Growth Factor Receptors Gene Expression and Akt Phosphorylation in Benign Human Thyroid Nodules are Unaffected by Chronic Thyrotropin Suppression

Abstract

Levothyroxine (L-T4)-based suppression of thyrotropin (TSH) secretion is widely used to prevent the growth of benign thyroid nodules, although the effectiveness of this approach has been demonstrated only in a subset of patients. In this study, we analyzed the in vivo effects of L-T4-mediated TSH suppression on elements of insulin/IGF-1-dependent growth-regulating pathways in tissues from patients with benign thyroid nodules. Nodular and non-nodular tissue specimens were collected from 63 patients undergoing thyroidectomy. 32 had received preoperative TSH suppressive therapy with TSH levels consistently below 0.5 mU/l (L-T4 group). TSH suppression had not been used in the other 31, and their TSH levels were normal (0.8–4 mU/l (control group). Quantitative RT-PCR was used to measure mRNA levels for TSH receptor, IGF1, IGF-1 receptor, insulin receptor, insulin receptor substrate 1 in nodular and non-nodular tissues from the 2 groups. Akt and phosphorylated Akt protein levels were detected by Western blot. Mean levels of mRNA for all genes tested were similar in the 2 groups, in both nodular and non-nodular tissues. The 2 groups were also similar in terms of phosphorylated Akt protein levels (measured by densitometric scan in 10 randomly selected nodules from each group). This is the first demonstration based on the study of human thyroid tissues that TSH suppression does not affect the expression of components of the insulin/IGF-1-dependent signaling pathways regulating thyrocyte growth. This may explain the lack of effectiveness of TSH-suppressive therapy in a substantial percentage of benign thyroid nodules.

Key words

TSH - IGF-1 receptor - insulin receptor

References

• 1 Castro MR, Caraballo PJ, Morris JC. Effectiveness of thyroid hormone suppressive therapy in benign solitary thyroid nodules: a meta-analysis.  J Clin Endocrinol Metab. 2002;  87 4154-4159
• 2 Filetti S, Durante C, Torlontano M. Nonsurgical approaches to the management of thyroid nodules.  Nat Clin Pract Endocrinol Metab. 2006;  2 384-394
• 3 Gharib H, Papini E, Paschke R. Thyroid nodules: a review of current guidelines, practices, and prospects.  Eur J Endocrinol. 2008;  159 493-505
• 4 Kimura T, Van Keymeulen A, Golstein J, Fusco A, Dumont JE, Roger P. Regulation of thyroid cell proliferation by TSH and other factors: a critical evaluation of in vitro models.  Endocr Rev. 2001;  22 631-656
• 5 Bruno R, Ferretti E, Tosi E, Arturi F, Giannasio P, Mattei T, Scipioni A, Presta I, Morisi R, Gulino A, Filetti S, Russo D. Modulation of thyroid-specific gene expression in normal and nodular human thyroid tissues from adults: An in vivo effect of thyrotropin.  J Clin Endocrinol Metab. 2005;  90 5692-5697
• 6 Hedinger C, Williams ED, Sobin LH. The WHO histological classification of thyroid tumors: a commentary on the second edition.  Cancer. 1989;  63 908-911
• 7 Livak KJ, Schmittgen TD. Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method.  Methods. 2001;  25 402-408
• 8 Russo D, Bulotta S, Bruno R, Arturi F, Giannasio P, Derwahl M, Bidart JM, Schlumberger M, Filetti S. Sodium/iodide symporter (NIS) and pendrin are expressed differently in hot and cold nodules of thyroid toxic multinodular goiter.  Eur J Endocrinol. 2001;  145 591-597
• 9 Cooper DS, Doherty GM, Haugen BR, Kloos RT, Lee SL, Mandel SJ, Mazzaferri EL, McIver B, Pacini F, Schlumberger M, Sherman SI, Steward DL, Tuttle RM. American Thyroid Association (ATA) Guidelines Taskforce on Thyroid Nodules and Differentiated Thyroid Cancer . Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer.  Thyroid. 2009;  19 1167-1214
• 10 Pacini F, Schlumberger M, Dralle H, Elisei R, Smit JW, Wiersinga W. European Thyroid Cancer Taskforce . European consensus for the management of patients with differentiated thyroid carcinoma of the follicular epithelium.  Eur J Endocrinol. 2006;  154 787-803
• 11 Derwahl M, Broecker M, Kraiem Z. Thyrotropin may not be the dominant growth factor in benign and malignant thyroid tumors.  J Clin Endocrinol Metab. 1999;  84 829-834
• 12 Dumont JE, Lamy F, Roger P, Maenhaut C. Physiological and pathological regulation of thyroid cell proliferation and differentiation by Thyrotropin and other factors.  Physiol Rev. 1992;  72 667-697
• 13 Frittitta L, Sciacca L, Catalfamo R, Ippolito A, Gangemi P, Pezzino V, Filetti S, Vigneri R. Functional insulin receptors are overexpressed in thyroid tumors: is this an early event in thyroid tumorigenesis?.  Cancer. 1999;  85 492-498
• 14 De Felice M, Postiglione MP, Di Lauro R. Thyrotropin receptor signaling in development and differentiation of the thyroid gland: insights from mouse models and human disease.  Endocrinology. 2004;  145 4062-4067
• 15 Shinohara M, Chung YJ, Saji M, Ringel MD. AKT in Thyroid Tumorigenesis and Progression.  Endocrinology. 2007;  148 942-947
• 16 De Vita G, Berlingieri MT, Visconti R, Castellone MD, Viglietto G, Baldassarre G, Zannini M, Bellacosa A, Tsichlis PN, Fusco A, Santoro M. Akt/protein kinase B promotes survival and hormone-independent proliferation of thyroid cells in the absence of dedifferentiated and transforming effects.  Cancer Res. 2000;  60 3916-3920
• 17 Saito J, Kohn AD, Roth RA, Hirai T, Kohn L, Ringel MD. Regulation of thyroid cell cycle progression and growth by insulin/IGF-1 via phosphotidylinositol 3 (OH)-kinase dependent AKT-mediated signaling.  Thyroid. 2001;  11 339-351
• 18 Weidinger C, Karger S, Krause K, Schierle K, Steinert F, Gimm O, Dralle H, Fuhrer D. Distinct Regulation of Intrinsic Apoptosis in Benign and Malignant Thyroid Tumours.  Horm Metab Res. 2010;  42 553-556
• 19 Mc Campbell AS, Broaddus RR, Loose DS, Davies PJA. Overexpression of the Insulin-Like Growth Factor I Receptor and activation of the AKT Pathway in Hyperplastic Endometrium.  Clin Cancer Res. 2006;  12 6373-6378
• 20 Russo D, Arturi F, Pontecorvi A, Filetti S. Genetic analysis in fine needle aspiration biopsy of the thyroid: a new tool for the clinic.  Trends Endocrinol Metab. 1999;  10 280-285

1 These authors contributed equally to the manuscript.

Correspondence