Hypothyroidism enhances tumor invasiveness and metastasis development

Area of Science:

• Endocrinology
• Oncology
• Molecular Biology

Background:

• Thyroid hormone receptors (TRs) loss may aid tumor development.
• The link between thyroid hormone levels and human cancer remains controversial.
• Hypothyroidism is inconsistently associated with liver and breast cancer risk.

Purpose of the Study:

• To investigate the impact of hypothyroidism on tumor progression and metastasis.
• To examine the role of thyroid hormone receptors (TRs) in cancer development.
• To clarify the relationship between thyroid status and cancer aggressiveness.

Main Methods:

• Xenografts of human hepatocarcinoma and breast cancer cells (parental and TRbeta1-expressing) were used.
• Cells were injected into euthyroid and hypothyroid nude mice.
• Tumor invasiveness, metastasis, and cellular phenotype were analyzed.

Main Results:

• TRbeta1-expressing cells showed repressed invasiveness and metastasis in euthyroid mice.
• In hypothyroid hosts, tumors exhibited increased mesenchymal phenotype, invasiveness, and metastasis.
• Hypothyroidism enhanced aggressiveness and metastasis, even in parental cells lacking TRs.
• Tumor growth was retarded in hypothyroid hosts, but invasiveness increased.

Conclusions:

• Host hypothyroidism modulates tumor progression and metastasis via stromal cell changes, independent of tumor cell TRs.
• Differential effects of hypothyroidism on tumor growth and invasiveness explain conflicting human cancer reports.
• Thyroid status significantly influences cancer aggressiveness and metastatic potential.