Cooperation of histone deacetylase inhibitors SAHA and valproic acid in promoting sodium/iodide symporter expression and function in rat Leydig testicular carcinoma cells.

The presence of the sodium/iodide symporter (NIS) is the prerequisite for the use of the radioiodine in the treatment of thyroid cancer. Thus, stimulators of NIS expression and function are currently investigated in cellular models of various human malignancies, also including extrathyroid cancers. In this study, we analyzed the effects of the histone deacetylase inhibitors (HDACi), suberoylanilide hydroxamic acid (SAHA) and valproic acid (VPA), on NIS expression and function in rat Leydig testicular carcinoma cells (LC540). LC540 cells were exposed to SAHA 3 µM and VPA 3 mM (alone and in combination), and cell viability evaluated by MTT assay and cell counting, NIS mRNA and protein levels by using, respectively, real-time RT-PCR and western blotting. NIS function was evaluated by iodide uptake assay. We found that both HDACi were able to stimulate the transcription of NIS gene, but not its protein expression, while the association of SAHA and VPA increased both NIS transcript and protein levels, resulting in significant sixfold enhancement of radioiodine uptake capacity of LC540 cells. These data demonstrate the presence of an epigenetic control of NIS expression in Leydig tumor cells, suggesting the possibility to use the combination of these two HDACi for a radioiodine-based treatment of these malignancies.

Sodium iodide symporter expression and radioiodine distribution in extrathyroidal tissues.

The functional role of the sodium iodide symporter (NIS) in extrathyroidal tissues was investigated by examining its mRNA and protein expression, together with the evidence of radioiodine (131)I uptake in 302 patients who underwent (131)I total body scanning, following the administration of high doses of (131)I for a papillary or follicular thyroid carcinoma. By using a real-time kinetic quantitative RT-PCR and immunohistochemistry, the expression of NIS protein was detected mainly in secretory tissues. In parallel, 1311 uptake was evidenced in the majority of patients in the salivary glands (in 39%) and stomach (in 78%), but was found in breast in only 4 young female patients. These data demonstrate a strong correlation between the organ radioactivity distribution, as observed in vivo, and NIS protein expression. Interestingly, (131)I is rarely concentrated by mammary glands, even when large doses are administered. Moreover, a (131)I transfer in secretion fluids may represent a potential source of contamination responsible for false positive images and diagnostic pitfalls.

Absence of sodium/iodide symporter gene mutations in differentiated human thyroid carcinomas.

Decrease or loss of the sodium iodide (Na+/I-) symporter (NIS) activity influences the suitability of using radioiodine to detect and treat metastatic thyroid tissues. In previous studies, the presence of the NIS transcript, albeit at lower expression levels, has been shown in most thyroid differentiated carcinomas. In this study we searched for point mutations or other genetic alterations that may be responsible for an altered function of the NIS protein in tumors that still express NIS transcripts. Tumoral cDNAs derived from seven differentiated thyroid carcinomas (DTC), five papillary and two follicular, were analyzed by direct sequencing after polymerase chain reaction (PCR) amplification of the structural gene of the Na+/I- symporter. Neither mutations nor other genetic abnormalities were detected in any tumor sample examined. The data indicate that mutations or other genetic alterations of the NIS structural gene are not a major cause of the reduced iodide uptake in DTC.

A Val 677 activating mutation of the thyrotropin receptor in a Hürthle cell thyroid carcinoma associated with thyrotoxicosis.

Thyroid nodules presenting as hot at 131I-scintigraphy are usually benign follicular adenomas. We report a 42-year-old female patient with an autonomously functioning Hürthle cell thyroid carcinoma causing thyrotoxicosis. Genetic analysis of her thyroid tumoral DNA revealed a heterozygotic activating mutation of the thyrotropin receptor (TSHR) gene that was located downstream to all of the other genetic alterations currently identified, and is due to a base substitution at codon 677 (normal cytosine replaced by guanine, CTG for GTG causing leucine substitution by valine in the seventh transmembrane domain of the receptor). This mutation was detected in the tumor, but not in the leucocytes from the same patient. The Val 677-TSHR mutant showed constitutive activity, in terms of cyclic adenosine monophosphate (cAMP) production, when permanently transfected in Chinese hamster ovary (CHO) cells. Gsp and ras oncogenes and the p53 tumor suppressor gene were not present in the Hürthle cell cancer. The TSHR mutation in this Hürthle cell carcinoma may be responsible for maintaining differentiated thyroid function and hyperthyroidism.

Changes in sleep spindle activity of subject with chronic somatosensitive and sensorial deficits. Preliminary results.

We investigated the effects of the somatosensitive and sensory afferent inputs on the thalamic generators of sleep spindles (SS) in adult subjects affected by posterior funiculi lesions (five subjects), deafness (four subjects) or blindness (four subjects). The density, duration and frequency of SS, as well as the index of spindling, were analyzed during stage 2 NREM. The results show that the subjects with somatosensitive and sensorial lesions spent much more time on SS activity than the control group (eight subjects), and had a significantly increased density (< .0001), duration (< .0005) and index of spindling (< .0001). On the other hand, the frequency of spindling was little modified (< .05). Moreover, among the three groups of patients, those with somatosensitive deficits showed the greatest SS activity. In conclusion, our results suggest that the thalamic generators of SS are markedly modulated by peripheral inputs in man.