Correlation between 99mTc-pertechnetate uptakes and expressions of human sodium iodide symporter gene in breast tumor tissues

FOXA1 Regulation Turns Benzamide HDACi Treatment Effect-Specific in BC, Promoting NIS Gene-Mediated Targeted Radioiodine Therapy

Human sodium iodide symporter (NIS) gene mediated radio-ablation is a successful procedure in thyroid cancer clinics. In recent years, natural expression of NIS is reported in breast cancer (BC) cases but is yet to make its mark as a therapeutic procedure in BC clinics. A pre-exposure to histone deacetylase (HDAC) inhibitors to amplify endogenous NIS expression was attempted, but achieving cancer tissue-specific enhancement of NIS in patients is an important challenge to win. Here, for the first time, we show that a benzamide class of HDACi (bHDACi) can significantly induce NIS gene expression and function (p < 0.05) in BC cells with minimal off-target effects. Transcription factor (TF) profiler and promoter binding array reveals 22 TFs differentially activated by CI-994, of which FOXA1 is identified as a unique and positive regulator of NIS. Clonogenic assay shows reduced survival with bHDACi + ¹³¹I combination treatment. Further, AR-42 and MS-275 treatment shows enhanced NIS expression in an orthotopic breast tumor model. Combining bHDACi with 1 mCi ¹³¹I shows 40% drop in signal (p < 0.05), indicating enhanced radio-ablation effect. Cerenkov imaging revealed higher accumulation of ¹³¹I in MS-275-treated tumors. Thus, bHDACi-mediated selective enhancement ensuring minimal off-target effect is a step further toward using NIS as a therapeutic target for BC.

Modulation of VEGF Expression and Oxidative Stress Response by Iodine Deficiency in Irradiated Cancerous and Non-Cancerous Breast Cells

Breast cancer remains a major concern and its physiopathology is influenced by iodine deficiency (ID) and radiation exposure. Since radiation and ID can separately induce oxidative stress (OS) and microvascular responses in breast, their combination could additively increase these responses. Therefore, ID was induced in MCF7 and MCF12A breast cell lines by medium change. Cells were then X-irradiated with doses of 0.05, 0.1, or 3 Gy. In MCF12A cells, both ID and radiation (0.1 and 3 Gy) increased OS and vascular endothelial growth factor (VEGF) expression, with an additive effect when the highest dose was combined with ID. However, in MCF7 cells no additive effect was observed. VEGF mRNA up-regulation was reactive oxygen species (ROS)-dependent, involving radiation-induced mitochondrial ROS. Results on total VEGF mRNA hold true for the pro-angiogenic isoform VEGF165 mRNA, but the treatments did not modulate the anti-angiogenic isoform VEGF165b. Radiation-induced antioxidant response was differentially regulated upon ID in both cell lines. Thus, radiation response is modulated according to iodine status and cell type and can lead to additive effects on ROS and VEGF. As these are often involved in cancer initiation and progression, we believe that iodine status should be taken into account in radiation prevention policies.

Uptake of [¹⁸F]tetrafluoroborate in MCF-7 Breast Cancer Cells is Induced after Stimulation of the Sodium Iodide Symporter

BACKGROUND

The human sodium iodide symporter (hNIS) has been the most important target in nuclear medicine regarding thyroid-related diseases. Although hNIS-expression can also be determined in extra-thyroidal tumors, imaging hNIS with positron emission tomography has not been exploited clinically.

OBJECTIVE

Here, we evaluated the accumulation of the novel hNIS-substrate [18F]tetrafluoroborate ([18F]TFB) in the endogenously hNIS-expressing breast cancer cell line MCF-7 after an improved radiosynthesis and pharmacological stimulation.

METHODS

[18F]TFB was prepared under mild reaction conditions (40°C, 25 min) and its uptake properties were investigated in MCF-7 cells pretreated with a combination of all-trans retinoic acid plus methasone-derivatives and compared to the clinically established tracers [131I]iodide and [99mTc]pertechnetate. Specificity of the tracer accumulation was assessed by inhibition experiments using NaBF4, KSO3F, KI and KIO3.

RESULTS

[18F]TFB was obtained with a radiochemical yield of 24.0 ± 6.6 % (n = 17) within 40 min after high pressure liquid chromatography-separation and with 26.8 ± 6.2 % (n = 13) within 45 min after adapting the procedure on a synthesis module using higher starting activities (> 10 GBq). After pharmacological treatment, a 4-fold increase in hNIS-expression on the MCF-7 cell surface was achieved, resulting in a significantly higher [18F]TFB uptake into the cells (up to 58-fold) as compared to control experiments. Inhibition studies using various NIS-substrates confirmed the specificity of [18F]TFB for hNIS.

CONCLUSION

[18F]TFB was shown to be a promising hNIS-substrate in our model using the human MCF-7 breast cancer cell line mandating in vivo evaluations in xenografted studies and in patients.

Iodine‑131 metabolic radiotherapy leads to cell death and genomic alterations through NIS overexpression on cholangiocarcinoma

Cholangiocarcinoma (CC) is an aggressive liver tumor with limited therapeutic options. Natrium-iodide symporter (NIS) mediates the uptake of iodine by the thyroid, representing a key component in metabolic radiotherapy using iodine-131 (¹³¹I) for the treatment of thyroid cancer. NIS expression is increased in CC, providing the opportunity for a novel therapeutic approach for this type of tumor. Thus, in this study, we aimed to evaluate therapeutic efficacy of ¹³¹I in two human CC cell lines. Uptake experiments analyzed the ¹³¹I uptake profiles of the tumor cell lines under study. The cells were irradiated with various doses of ¹³¹I to evaluate and characterize the effects of metabolic radiotherapy. NIS protein expression was assessed by immunofluorescence methods. Cell survival was evaluated by clonogenic assay and flow cytometry was used to assess cell viability, and the type of death and alterations in the cell cycle. The genomic and epigenetic characterization of both CC cells was performed before and after irradiation. NIS gene expression was evaluated in the CC cells by RT-qPCR. The results revealed that CC cells had a higher expression of NIS. ¹³¹I induced a decrease in cell survival in a dose-dependent manner. With the increasing irradiation dose, a decrease in cell viability was observed, with a consequent increase in cell death by initial apoptosis. Karyotype and array comparative genomic hybridization (aCGH) analyses revealed that both CC cell lines were near-triploid with several numerical and structural chromosomal rearrangements. NIS gene expression was increased in the TFK-1 and HuCCT1 cells in a time-dependent manner. On the whole, the findings of this study demonstrate that the presence of NIS in cholangiocarcinoma cell lines is crucial for the decreased cell viability and survival observed following the exposure of cholangiocarcinoma cells to ¹³¹I.

Targeting Novel Sodium Iodide Symporter Interactors ADP-Ribosylation Factor 4 and Valosin-Containing Protein Enhances Radioiodine Uptake

The sodium iodide symporter (NIS) is required for iodide uptake, which facilitates thyroid hormone biosynthesis. NIS has been exploited for over 75 years in ablative radioiodine (RAI) treatment of thyroid cancer, where its ability to transport radioisotopes depends on its localization to the plasma membrane. The advent of NIS-based in vivo imaging and theranostic strategies in other malignancies and disease modalities has recently increased the clinical importance of NIS. However, NIS trafficking remains ill-defined. Here, we used tandem mass spectrometry followed by coimmunoprecipitation and proximity ligation assays to identify and validate two key nodes-ADP-ribosylation factor 4 (ARF4) and valosin-containing protein (VCP)-controlling NIS trafficking. Using cell-surface biotinylation assays and highly inclined and laminated optical sheet microscopy, we demonstrated that ARF4 enhanced NIS vesicular trafficking from the Golgi to the plasma membrane, whereas VCP-a principal component of endoplasmic reticulum (ER)-associated degradation-governed NIS proteolysis. Gene expression analysis indicated VCP expression was particularly induced in aggressive thyroid cancers and in patients who had poorer outcomes following RAI treatment. Two repurposed FDA-approved VCP inhibitors abrogated VCP-mediated repression of NIS function, resulting in significantly increased NIS at the cell-surface and markedly increased RAI uptake in mouse and human thyroid models. Collectively, these discoveries delineate NIS trafficking and highlight the new possibility of systemically enhancing RAI therapy in patients using FDA-approved drugs. SIGNIFICANCE: These findings show that ARF4 and VCP are involved in NIS trafficking to the plasma membrane and highlight the possible therapeutic role of VCP inhibitors in enhancing radioiodine effectiveness in radioiodine-refractory thyroid cancer.

Mannose glycosylation is an integral step for NIS localization and function in human breast cancer cells

Chasing an intriguing biological question on the disparity of sodium iodide symporter (NIS, officially known as SLC5A5) expression and function in the clinical scenario of breast cancer, this study addresses key molecular defects involved. NIS in cancer patients has primarily been recorded to be a cytoplasmic protein, thus limiting the scope for targeted radio-iodine therapy. We developed NIS transgene-overexpressing MCF-7 breast cancer cells, and found a few clonal derivatives that show predominant expression of NIS in the plasma membrane. The majority of clones, however, showed cytosolic NIS expression over long passages. Cells expressing membranous NIS show unperturbed dynamic trafficking of NIS through secretory pathway organelles when compared to cells expressing cytoplasmic NIS or to parental cells. Further, treatment of cells expressing membranous NIS with specific glycosylation inhibitors highlighted the importance of inherent glycosylation processing and an 84 gene signature glycosylation RT-Profiler array revealed that clones expressing NIS in their membrane cluster separately compared to the other cells. We further confirm a role of three differentially expressed genes, i.e. MAN1B1, MAN1A1 and MAN2A1, in regulating NIS localization by RNA interference. Thus, this study shows the important role of mannosidase in N-glycosylation processing in order to correctly traffic NIS to the plasma membrane in breast cancer cells.This article has an associated First Person interview with the first author of the paper.

The antigenic link between thyroid autoimmunity and breast cancer

The association between breast cancer and benign thyroid disorders, in particular thyroid autoimmunity, has been debated for decades. Autoantibodies to thyroid peroxidase, the hallmark of thyroid autoimmunity, have a higher prevalence among patients with breast cancer compared with the general population. Furthermore a correlation between their positivity and a better prognosis of breast cancer was found in several independent small-scale studies, even if such observation was not confirmed in a subsequent retrospective study conducted on the largest patient cohort to date. The thyroid and mammary glands present several biological similarities, therefore the hypothesis of an immune response to shared thyroid/breast antigens could in part explain the association between thyroid autoimmunity and breast cancer. The sodium iodide symporter is expressed in both glands, however it seems unlikely to be the key common antigen, considering that autoantibodies targeting it are rare. Instead thyroid peroxidase, one of the major thyroid autoantigens, is also expressed in breast tissue and therefore represents the main antigenic link between thyroid autoimmunity and breast cancer. Furthermore lactoperoxidase, an enzyme of the same family that shares structural similarities with thyroid peroxidase, is expressed in neoplastic breast cells and is responsible for the cross-reactivity with some autoantibodies to thyroid peroxidase. Novel strategies for the diagnosis and treatment of breast cancer might take advantage of the antigenic link between thyroid and breast tissues.

Differentiated thyroid cancer theranostics: radioiodine and beyond

The term theranostics is the combination of a diagnostic tool that helps to define the right therapeutic tool for specific disease. It signifies the "we know which sites require treatment (diagnostic scan) and confirm that those sites have been treated (post-therapy scan)" demonstrating the achievable tumor dose concept. This term was first used by John Funkhouser at the beginning of the 90s, at the same time the concept of personalized medicine appeared. In nuclear medicine, theranostics is easy to apply and understand because of an easy switch from diagnosis to therapy with the same vector. It helps in maximizing tumor dose and sparing normal tissue with high specific and rapid uptake in metastasis. The oldest application of this concept is radioactive iodine I-131 (RAI). The first treatment based on the theranostic concept was performed on thyroid cancer patients with RAI in 1946. From then on management of differentiated thyroid cancer (DTC) has evolved on the multimodality concept. We now use the term "our" patient instead of "my" patient to signify this. However, the initial surgical management followed by RAI as per the theranostics has remained the mainstay in achieving a cure in most of DTC patients. The normal thyroid cells metabolise iodine, the principle of which is utilized in imaging of the thyroid gland with isotopes of iodine. RAI treatment of DTC is based on the principle of sodium iodide symporter (NIS) expressing thyroid cells with DTC cells having the ability of trapping circulating RAI successfully helping in treatment of residual and metastatic disease. NIS is usually negative in poorly differentiated cells and is inversely proportional to Glucose transporter receptor Type 1 expression. Both positive and negative NIS are the key components of the theranostic approach in treatment of DTC. Presence or absence of NIS is documented by either whole body iodine scintigraphy (WBS) or 2-deoxy-2(¹⁸F) fludeoxyglucose (FDG) positron emission tomography computed tomography (PET-CT). Currently, single photon emission CT and CT (SPECT-CT) has significantly improved the precision and sensitivity of whole body iodine scintigraphy with its capability of accurate localization of disease foci whether iodine avid or non-avid. This has helped in a more personalized approach in treatment. This review will give an overview of the role of NIS in the theranostic approach to management with RAI, its current status and also the molecular approach to treatment in RAI refractory disease.

Review of the possible association between thyroid and breast carcinoma

Background

Thyroid and breast cancer are two of the malignant diseases with highest incidence in females. Based on clinical experience, breast and thyroid cancer often occur metachronously or synchronously. Therefore, thyroid and breast cancer might share some common etiological factors. The relationship between these diseases has attracted substantial attention, and because these two glands are both regulated by the hypothalamic-pituitary axis, such a relationship is not surprising. A study of this relationship will be useful for obtaining a better understanding of the mechanism by which these two malignancies co-occur.

Main body

This study reviewed the progress in research on the roles of iodine intake, folate metabolism, obesity, gonadal hormones, and thyroid hormone in thyroid and breast cancer. These studies evaluating the etiological roles of these factors in linking breast and thyroid cancer might also improve our understanding and identify new therapeutic approaches, such as sodium/iodide symporter-mediated radioiodine therapy and thyroid-stimulating hormone receptor antagonists, for breast cancer. In addition, some specific treatments for each cancer, such as radiotherapy for breast cancer or radioactive iodine therapy for thyroid cancer, might be risk factors for secondary malignances, including breast and thyroid cancer.

Conclusions

Studies of the precise relationship between the co-occurrence of breast and thyroid cancer will certainly improve our understanding of the biological behaviors of these two malignancies and direct evidence-based clinical practice.

Regression of experimental NIS-expressing breast cancer brain metastases in response to radioiodide/gemcitabine dual therapy

Treating breast cancer brain metastases (BCBMs) is challenging. Na⁺/I⁻ symporter (NIS) expression in BCBMs would permit their selective targeting with radioiodide (¹³¹I⁻). We show impressive enhancement of tumor response by combining¹³¹I⁻ with gemcitabine (GEM), a cytotoxic radiosensitizer. Nude mice mammary fat-pad (MFP) tumors and BCBMs were generated with braintropic MDA-MB-231Br cells transduced with bicistronically-linked NIS and firefly luciferase cDNAs. Response was monitored in vivo via bioluminescent imaging and NIS tumor expression.¹³¹I⁻/GEM therapy inhibited MFP tumor growth more effectively than either agent alone. BCBMs were treated with: high or low-dose GEM (58 or 14.5 mg/Kg×4); ¹³¹I⁻ (1mCi or 2×0.5 mCi 7 days apart); and ¹³¹I⁻/GEM therapy. By post-injection day (PID) 25, 82-86% of controls and 78-83% of ¹³¹I⁻-treated BCBM grew, whereas 17% low-dose and 36% high-dose GEM regressed. The latter tumors were smaller than the controls with comparable NIS expression (~20% of cells). High and low-dose ¹³¹I⁻/GEM combinations caused 89% and 57% tumor regression, respectively. High-dose GEM/¹³¹I⁻ delayed tumor growth: tumors increased 5-fold in size by PID45 (controls by PID18). Although fewer than 25% of cells expressed NIS, GEM/¹³¹I⁻ caused dramatic tumor regression in NIS-transduced BCBMs. This effect was synergistic, and supports the hypothesis that GEM radiosensitizes cells to ¹³¹I⁻.

The correlation between breast cancer and urinary iodine excretion levels

Objective

To compare urinary iodine excretion levels in patients with breast cancer and control subjects.

Methods

In this prospective pilot study, patients with breast cancer and normal controls were recruited. Age and menopausal status were recorded. Levels of serum thyroid-stimulating hormone, blood urea nitrogen and creatinine and urine iodine concentration (UIC) were measured. UIC levels were divided into three categories: low (<100 µg/l), normal (100–200 µg/l) or high (>200 µg/l).

Results

A total of 24 patients with breast cancer and 48 controls were included in the study. There were no statistically significant differences between the two groups with regard to thyroid-stimulating hormone, blood urea nitrogen or creatinine levels. When considered overall, there was no statistical difference in UIC between patients and controls. However, comparisons within each category (low, normal or high UIC) showed a significantly higher percentage of patients with breast cancer had a high UIC compared with controls.

Conclusions

A high UIC was seen in a significantly higher percentage of patients with breast cancer than controls. UIC may have a role as a marker for breast cancer screening. Further studies evaluating UIC and iodine utilization in patients with breast cancer are warranted.

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.

Enhancement of human sodium iodide symporter gene therapy for breast cancer by HDAC inhibitor mediated transcriptional modulation

The aberrant expression of human sodium iodide symporter (NIS) in breast cancer (BC) has raised the possibility of using targeted radioiodide therapy. Here we investigate modulation of endogenous, functional NIS expression by histone deacetylase inhibitors (HDACi) in vitro and in vivo. Luciferase reporter based initial screening of six different HDACi shows 2–10 fold enhancement of NIS promoter activity in majority of the cell types tested. As a result of drug treatment, endogenous NIS transcript and protein shows profound induction in BC cells. To get an insight on the mechanism of such transcriptional activation, role of Stat4, CREB and other transcription factors are revealed by transcription factor profiling array. Further, NIS-mediated intracellular iodide uptake also enhances substantially (p < 0.05) signifying functional relevance of the transcriptional modulation strategy. Gamma camera imaging confirms 30% higher uptake in VPA or NaB treated BC tumor xenograft. Corroborating with such functional impact of NIS, significant reduction in cell survival (p < 0.005) is observed in VPA, NaB or CI994 drug and ¹³¹I combination treatment in vivo indicating effective radioablation. Thus, for the first time this study reveals the mechanistic basis and demonstrates functional relevance of HDACi pre-treatment strategy in elevating NIS gene therapy approach for BC management in clinic.

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.

Combined 2-deoxy glucose and metformin improves therapeutic efficacy of sodium-iodide symporter-mediated targeted radioiodine therapy in breast cancer cells

Radiosensitization using either metformin or 2-deoxy-d-glucose (2-DG) in various cancer cells has been reported. The present study reveals novel information on combining these drugs to enhance radiosensitization effect in breast cancer (BC) cells. Responses to low-dose Cobalt60 radiation, as well as a newly emerged radioiodine therapy target for BC, that is, sodium-iodide symporter (NIS or SLC5A5) protein, are tested. As therapeutic potential of NIS in BC is often limited due to low uptake and fast efflux rate of iodine, the scope of these two radiosensitizers to further improve NIS-mediated ¹³¹I therapeutic efficacy is explored. Two BC cell lines, MCF-7, and MDA MB231 are tested to optimize minimal drug doses required for radiosensitization. A combination of 2 mM metformin and 20 mM 2-DG with 2 grey (Gy) Cobalt60 radiation shows significant radiosensitization effect (P=0.0002). In cells treated with the combination therapy, increased γH2A.X foci formation was noted. Further, MCF-7 BC cells overexpressing NIS (MCF-7 NIS) was established, and using the optimized drug concentrations, significant radiosensitization (P=0.0019) by 50 μ Ci ¹³¹I usage was found to be the case as well. Apoptosis data corroborates with the result of clonogenic assay showing significant increase in apoptotic population upon dual drug-mediated radiosensitization. In case of metformin treatment, lowered adenosine triphosphate (ATP) content of the cell has been observed. The encouraging radiosensitization effect observed using combined 2-DG and metformin may aid in reducing Cobalt60 radiation exposure or for targeted radioiodine therapy in BC cells with NIS expression. This study indicates high potential of this drug combination in sensitizing BC cells for NIS-mediated-targeted radioiodine therapy, which otherwise may have lacked efficacy.

Molecular imaging of oncolytic viral therapy

Oncolytic viruses have made their mark on the cancer world as a potential therapeutic option, with the possible advantages of reduced side effects and strengthened treatment efficacy due to higher tumor selectivity. Results have been so promising, that oncolytic viral treatments have now been approved for clinical trials in several countries. However, clinical studies may benefit from the ability to noninvasively and serially identify sites of viral targeting via molecular imaging in order to provide safety, efficacy, and toxicity information. Furthermore, molecular imaging of oncolytic viral therapy may provide a more sensitive and specific diagnostic technique to detect tumor origin and, more importantly, presence of metastases. Several strategies have been investigated for molecular imaging of viral replication broadly categorized into optical and deep tissue imaging, utilizing several reporter genes encoding for fluorescence proteins, conditional enzymes, and membrane protein and transporters. Various imaging methods facilitate molecular imaging, including computer tomography, magnetic resonance imaging, positron emission tomography, single photon emission CT, gamma-scintigraphy, and photoacoustic imaging. In addition, several molecular probes are used for medical imaging, which act as targeting moieties or signaling agents. This review will explore the preclinical and clinical use of in vivo molecular imaging of replication-competent oncolytic viral therapy.

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.

Quantitative immunohistochemical analysis reveals association between sodium iodide symporter and estrogen receptor expression in breast cancer

BACKGROUND

Human sodium iodide symporter (hNIS) gene over-expression is under active consideration worldwide as an alternative target molecule for breast cancer (BC) diagnosis and targeted radio-iodine treatment. However, the field demands better stratified analysis of endogenous hNIS expression across major BC subtypes. Therefore, we have analyzed subtype-specific variation of hNIS overexpression in breast tumor tissue samples by immunohistochemistry (IHC) and also report the development of a homogeneous, quantitative analysis method of digital IHC images.

METHODS

hNIS expression was analyzed from 108 BC tissue samples by IHC. Sub-cellular localization of hNIS protein was analyzed by dual immunofluorescence (IF) staining method using hNIS and HER2 antibodies. An ImageJ based two-step digital analysis method was developed and applied for the bias-free analysis of the images.

RESULTS

Staining of the tumor samples show 70% cases are hNIS positive indicating high incidence of hNIS positive cases in BC. More importantly, a subtype specific analysis done for the first time shows that hNIS expression is overly dominated in estrogen receptor (ER) positive cases than the receptor negative cases. Further, 56% of the ER+ve, PgR+ve, HER2-ve and 36% of ER+ve, PgR+ve, HER2+ve cases show highest intensity staining equivalent to the thyroid tissue. A significant positive correlation is also observed between hNIS and estrogen receptor expression (p = 0.0033, CI = 95%) suggesting hNIS mediated targeted radio-iodine therapy procedures may benefit both ER+ve, PgR+ve, HER2-ve as well as HER2+ve cases. Further, in a few cases, hNIS and HER2 protein localization is demonstrated by overlapping membrane co-expression. ImageJ based image analysis method shows over 70% match with manual pathological scoring method.

CONCLUSION

The study indicates a positive link between hNIS and ER expression in BC. The quantitative IHC image analysis method reported here will further help in patient stratification and potentially benefit global clinical assessment where hNIS mediated targeted ¹³¹I radio-ablative therapy is aimed.

Functional Radionuclide Imaging, In-Vitro Radioiodine Uptake Estimation and RT-PCR in the Evaluation of Sodium Iodide Symporter (NIS) Expression and Functionality in Breast Cancer: A Pilot Study

Breast cancer is a common malignancy in females, which is considered as a systemic disease, whose treatment involves combined modality including systemic as well as local treatment. Recent studies have shown that breast cancer also expresses Sodium Iodide Symporter (NIS) gene, like in the thyroid, which is the factor responsible for the uptake of iodide by the thyroid, enabling radioiodine therapy of thyroid disorders. This study aimed to evaluate various radionuclide imaging characteristics, in vitro radioiodine uptake (RAIU) and evaluation of NIS expression by using Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) to explore sodium iodide symporter (NIS) expression and iodine uptake in breast cancer and to explor e whether radioiodine can be used for the diagnosis and treatment of breast cancer. Ways of differential regulation of NIS expression in breast cancer has also been explored. Female patients with palpable breast lump and histologically proven infiltrating duct carcinoma were taken up for the study, which included 50 females of mean age 49 years. (range: 23-73 years). The patients were categorized into different groups, depending on the type of the study performed. The uptake patterns in various imaging modalities were analyzed and compared with invitro and RT-PCR studies. 68 % of breast cancer cases showed (99m)Tc-pertechnetate uptake at the initial images. This finding could partly be due to tumor vascularity, which is usually higher compared to the normal tissues. The uptake in the delayed imaging could be related to that due to NIS in the breast. Use of perchlorate or stable iodine did not alter the pertechnetate uptake pattern in breast tumor. Good correlation between (99m)Tc-pertechnetate and (99m)Tc-tetrofosmin uptake in breast cancer was demonstrated. In vitro radioactive iodine uptake in the breast tumor was significantly higher than that in the normal breast tissue. Only 42 % of breast tumor samples studied using RT-PCR showed NIS expression. Correlation between (99m)Tc-pertechnetate uptake and NIS expression could not be well established. Further studies with higher dose of radioiodine and/or mechanisms of differentially blocking the thyroid are required to assess the feasibility of radioiodine therapy for breast cancer.

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.

Applications of 211At and 223Ra in targeted alpha-particle radiotherapy

Targeted radiotherapy using agents tagged with α-emitting radionuclides is gaining traction with several clinical trials already undertaken or ongoing, and others in the advanced planning stage. The most commonly used α-emitting radionuclides are 213Bi, 211At, 223Ra and 225Ac. While each one of these has pros and cons, it can be argued that 211At probably is the most versatile based on its half life, decay scheme and chemistry. On the other hand, for targeting bone metastases, 223Ra is the ideal radionuclide because simple cationic radium can be used for this purpose. In this review, we will discuss the recent developments taken place in the application of 211At-labeled radiopharmaceuticals and give an overview of the current status of 223Ra for targeted α-particle radiotherapy.

Sodium iodide symporter for nuclear molecular imaging and gene therapy: from bedside to bench and back

Molecular imaging, defined as the visual representation, characterization and quantification of biological processes at the cellular and subcellular levels within intact living organisms, can be obtained by various imaging technologies, including nuclear imaging methods. Imaging of normal thyroid tissue and differentiated thyroid cancer, and treatment of thyroid cancer with radioiodine rely on the expression of the sodium iodide symporter (NIS) in these cells. NIS is an intrinsic membrane protein with 13 transmembrane domains and it takes up iodide into the cytosol from the extracellular fluid. By transferring NIS function to various cells via gene transfer, the cells can be visualized with gamma or positron emitting radioisotopes such as Tc-99m, I-123, I-131, I-124 and F-18 tetrafluoroborate, which are accumulated by NIS. They can also be treated with beta- or alpha-emitting radionuclides, such as I-131, Re-186, Re-188 and At-211, which are also accumulated by NIS. This article demonstrates the diagnostic and therapeutic applications of NIS as a radionuclide-based reporter gene for trafficking cells and a therapeutic gene for treating cancers.

Microarray analysis of genes associated with cell surface NIS protein levels in breast cancer

Background

Na⁺/I^- symporter (NIS)-mediated iodide uptake allows radioiodine therapy for thyroid cancer. NIS is also expressed in breast tumors, raising potential for radionuclide therapy of breast cancer. However, NIS expression in most breast cancers is low and may not be sufficient for radionuclide therapy. We aimed to identify biomarkers associated with NIS expression such that mechanisms underlying NIS modulation in human breast tumors may be elucidated.

Methods

Published oligonucleotide microarray data within the National Center for Biotechnology Information Gene Expression Omnibus database were analyzed to identify gene expression tightly correlated with NIS mRNA level among human breast tumors. NIS immunostaining was performed in a tissue microarray composed of 28 human breast tumors which had corresponding oligonucleotide microarray data available for each tumor such that gene expression associated with cell surface NIS protein level could be identified.

Results and Discussion

NIS mRNA levels do not vary among breast tumors or when compared to normal breast tissues when detected by Affymetrix oligonucleotide microarray platforms. Cell surface NIS protein levels are much more variable than their corresponding NIS mRNA levels. Despite a limited number of breast tumors examined, our analysis identified cysteinyl-tRNA synthetase as a biomarker that is highly associated with cell surface NIS protein levels in the ER-positive breast cancer subtype.

Conclusions

Further investigation on genes associated with cell surface NIS protein levels within each breast cancer molecular subtype may lead to novel targets for selectively increasing NIS expression/function in a subset of breast cancers patients.

Insertion of the human sodium iodide symporter to facilitate deep tissue imaging does not alter oncolytic or replication capability of a novel vaccinia virus

INTRODUCTION

Oncolytic viruses show promise for treating cancer. However, to assess therapeutic efficacy and potential toxicity, a noninvasive imaging modality is needed. This study aimed to determine if insertion of the human sodium iodide symporter (hNIS) cDNA as a marker for non-invasive imaging of virotherapy alters the replication and oncolytic capability of a novel vaccinia virus, GLV-1h153.

METHODS

GLV-1h153 was modified from parental vaccinia virus GLV-1h68 to carry hNIS via homologous recombination. GLV-1h153 was tested against human pancreatic cancer cell line PANC-1 for replication via viral plaque assays and flow cytometry. Expression and transportation of hNIS in infected cells was evaluated using Westernblot and immunofluorescence. Intracellular uptake of radioiodide was assessed using radiouptake assays. Viral cytotoxicity and tumor regression of treated PANC-1tumor xenografts in nude mice was also determined. Finally, tumor radiouptake in xenografts was assessed via positron emission tomography (PET) utilizing carrier-free 124I radiotracer.

RESULTS

GLV-1h153 infected, replicated within, and killed PANC-1 cells as efficiently as GLV-1h68. GLV-1h153 provided dose-dependent levels of hNIS expression in infected cells. Immunofluorescence detected transport of the protein to the cell membrane prior to cell lysis, enhancing hNIS-specific radiouptake (P < 0.001). In vivo, GLV-1h153 was as safe and effective as GLV-1h68 in regressing pancreatic cancer xenografts (P < 0.001). Finally, intratumoral injection of GLV-1h153 facilitated imaging of virus replication in tumors via 124I-PET.

CONCLUSION

Insertion of the hNIS gene does not hinder replication or oncolytic capability of GLV-1h153, rendering this novel virus a promising new candidate for the noninvasive imaging and tracking of oncolytic viral therapy.

KT5823 differentially modulates sodium iodide symporter expression, activity, and glycosylation between thyroid and breast cancer cells

Na(+)/I(-) symporter (NIS)-mediated iodide uptake into thyroid follicular cells serves as the basis of radioiodine therapy for thyroid cancer. NIS protein is also expressed in the majority of breast tumors, raising potential for radionuclide therapy of breast cancer. KT5823, a staurosporine-related protein kinase inhibitor, has been shown to increase thyroid-stimulating hormone-induced NIS expression, and thus iodide uptake, in thyroid cells. In this study, we found that KT5823 does not increase but decreases iodide uptake within 0.5 h of treatment in trans-retinoic acid and hydrocortisone-treated MCF-7 breast cancer cells. Moreover, KT5823 accumulates hypoglycosylated NIS, and this effect is much more evident in breast cancer cells than thyroid cells. The hypoglycosylated NIS is core glycosylated, has not been processed through the Golgi apparatus, but is capable of trafficking to the cell surface. KT5823 impedes complex NIS glycosylation at a regulatory point similar to brefeldin A along the N-linked glycosylation pathway, rather than targeting a specific N-glycosylated site of NIS. KT5823-mediated effects on NIS activity and glycosylation are also observed in other breast cancer cells as well as human embryonic kidney cells expressing exogenous NIS. Taken together, KT5823 will serve as a valuable pharmacological reagent to uncover mechanisms underlying differential NIS regulation between thyroid and breast cancer cells at multiple levels.

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.

The biology of the sodium iodide symporter and its potential for targeted gene delivery

The sodium iodide symporter (NIS) is responsible for thyroidal, salivary, gastric, intestinal and mammary iodide uptake. It was first cloned from the rat in 1996 and shortly thereafter from human and mouse tissue. In the intervening years, we have learned a great deal about the biology of NIS. Detailed knowledge of its genomic structure, transcriptional and post-transcriptional regulation and pharmacological modulation has underpinned the selection of NIS as an exciting approach for targeted gene delivery. A number of in vitro and in vivo studies have demonstrated the potential of using NIS gene therapy as a means of delivering highly conformal radiation doses selectively to tumours. This strategy is particularly attractive because it can be used with both diagnostic (99mTc, 125I, 124I)) and therapeutic (131I, 186Re, 188Re, 211At) radioisotopes and it lends itself to incorporation with standard treatment modalities, such as radiotherapy or chemoradiotherapy. In this article, we review the biology of NIS and discuss its development for gene therapy.

Stimulation of retinoic acid-induced functional sodium iodide symporter (NIS) expression and cytotoxicity of ¹³¹I by carbamazepine in breast cancer cells

The sodium iodide symporter (NIS) mediates the active iodide uptake in the thyroid gland as well as lactating breast tissue. Recently, we reported significant stimulation of all-trans retinoic acid (atRA)-induced NIS expression in the estrogen-receptor positive human breast cancer cell line MCF-7 by dexamethasone (Dex) in vitro and in vivo, which might offer the potential to image and treat breast cancer with radioiodine. In this study, based on its known interaction with the pregnane-X-receptor (PXR) forming a heterodimer with the retinoid-X-receptor (RXR), we examined the effect of carbamazepine (CBZ), a potent activator of PXR, on atRA-induced NIS expression and therapeutic efficacy of (131)I in MCF-7 cells. For this purpose, functional NIS expression in MCF-7 cells was examined by iodide uptake assay, quantitative real-time PCR as well as Western blot analysis, followed by investigation of (131)I cytotoxicity in vitro after incubation with CBZ (4, 25, 100 μM) in the presence of atRA (1 μM) with or without Dex (100 nM). Incubation with CBZ stimulated atRA-induced iodide accumulation up to twofold in a concentration-dependent manner, while atRA/Dex-stimulated iodide uptake was further stimulated up to 1.5-fold by additional CBZ treatment based on significantly increased NIS mRNA and protein levels. This stimulatory effect of CBZ was shown to be dependent on the PI3K-Akt pathway without involvement of mTOR. In contrast, treatment with CBZ alone had no effect on functional NIS expression. Moreover, selective cytotoxicity of (131)I was significantly increased from approximately 20% in MCF-7 cells treated with atRA alone to 50% after treatment with CBZ in the presence of atRA, which was further enhanced to 90% after combined treatment with atRA/Dex/CBZ. In conclusion, CBZ represents another potent stimulator of atRA-induced functional NIS expression resulting in an enhanced selective killing effect of (131)I in MCF-7 breast cancer cells.

The pan-DAC inhibitor LBH589 is a multi-functional agent in breast cancer cells: cytotoxic drug and inducer of sodium-iodide symporter (NIS)

New drugs with anti-tumor activity, also able to modify the expression of selected molecules, are under evaluation in breast cancer which is becoming resistant to conventional treatment, or in metastatic disease. The sodium-iodide symporter (NIS), which mediates iodide uptake into thyroid cells, and is the molecular basis of radioiodine imaging and therapy in thyroid cancer, is also expressed in a large portion of breast tumors. Since NIS expression in breast cancer is not sufficient for a significant iodide uptake, drugs able to induce its expression and correct function are under evaluation. In the present study, we report for the first time that the pan-deacetylase (DAC) inhibitor LBH589 (panobinostat) significantly induced NIS, both as mRNA and as protein, through the increase of NIS promoter activity, with the final consequence of obtaining a significant up-take of iodide in MCF7, T47D, and MDA-MB231 breast cancer cells. Moreover, we observed that LBH589 causes a significant reduction in cell viability of estrogen-sensitive and -insensitive breast cancer cells within nanomolar range. The anti-tumor effect of LBH589 is sustained by apoptosis induction and cell cycle arrest in G(2)/M. In conclusion, our data suggest that LBH589 might be a powerful tool in the management of breast cancer due to its multiple effects and support a potential application of LBH589 in the diagnosis and treatment of this disease.

Endogenous expression of the sodium iodide symporter mediates uptake of iodide in murine models of colorectal carcinoma

The sodium iodide symporter (NIS) mediates iodide uptake into the thyroid. Because of this mechanism, differentiated thyroid cancer is susceptible for radioiodine therapy. Functional NIS expression in extrathyroidal tumors has been reported mainly in breast cancer. We screened colorectal tumors for NIS expression and investigated the mechanisms regulating NIS activity. Cell lines were screened for iodide uptake in vitro and NIS expression was evaluated by real-time RT-PCR, immunocytochemistry and immunoblotting. Iodide and pertechnetate uptake were evaluated in allograft tumors by biodistribution studies and scintigraphy. Tumors of transgenic mouse models for colorectal cancer harboring mutations in the oncogenes KRAS, beta-catenin or the tumor-suppressor gene adenomatous-polyposis coli (APC) were screened for NIS expression by RT-PCR. In vitro, functional NIS activity was detected in murine CMT93 rectal carcinoma cells and NIS expression was verified on mRNA and protein level. Inhibition of tyrosine kinases increased iodide uptake. Inhibition of tyrosine phosphatases decreased iodide uptake. In vivo, functional NIS expression was preserved in CMT93 tumors and tumor uptake could be enhanced by treatment of mice with tyrosine kinase inhibitors. In transgenic murine models of colorectal cancer, 14% of endogenous tumors expressed elevated levels of NIS mRNA. We conclude that NIS is functionally expressed in a subset of murine colorectal tumors and its activity is regulated by tyrosine phosphorylation. Therefore, with specific tyrosine kinase inhibition, these tumors might be susceptible for radioiodine treatment. Further studies are justified to identify the specific pathways regulating NIS activity and to transfer these findings to human cell lines and tissues.

Effects of theophylline on radioiodide uptake in MCF-7 breast cancer and NIS gene-transduced SNU-C5 colon cancer cells

BACKGROUND

We investigated whether theophylline has the potential to increase radioiodide uptake in nonthyroidal cancer cells.

MATERIALS AND METHODS

MCF-7 cells that express endogenous sodium/iodide symporter (NIS) and SNU-C5 cells adenovirally transduced with the human NIS gene (SNU-C5/NIS) were treated with 10(-7)-2x10(-4) mol/L theophylline for 24 hours before incubation with (125)I, and then, radioiodide uptake and retention were measured. NIS expression was assessed by immunohistochemistry and Western blot analysis, using an antihuman NIS monoclonal antibody.

RESULTS

Theophylline at 10(-6)-2x10(-4) mol/L significantly and dose dependently augmented radioiodide uptake in MCF-7 cells and at 10(-6)-10(-5) mol/L in SNU-C5/NIS cells, without affecting radioiodide efflux. Abrogation by KClO(4)(-) demonstrated that the effect of theophylline occurred through specific iodide transport. Immunohistochemistry revealed dose-dependent increases of NIS staining in MCF-7 and SNU-C5/NIS cells by 10(-6)-10(-4) and 10(-6)-10(-5) mol/L theophylline, respectively. Western blot analysis demonstrated similar findings, showing increased expression of NIS on the membrane of SNU-C5/NIS and MCF-7 cells by theophylline treatment.

CONCLUSIONS

Theophylline can augment radioiodide uptake in breast cancer cells and NIS gene-transduced cancer cells through the upregulation of NIS expression. Therefore, further investigations are warranted to explore the potential utility of this phenomenon for enhancing radioiodide-based imaging and therapies of NIS gene-transduced cancer cells.

Endogenous NIS expression in triple-negative breast cancers

BACKGROUND

The sodium iodide symporter (NIS) mediates iodide transport into cells and has been identified in approximately 70% of breast cancers. Functional NIS expression raises the possibility of using (131)I for therapeutic targeting of tumor cells. Treatment of triple-negative breast cancers [estrogen/progesterone receptor-negative and HER2-negative (ER-/PR-/HER2-)] is primarily limited to chemotherapy. Our aim was to characterize NIS expression in this subset of tumors.

METHODS

Archival tissue sections from 23 women with triple-negative breast cancer were analyzed for NIS expression using immunohistochemical methods and an anti-human NIS antibody. Tumors were evaluated for the presence of plasma membrane immunoreactivity. One patient with a NIS-expressing positive tumor underwent (123)I scintigraphic imaging with dosimetric analysis.

RESULTS

Fifteen cases (65.2%) demonstrated NIS-positivity with 11 tumors (47.8%) exhibiting strong expression. Plasma membrane immunoreactivity was observed in four breast cancers and was equivocal in another four tumors. Tumor-specific radioiodide uptake was demonstrated by (123)I scintigraphy in a patient with a large primary breast cancer unresponsive to neoadjuvant therapy. The tumor concentrated 2.05, 1.53, and 1.96 times more isotope than normal breast tissue at 1, 5, and 21 h. The relative increased uptake is consistent with positive NIS expression in the tumor on definitive surgery; however, the cumulative concentration in the tumor was not sufficient to achieve a therapeutic effect, had the isotope been (131)I.

CONCLUSIONS

NIS is strongly expressed in a significant proportion of triple-negative breast cancer cells, suggesting a potential role for NIS-directed (131)I-radioablative strategies in this patient population.

The Na+/I- symporter mediates active iodide uptake in the intestine

Absorption of dietary iodide, presumably in the small intestine, is the first step in iodide (I(-)) utilization. From the bloodstream, I(-) is actively taken up via the Na(+)/I(-) symporter (NIS) in the thyroid for thyroid hormone biosynthesis and in such other tissues as lactating breast, which supplies I(-) to the newborn in the milk. The molecular basis for intestinal I(-) absorption is unknown. We sought to determine whether I(-) is actively accumulated by enterocytes and, if so, whether this process is mediated by NIS and regulated by I(-) itself. NIS expression was localized exclusively at the apical surface of rat and mouse enterocytes. In vivo intestine-to-blood transport of pertechnetate, a NIS substrate, was sensitive to the NIS inhibitor perchlorate. Brush border membrane vesicles accumulated I(-) in a sodium-dependent, perchlorate-sensitive manner with kinetic parameters similar to those of thyroid cells. NIS was expressed in intestinal epithelial cell line 6, and I(-) uptake in these cells was also kinetically similar to that in thyrocytes. I(-) downregulated NIS protein expression and its own NIS-mediated transport both in vitro and in vivo. We conclude that NIS is functionally expressed on the apical surface of enterocytes, where it mediates active I(-) accumulation. Therefore, NIS is a significant and possibly central component of the I(-) absorption system in the small intestine, a system of key importance for thyroid hormone biosynthesis and thus systemic intermediary metabolism.

Do cell surface trafficking impairments account for variable cell surface sodium iodide symporter levels in breast cancer?

The Na(+)/I(-) symporter (NIS) is a transmembrane glycoprotein that mediates iodide uptake into thyroid follicular cells and serves as the molecular basis of radioiodine imaging and therapy for thyroid cancer patients. The finding that NIS protein is present in 80-90% of breast tumors suggests that breast cancer patients may also benefit from NIS-mediated radionuclide imaging and targeted therapy. However, only 17-25% of NIS-positive breast tumors have detectable radionuclide uptake activity. The discrepancy between NIS expression and radionuclide uptake activity is most likely contributed by variable cell surface NIS protein levels. Apart from the prevalent view that NIS cell surface trafficking impairments account for the variability, our current study proposes that differential levels of NIS expression may also account for variable cell surface NIS levels among breast tumors. We address the need to confirm the identity of intracellular NIS staining to reveal the mechanisms underlying variable cell surface NIS levels. In addition, we warrant a quantitative correlation between cell surface NIS levels and radionuclide uptake activity in patients such that the cell surface NIS levels required for radionuclide imaging can be defined and the defects impairing NIS activity can be recognized.

Comparison of 99mtechnetium-pertechnetate and 123iodide SPECT with FDG-PET in patients suspicious for breast cancer

PURPOSE

Breast carcinomas express the Na(+)/I() symporter and may-albeit not a routine procedure-be imaged with (123)iodide ((123)I) and (99m)technetium-pertechnetate ((99m)TcO(4)(-)) scintigraphy. The aim of our prospective study was the comparison of (99m)TcO(4)(-)--and (123)I-single-photon emission computed tomography (SPECT) with (18)F-2-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) in patients suspicious for breast cancer.

METHODS

Twenty-nine (29) untreated patients suspected of having breast carcinoma were prospectively examined with thorax SPECT with (99m)TcO(4)(-) (n=19) or (123)I (n=10), respectively, and FDG-PET (n=29) prior to biopsy. Tumor-to-background ratios (TBRs) were calculated for SPECT findings. Mean and maximum standardized uptake values (SUVs) were calculated for PET findings. Findings were compared in an intra-individual lesion-to-lesion analysis.

RESULTS

In 28 of 29 patients, malignancy was verified with histopathology. In imaging the primary tumor, sensitivities of (99m)TcO(4)(-)-SPECT, (123)I-SPECT, and FDG-PET were 63%, 67%, and 89%, respectively. TBR maximum was 2.6+/-1.1 in (99m)TcO(4)()-SPECT and 2.3+/-0.6 in (123)I-SPECT. In FDG-PET, mean tumor SUV was 4.1+/-4 and maximum tumor SUV was 5.4+/-5.1. In contrast to FDG-PET, (99m)TcO(4)()-SPECT was ineffective in imaging nodal and distant metastases in the thorax, and (123)I-SPECT failed in imaging lymph node infiltrations. Distant metastases were not present in patients of the (123)I group, and the value of (123)I-SPECT was not evaluated.

CONCLUSIONS

In contrast to FDG-PET, (99m)TcO(4)(-) and (123)I-SPECT are ineffective in imaging breast carcinoma in clinical practice.

PI3K activation is associated with intracellular sodium/iodide symporter protein expression in breast cancer

Background

The sodium/iodide symporter (NIS) is a membrane glycoprotein mediating active iodide uptake in the thyroid gland and is the molecular basis for radioiodide imaging and therapeutic ablation of thyroid carcinomas. NIS is expressed in the lactating mammary gland and in many human breast tumors, raising interest in similar use for diagnosis and treatment. However, few human breast tumors have clinically evident iodide uptake ability. We previously identified PI3K signaling as important in NIS upregulation in transgenic mouse models of breast cancer, and the PI3K pathway is commonly activated in human breast cancer.

Methods

NIS expression, subcellular localization, and function were analyzed in MCF-7 human breast cancer cells and MCF-7 cells stably or transiently expressing PI3K p110alpha subunit using Western blot of whole cell lysate, cell surface biotinylation Western blot and immunofluorescence, and radioiodide uptake assay, respectively. NIS localization was determined in a human breast cancer tissue microarray using immunohistochemical staining (IHC) and was correlated with pre-existing pAkt IHC data. Statistical analysis consisted of Student's t-test (in vitro studies) or Fisher's Exact Test (in vivo correlational studies).

Results

In this study, we demonstrate that PI3K activation in MCF-7 human mammary carcinoma cells leads to expression of underglycosylated NIS lacking cell surface trafficking necessary for iodide uptake ability. PI3K activation also appears to interfere with cell surface trafficking of exogenous NIS as well as all-trans retinoic acid-induced endogenous NIS. A correlation between NIS expression and upregulation of PI3K signaling was found in a human breast cancer tissue microarray.

Conclusion

Thus, the PI3K pathway likely plays a major role in the discordance between NIS expression and iodide uptake in breast cancer patients. Further study is warranted to realize the application of NIS-mediated radioiodide ablation in breast cancer.

Functional sodium iodide symporter expression in breast cancer xenografts in vivo after systemic treatment with retinoic acid and dexamethasone

CONTEXT

The sodium iodide symporter (NIS) mediates iodide uptake in the thyroid gland as well as in lactating breast, and is also expressed in the majority of breast cancers. Recently, we have reported stimulation of all-trans retinoic acid (atRA)-induced NIS expression in the human breast cancer cell line MCF-7 by dexamethasone (Dex), resulting in an enhanced therapeutic effect of (131)I in vitro.

OBJECTIVE

In the current study we examined the efficacy of Dex stimulation of atRA-induced NIS expression in vivo in MCF-7 xenotransplants in nude mice.

DESIGN

After systemic treatment with atRA alone or in combination with Dex, iodide accumulation in the tumors was assessed by gamma camera imaging and gamma counter analysis. In addition, NIS expression was examined on RNA and protein level by RT-PCR and immunohistochemistry, respectively.

RESULTS

Using gamma camera imaging after intraperitoneal injection of 18.5 MBq (123)I, no iodide accumulation was detected in tumors of untreated mice or mice treated with atRA only. After combined treatment with atRA/Dex significant (123)I accumulation was detected in MCF-7 xenografts, which, by ex vivo gamma counting revealed a 3.3-fold increase in iodide accumulation as compared to control tumors. Surprisingly, in a subset of mice treated with atRA or atRA/Dex iodide accumulation was also detected in the normal mammary glands. In a normal human mammary epithelial cell line HB-2, however, no functional NIS expression was induced after treatment with atRA and/or Dex in vitro. Further, NIS mRNA and protein expression was detected in atRA/Dex treated MCF-7 tumors by RT-PCR and immunohistochemistry, respectively.

CONCLUSION

Treatment with Dex in the presence of atRA is able to induce significant amounts of iodide accumulation in breast cancer xenotransplants in vivo due to stimulation of functional NIS protein expression, which opens exciting perspectives for a possible diagnostic and therapeutic role of radioiodine in the treatment of breast cancer.

Mammary radioiodine accumulation due to functional sodium iodide symporter expression in a benign fibroadenoma

The sodium iodide symporter (NIS) has been characterized to mediate the active transport of iodide not only in the thyroid gland but also in various non-thyroidal tissues, including lactating mammary gland and the majority of breast cancers, thereby offering the possibility of diagnostic and therapeutic radioiodine application in breast cancer. In this report, we present a 57-year-old patient with multifocal papillary thyroid carcinoma, who showed focal radioiodine accumulation in a lesion in the right breast on a posttherapy (131)I scan following radioiodine therapy. CT and MR-mammography showed a focal solid lesion in the right breast suggestive of a fibroadenoma, which was confirmed by histological examination. Immunostaining of paraffin-embedded tumor tissue sections using a human NIS antibody demonstrated NIS-specific immunoreactivity confined to epithelial cells of mammary ducts. In conclusion, in a thyroid cancer patient we identified a benign fibroadenoma of the breast expressing high levels of functionally active NIS protein as underlying cause of focal mammary radioiodine accumulation on a posttherapy (131)I scan. These data show for the first time that functional NIS expression is not restricted to lactating mammary gland and malignant breast tissue, but can also be detected in benign breast lesions, such as fibroadenomata of the breast.

Hydrocortisone and purinergic signaling stimulate sodium/iodide symporter (NIS)-mediated iodide transport in breast cancer cells

The sodium/iodide symporter (NIS) mediates a remarkably effective targeted radioiodide therapy in thyroid cancer; this approach is an emerging candidate for treating other cancers that express NIS, whether endogenously or by exogenous gene transfer. Thus far, the only extrathyroidal malignancy known to express functional NIS endogenously is breast cancer. Therapeutic efficacy in thyroid cancer requires that radioiodide uptake be maximized in tumor cells by manipulating well-known regulatory factors of NIS expression in thyroid cells, such as TSH, which stimulates NIS expression via cAMP. Similarly, therapeutic efficacy in breast cancer will likely depend on manipulating NIS regulation in mammary cells, which differs from that in the thyroid. Human breast adenocarcinoma MCF-7 cells modestly express endogenous NIS when treated with all-trans-retinoic acid (tRa). We report here that hydrocortisone and ATP each markedly stimulates tRa-induced NIS protein expression and plasma membrane targeting in MCF-7 cells, leading to at least a 100% increase in iodide uptake. Surprisingly, the adenyl cyclase activator forskolin, which promotes NIS expression in thyroid cells, markedly decreases tRa-induced NIS protein expression in MCF-7 cells. Isobutylmethylxanthine increases tRa-induced NIS expression in MCF-7 cells, probably through a purinergic signaling system independent of isobutylmethylxanthine's action as a phosphodiesterase inhibitor. We also observed that neither iodide, which at high concentrations down-regulates NIS in the thyroid, nor cAMP has a significant effect on NIS expression in MCF-7 cells. Our findings may open new strategies for breast-selective pharmacological modulation of functional NIS expression, thus improving the feasibility of using radioiodide to effectively treat breast cancer.

Treatment with rhenium-188-perrhenate and iodine-131 of NIS-expressing mammary cancer in a mouse model remarkably inhibited tumor growth

INTRODUCTION

Novel therapeutic modalities are needed for breast cancer patients in whom standard treatments are not effective. Mammary gland sodium/iodide symporter has been identified as a molecular target in breast cancers in humans and in some transgenic mouse models. We report the results of a therapy study with (131)I(-) and (188)ReO(4)(-) of breast cancer in polyoma middle T oncoprotein (PyMT) transgenic mice endogenously expressing the Na(+)/I(-) symporter (NIS).

METHODS

PyMT mice (12-13 weeks old) with one palpable tumor of 0.5-0.8 cm in diameter were used. For the therapy studies, PyMT mice were (1) treated with two intraperitoneal injections of 1.5 mCi of (188)ReO(4)(-) 1 week apart, (2) pretreated for 1 week with 5 microg of triiodothyronine (T3) followed by two intraperitoneal injections of 1.5 mCi of (131)I(-) 1 week apart or (3) left untreated. The tumor and normal organ uptakes were assessed by scintigraphic imaging. The thyroid function of treated and control animals was evaluated at the completion of the study by measuring the T3/thyroxine (T4) ratio in their blood.

RESULTS

There was significant uptake of (131)I(-) and (188)ReO(4)(-) in the primary palpable tumors as well as in nonpalpable tumors, stomachs and thyroids. The tumor uptake after the second injection was 10 times lower in comparison with the first injection. Tumor growth was significantly inhibited in both the (131)I(-) and (188)ReO(4)(-) groups in comparison with the control group, and tumors in the (188)ReO(4)(-) group increased in size significantly less than in the (131)I(-) group. The T3/T4 ratios were calculated to be 27 and 25 for the control group and the (188)ReO(4)(-) group, respectively; for (131)I(-), both the T3 and T4 levels were below detection limit, demonstrating much less effect on the thyroids of treatment with (188)ReO(4)(-) than with (131)I(-).

CONCLUSIONS

These results prove that NIS expression in breast tumors in animal models allows specific, efficient and safe treatment with a variety of radionuclides transported by NIS.

The relationship between expression of the sodium/iodide symporter gene and the status of hormonal receptors in human breast cancer tissue

PURPOSE

It has been reported that the sodium/iodide symporter (NIS) gene is expressed in several breast cancer tissues, suggesting the possibility of radionuclide imaging and therapy. However, the regulatory mechanism of NIS gene expression in breast cancer is not yet understood. To assess the relationship between the hormonal status and the NIS expression in breast cancer tissue, we investigated the NIS expression and correlated it to the expression of the thyrotropin receptor (thyroid stimulating hormone receptor, TSH-R), the estrogen receptor (ER) and the progesterone receptor (PR) in human breast cancer tissues.

MATERIALS AND METHODS

Breast cancer tissues were obtained from 44 patients. Pathological examination showed 2 cases of Grade I, 17 of Grade II, 22 of Grade III, and 3 of unknown grade. We measured the expression of NIS and TSH-R genes by using RT-PCR and we measured the status of ER and PR by using immunohistochemistry.

RESULTS

The NIS gene was expressed in 15 (34%) of the 44 breast cancer tissues. The NIS gene was expressed in 32% of the cases with TSH-R gene expression. The NIS gene was expressed in 40% of the breast cancer tissues with a positive PR and in 31% with a negative PR (p>0.05). It was positive for PR in 18% of the cases and negative for PR in 39% of the cases (p>0.05).

CONCLUSION

The NIS gene is expressed in approximately one-third of the human breast cancer tissues. Its expression was not related to the presence of the TSH-R gene or hormonal receptors, ER and PR.

In vivo radioiodide imaging and treatment of breast cancer xenografts after MUC1-driven expression of the sodium iodide symporter

PURPOSE

Expression of the sodium iodide symporter (NIS) in the thyroid gland provides for effective imaging and treatment of thyroid cancer using radiolabeled iodide. Transfer of NIS into other tumors would expand the utility of this treatment to tumors of nonthyroid origin. MUC1 is a transmembrane glycoprotein that is overexpressed in many tumor types, including breast, pancreatic, and ovarian. The aim of this study was to create a construct containing NIS under the control of the MUC1 promoter to target expression specifically to MUC1-positive breast cancer cells.

EXPERIMENTAL DESIGN

A replication-deficient adenoviral construct was created containing the MUC1 promoter followed by the human NIS gene. Iodide uptake assays, Western blot, and immunohistochemistry were used to confirm NIS expression and function. Breast cancer xenografts in mice were infected with Ad5/MUC1/NIS and then imaged and treated using radioiodide.

RESULTS

A 58-fold increase in iodide uptake was observed in infected MUC1-positive T47D cells with no significant increase observed in MUC1-negative MDA-MB-231 cells or in cells infected with the control virus. The in vivo study yielded clear images of Ad/MUC1/NIS-infected tumor xenografts using (123)I. Administration of a therapeutic dose of (131)I resulted in an 83% reduction in tumor volume, whereas control tumors continued to increase in size (P < 0.01).

CONCLUSIONS

These results show that the MUC1 promoter is capable of directing efficient and selective expression of the NIS gene in MUC1-positive breast tumor cells. This could potentially have applications for both imaging and therapy in a range of MUC1-positive tumor types.

Differential regulation of sodium/iodide symporter gene expression by nuclear receptor ligands in MCF-7 breast cancer cells

The sodium/iodide symporter (NIS) mediates iodide uptake in lactating breast tissue and is expressed in some breast cancers. We have previously demonstrated that all-trans retinoic acid (tRA) stimulates NIS gene expression and the selective cytotoxic effect of beta-emitting radioiodide-131 ((131)I) in both in vitro and in vivo MCF-7 breast cancer cell systems. We studied the ability of natural and synthetic retinoids, in combination with other nuclear receptor ligands, to achieve greater and more sustained induction of NIS in MCF-7 cells and enhance (131)I-mediated cytotoxicity. Selective stimulation of retinoic acid receptor (RAR) beta/gamma produced marked NIS induction; and selective stimulation of RARalpha, RARgamma, or retinoid X receptor produced more modest induction. Maximal NIS induction was seen with 9-cis retinoic acid and AGN190168, a RAR beta/gamma-agonist. Dexamethasone (Dex), but not the other nuclear receptor ligands, in combination with tRA synergistically induced iodide uptake and NIS mRNA expression, predominantly by prolonging NIS mRNA half-life. The addition of Dex reduced the EC(50) of tRA for NIS stimulation to approximately 7%, such that 10(-7) m tRA with addition of Dex enhanced iodide uptake and selective cytotoxicity of (131)I greater than 10(-6) m tRA alone. AGN190168 combined with Dex synergistically increased iodide uptake and significantly prolonged induction (5 d) of iodide uptake compared with that induced by the combination of tRA/Dex or 9-cis retinoic acid/Dex. The addition of Dex reduced the effective dose of retinoid and prolonged the induction of NIS, especially with AGN190168, suggesting higher efficacy of (131)I after combination treatment.

The Na+/I- symporter mediates iodide uptake in breast cancer metastases and can be selectively down-regulated in the thyroid

PURPOSE

The Na(+)/I(-) symporter (NIS) is a key plasma membrane protein that mediates active iodide (I(-)) transport in the thyroid, lactating breast, and other tissues. Functional NIS expression in thyroid cancer accounts for the longstanding success of radioactive iodide ((131)I) ablation of metastases after thyroidectomy. Breast cancer is the only other cancer demonstrating endogenous functional NIS expression. Until now, NIS activity in breast cancer metastases (BCM) was unproven.

EXPERIMENTAL DESIGN

Twenty-seven women were scanned with (99m)TcO(4)(-) or (123)I(-) to assess NIS activity in their metastases. An (131)I dosimetry study was offered to patients with I(-)-accumulating tumors. Selective down-regulation of thyroid NIS was tested in 13 patients with T(3) and in one case with T(3) + methimazole (MMI; blocks I(-) organification). NIS expression was evaluated in index and/or metastatic tumor samples by immunohistochemistry.

RESULTS

I(-) uptake was noted in 25% of NIS-expressing tumors (two of eight). The remaining cases did not show NIS expression or activity. Thyroid I(-) uptakes were decreased to </=2.8% at 24 h in T(3)-treated patients and 1/100 normal with T(3)/MMI. Uptake (2.9%) was calculated in a peribronchial metastasis on (131)I dosimetry scans at 4 h with disappearance of the signal by 24 h. We estimated a therapeutic dose of 3000 cGy could be achieved in this metastasis with 100 mCi of (131)I if the tumor exhibited the same dynamics as the T(3)/MMI-suppressed thyroid.

CONCLUSIONS

This is the first article of in vivo, scintigraphically detected, NIS-mediated I(-) accumulation in human BCM. T(3)/MMI down-regulation of thyroid NIS makes (131)I-radioablation of BCM possible with negligible thyroid uptake and radiation damage.

Imaging of adenovirus-mediated expression of human sodium iodide symporter gene by 99mTcO4 scintigraphy in mice

We have evaluated the feasibility of human sodium iodide symporter (hNIS) as a reporter gene in vitro and in vivo. Recombinant adenovirus encoding hNIS (Rad-hNIS) was introduced to FRO cell for 48 hours. Western blotting and 99mTcO4 uptake study revealed functional hNIS expression in the cell. Rad-hNIS was injected to BALB/c mice via tail vein. 99mTcO4 gamma scintigraphy, biodistribution study, and RT-PCR analysis demonstrated a preferential hepatic uptake of 99mTcO4, which was observed for up to one week. Thus, hNIS can be utilized as an effective reporter gene for noninvasive/repeated imaging, in combination with 99mTcO4.

The Na/I symporter (NIS): imaging and therapeutic applications

The Na(+)/I(-) symporter (NIS) is the plasma membrane glycoprotein that mediates the active uptake of I(-) in the thyroid, ie, the crucial first step in thyroid hormone biosynthesis. NIS also mediates I(-) uptake in other tissues, such as salivary glands, gastric mucosa, and lactating (but not nonlactating) mammary gland. The ability of thyroid cancer cells to actively transport I(-) via NIS provides a unique and effective delivery system to detect and target these cells for destruction with therapeutic doses of radioiodide. Breast cancer is the only malignancy other than thyroid cancer to have been shown to functionally express NIS endogenously. The considerable potential diagnostic and therapeutic use of radioiodide in breast cancer is currently being assessed. On the other hand, exogenous NIS gene transfer has successfully been carried out into a variety of other cell lines and tumors, including A375 human melanoma tumors, and SiHa cervix cancer, human glioma, and hepatoma cell lines. Most notably, significant radioiodine therapy results have been obtained in the NIS-transfected human prostatic adenocarcinoma cell line LNCaP and in NIS-transfected myeloma cells, both of which exhibited prolonged retention of radio iodide even in the absence of I(-) organification. The therapeutic potential of alternative NIS-transported radioisotopes with different decay properties and a shorter, physical half-life than 131I(-), such as beta-emitter 188Rhenium (188ReO(4)-) and alpha-emitter 211Astatine (211At(-)), has been evaluated. In conclusion, it is clear that the remarkable progress made in the last few years in the molecular characterization of NIS has created new opportunities for the development of diagnostic and therapeutic applications for NIS in nuclear medicine.

Systemic Retinoic Acid Treatment Induces Sodium/Iodide Symporter Expression and Radioiodide Uptake in Mouse Breast Cancer Models

Lactating breast tissue and some breast cancers express the sodium/iodide symporter (NIS) and concentrate iodide. We recently demonstrated that all-trans retinoic acid (tRA) induces both NIS gene expression and iodide accumulation in vitro in well-differentiated human breast cancer cells (MCF-7). In the present study, we investigated the in vivo efficacy and specificity of tRA-stimulated iodide accumulation in mouse breast cancer models. Immunodeficient mice with MCF-7 xenograft tumors were treated with systemic tRA for 5 days. Iodide accumulation in the xenograft tumors was markedly increased, approximately 15-fold greater than levels without treatment, and the effects were tRA dose dependent. Iodide accumulation in other organs was not significantly influenced by tRA treatment. Significant induction of NIS mRNA and protein in the xenograft tumors was observed after tRA treatment. Iodide accumulation and NIS mRNA expression were also selectively induced in breast cancer tissues in transgenic mice expressing the oncogene, polyoma virus middle T antigen. These data demonstrate selective induction of functional NIS in breast cancer by tRA. Treatment with short-term systemic retinoic acid, followed by radioiodide administration, is a potential tool in the diagnosis and treatment of some differentiated breast cancer.