[Growth and invasion in differentiated thyroid carcinoma. Function of different growth factors]

Aggressiveness of follicular (FTC) and papillary thyroid cancer (PTC) varies widely. Tumorigenesis is associated with an imbalance of growth-promoting and growth-constraining factors. We investigated the effects of thyrotropin (TSH), epidermal growth factor (EGF) and transforming growth factor beta 1 (TGF-beta 1) on invasion and growth of 3 FTC- and 2 PTC-cell lines. Invasion (penetration through an 8 microns pore membrane, covered by Matrigel) and growth were measured using the MTT-method. EGF (10 ng/ml) and TSH in low concentrations (1 mU/ml) stimulated invasion and growth of FTC and PTC, whereas TGF-beta 1 (10 ng/ml) and TSH in high concentrations (100 mU/ml) were inhibiting. The parental cell line FTC133 was considerably more responsive to all growth factors than the metastatic clones. Invasion of FTC133 was enhanced by 42% (EGF) and 21% (TSH), invasion of FTC236 by 8% (EGF and TSH). Conversely, invasion of FTC133 was inhibited by 32% (TGF-beta 1) and 21% (TSH), invasion of FTC236 by 18% (TGF-beta 1) and 11% (TSH). TSH, EGF and TGF-beta 1 have an important impact on differentiated thyroid cancer cells and metastases may have developed by escaping from the normal control of growth factors.