Functional characterization of human thyroid tissue with immunohistochemistry

Immunohistochemistry provides insights in the expression of functional proteins and of their localization in normal thyroid tissue and in thyroid diseases. In hyperfunctional thyroid tissues, staining for sodium/iodide symporter (NIS), pendrin, thyroid peroxidase (TPO), and thyroglobulin (Tg) is increased. In hypofunctioning thyroid tissues, NIS staining is markedly decreased; in benign hypofunctioning adenomas, the expression of the other functional proteins is unmodified or slightly decreased, whereas their expression is profoundly decreased or absent in differentiated thyroid carcinoma

Gene expression signature discriminates sporadic from post-radiotherapy-induced thyroid tumors

Both external and internal exposure to ionizing radiation are strong risk factors for the development of thyroid tumors. Until now, the diagnosis of radiation-induced thyroid tumors has been deduced from a network of arguments taken together with the individual history of radiation exposure. Neither the histological features nor the genetic alterations observed in these tumors have been shown to be specific fingerprints of an exposure to radiation. The aim of our work is to define ionizing radiation-related molecular specificities in a series of secondary thyroid tumors developed in the radiation field of patients treated by radiotherapy. To identify molecular markers that could represent a radiation-induction signature, we compared 25K microarray transcriptome profiles of a learning set of 28 thyroid tumors, which comprised 14 follicular thyroid adenomas (FTA) and 14 papillary thyroid carcinomas (PTC), either sporadic or consecutive to external radiotherapy in childhood. We identified a signature composed of 322 genes which discriminates radiation-induced tumors (FTA and PTC) from their sporadic counterparts. The robustness of this signature was further confirmed by blind case-by-case classification of an independent set of 29 tumors (16 FTA and 13 PTC). After the histology code break by the clinicians, 26/29 tumors were well classified regarding tumor etiology, 1 was undetermined, and 2 were misclassified. Our results help shed light on radiation-induced thyroid carcinogenesis, since specific molecular pathways are deregulated in radiation-induced tumors

Increased expression of AP2 and Sp1 transcription factors in human thyroid tumors: a role in NIS expression regulation?

BACKGROUND: Sodium/iodide symporter (NIS) is a key protein in iodide transport by thyroid cells and this activity is a prerequisite for effective radioiodide treatment of thyroid cancer. In the majority of thyroid cancers, however, iodide uptake is reduced, probably as a result of decreased NIS protein expression. METHODS: To identify the mechanisms that negatively affect NIS expression in thyroid tumors, we performed electrophoresis mobility shift assays and immunoblot analysis of nuclear protein extracts from normal and tumoral thyroid tissues from 14 unrelated patients. RESULTS: Two proteins closely related to the transcription factors AP2 and Sp1 were identified in the nuclear extracts. Expression of both AP2 and Sp1 in nuclear extracts from thyroid tumors was significantly higher than that observed in corresponding normal tissues. CONCLUSION: These observations raise the possibility that NIS expression, and subsequently iodide transport, are reduced in thyroid tumors at least in part owing to alterations in the binding activity of AP2 and Sp1 transcription factors to NIS promoter

Hes1 Is Required for Appropriate Morphogenesis and Differentiation during Mouse Thyroid Gland Development

Notch signalling plays an important role in endocrine development, through its target gene Hes1. Hes1, a bHLH transcriptional repressor, influences progenitor cell proliferation and differentiation. Recently, Hes1 was shown to be expressed in the thyroid and regulate expression of the sodium iodide symporter (Nis). To investigate the role of Hes1 for thyroid development, we studied thyroid morphology and function in mice lacking Hes1. During normal mouse thyroid development, Hes1 was detected from E9.5 onwards in the median anlage, and at E11.5 in the ultimobranchial bodies. Hes1−/− mouse embryos had a significantly lower number of Nkx2-1-positive progenitor cells (p<0.05) at E9.5 and at E11.5. Moreover, Hes1−/− mouse embryos showed a significantly smaller total thyroid surface area (−40 to −60%) compared to wild type mice at all study time points (E9.5−E16.5). In both Hes1−/− and wild type mouse embryos, most Nkx2-1-positive thyroid cells expressed the cell cycle inhibitor p57 at E9.5 in correlation with low proliferation index. In Hes1−/− mouse embryos, fusion of the median anlage with the ultimobranchial bodies was delayed by 3 days (E16.5 vs. E13.5 in wild type mice). After fusion of thyroid anlages, hypoplastic Hes1−/− thyroids revealed a significantly decreased labelling area for T4 (−78%) and calcitonin (−65%) normalized to Nkx2-1 positive cells. Decreased T4-synthesis might be due to reduced Nis labelling area (−69%). These findings suggest a dual role of Hes1 during thyroid development: first, control of the number of both thyrocyte and C-cell progenitors, via a p57-independent mechanism; second, adequate differentiation and endocrine function of thyrocytes and C-cells

Tumor-Associated Macrophages (TAMs) Form an Interconnected Cellular Supportive Network in Anaplastic Thyroid Carcinoma

BACKGROUND: A relationship between the increased density of tumor-associated macrophages (TAMs) and decreased survival was recently reported in thyroid cancer patients. Among these tumors, anaplastic thyroid cancer (ATC) is one of the most aggressive solid tumors in humans. TAMs (type M2) have been recognized as promoting tumor growth. The purpose of our study was to analyze with immunohistochemistry the presence of TAMs in a series of 27 ATC. METHODOLOGY/PRINCIPAL FINDINGS: Several macrophages markers such as NADPH oxidase complex NOX2-p22phox, CD163 and CD 68 were used. Immunostainings showed that TAMs represent more than 50% of nucleated cells in all ATCs. Moreover, these markers allowed the identification of elongated thin ramified cytoplasmic extensions, bestowing a "microglia-like" appearance on these cells which we termed "Ramified TAMs" (RTAMs). In contrast, cancer cells were totally negative. Cellular stroma was highly simplified since apart from cancer cells and blood vessels, RTAMs were the only other cellular component. RTAMs were evenly distributed and intermingled with cancer cells, and were in direct contact with other RTAMs via their ramifications. Moreover, RTAMs displayed strong immunostaining for connexin Cx43. Long chains of interconnected RTAMs arose from perivascular clusters and were dispersed within the tumor parenchyma. When expressed, the glucose transporter Glut1 was found in RTAMs and blood vessels, but rarely in cancer cells. CONCLUSION: ATCs display a very dense network of interconnected RTAMs in direct contact with intermingled cancer cells. To our knowledge this is the first time that such a network is described in a malignant tumor. This network was found in all our studied cases and appeared specific to ATC, since it was not found in differentiated thyroid cancers specimens. Taken together, these results suggest that RTAMs network is directly related to the aggressiveness of the disease via metabolic and trophic functions which remain to be determined

Defects in iodide metabolism in thyroid cancer and implications for the follow-up and treatment of patients

The two major steps of iodine metabolism-uptake and organification - are altered in thyroid cancer tissues. Organification defects result in a rapid discharge of radioiodine from thyroid cells, a short effective half-life of iodine, and a low rate of thyroid hormone synthesis. These defects are mainly due to decreased expression of functional genes encoding the sodium-iodide symporter and thyroid peroxidase and could result in a low radiation dose to thyroid cancer cells. TSH stimulation that is achieved with injections of recombinant human TSH, or long-term withdrawal of thyroid hormone treatment increases iodine-131 uptake in two-thirds of patients with metastatic disease and increases thyroglobulin production in all patients with metastases, even in the absence of detectable uptake. Serum thyroglobulin determination obtained following TSH stimulation and neck ultrasonography is the most sensitive combination for the detection of small tumor foci. Radioiodine treatment is effective when a high radiation dose can be delivered (in patients with high uptake and retention of radioiodine) and when tumor foci are sensitive to the effects of radiation therapy (younger patients, with a well-differentiated tumor and/or with small metastases). The other patients rarely respond to radioiodine treatment, and when progression occurs, other treatment modalities should be considered. Novel strategies are currently being explored to restore iodine uptake in cancer cells that are unable to concentrate radioiodine

Current Concepts in the Management of Unilateral Recurrent Nerve Paralysis after Tyroid Surgery

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Transposition of the thyroid iodide uptake and organification system in nonthyroid tumor cells by adenoviral vector-mediated gene transfers

Radioactive iodine ( 131I) is routinely used for the treatment of differentiated thyroid cancers. Attempts have been made to enlarge this therapeutic strategy to nonthyroid tumors by coupling radioactive iodide administration with transfer of the sodium iodide symporter (NIS) gene into target cells, for example with an adenoviral vector (AdNIS). Although efficient iodide uptake was achieved in the tumors treated with AdNIS, no therapeutic effect could be observed with 131I, most probably because the iodide retention time in the target cells was short. To circumvent this problem, we propose to organify the iodide taken up, as it occurs in the thyroid. We constructed a recombinant adenovirus encoding the human thyroperoxidase (TPO) gene under the control of the cytomegalovirus early promoter (AdTPO). Infection of nonthyroid tumor cells with this virus led to production of an enzymatically active protein. A significant increase in iodide organification could be observed in cells coinfected with both AdNIS and AdTPO in the presence of exogenous hydrogen peroxide. However, the levels of iodide organification obtained were too low to significantly increase the iodide retention time in the target cells

Expression of pendrin and the Pendred Syndrome (PDS) gene in human thyroid tissues

The gene recently cloned that is responsible for the Pendred syndrome (PDS), an autosomal recessive disease characterized by goiter and congenital sensorineural deafness, is mainly expressed in the thyroid gland. Its product, designated pendrin, was shown to transport chloride and iodide. To investigate whether the PDS gene is altered during thyroid tumorigenesis, PDS gene expression and pendrin expression were studied using real-time kinetic quantitative PCR and antipeptide antibodies, respectively, in normal, benign, and malignant human thyroid tissues. The results were then compared to those observed for sodium/iodide symporter (NIS) expression. In normal tissue, pendrin is localized at the apical pole of thyrocytes, and this in contrast to the basolateral location of NIS. Immunostaining for pendrin was heterogeneous both inside and among follicles. In hyperfunctioning adenomas, the PDS messenger ribonucleic acid level was in the normal range, although immunohistochemical analysis showed strong staining in the majority of follicular cells. In hypofunctioning adenomas, mean PDS gene expression was similar to that detected in normal thyroid tissues, but pendrin immunostaining was highly variable. In thyroid carcinomas, PDS gene expression was dramatically decreased, and pendrin immunostaining was low and was positive only in rare tumor cells. This expression profile was similar to that observed for the NIS gene and its protein product. In conclusion, our study demonstrates that pendrin is located at the apical membrane of thyrocytes and that PDS gene expression is decreased in thyroid carcinomas