Thyroidal iodide transport and thyroid cancer

The master role of polarized NIS expression in regulating iodine metabolism in the human body

Objective

The aim of this study was to investigate how polarized sodium iodide symporter (NIS) expression may regulate iodide metabolism in vivo.

Materials and methods

Polarized NIS expression was analyzed in tissues that accumulate iodide by the use of immunohistochemistry and polyclonal antibody against the C-terminal end of human NIS (hNIS).

Results

Iodide absorption in the human intestine occurs via NIS expressed in the apical membrane. Iodide is secreted into the lumen of the stomach and salivary glands via NIS expressed in the basolateral membrane and then circulates back from the small intestine to the bloodstream via NIS expressed in the apical membrane.

Conclusion

Polarized NIS expression in the human body regulates intestinal-bloodstream recirculation of iodide, perhaps prolonging the availability of iodide in the bloodstream. This leads to more efficient iodide trapping by the thyroid gland. Understanding the regulation and manipulating gastrointestinal iodide recirculation could increase radioiodine availability during theranostic NIS applications.

Implication of different clinical and pathological variables in patients with differentiated thyroid cancer on successful ablation for 3700 MBq (131)I: a single Egyptian institutional experience over 14 years

OBJECTIVE

Is to investigate possible factors predicting success of ablation for 3700 MBq radioactive iodine 131 in patients with differentiated thyroid cancer (DTC) following near total thyroidectomy.

METHODS

This retrospective study enrolled 272 patients between 2000 and 2014. The success or failure of ablation was assessed 6 months after given the dose and our criteria for complete successful remnant ablation defined as: Negative (131)I whole body scan with no residual functioning thyroid tissue or distant functioning metastases and stimulated thyroglobulin (Tg) level less than 2 ng/ml. Different clinical and pathological factors, such as age, gender, tumor histology, grade and variants, size of primary malignant lesion, stage, and risk assessment according to the American (ATA) and European Thyroid Association (ETA) guidelines, associated pathology, tumor mutifocality, lymph node (LN) metastases and their number, invasiveness of the tumor (capsular invasion of the nodule, extra-thyroidal extension, and vascular invasion), baseline stimulated Tg level, and pre-ablative diagnostic scan were assessed.

RESULTS

There were 185 successful ablations (68 %). The baseline-stimulated Tg measured before the ablation was the only independent predictor of ablation success in multivariate analysis (P < 0.0001) with odds ratio (OR) of 2.64 (95 % CI: 1.54-4.54) and the optimal cutoff for this was 3.8 ng/mL. On the univariate analysis, LN metastases was predictor of ablation failure (P value = 0.03).

CONCLUSION

Baseline-stimulated Tg level is clinically important and had a significant predictive value for successful ablation; therefore, higher pre-ablation Tg should potentially be incorporated in the decision making for (131)I dosage or other treatment. In accordance with other studies, this is also applicable to cervical lymph nodal involvement and thyroid capsule invasion.

New therapies for dedifferentiated papillary thyroid cancer

The number of thyroid cancers is increasing. Standard treatment usually includes primary surgery, thyroid-stimulating hormone suppressive therapy, and ablation of the thyroid remnant with radioactive iodine (RAI). Despite the generally good prognosis of thyroid carcinoma, about 5% of patients will develop metastatic disease, which fails to respond to RAI, exhibiting a more aggressive behavior. The lack of specific, effective and well-tolerated drugs, the scarcity of data about the association of multi-targeting drugs, and the limited role of radioiodine for dedifferentiated thyroid cancer, call for further efforts in the field of new drugs development. Rearranged during transfection (RET)/papillary thyroid carcinoma gene rearrangements, BRAF (B-RAF proto-oncogene, serine/threonine kinase) gene mutations, RAS (rat sarcoma) mutations, and vascular endothelial growth factor receptor 2 angiogenesis pathways are some of the known pathways playing a crucial role in the development of thyroid cancer. Targeted novel compounds have been demonstrated to induce clinical responses and stabilization of disease. Sorafenib has been approved for differentiated thyroid cancer refractory to RAI.

Comparison between low and high radioactive iodine (131I) reablation dose in patients with papillary thyroid cancer

AIM

The aim of this study was to assess ablation outcome after a second ablation dose and compare the ablation rate after low and high reablation doses of iodine-131 ((131)I) after failure of the first ablation with 3700 MBq.

PATIENTS AND METHODS

The study included 81 patients with papillary thyroid cancer; they failed to achieve complete ablation after a first ablative dose of 3700 MBq. Their first follow-up (131)I whole-body scan carried out 6-9 months after ablation showed small residual functioning tissue in the thyroid bed, with no functioning metastases. This is associated with unsuppressed serum thyroglobulin level (Tg) higher than 2 ng/ml. The patients received a second ablation dose, which was low (1110 MBq) in 37 patients and high in the remaining 44 patients (2960 MBq in 36 patients and 3700 MBq in eight patients). A whole-body scan and Tg level assessment were carried out 6-9 months later. The criteria for complete ablation included absence of residual functioning thyroid tissue and a Tg level lower than 2 ng/ml.

RESULTS

The overall successful complete ablation rate after the second reablation dose was 75%. This was achieved in 27 of 37 patients (73%) who received a low reablation dose and in 34 of 44 patients (77%) who received a high reablation dose; no statistically significant difference was found between the two groups (P>0.05).

CONCLUSION

In patients with papillary thyroid cancer who failed to achieve complete ablation after the first ablation dose of 3700 MBq, the overall complete ablation rate after both a low and a high second (131)I dose was 75%, with no statistically significant difference in ablation rate between low (1110 MBq) and high (2960 and 3700 MBq) doses (73 and 77%, respectively).

Prognostic value of p27 in follicular thyroid carcinoma and its relation to radioactive iodine response: does it aid in the modification of risk stratification?

INTRODUCTION

Follicular thyroid carcinoma (FTC) is the second most common type of thyroid cancer. Genetic studies have demonstrated that the loss of expression and function of Cdk inhibitor p27 leads to the development of multiple-organ hyperplasia and malignancy, including thyroid carcinoma.

AIM OF WORK

(1) To assess the prognostic value of the quantitative expression of p27 in correlation with clinicopathologic prognostic indicators in FTC. (2) To explore its predictive value in the assessment of response to radioactive I-131 therapy in metastatic FTC patients.

MATERIALS AND METHODS

This retrospective study was conducted on 43 histopathologically confirmed FTC patients referred to the nuclear medicine department, National Cancer Institute, Cairo University between July 2001 and December 2010, for radioactive I-131 therapy. Clinicopathologic parameters, details of radioactive I-131 therapy and its outcome, and a serial follow-up serum thyroglobulin levels and I-131 whole body scan were obtained from their medical records. Quantitative expression of p27 using immunostaining was analyzed using paraffin blocks of thyroidectomy specimens in all patients.

RESULTS

With respect to clinicopathologic characteristics, p27 expression was found to be significantly lower in patients with vascular invasion (P=0.024) and in patients with an advanced-stage disease (P=0.048). A significant difference was detected between the risk stratification and the quantitative expression of p27. A statistically significant difference was obtained with respect to immunohistochemical expression of p27 between the metastatic and nonmetastatic patients as well as age, growth characteristics, tumor size, vascular invasion, and extrathyroidal extension. Despite the observed trend in patients with a low p27 expression, to have a worse response to iodine therapy, and a poor overall survival, the point of statistical significance could not be reached.

CONCLUSIONS

In this preliminary study, p27 quantitative expression appeared to provide a complementary valuable predictor with other prognostic variables for risk stratification in FTC patients. Response to I-131 therapy in FTC in relation to p27 expression should be thoroughly investigated including large-scale studies and more homogenous risk groups.

The PARP inhibitor PJ34 modifies proliferation, NIS expression and epigenetic marks in thyroid cancer cell lines

Since PARP-1 is supposed to be part of a multimeric repressor of sodium iodide symporter (NIS) expression, in this study the effect of the PARP inhibitor PJ34 on several properties of thyroid cancer cell lines was investigated. In TPC1, BCPAP, FRO, WRO cell lines PJ34 induced a strong increase in NIS mRNA levels. In BCPAP and TPC1 cells also significant increase of radio-iodine uptake was induced. Accordingly, in transfection experiments performed in TPC1 cells, treatment with PJ34 increased NIS promoter activity without affecting PARP-1 binding to the promoter sequence. We also investigated the epigenetic status of NIS promoter after PJ34 treatment in TPC1 cell line: in addition to an increase of histone modification activation marks (H3K9K14ac, H3K4me3), surprisingly we observed also an increase of H3K27me3, a classical repressive mark. Our data demonstrate that in various thyroid cancer cell lines PARP inhibition increases NIS gene expression through a particular modulation of transcriptional regulatory mechanisms. Therefore, we suggest that PARP inhibitors may deserve future investigations as tools for medical treatment of thyroid cancer.

Human TSH receptor ligands as pharmacological probes with potential clinical application

The biologic role of thyroid-stimulating hormone (TSH; thyrotropin) as an activator (agonist) of the TSH receptor (TSHR) in the hypothalamic-pituitary-thyroid axis is well known and activation of TSHR by recombinant human TSH is used clinically in patients with thyroid cancer. TSHR ligands other than TSH could be used to probe TSHR biology in thyroidal and extrathyroidal tissues, and potentially be employed in patients. A number of different TSHR ligands have been reported, including TSH analogs, antibodies and small-molecule, drug-like compounds. In this review, we will provide an update on all these classes of TSHR agonists and antagonists but place emphasis on small-molecule ligands.

The importance of sodium/iodide symporter (NIS) for thyroid cancer management

The thyroid gland has the ability to uptake and concentrate iodide, which is a fundamental step in thyroid hormone biosynthesis. Radioiodine has been used as a diagnostic and therapeutic tool for several years. However, the studies related to the mechanisms of iodide transport were only possible after the cloning of the gene that encodes the sodium/iodide symporter (NIS). The studies about the regulation of NIS expression and the possibility of gene therapy with the aim of transferring NIS gene to cells that normally do not express the symporter have also become possible. In the majority of hypofunctioning thyroid nodules, both benign and malignant, NIS gene expression is maintained, but NIS protein is retained in the intracellular compartment. The expression of NIS in non-thyroid tumoral cells in vivo has been possible through the transfer of NIS gene under the control of tissue-specific promoters. Apart from its therapeutic use, NIS has also been used for the localization of metastases by scintigraphy or PET-scan with 124I. In conclusion, NIS gene cloning led to an important development in the field of thyroid pathophysiology, and has also been fundamental to extend the use of radioiodine for the management of non-thyroid tumors.