Estrogen promotes growth of human thyroid tumor cells by different molecular mechanisms.
Thyroid tumors are about 3 times more frequent in females than in males. Epidemiological studies suggest that the use of estrogens may contribute to the pathogenesis of thyroid tumors. In a very recent study a direct growth stimulatory effect of 17beta-estradiol was demonstrated in FRTL-5 rat thyroid cells. In this work the presence of estrogen receptors alpha and beta in thyroid cells derived from human goiter nodules and in human thyroid carcinoma cell line HTC-TSHr was demonstrated. There was no difference between the expression levels of estrogen receptor alpha in males and females, but there was a significant increase in expression levels in response to 17beta-estradiol. Stimulation of benign and malignant thyroid cells with 17beta-estradiol resulted in an increased proliferation rate and an enhanced expression of cyclin D1 protein, which plays a key role in the regulation of G(1)/S transition in the cell cycle. In malignant tumor cells maximal cyclin D1 expression was observed after 3 h, whereas in benign cells the effect of 17beta-estradiol was delayed. ICI 182780, a pure estrogen antagonist, prevented the effects of 17beta-estradiol. In addition, 17beta-estradiol was found to modulate activation of mitogen-activated protein (MAP) kinase, whose activity is mainly regulated by growth factors in thyroid carcinoma cells. In response to 17beta-estradiol, both MAP kinase isozymes, extracellular signal-regulated protein kinases 1 and 2, were strongly phosphorylated in benign and malignant thyroid cells. Treatment of the cells with 17beta-estradiol and MAP kinase kinase 1 inhibitor, PD 098059, prevented the accumulation of cyclin D1 and estrogen-mediated mitogenesis. Our data indicate that 17beta-estradiol is a potent mitogen for benign and malignant thyroid tumor cells and that it exerts a growth-promoting effect not only by binding to nuclear estrogen receptors, but also by activation of the MAP kinase pathway.
Manole
D
D
Division of Endocrinology, Department of Medicine, St. Hedwig Hospital, 10115 Berlin, Germany.
Schildknecht
B
B
Gosnell
B
B
Adams
E
E
Derwahl
M
M
D000230:Adenocarcinoma / Q000737:chemistry / Q000378:metabolism / Q000473:pathology*; D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects*; D019938:Cyclin D1 / Q000032:analysis; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D006042:Goiter / Q000378:metabolism / Q000473:pathology; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D011960:Receptors, Estrogen / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013961:Thyroid Gland / Q000737:chemistry; D013964:Thyroid Neoplasms / Q000737:chemistry / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D011960:Receptors, Estrogen; D019938:Cyclin D1; D004958:Estradiol; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases