OBJECTIVE: The expression of two recently identified iodide transporters, namely the sodium/iodide symporter (NIS) and pendrin, the product of the gene responsible for the Pendred syndrome (PDS), was studied in a series of various extra-thyroidal human tissues, and especially in those known to concentrate iodide. METHODS: To this end, we used real-time kinetic quantitative PCR to detect NIS and PDS transcripts and immunohistochemistry for the analysis of their protein products. RESULTS: NIS gene and protein expression was detected in most tissues known to concentrate iodine, and particularly in salivary glands and stomach. In contrast, PDS gene expression was restricted to a few tissues, such as kidney and Sertoli cells. Interestingly, in kidney, pendrin immunostaining was detected at the apical pole of epithelial cells of the thick ascending limb of the Henle's loop and of the distal convoluted tubule. CONCLUSION: This study provides new insights on the localization and expression of two genes involved in iodide transport and emphasizes the interest of combining real-time quantitative PCR and immunohistochemistry for the comparison of gene and protein expression in tissues.
L Lacroix, C Mian, B Caillou, M Talbot, S Filetti, M Schlumberger and JM Bidart
L Vayre, JC Sabourin, B Caillou, M Ducreux, M Schlumberger and JM Bidart
131Iodine concentration has been described in several extra-thyroidal tissues. Recent evidence has shown that iodine uptake is achieved by the recently cloned human Na(+)/I(-) symporter (hNIS) gene. However, conflicting results were observed in the expression of hNIS transcripts in extra-thyroidal tissues. In order to document further the distribution of hNIS, we investigated its expression using an immunohistochemical method, based on a polyclonal antibody raised against a synthetic peptide. Various extra-thyroidal tissues were examined, particularly from the digestive tract. Our results confirm that the salivary glands and the stomach express hNIS protein significantly. In contrast, hNIS was undetectable in the colon but the rectal mucosa, which has never been examined, exhibited positive immunohistochemical staining. Other digestive tissues, including the oesophagus, small intestine and appendix, were negative. Weak staining was observed in the mammary gland, indicating that hNIS is expressed in this tissue. The pancreas, skin, ovaries, spleen and kidney showed no positive immunostaining.
L Lacroix, C Mian, T Barrier, M Talbot, B Caillou, M Schlumberger and JM Bidart
OBJECTIVE: Genetic alterations involving the thyroid transcription factor PAX8 and the peroxisome proliferator-activated receptor gamma 1 (PPARgamma1) genes have been described in thyroid neoplasms. We investigated in a series of thyroid samples, including 14 normal, 13 hyperfunctioning tissues, 26 follicular adenomas, 21 follicular and 41 papillary carcinomas, both the frequency of the PAX8-PPARgamma1 rearrangement and the expression of the PAX8 and PPARgamma transcripts. METHODS: Using RT-PCR followed by sequencing PCR products, PAX8-PPARgamma1 translocation was not detected in benign tissues nor in papillary carcinomas and was detected in 4 (19%) of 21 follicular carcinomas and in one (4%) of 26 follicular adenomas. RESULTS: Specific real-time quantitative RT-PCR (Q RT-PCR) methods detected high levels of PPARgamma transcripts in follicular carcinomas presenting the rearrangement. Interestingly, the level of PPARgamma transcripts was significantly decreased in papillary carcinomas in comparison with those found in benign adenomas and follicular carcinomas. Finally, PAX8 gene expression was decreased in both papillary and follicular thyroid carcinomas, and in these tumors to the same extent in the presence or absence of the rearrangement. These alterations in both PPARgamma and PAX8 gene expression may explain the poorly differentiated histotype of follicular carcinomas harboring the translocation.Immunohistochemistry showed that nuclear PPARgamma staining was weak in normal tissues, adenomas, papillary carcinomas and in some follicular carcinomas, and strong in the follicular carcinomas positive for the PAX8-PPARgamma1 translocation, but also in some follicular tumors in which no translocation could be evidenced. CONCLUSION: These observations confirm that the PAX8-PPARgamma1 translocation characterizes a subset of thyroid follicular carcinomas but is not a specific marker of carcinoma and that its frequency is lower than that initially reported. Finally, immunohistochemistry is not a reliable method for the specific detection of the translocation, that can be specifically evidenced by Q RT-PCR.
S Filetti, JM Bidart, F Arturi, B Caillou, D Russo and M Schlumberger
The recent cloning of the gene encoding the sodium/iodide symporter (NIS) has enabled better characterization of the molecular mechanisms underlying iodide transport, thus opening the way to clarifying its role in thyroid diseases. Several studies, at both the mRNA and the protein expression levels, have demonstrated that TSH, the primary regulator of iodide uptake, upregulates NIS gene expression and NIS protein abundance, both in vitro and in vivo. However, other factors, including iodide, retinoic acid, transforming growth factor-beta, interleukin-1alpha and tumour necrosis factor alpha, may participate in the regulation of NIS expression. Investigation of NIS mRNA expression in different thyroid tissues has revealed increased levels of expression in Graves' disease and toxic adenomas, whereas a reduction or loss of NIS transcript was detected in differentiated thyroid carcinomas, despite the expression of other specific thyroid markers. NIS mRNA was also detected in non-thyroid tissues able to concentrate radioiodine, including salivary glands, stomach, thymus and breast. The production of specific antibodies against the NIS has facilitated study of the expression of the symporter protein. Despite of the presence of high levels of human (h)NIS mRNA, normal thyroid glands exhibit a heterogeneous expression of NIS protein, limited to the basolateral membrane of the thyrocytes. By immunohistochemistry, staining of hNIS protein was stronger in Graves' and toxic adenomas and reduced in thyroid carcinomas. Measurement of iodide uptake by thyroid cancer cells is the cornerstone of the follow-up and treatment of patients with thyroid cancer. However, radioiodide uptake is found only in about 67% of patients with persistent or recurrent disease. Several studies have demonstrated a decrease in or a loss of NIS expression in primary human thyroid carcinomas, and immunohistochemical studies have confirmed this considerably decreased expression of the NIS protein in thyroid cancer tissues, suggesting that the low expression of NIS may represent an early abnormality in the pathway of thyroid cell transformation, rather than being a consequence of cancer progression. The relationship between radioiodine uptake and NIS expression by thyroid cancer cells require further study. New strategies, based on manipulation of NIS expression, to obtain NIS gene reactivation or for use as NIS gene therapy in the treatment of radiosensitive cancer, are also being investigated.
S Leboulleux, E Baudin, J Young, B Caillou, V Lazar, G Pellegriti, M Ducreux, G Schaison and M Schlumberger
Neuroendocrine tumors (NET) of the thyroid gland are rare. Apart from medullary thyroid carcinoma (MTC), metastases of gastroenteropancreatic (GEP) NET may also occur. Features of six patients (five men, one female: age range, 39-67 years) with thyroid metastases from a GEP-NET are described. Thyroid metastases were bilateral in all patients and were associated with enlarged neck lymph nodes in five. In four cases, the thyroid tumor was either the first sign of the disease (n = 2) or was an isolated site of recurrence (n = 2). The tumors were well (n = 3) or poorly differentiated (n = 3). Five tumors for which the primary site could be determined corresponded to foregut-derived tumors (3 lungs, 1 thymus and 1 pancreatic NET). One tumor demonstrated calcitonin (CT) production as shown by immunohistochemistry and elevated plasma CT levels. However, the disease history and the clinical features strongly favored a metastasizing GEP-NET. No tumoral RET proto-oncogene mutation was found in this patient. The differential diagnosis between metastatic GEP-NET and MTC is crucial because prognosis, work-up, and treatment differ greatly.
S Leboulleux, D Deandreis, A Al Ghuzlan, A Aupérin, D Goéré, C Dromain, D Elias, B Caillou, J P Travagli, T De Baere, J Lumbroso, J Young, M Schlumberger and E Baudin
Peritoneal carcinomatosis (PC) is a rare site of distant metastases in patients with adrenocortical cancer (ACC). One preliminary study suggests an increased risk of PC after laparoscopic adrenalectomy (LA) for ACC.
The objective of the study was to search for risk factors of PC including surgical approach.
This was a retrospective cohort study conducted in an institutional practice.
Sixty-four consecutive patients with ACC seen at our institution between 2003 and 2009 were included. Mean tumor size was 132 mm. Patients had stage I disease in 2 cases, stage II disease in 32 cases, stage III disease in 7 cases, stage IV disease in 21 cases, and unknown stage disease in 2 cases. Surgery was open in 58 cases and laparoscopic in 6 cases.
The main outcome was the risk factors of PC.
PC occurred in 18 (28%) patients. It was present at initial diagnosis in three cases and occurred during follow-up in 15 cases. The only risk factor of PC occurring during follow-up was the surgical approach with a 4-year rate of PC of 67% (95% confidence interval (CI), 30–90%) for LA and 27% (95% CI, 15–44%) for open adrenalectomy (P=0.016). Neither tumor size, stage, functional status, completeness of surgery, nor plasma level of op'DDD was associated with the occurrence of PC.
We found an increased risk of PC after LA for ACC. Whether this is related to an inappropriate surgical approach or to insufficient experience in ACC surgery should be clarified by a prospective program.