Transforming growth factor-ß1 is more expressed in thyroid follicular adenoma than in normal tissue

Abstract

It is well known that TSH is the main factor responsible for thyrocyte proliferation and growth. Recent studies have shown that other growth factors, including transforming growth factor-beta 1 (TGF-beta 1), have an important role in the control of thyrocyte proliferation and differentiation. The aim of the study was to evaluate the expression of the TGF-beta 1 gene in thyroid follicular adenoma (FA) by Northern analysis, and its protein localization by immunohistochemistry. Surgically removed thyroid tissue from 56 patients with thyroid FA was screened for the study. Normal thyroid tissue from 4 patients with papillary carcinoma was used as a control. Sixteen FA (8 with a "cold" and 8 with a "hot" scintiscan pattern) having homogeneous histological characteristics were subsequently selected. FA showed greater TGF-beta 1 gene expression than control tissue. There was not a statistically significant difference between "cold" and "hot" FA. Immunohistochemistry analysis showed that TGF-beta 1 was located in various histological structures of the adenomas (thyrocytes, endothelium, perinervium and connective tissue); on the other hand, perinodular and control tissue did not show appreciable TGF-beta 1 protein. Our data suggest that TGF-beta 1 may be involved in the pathogenesis of FA. The different TGF-beta 1 distribution in thyrocytes, endothelium, perinervium and connective tissue in FA suggests that TGF-beta 1 may be variably expressed during the natural history of FA. Since no significant difference in TGF-beta 1 gene expression between "hot" and "cold" adenomas was found, it appears that other factors are involved in their functional differentiation.

Acquired and naturally occurring resistance of thyroid follicular cells to the growth inhibitory action of transforming growth factor-β1 (TGF-β1)

“…Thirdly, the suggestion that the low iodine concentration in human goitres may decrease TGF-ßl and thereby cause goitre growth (Grubeck-Loebenstein et al 1989), stands in contrast to the prevailing view that low intrathyroidal iodine is a consequence, not a cause, of sporadic goitre growth and that the iodine content and handling may change from one follicle to the next (Schürch et al 1990, Aeschimann et al 1994). In addition, TGF-ß overexpression appears to be identical in 'hot' and 'cold' nodules (Morosini et al 1994). …”

Role of reduced expression of SMAD4 in papillary thyroid carcinoma

“…Several studies on surgical samples and on thyroid cell cultures have been performed showing the role of TGFb and other members of TGFb superfamily in thyroid proliferative diseases: benign cases (Morosini et al 1994) and malignant ones (Heldin et al 1999, Kimura et al 1999, Cerutti et al 2003. These data support the hypothesis that this growth factor is important in thyroid cell physiology, modulating thyroid functions and proliferation, and justify the need to study also the proteins involved in signaling from the cytoplasm to the nucleus.…”

Role of Transforming Growth Factor Beta in the Regulation of Thyroid Function and Growth

“…In other studies TGF-b1 was detected by immunohistochemistry and was found not only in thyrocytes but also in endothelial and connective tissue cells. TGF-b1 showed increased concentration in thyroid nodules, compared to the surrounding normal tissue (73).…”