维甲酸诱导甲状腺癌细胞摄碘的实验研究

目的探讨全反式维甲酸(ATRA)诱导甲状腺癌细胞系的钠碘同向转运体(NIS)表达及其碘摄取。方法通过ATRA诱导甲状腺癌细胞系滤泡状甲状腺癌细胞株(FIE-133)、乳头状甲状腺癌细胞株(W3)及未分化甲状腺癌细胞株(8505C)后，经逆转录．聚合酶链反应(RT-PCR)及Western blot检测甲状腺癌细胞系的NIS mRNA及其蛋白质表达，并测定甲状腺癌细胞系诱导后的摄碘变化。结果ATRA诱导甲状腺癌细胞系48h后，FTG-133和W3的NIS mRNA及蛋白质表达增高，8505C未见变化；ATRA诱导甲状腺癌细胞系2周后．FTC-133和W3的摄碘增高。结论ATRA能诱导分化型甲状腺癌细胞摄碘增高，为ATRA诱导分化治疗甲状腺癌提供了依据。     

全反式维甲酸对甲状腺癌细胞NIS基因表达及摄碘水平的影响

目的探讨全反式维甲酸(ATRA)对甲状腺癌细胞株钠／碘同向转运体(NIS)基因表达及摄碘水平的影响。方法以不同浓度ATRA作用于3株甲状腺癌细胞(FIE-133、K1、8505C)，利用半定量逆转录-聚合酶链反应(RT-PCR)检测NIS mRNA表达，并测定细胞摄碘水平。结果ATRA在10^-7～10^-4mol／L范围内可剂量依赖性上调FTC-133细胞NIS mRNA的表达，增强FIE-133细胞的摄碘能力；ATRA在10^-6～10^-4mol／L范围内可上调K1细胞NIS mRNA的表达，并增加其摄碘水平；不同浓度组均未见8505C细胞NIS mRNA的表达和摄碘水平增加。结论ATRA可上调FIE-133、K1细胞NIS基因表达，提高其摄碘能力，这为ATRA用于分化型甲状腺癌的^131I治疗提供了实验依据。     

重组NIS基因腺相关病毒的制备及其在甲状腺癌细胞系表达

目的探讨钠碘同向转运体（NIS）基因介导的甲状腺癌基因治疗的可行性。方法构建腺相关病毒载体质粒pGA—NIS，并采用磷酸钙沉淀法制备重组NIS基因的腺相关病毒rAAV—NIS，体外感染甲状腺癌细胞系FTC-133、8505C后，通过免疫荧光检测被感染细胞的NIS蛋白表达，并通过摄碘实验及NaClO4摄碘抑制实验验证其表达的NIS蛋白功能和特性。结果成功制备了重组NIS基因的rAAV—NIS，其感染肿瘤细胞所表达的NIS蛋白位于细胞膜上，且具有介导碘摄取的功能，以及被NaClO4抑制的特性，表明与正常甲状腺细胞的NIS具有相同的功能和特性。感染细胞的碘摄取较未感染细胞明显增高。结论rAAV—NIS能介导甲状腺癌细胞的碘摄取，为甲状腺癌NIS基因介导的基因治疗提供了实验依据。     

曲古菌素A对甲状腺癌细胞NIS基因表达和摄碘功能的影响

目的探讨曲古菌素A（TSA）对甲状腺癌细胞中钠／碘同向转运蛋白（NIS）基因表达和摄取碘的影响。方法以不同浓度的TSA诱导滤泡状甲状腺癌细胞FFC-133及乳头状甲状腺癌细胞K1,利用反转录-聚合酶链反应（RT—PCR）分析经诱导后2株甲状腺癌细胞中NISmRNA的表达,以NIS／3-磷酸甘油醛脱氢酶（GAPDH）的条带密度比值作为mRNA表达强度,并检测诱导前后甲状腺癌细胞对放射性碘摄取的变化。2组数据间比较采用独立样本t检验,多组数据间比较用One．wayANONA方差分析。结果20,50,75,100和150nmol／LTSA诱导48h后,甲状腺癌细胞FFC-133的NISmRNA表达较未诱导对照组增加了1．5至13．7倍,各TSA浓度组间FTC-133NISmRNA表达差异有统计学意义（F=32．56,P〈0．01）;而K1的NISmRNA表达没有明显变化,TSA浓度为50和75nmol／L时表达有所增加（NIS／GAPDH条带密度比值分别为0．62±0．16,0．60±0．23）,但与对照组（O．41±0．18）比较差异无统计学意义（F=2．823,P〉0．05）。细胞摄取碘实验显示,50和75nmol／LTSA诱导48h后,FTC-133的摄碘增加[（15．42±0．42）×10’和（18．98±1．33）×10^3计数·min^-1／10^5个细胞],与对照组[（8．46±0．84）×10^3计数·min^-1／10%5个细胞]比较,差异有统计学意义（t值分别为3．018和3．557,P均〈0．05）;而50和75nmol／LTSA作用后K1对碘的摄取也有增加[（5．83±1．09）×10^3和（6．97±0．65）×10^3计数·min^-1／10^5个细胞],但与对照组[（5．37±0．88）×10^3计数·min^-1／10^5个细胞]比较,差异无统计学意义（t值分别为0．185和0．332,P均〉0．05）。结论TSA能明显诱导滤泡状甲状腺癌细胞的NISmRNA表达升高和摄碘增加,而对乳头状甲状腺癌细胞作用不明显。     

杆状病毒介导NIS基因放射治疗甲状腺癌的实验研究

目的探讨重组钠／碘同向转运体(NIS)基因杆状病毒介导甲状腺癌细胞放射性碘治疗的可行性。方法构建杆状病毒载体质粒(pFBNIS)并制备重组NIS杆状病毒(BacNIS)，体外感染甲状腺癌细胞，通过免疫荧光检测NIS蛋白的表达，通过动态摄碘及NaC104摄碘抑制实验观察表达蛋白的功能和特性；进行^131I杀伤细胞的克隆形成实验。结果成功构建了重组NIS杆状病毒，受巨细胞病毒(CMV)极早期基因启动子调控；BacNIS体外感染的甲状腺癌细胞表达的NIS蛋白具有摄碘功能和NaC104抑制的特性；BacNIs感染的肿瘤细胞可被^131I有效杀伤。结论BacNIS是介导肿瘤细胞摄碘的有效方法，为杆状病毒介导NIS基因治疗失分化甲状腺癌转移灶提供依据。     

维甲酸对人乳腺癌细胞NIS基因表达和摄碘功能的影响

目的探讨9-顺-维甲酸（9-cis—RA）对人乳腺癌细胞钠／碘同向转运体（NIS）基因功能表达的影响。方法应用9-cis—RA和全反式维甲酸（ATRA）分别在不同浓度下对雌激素受体（ER）阳性的乳腺癌细胞（MCF-7）和ER阴性的乳腺癌细胞（MDA—MB-231）进行干预，于不同时间点提取细胞总RNA，通过半定量逆转录-聚合酶链反应（RT—PCR）检测乳腺癌细胞NIS mRNA表达水平的变化；在体外培养条件下研究RA刺激后乳腺癌细胞对放射性碘的摄取情况。结果9-cis—RA处理后，MCF-7细胞NIS mRNA表达增强，呈浓度依赖性（F=114．17，P〈0．001），在10^-6mol／L浓度下NIS mRNA的表达随时间上调，16h时达到最高，是对照组（0h）的8．2倍（q=8．32，P〈0．01），此后随时间逐渐下调；且9-cis—RA（10^-6mol／L，24h）的作用强于ATRA（t=6．572，P〈0．01）。MDA—MB-231基础状态下几乎无NIS表达，9-cis—RA刺激后可上调其表达（t=20．195，P〈0．001），但表达量（NIS／B—actin）远低于MCF-7（t=10．395，P〈0．001）。碘摄取实验表明，10^-6mol／L 9-cis—RA干预12h后，MCF-7细胞摄碘开始增加，干预24h时碘摄取达最大，是基础状态下的3．2倍，其摄碘能力可被KCl0。抑制。结论9-cis—RA能明显增强ER阳性的MCF-7细胞NIS基因的表达及摄碘功能。     

维甲酸联合曲古抑素诱导及治疗荷人甲状腺滤泡状癌裸鼠的实验研究

目的探讨全反式维甲酸（ATRA）和曲古抑素（TSA）对人甲状腺滤泡状癌细胞株（FTC-133）和荷人甲状腺滤泡状癌裸鼠（NMB—hFTC）肿瘤模型摄碘能力的影响。方法不同量ATRA、TSA诱导VFC-133细胞：ARTA 1．0×10^-6mo／L（A低组）、1．0×10^-4mol／L（A高组）、TSA1．65×10^-7mol／L（T组）、A低＋T组、A高＋T组和无水乙醇（对照组）,96h后行HE染色,测定FTC-133细胞摄碘率;制备NMB—hFTC,成瘤后分组：ATRA组（2mg／kg灌胃）、TSA组（10mg／kg腹腔注射）、联合组（ATRA＋TSA,用量同前）、对照组（生理盐水灌胃＋腹腔注射,均为10ml／kg）,剂量均按鼠体质量给予。给药22d后,腹腔注射37MBq ^131I,分别于注射后4,6,12和24h行γ显像,测定体内生物分布;显像后取肿瘤组织行HE染色观察细胞形态。实验结果采用SPSS13．0软件进行单因素方差分析。结果FTC-133细胞摄碘率A低＋T组、A高＋T组分别为（23885±616．0）和（13849±728．2）计数·min^-1·10^-6细胞,其他各组在（985±84．2）～（17600±782．7）计数·min^-1·10^-6细胞范围内,各组间比较差异有统计学意义（F=600．879,P〈0．001）。^131I注射后6,12和24h联合组裸鼠种植瘤％ID／g分别为6．17±0．46,9．34±0．61,11．19±0．98,其余各组保持在（1．97±0．34）～（5．14±0．65）之间;肿瘤质量各组间比较差异有统计学意义（F=3．723,P〈0．05）。结论ATRA联合TSA,可增强FTC-133细胞和NMB—hFTC病灶的分化、摄碘能力,达到增强^131I杀死甲状腺癌病灶的协同作用。     

钠/碘同向转运体在甲状腺癌131Ⅰ治疗中的应用

钠/碘同向转运体(Na+/I-symporter,NIS)是一种膜蛋白,介导甲状腺滤泡细胞的碘转运,在甲状腺癌的病理生理及131Ⅰ治疗中起着重要的作用.多数研究表明,甲状腺癌的NIS mRNA及蛋白表达水平降低;维甲酸、去甲基化及组蛋白脱乙酰酶抑制剂可刺激失分化甲状腺癌细胞的NIS表达,为甲状腺癌.131Ⅰ的有效治疗进行了有益的探索.NIS基因的克隆和其特性的揭示为甲状腺癌的靶向基因放射治疗提供了可能.     

重组NIS基因腺病毒的制备及在心肌细胞中的特异表达

目的 构建肌凝蛋白轻链-2(MLC-2v)启动子调控的NIS腺病毒载体,探讨外源基因在心肌细胞中的特异性表达和NIS作为报告基因的可行性.方法 将MLC-2v启动子和NIS基因亚克隆至腺病毒穿梭载体,再与含有骨架质粒(pAdEasy-1)的大肠杆菌(BJ5183)同源重组,经人胚肾细胞(HEK293)包装并扩增得到重组腺病毒Ad-MLC-NIS,同时构建巨细胞病毒(CMV)启动子调控的腺病毒Ad-CMV-NIS、仅含有启动子的腺病毒Ad-MLC和仅含有NIS基因片段的腺病毒Ad-NIS作为对照组.腺病毒体外感染心肌细胞和非心肌细胞,通过Western blot检测NIS蛋白的表达,行动态摄碘及NaClO4摄碘抑制实验观察NIS蛋白的功能和特性.通过台盼蓝染色实验检测腺病毒感染及NIS摄碘情况对心肌细胞活力和增殖的影响.结果 成功构建重组NIS腺病毒.Western blot检测示感染Ad-CMV-NIS的心肌细胞和非心肌细胞均呈NIS蛋白高表达;感染Ad-MLC-NIS的非心肌细胞出现微量蛋白表达,而心肌细胞中NIS蛋白高表达.动态摄碘实验示感染Ad-MLC-NIS的H9C2细胞、A549细胞、U87细胞摄碘峰值分别为5844.0、833.6、846.0放射性计数·min-1.H9C2细胞的摄碘被NaClO4抑制.感染复数(MOI)为100的腺病毒感染心肌细胞,感染和摄碘实验对心肌细胞活力和增殖的影响较小.结论 MLC-2v启动子调控的腺病毒载体可使外源基因NIS在心肌细胞内特异性表达,表达的NIS蛋白具有摄碘功能,为NIS在心肌中作为报告基因的研究奠定了基础.     

重组质粒hTSHR转染低分化甲状腺癌细胞株后对摄碘能力及特异性基因表达的影响

目的 探讨重组真核表达质粒pcDNA3.1/人TSH受体（hTSHR）体外转染TSHR表达下降的低分化滤泡状甲状腺癌细胞株后,细胞摄取放射性碘功能以及甲状腺癌相关基因mRNA表达 的变化.方法 pcDNA3.1/hTSHR转化DH5a感受态菌,进行扩增、酶切,再以核苷酸测序方法鉴定.体外转染pcDNA3.1/hTSHR,通过免疫荧光检测TSHR表达产物,井型γ计数仪检测摄碘率,相对定量实时荧光PCR验证其表达的TSHR蛋白功能和特性.采用SPSS 13.0软件,对计量资料行t检验.结果pcDNA3.1/hTSHR经PCR扩增hTSHR-cDNA片段约113 kb,Kpn Ⅰ和Xha Ⅰ双酶切：hTSHR-cDNA的片段约2.3 kb,pcDNA3.1（＋）的片段约5.5 kb,均同预期片段大小相符;核苷酸测序方法鉴定测序结果与GenBank中收录的hTSHR全长序列一致,表明真核表达质粒构建正确.在hTSH刺激下,转染pcDNA3.1/hTSHR细胞与转染pcDNA3.1（＋）细胞比较：（1）在甲状腺肿瘤细胞胞质、胞膜有增强的绿色荧光,（2）前者125 I摄取率是后者的2.9倍（t=28.63,P＜0.01）,（3）甲状腺碘摄取相关基因TSHR、钠碘转运体（NIS）、甲状腺过氧化物酶（TPO）、Tg的mRNA的表达分别升高1.74倍（t=5.959,P＜0.01）、7.2倍（t=3.807,P＜0.05）、2.88倍（t=4.769,P＜0.01）和2.67倍（t=6.388,P＜0.01）.结论 pcDNA3.1/hTSHR体外转染甲状腺癌肿瘤细胞后,可有效提高碘的摄取;这可为放射性碘治疗失分化甲状腺癌提供新的实验依据.     

Efficacy of lentiviral-mediated transfection of hTSHR in poorly differentiated thyroid carcinoma cell line

IntroductionDedifferentiated thyroid cancer is often incurable because it does not respond to radioiodine. This study aimed to investigate iodide uptake and the expressions of thyroid-specific molecules after the transfection of human thyrotropin receptor (hTSHR) gene in poorly differentiated follicular thyroid cancer cell line (FTC-133).MethodspGC-FU-hTSHR-GFP-lentivirus and pGC-FU-GFP-lentivirus were added into FTC-133 cells respectively. The parental cells were defined as the blank group. Cells transduced with pGC-FU-GFP and pGC-FU-hTSHR-GFP were defined as the control group and experimental group respectively. The efficiency of transfection was observed under a fluorescence microscope. ¹²⁵I uptake by FTC-133 was analyzed by measuring the radioactivity. Real time-PCR, western blotting and radioimmunoassay were applied to detect the expressions of mRNAs and proteins of Na⁺/I^? symporter (NIS), thyroid-stimulating hormone receptor (TSHR), thyroid peroxidase (TPO) and thyroglobulin (Tg) in FTC-133.ResultsThe green fluorescence was present in 80% of the transduced cells under fluorescence microscope. The iodine uptake of cells transduced with pGC-FU-TSHR-GFP was 3.3 times higher than that in the other two groups (P < 0.01). NIS, TSHR, TPO and Tg had been significantly up-regulated in the experimental group as compared to the control group (P < 0.01) and the blank group (P < 0.01).ConclusionThe hTSHR transfection in FTC-133 improved the expression of thyroid-specific molecules including TSHR, NIS, TPO and Tg and radioiodide uptake.     

Enhanced expression of adenovirus-mediated sodium iodide symporter gene in MCF-7 breast cancer cells with retinoic acid treatment.

Increased expression of the sodium iodide symporter (NIS) is required for effective radioiodine treatment and reporter gene imaging of breast cancer. We investigated the effect of retinoic acid on adenovirus-mediated expression of the human NIS gene in the MCF-7 breast cancer cell line. METHODS: The MCF-7 cell line was infected with recombinant adenovirus carrying the human NIS gene (Rad-NIS). Levels of NIS messenger RNA (mRNA) and protein expression and radioiodine ((125)I) uptake were measured to evaluate adenovirus-mediated NIS gene expression in wild-type and Rad-NIS-infected MCF-7 cells after treatment with all-trans-retinoic acid (ATRA; 10(-8)-10(-6) mol/L). RESULTS: The transduction efficiency of adenovirus in MCF-7 cells at a multiplicity of infection (MOI) of 50 was >60%. After incubation with 10(-6) mol/L ATRA, the mRNA level in Rad-NIS-infected MCF-7 cells increased to 118.5 times that of wild-type MCF-7 cells, whereas the mRNA level in wild-type MCF-7 cells showed only a 2.1-fold increase. Western blot, immunocytochemical staining, and flow cytometry analyses showed that NIS protein expression in MCF-7 cells infected with Rad-NIS increased after ATRA treatment. With ATRA treatment, the amount of (125)I uptake increased in a dose-dependent manner (P < 0.001). The (125)I uptake in wild-type MCF-7 cells increased 3.1-, 5.5-, and 7.6-fold with treatment with 10(-8), 10(-7), and 10(-6) mol/L ATRA, respectively. Rad-NIS-infected cells showed a 4.0-fold increase in (125)I uptake. Treatment of Rad-NIS-infected cells with 10(-8), 10(-7), and 10(-6) mol/L ATRA increased (125)I uptake by 4.9-, 8.2-, and 27.6-fold, respectively, compared with wild-type MCF-7 cells. The level of NIS expression in Rad-NIS-infected MCF-7 cells treated with 10(-6) mol/L ATRA (245.0 +/- 13.7 pmol/10(6) cells) was much greater than the sum of the expression levels seen in ATRA-treated wild-type cells and Rad-NIS-infected wild-type cells. CONCLUSION: Retinoic acid increases adenovirus-mediated NIS expression in MCF-7 cells. Our results indicate that improved efficiency of NIS gene therapy or reporter imaging in breast cancer may be possible with retinoic acid treatment.     

Dedifferentiation of differentiated thyroid carcinoma cell line FTC-133 is enhanced by 131I pretreatment

Introduction

Differentiated thyroid carcinoma (DTC) usually has a high iodine uptake. However, dedifferentiation of DTC with decreased or no radioiodine (¹³¹I) uptake is observed in clinical practice, with poor prognosis. The aim of this study was to investigate the effects of ¹³¹I radiation on radioiodine uptake (RAIU) and the expression of thyroid-specific molecules.

Methods

FTC-133 cells were treated with ¹³¹I, the dosage dictated by methylthiazol tetrazolium test results and preliminary experiments. The experimental cell group was incubated with ¹³¹I for 48 h and then cultured for 3 months in ¹³¹I-free medium. The control group was set without ¹³¹I. Primary cells were defined as the blank group. Following treatment, RAIU was measured with a gamma counter as the counts/cell number. Na⁺/I⁻ symporter (NIS), thyroid-stimulating hormone receptor (TSHR), thyroid peroxidase (TPO) and thyroglobulin (Tg) levels were detected by Western blotting and radioimmunoassay, and their mRNAs were detected by real-time polymerase chain reaction.

Results

RAIU of FTC-133 cells decreased gradually after coincubation with ¹³¹I and did not recover even if ¹³¹I was removed. The relative RAIU of the control and experimental groups was 0.567 and 0.182, respectively, a statistically significant difference (P<.01). Expression of NIS, TSHR, TPO and Tg decreased in the experimental group to a statistically significant degree compared to that of controls (P<.05).

Conclusion

Changes in the mRNA levels were in accordance with the expression of thyroid-specific proteins. Thus, FTC-133 cells undergo dedifferentiation during long-term culture in vitro, and ¹³¹I may promote this progress.     

Establishment and characterization of a breast cancer cell line expressing Na+/I- symporters for radioiodide concentrator gene therapy.

131I therapy is a widely accepted treatment for metastatic differentiated thyroid cancer. To investigate the feasibility of 131I therapy for breast cancer, we established breast cancer cells stably expressing Na-/I- symporter (NIS) gene that can be modulated and studied in vitro and in vivo. METHODS: We transfected rat NIS genes into a human breast cancer cell line (MCF7) by electroporation. Iodide accumulation was evaluated under various extracellular concentrations of sodium and iodide, and iodide efflux was also assessed. Biodistribution and tumor imaging were studied using tumor-bearing mice. RESULTS: A novel cell line (MCF3B), stably expressing the NIS gene, was established from MCF7. MCF3B took up 44 times more radioiodide in vitro than MCF7 did. Iodide uptake was completely inhibited by 1 mmol/L perchlorate and was dependent on external sodium and iodide concentrations. Iodide efflux from MCF3B cells was slower (half-life [T 1/2] > 27 min) than from FRTL5 thyroid cells (T 1/2 = 4 min). In the biodistribution study using MCF3B-xenografted mice, high tumor uptake of 125I was shown (16.73%) at 1 h after injection, and tumor-to-normal tissue ratios were also high (4.84-21.28), except in the stomach (0.47). However, the iodide accumulation in the tumor lessened with time, reaching less than 1% at 24 h after injection. CONCLUSION: Our preliminary data indicate that NIS-based gene therapy may be applied by concentrating a lethal dose of radiation in tumor cells in vivo, but further investigation is necessary to determine a method of maintaining radioiodine in the cells to allow greater therapeutic effects.     

Re-induction of cell differentiation and 131I uptake in dedifferentiated FTC-133 cell line by TSHR gene transfection

IntroductionRadioiodine therapy is commonly used to treat differentiated thyroid cancer (DTC), but a major challenge is dedifferentiation of DTC with the loss of radioiodine uptake. TSHR is a key molecule regulating thyrocyte proliferation and function. This study aimed to test the therapeutic potential of TSHR in dedifferentiated DTC by gene transfection in order to restore cell differentiation and radioiodine uptake.MethodsDedifferentiated FTC-133 (dFTC-133) cells were obtained by monoclonal culture of FTC-133 cell line after ¹³¹I radiation. Recombinant plasmid pcDNA3.1-hTSHR was transfected into dFTC-133 cells by using Lipofectamine 2000 reagent. Immunofluorescence analysis was carried out to confirm TSHR expression and its location. Radioiodine uptake assay was thereafter investigated. mRNAs and proteins of TSHR and other thyroid differentiated markers were detected by real-time PCR and western blot respectively.ResultsAmong the thyroid specific genes in dFTC-133 cells with stable low radioiodine uptake, TSHR was down-regulated most significantly compared with FTC-133. Then, after TSHR gene transfection, augmented expression of TSHR was observed in dFTC-133 cell surface and cytoplasm by immunofluorescence analysis. It was found that ¹²⁵I uptake was 2.9 times higher (t = 28.63, P < .01) in cells with TSHR transfection than control. The mRNAs of TSHR, NIS, TPO and Tg were also significantly increased by 1.7 times (t = 13.8, P < .05), 4 times (t = 28.52, P < .05), 1.5 times (t = 14.43, P < .05) and 2.2 times (t = 19.83, P < .05) respectively compared with control group.ConclusionDecreased TSHR expression correlated with FTC-133 ongoing dedifferentiation. TSHR transfection contributed to the re-differentiation of dedifferentiated thyroid follicular carcinoma cells.     

Establishment of radioactive astatine and iodine uptake in cancer cell lines expressing the human sodium/iodide symporter

The sodium/iodide symporter (NIS) has been recognized as an attractive target for radioiodine-mediated cancer gene therapy. In this study we investigated the role of human NIS for cellular uptake of the high LET alpha-emitter astatine-211 ((211)At) in comparison with radioiodine as a potential radionuclide for future applications. A mammalian NIS expression vector was constructed and used to generate six stable NIS-expressing cancer cell lines (three derived from thyroid carcinoma, two from colon carcinoma, one from glioblastoma). Compared with the respective control cell lines, steady state radionuclide uptake of NIS-expressing cell lines increased up to 350-fold for iodine-123 ((123)I), 340-fold for technetium-99m pertechnetate ((99m)TcO(4)(-)) and 60-fold for (211)At. Cellular (211)At accumulation was found to be dependent on extracellular Na(+) ions and displayed a similar sensitivity towards sodium perchlorate inhibition as radioiodide and (99m)TcO(4)(-) uptake. Heterologous competition with unlabelled NaI decreased NIS-mediated (211)At uptake to levels of NIS-negative control cells. Following uptake both radioiodide and (211)At were rapidly (apparent t(1/2) 3-15 min) released by the cells as determined by wash-out experiments. Data of scintigraphic tumour imaging in a xenograft nude mice model of transplanted NIS-modified thyroid cells indicated that radionuclide uptake in NIS-expressing tumours was up to 70 times ((123)I), 25 times ((99m)TcO(4)(-)) and 10 times ((211)At) higher than in control tumours or normal tissues except stomach (3-5 times) and thyroid gland (5-10 times). Thirty-four percent and 14% of the administered activity of (123)I and (211)At, respectively, was found in NIS tumours by region of interest analysis ( n=2). Compared with cell culture experiments, the effective half-life in vivo was greatly prolonged (6.5 h for (123)I, 5.2 h for (211)At) and preliminary dosimetric calculations indicate high tumour absorbed doses (3.5 Gy/MBq(tumour) for (131)I and 50.3 Gy/MBq(tumour) for (211)At). In conclusion, NIS-expressing tumour cell lines of different origin displayed specific radionuclide uptake in vitro and in vivo. We provide first direct evidence that the high-energy alpha-emitter (211)At is efficiently transported by NIS. Application of (211)At may direct higher radiation doses to experimental tumours than those calculated for (131)I. Thus, (211)At may represent a promising alternative radionuclide for future NIS-based tumour therapy.