changes in cell cycle regulators and apoptosis-related genes.
- Analysis of neuroendocrine and growth factor gene expression.
Main Results:
- TH treatment downregulated 40 genes and upregulated 7 genes, many neuroendocrine in nature.
- Key cell cycle regulators (e.g., cyclin-dependent kinase 2, cyclin A, p57, E2F1) were downregulated, while p15 and p19ARF were induced.
- Expression of growth factors (e.g., brain-derived neurotrophic factor) and their receptors (e.g., trkB) decreased, with some genes showing rapid TH response.
Conclusions:
- TH induces thyrotropic tumor involution through coordinated changes in gene expression.
- Repression of growth factors and cell cycle genes, alongside induction of apoptosis-related factors, contributes to TH-mediated growth arrest.
- Identified potential direct targets of TH, offering insights into therapeutic strategies for these tumors.