Intronic elements in the Na+/I- symporter gene (NIS) interact with retinoic acid receptors and mediate initiation of transcription

The Role of Iodine for Thyroid Function in Lactating Women and Infants

Iodine is a micronutrient needed for the production of thyroid hormones, which regulate metabolism, growth, and development. Iodine deficiency or excess may alter the thyroid hormone synthesis. The potential effects on infant development depend on the degree, timing, and duration of exposure. The iodine requirement is particularly high during infancy because of elevated thyroid hormone turnover. Breastfed infants rely on iodine provided by human milk, but the iodine concentration in breast milk is determined by the maternal iodine intake. Diets in many countries cannot provide sufficient iodine, and deficiency is prevented by iodine fortification of salt. However, the coverage of iodized salt varies between countries. Epidemiological data suggest large differences in the iodine intake in lactating women, infants, and toddlers worldwide, ranging from deficient to excessive intake. In this review, we provide an overview of the current knowledge and recent advances in the understanding of iodine nutrition and its association with thyroid function in lactating women, infants, and toddlers. We discuss risk factors for iodine malnutrition and the impact of targeted intervention strategies on these vulnerable population groups. We highlight the importance of appropriate definitions of optimal iodine nutrition and the need for more data assessing the risk of mild iodine deficiency for thyroid disorders during the first 2 years in life.

The Transcription Factor Elf3 Is Essential for a Successful Mesenchymal to Epithelial Transition

The epithelial to mesenchymal transition (EMT) and the mesenchymal to epithelial transition (MET) are two critical biological processes that are involved in both physiological events such as embryogenesis and development and also pathological events such as tumorigenesis. They present with dramatic changes in cellular morphology and gene expression exhibiting acute changes in E-cadherin expression. Despite the comprehensive understanding of EMT, the regulation of MET is far from being understood. To find novel regulators of MET, we hypothesized that such factors would correlate with Cdh1 expression. Bioinformatics examination of several expression profiles suggested Elf3 as a strong candidate. Depletion of Elf3 at the onset of MET severely impaired the progression to the epithelial state. This MET defect was explained, in part, by the absence of E-cadherin at the plasma membrane. Moreover, during MET, ELF3 interacts with the Grhl3 promoter and activates its expression. Our findings present novel insights into the regulation of MET and reveal ELF3 as an indispensable guardian of the epithelial state. A better understanding of MET will, eventually, lead to better management of metastatic cancers.

Decreased All- trans Retinoic Acid-Induced Expression of Sodium-Iodide Transporter in Mammary Epithelial Cells Caused by Conjugated Linoleic Acid Isomers

Expression of sodium-iodide symporter (NIS) is stimulated by sterol-regulatory-element-binding transcription factors (SREBFs) in mammary epithelial MCF-7 cells. Because conjugated linoleic acid (CLA) isomers have been shown to inhibit transcriptional activity of SREBFs in the mammary gland, the hypothesis was tested that CLA isomers inhibit NIS expression induced by all- trans retinoic acid (ATRA) in MCF-7 cells through inhibiting SREBF activity. c9t11-CLA and t10c12-CLA decreased ATRA-induced NIS-mRNA expression from 1.00 (ATRA alone) to 0.80 ± 0.12 (200 μM c9t11-CLA, P < 0.05) and 0.62 ± 0.10 (200 μM t10c12-CLA, P < 0.05), NIS-protein expression from 1.00 (ATRA alone) to 0.77 ± 0.08 (200 μM c9t11-CLA, P < 0.05) and 0.63 ± 0.05 (200 μM t10c12-CLA, P < 0.05), and NIS-promoter activity from 1.00 (ATRA alone) to 0.74 ± 0.13 (200 μM c9t11-CLA, P < 0.05) and 0.76 ± 0.13 (200 μM t10c12-CLA, P < 0.05); however, c9t11-CLA and t10c12-CLA increased the mRNA levels of SREBF isoforms and their target genes. In contrast, the mRNA expression of peroxisome-proliferator-activated receptor γ (PPARG) was strongly induced by ATRA alone but decreased by CLA isomers from 1.00 (ATRA alone) to 0.80 ± 0.06 (200 μM c9t11-CLA, P < 0.05) and 0.86 ± 0.06 (200 μM t10c12-CLA, P < 0.05). Overexpression of PPARγ in MCF-7 cells increased basal NIS-promoter activity, and treatment with the PPARγ ligand troglitazone stimulated ATRA-induced NIS-promoter activity. In conclusion, the results suggest that CLA isomers exert their effect on the expression of NIS by decreasing PPARG expression in MCF-7 cells.

Tumor suppressor protein p53 exerts negative transcriptional regulation on human sodium iodide symporter gene expression in breast cancer

PURPOSE

Aberrant expression of human sodium iodide symporter (NIS) in breast cancer (BC) is well documented but the transcription factors (TF) regulating its aberrant expression is poorly known. We identify the presence of three p53 binding sites on the human NIS promoter sequence by conducting genome-wide TF analysis, and further investigate their regulatory role.

METHODS

The differences in transcription and translation were measured by real-time PCR, luciferase reporter assay, site-directed mutagenesis, in vivo optical imaging, and chromatin immunoprecipitation. The relation of NIS and p53 in clinical samples was judged by TCGA data analysis and immunohistochemistry.

RESULTS

Overexpression of wild-type p53 as a transgene or pharmacological activation by doxorubicin drug treatment shows significant suppression of NIS transcription in multiple BC cell types which also results in lowered NIS protein content and cellular iodide intake. NIS repression by activated p53 is further confirmed by non-invasive bioluminescence imaging in live cell and orthotropic tumor model. Abrogation of p53-binding sites by directional mutagenesis confirms reversal of transcriptional activity in wild-type p53-positive BC cells. We also observe direct binding of p53 to these sites on the human NIS promoter. Importantly, TCGA data analysis of NIS and p53 co-expression registers an inverse relationship between the two candidates.

CONCLUSION

Our data for the first time highlight the role of p53 as a negative regulator of functional NIS expression in BC, where the latter is a potential targeted radioiodine therapy candidate. Thus, the study provides an important insight into prospective clinical application of this approach that may significantly impact the patient with mutant versus wild-type p53 profile.

The Thyroid Na+/I- Symporter: Molecular Characterization and Genomic Regulation

Iodide (I-) is an essential constituent of the thyroid hormones triiodothyronine (T₃) and thyroxine (T₄), and the iodide concentrating mechanism of the thyroid gland is essential for the synthesis of these hormones. In addition, differential uptake of iodine isotopes (radioiodine) is a key modality for the diagnosis and therapy of thyroid cancer. The sodium dependent iodide transport activity of the thyroid gland is mainly attributed to the functional expression of the Na+/I- Symporter (NIS) localized at the basolateral membrane of thyrocytes. In this paper, we review and summarize current data on molecular characterization, on structure and function of NIS protein, as well as on the transcriptional regulation of NIS encoding gene in the thyroid gland. We also propose that a better and more precise understanding of NIS gene regulation at the molecular level in both healthy and malignant thyroid cells may lead to the identification of small molecule candidates. These could then be translated into clinical practice for better induction and more effective modulation of radioiodine uptake in dedifferentiated thyroid cancer cells and in their distant metastatic lesions.

Sterol regulatory element-binding proteins are regulators of the sodium/iodide symporter in mammary epithelial cells

The sodium/iodide symporter (NIS), which is essential for iodide concentration in the thyroid, is reported to be transcriptionally regulated by sterol regulatory element-binding proteins (SREBP) in rat FRTL-5 thyrocytes. The SREBP are strongly activated after parturition and throughout lactation in the mammary gland of cattle and are important for mammary epithelial cell synthesis of milk lipids. In this study, we tested the hypothesis that the NIS gene is regulated also by SREBP in mammary epithelial cells, in which NIS is functionally expressed during lactation. Regulation of NIS expression and iodide uptake was investigated by means of inhibition, silencing, and overexpression of SREBP and by reporter gene and DNA-binding assays. As a mammary epithelial cell model, the human MCF-7 cell line, a breast adenocarcinoma cell line, which shows inducible expression of NIS by all-trans retinoic acid (ATRA), and unlike bovine mammary epithelial cells, is widely used to investigate the regulation of mammary gland NIS and NIS-specific iodide uptake, was used. Inhibition of SREBP maturation by treatment with 25-hydroxycholesterol (5 µM) for 48h reduced ATRA (1 µM)-induced mRNA concentration of NIS and iodide uptake in MCF-7 cells by approximately 20%. Knockdown of SREBP-1c and SREBP-2 by RNA interference decreased the mRNA and protein concentration of NIS by 30 to 50% 48h after initiating knockdown, whereas overexpression of nuclear SREBP (nSREBP)-1c and nSREBP-2 increased the expression of NIS in MCF-7 cells by 45 to 60%, respectively, 48h after initiating overexpression. Reporter gene experiments with varying length of NIS promoter reporter constructs revealed that the NIS 5'-flanking region is activated by nSREBP-1c and nSREBP-2 approximately 1.5- and 4.5-fold, respectively, and activation involves a SREBP-binding motif (SRE) at -38 relative to the transcription start site of the NIS gene. Gel shift assays using oligonucleotides spanning either the wild-type or the mutated SRE at -38 of the NIS 5'-flanking region showed that in vitro-translated nSREBP-1c and nSREBP-2 bind only the wild-type but not the mutated SRE at -38 of NIS. Collectively, the present results from cell culture experiments with human mammary epithelial MCF-7 cells and from genetic studies show for the first time that the NIS gene and iodide uptake are regulated by SREBP in cultured human mammary epithelial cells. Future studies are necessary to clarify if the regulation of NIS expression and iodide uptake by SREBP also applies to the lactating bovine mammary epithelium.

Iodide transport and breast cancer

Breast cancer is the second most common cancer worldwide and the leading cause of cancer death in women, with incidence rates that continue to rise. The heterogeneity of the disease makes breast cancer exceptionally difficult to treat, particularly for those patients with triple-negative disease. To address the therapeutic complexity of these tumours, new strategies for diagnosis and treatment are urgently required. The ability of lactating and malignant breast cells to uptake and transport iodide has led to the hypothesis that radioiodide therapy could be a potentially viable treatment for many breast cancer patients. Understanding how iodide is transported, and the factors regulating the expression and function of the proteins responsible for iodide transport, is critical for translating this hypothesis into reality. This review covers the three known iodide transporters - the sodium iodide symporter, pendrin and the sodium-coupled monocarboxylate transporter - and their role in iodide transport in breast cells, along with efforts to manipulate them to increase the potential for radioiodide therapy as a treatment for breast cancer.

Upregulation of sodium iodide symporter (NIS) protein expression by an innate immunity component: Promising potential for targeting radiosensitive retinoblastoma

Retinoblastoma (RB), a malignant tumour of the eye arising from developing retina, is the most frequent primary intraocular malignancy of childhood. Its primary management with chemotherapy involves combination regimen of etoposide, vincristine and carboplatin and intra vitreal chemotherapy using melphalan when vitreous seeds develop. Radiotherapy is another effective mode in treating RB. We recently explored the notion if radiotherapy in RB can be mediated via Sodium Iodide Symporter (NIS), an intrinsic membrane glycoprotein which is a key regulator of iodide access to thyroid gland. Its expression has been exploited successfully for diagnostic imaging and molecular radionuclide-based therapy of thyroid cancer. We determined that NIS is expressed endogenously in RB tumour tissues, and in retinoblastoma cell lines Y79 and Weri-Rb-1, and therefore made an attempt to enhance the endogenously low expression of NIS protein in both Y79 and Weri-Rb-1 cells. Here we report about the potential of bovine lactoferrin (bLf) which is a known chemo preventive and emerging safe anti-cancer bio drug, as well as a natural transcriptional activator of genes, to enhance the endogenous expression of NIS in Y79 and Weri-Rb-1 cells. Real time PCR revealed that both cell lines express mRNA of lactoferrin receptors while flow cytometry and confocal microscopy showed the cells efficiently internalize bLf which upregulates NIS expression. These findings highlight an important step that could be taken towards the development of less harmful approaches for the treatment of RB by employing natural supplement bLf (with its clinically proven safe profile), and warrants further studies in future, focussing on enhancing NIS expression in RB cells and NIS functional assays in these cells.

Sodium iodide symporter (NIS) in extrathyroidal malignancies: focus on breast and urological cancer

Background

Expression and function of sodium iodide symporter (NIS) is requisite for efficient iodide transport in thyrocytes, and its presence in cancer cells allows the use of radioiodine as a diagnostic and therapeutic tool in thyroid neoplasia. Discovery of NIS expression in extrathyroidal tissues, including transformed cells, has opened a novel field of research regarding NIS-expressing extrathyroidal neoplasia. Indeed, expression of NIS may be used as a biomarker for diagnostic, prognostic, and therapeutic purposes. Moreover, stimulation of endogenous NIS expression may permit the radioiodine treatment of extrathyroidal lesions by concentrating this radioisotope.

Results

This review describes recent findings in NIS research in extrathyroidal malignancies, focusing on breast and urological cancer, emphasizing the most relevant developments that may have clinical impact.

Conclusions

Given the recent progress in the study of NIS regulation as molecular basis for new therapeutic approaches in extrathyroidal cancers, particular attention is given to studies regarding the relationship between NIS and clinical-pathological aspects of the tumors and the regulation of NIS expression in the experimental models.

The sodium/iodide symporter NIS is a transcriptional target of the p53-family members in liver cancer cells

Thyroid iodide accumulation via the sodium/iodide symporter (NIS; SLC5A5) has been the basis for the longtime use of radio-iodide in the diagnosis and treatment of thyroid cancers. NIS is also expressed, but poorly functional, in some non-thyroid human cancers. In particular, it is much more strongly expressed in cholangiocarcinoma (CCA) and hepatocellular carcinoma (HCC) cell lines than in primary human hepatocytes (PHH). The transcription factors and signaling pathways that control NIS overexpression in these cancers is largely unknown. We identified two putative regulatory clusters of p53-responsive elements (p53REs) in the NIS core promoter, and investigated the regulation of NIS transcription by p53-family members in liver cancer cells. NIS promoter activity and endogenous NIS mRNA expression are stimulated by exogenously expressed p53-family members and significantly reduced by member-specific siRNAs. Chromatin immunoprecipitation analysis shows that the p53–REs clusters in the NIS promoter are differentially occupied by the p53-family members to regulate basal and DNA damage-induced NIS transcription. Doxorubicin strongly induces p53 and p73 binding to the NIS promoter, leading to an increased expression of endogenous NIS mRNA and protein in HCC and CCA cells, but not in PHH. Silencing NIS expression reduced doxorubicin-induced apoptosis in HCC cells, pointing to a possible role of a p53-family-dependent expression of NIS in apoptotic cell death. Altogether, these results indicate that the NIS gene is a direct target of the p53 family and suggests that the modulation of NIS by DNA-damaging agents is potentially exploitable to boost NIS upregulation in vivo.

Sterol regulatory element-binding proteins are regulators of the NIS gene in thyroid cells

The uptake of iodide into the thyroid, an essential step in thyroid hormone synthesis, is an active process mediated by the sodium-iodide symporter (NIS). Despite its strong dependence on TSH, the master regulator of the thyroid, the NIS gene was also reported to be regulated by non-TSH signaling pathways. In the present study we provide evidence that the rat NIS gene is subject to regulation by sterol regulatory element-binding proteins (SREBPs), which were initially identified as master transcriptional regulators of lipid biosynthesis and uptake. Studies in FRTL-5 thyrocytes revealed that TSH stimulates expression and maturation of SREBPs and expression of classical SREBP target genes involved in lipid biosynthesis and uptake. Almost identical effects were observed when the cAMP agonist forskolin was used instead of TSH. In TSH receptor-deficient mice, in which TSH/cAMP-dependent gene regulation is blocked, the expression of SREBP isoforms in the thyroid was markedly reduced when compared with wild-type mice. Sterol-mediated inhibition of SREBP maturation and/or RNA interference-mediated knockdown of SREBPs reduced expression of NIS and NIS-specific iodide uptake in FRTL-5 cells. Conversely, overexpression of active SREBPs caused a strong activation of the 5'-flanking region of the rat NIS gene mediated by binding to a functional SREBP binding site located in the 5'-untranslated region of the rat NIS gene. These findings show that TSH acts as a regulator of SREBP expression and maturation in thyroid epithelial cells and that SREBPs are novel transcriptional regulators of NIS.

Tremendous intron length differences of the BmKBT and a novel BmKBT-like peptide genes provide a mechanical basis for the rapid or constitutive expression of the peptides

The cDNA sequence encoding a novel BmKBT-like peptide (referred to as BmKBy) was cloned and sequenced from the scorpion Mesobuthus martensii Karsch. Functional analysis indicated that both BmKBT and BmKBy possess strong toxicity in mice, but very weak toxicity in cotton bollworm. Phylogenetic analysis showed that BmKBy and BmKBT represent evolutionary intermediates between the α- and β-toxins from scorpions. The genomic sequences of BmKBT and BmKBy were also obtained. It is interesting to see that two genes, which contain an intron of 225 and 1529bp, respectively, exactly code for the BmKBT peptide. One gene, which contains an intron of 1312bp, codes for BmKBy. Given that genes with long introns favor constitutive expression, whereas those with short introns are rapidly regulated in response to stimulations, the BmKBT_a and BmKBT_b genes provide a mechanical basis for either constitutive expression or rapid generation of the toxic peptides in response to different signals.

Novel roles for KLF1 in erythropoiesis revealed by mRNA-seq

KLF1 (formerly known as EKLF) regulates the development of erythroid cells from bi-potent progenitor cells via the transcriptional activation of a diverse set of genes. Mice lacking Klf1 die in utero prior to E15 from severe anemia due to the inadequate expression of genes controlling hemoglobin production, cell membrane and cytoskeletal integrity, and the cell cycle. We have recently described the full repertoire of KLF1 binding sites in vivo by performing KLF1 ChIP-seq in primary erythroid tissue (E14.5 fetal liver). Here we describe the KLF1-dependent erythroid transcriptome by comparing mRNA-seq from Klf1^+/+ and Klf1^−/− erythroid tissue. This has revealed novel target genes not previously obtainable by traditional microarray technology, and provided novel insights into the function of KLF1 as a transcriptional activator. We define a cis-regulatory module bound by KLF1, GATA1, TAL1, and EP300 that coordinates a core set of erythroid genes. We also describe a novel set of erythroid-specific promoters that drive high-level expression of otherwise ubiquitously expressed genes in erythroid cells. Our study has identified two novel lncRNAs that are dynamically expressed during erythroid differentiation, and discovered a role for KLF1 in directing apoptotic gene expression to drive the terminal stages of erythroid maturation.

The sodium iodide symporter (NIS): regulation and approaches to targeting for cancer therapeutics

Expression of the sodium iodide symporter (NIS) is required for efficient iodide uptake in thyroid and lactating breast. Since most differentiated thyroid cancer expresses NIS, β-emitting radioactive iodide is routinely utilized to target remnant thyroid cancer and metastasis after total thyroidectomy. Stimulation of NIS expression by high levels of thyroid-stimulating hormone is necessary to achieve radioiodide uptake into thyroid cancer that is sufficient for therapy. The majority of breast cancer also expresses NIS, but at a low level insufficient for radioiodine therapy. Retinoic acid is a potent NIS inducer in some breast cancer cells. NIS is also modestly expressed in some non-thyroidal tissues, including salivary glands, lacrimal glands and stomach. Selective induction of iodide uptake is required to target tumors with radioiodide. Iodide uptake in mammalian cells is dependent on the level of NIS gene expression, but also successful translocation of NIS to the cell membrane and correct insertion. The regulatory mechanisms of NIS expression and membrane insertion are regulated by signal transduction pathways that differ by tissue. Differential regulation of NIS confers selective induction of functional NIS in thyroid cancer cells, as well as some breast cancer cells, leading to more efficient radioiodide therapy for thyroid cancer and a new strategy for breast cancer therapy. The potential for systemic radioiodide treatment of a range of other cancers, that do not express endogenous NIS, has been demonstrated in models with tumor-selective introduction of exogenous NIS.

Bexarotene via CBP/p300 induces suppression of NF-κB-dependent cell growth and invasion in thyroid cancer

PURPOSE

Retinoic acid (RA) treatment has been used for redifferentiation of metastatic thyroid cancer with loss of radioiodine uptake. The aim of this study was to improve the understanding of RA resistance and investigate the role of bexarotene in thyroid cancer cells.

EXPERIMENTAL DESIGN

A model of thyroid cancer cell lines with differential response to RA was used to evaluate the biological effects of retinoid and rexinoid and to correlate this with RA receptor levels. Subsequently, thyroid cancer patients were treated with 13-cis RA and bexarotene and response evaluated on radioiodine uptake reinduction on posttherapy scan and conventional imaging.

RESULTS

In thyroid cancer patients, 13-cis RA resistance can be bypassed in some tumors by bexarotene. A decreased tumor growth without differentiation was observed confirming our in vitro data. Indeed, we show that ligands of RARs or RXRs exert different effects in thyroid cancer cell lines through either differentiation or inhibition of cell growth and invasion. These effects are associated with restoration of RARβ and RXRγ levels and downregulation of NF-κB targets genes. We show that bexarotene inhibits the transactivation potential of NF-κB in an RXR-dependent manner through decreased promoter permissiveness without interfering with NF-κB nuclear translocation and binding to its responsive elements. Inhibition of transcription results from the release of p300 coactivator from NF-κB target gene promoters and subsequent histone deacetylation.

CONCLUSION

This study highlights dual mechanisms by which retinoids and rexinoids may target cell tumorigenicity, not only via RARs and RXRs, as expected, but also via NF-κB pathway.

The sodium iodide symporter (NIS) and potential regulators in normal, benign and malignant human breast tissue

Introduction

The presence, relevance and regulation of the Sodium Iodide Symporter (NIS) in human mammary tissue remains poorly understood. This study aimed to quantify relative expression of NIS and putative regulators in human breast tissue, with relationships observed further investigated in vitro.

Methods

Human breast tissue specimens (malignant n = 75, normal n = 15, fibroadenoma n = 10) were analysed by RQ-PCR targeting NIS, receptors for retinoic acid (RARα, RARβ), oestrogen (ERα), thyroid hormones (THRα, THRβ), and also phosphoinositide-3-kinase (PI3K). Breast cancer cells were treated with Retinoic acid (ATRA), Estradiol and Thyroxine individually and in combination followed by analysis of changes in NIS expression.

Results

The lowest levels of NIS were detected in normal tissue (Mean(SEM) 0.70(0.12) Log₁₀ Relative Quantity (RQ)) with significantly higher levels observed in fibroadenoma (1.69(0.21) Log₁₀RQ, p<0.005) and malignant breast tissue (1.18(0.07) Log₁₀RQ, p<0.05). Significant positive correlations were observed between human NIS and ERα (r = 0.22, p<0.05) and RARα (r = 0.29, p<0.005), with the strongest relationship observed between NIS and RARβ (r = 0.38, p<0.0001). An inverse relationship between NIS and PI3K expression was also observed (r = −0.21, p<0.05). In vitro, ATRA, Estradiol and Thyroxine individually stimulated significant increases in NIS expression (range 6–16 fold), while ATRA and Thyroxine combined caused the greatest increase (range 16–26 fold).

Conclusion

Although NIS expression is significantly higher in malignant compared to normal breast tissue, the highest level was detected in fibroadenoma. The data presented supports a role for retinoic acid and estradiol in mammary NIS regulation in vivo, and also highlights potential thyroidal regulation of mammary NIS mediated by thyroid hormones.

NF-kappaB p65 subunit mediates lipopolysaccharide-induced Na(+)/I(-) symporter gene expression by involving functional interaction with the paired domain transcription factor Pax8

The Gram-negative bacterial endotoxin lipopolysaccharide (LPS) elicits a variety of biological responses. Na(+)/I(-) symporter (NIS)-mediated iodide uptake is the main rate-limiting step in thyroid hormonogenesis. We have recently reported that LPS stimulates TSH-induced iodide uptake. Here, we further analyzed the molecular mechanism involved in the LPS-induced NIS expression in Fisher rat thyroid cell line 5 (FRTL-5) thyroid cells. We observed an increase in TSH-induced NIS mRNA expression in a dose-dependent manner upon LPS treatment. LPS enhanced the TSH-stimulated NIS promoter activity denoting the NIS-upstream enhancer region (NUE) as responsible for the stimulatory effects. We characterized a novel putative conserved kappaB site for the transcription factor nuclear factor-kappaB (NF-kappaB) within the NUE region. NUE contains two binding sites for the transcription factor paired box 8 (Pax8), main regulator of NIS transcription. A physical interaction was observed between the NF-kappaB p65 subunit and paired box 8 (Pax8), which appears to be responsible for the synergic effect displayed by these transcription factors on NIS gene transcription. Moreover, functional blockage of NF-kappaB signaling and site-directed mutagenesis of the kappaB cis-acting element abrogated LPS stimulation. Silencing expression of p65 confirmed its participation as an effector of LPS-induced NIS stimulation. Furthermore, chromatin immunoprecipitation corroborated that NIS is a novel target gene for p65 transactivation in response to LPS. Moreover, we were able to corroborate the LPS-stimulatory effect on thyroid cells in vivo in LPS-treated rats, supporting that thyrocytes are capable of responding to systemic infections. In conclusion, our results reveal a new mechanism involving p65 in the LPS-induced NIS expression, denoting a novel aspect in thyroid cell differentiation.