Increased Radioiodine Uptake of Thyroid Cell Cultures after External Irradiation

BACKGROUND: Radioiodine uptake (RIU) is one of the main prognostic factors for curative results of radioiodine therapy in patients with differentiated thyroid cancer. Some days after application of (131)I, the uptake of a subsequent administration of radioiodine was found to be reduced. In contrast, early after irradiation with high-energy photons glucose and amino acid uptake were observed to be increased. Effects of external irradiation on RIU of thyrocytes using high-energy photons have not been investigated so far. MATERIAL AND METHODS: Two different cell lines (FRTL-5 and ML-1 cells) derived from thyroid tissue were studied in vitro. Cell lines were either incubated with (131)I only (controls) or additionally irradiated with single doses of 6 or 10 Gy of high-energy photons using a linear accelerator. Cell number and RIU were determined 24-96 h after (131)I application. RIU measurements were repeated after application of sodium perchlorate in excess to investigate specificity of the uptake. Statistical analyses were performed using non-parametric tests. RESULTS: Incubation with radioiodine as well as irradiation with high-energy photons slowed down proliferation in investigated cell lines significantly. Irradiation with solely (131)I resulted in stable or slightly decreased iodide uptake. Compared to those cells, the RIU increased significantly in externally irradiated cells, i. e., additional irradiation with 10 Gy resulted in an almost threefold increase of RIU in FRTL-5 after 72 h. The increase of RIU after irradiation was dose-dependent in both cell lines and could be blocked by perchlorate excess. CONCLUSION: It could be demonstrated that external irradiation increases RIU in thyroid cell cultures early after irradiation. The increase was dose-dependent and specific, as it could be blocked by perchlorate. This effect appears to be similar to the increase of other actively transported substances after irradiation with high-energy photons. Therefore, the results of this study may contribute to the knowledge of a generalized irradiation-induced mechanism which causes the activation of different cellular transporters. The clinical impact of these findings on combined therapy concepts has to be investigated in further experiments.     

The Effect of Tanespimycin (17-AAG) on Radioiodine Accumulation in Sodium-Iodide Symporter Expressing Cells

Purpose

The heat shock protein 90 inhibitor, tanespimycin, is an anticancer agent known to increase iodine accumulation in normal and cancerous thyroid cells. Iodine accumulation is regulated by membrane proteins such as sodium iodide symporter (NIS) and pendrin (PDS), and thus we attempted to characterize the effects of tanespimycin on those genes.

Methods

Cells were incubated with tanespimycin in order to evaluate ¹²⁵I accumulation and efflux ability. Radioiodine uptake and efflux were measured by a gamma counter and normalized by protein amount. RT-PCR were performed to measure the level of gene expression.

Results

After tanespimycin treatment, ¹²⁵I uptake was increased by ∼2.5-fold in FRTL-5, hNIS-ARO, and hNIS-MDA-MB-231 cells, but no changes were detected in the hNIS-HeLa cells. Tanespimycin significantly reduced the radioiodine efflux rate only in the FRTL-5 cells. In the FRTL-5 and hNIS-ARO cells, PDS mRNA levels were markedly reduced; the only other observed alteration in the levels of NIS mRNA after tanespimycin treatment was an observed increase in the hNIS-ARO cells.

Conclusions

These results indicate that cellular responses against tanespimycin treatment differed between the normal rat thyroid cells and human cancer cells, and the reduction in the ¹²⁵I efflux rate by tanespimycin in the normal rat thyroid cells might be attributable to reduced PDS gene expression.     

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.     

Enhanced antiproliferative effects of combination hexokinase II shRNA and NIS gene therapy on vascular smooth muscle cells

IntroductionThis study was designed to determine the antiproliferative effects of combination gene therapy using sodium iodide symporter (NIS)-based radioiodine and lentivirus-mediated short hairpin RNA (shRNA) against hexokinase II (HKII) on vascular smooth muscle cells (VSMCs).MethodsA7r5 rat VSMCs were stably transfected with a dual-expression vector of NIS and Fluc (A7r5-NL cells). Functional assessment was performed by radioiodine uptake assay, luciferase assay and confocal microscopy. After exposure to lentivirus-HKII-shRNA, the ¹⁸F-FDG uptake test and HK activity assay were performed. The effects of combination therapy with ¹³¹I and lentivirus-HKII-shRNA on VSMCs were assessed with an in vitro clonogenic assay. In vivo bioluminescence and nuclear imaging were undertaken using a xenografted mouse model.ResultsIn vitro functional assessment confirmed expression of NIS and Fluc genes in A7r5-NL, but not in parent A7r5 cells. Transfection of lentivirus-HKII-shRNA resulted in a significant decrease in messenger RNA expression of the HKII gene, ¹⁸F-FDG uptake and HK activity. The cell survival rate of A7r5-NL decreased to 61.9% and 90.5% by single therapy with 7.4 MBq of ¹³¹I or lentivirus-HKII-shRNA, respectively, and further decreased to 42.9% by combined therapy (P<.05). In vivo bioluminescent and gamma camera images clearly demonstrated optical signals and ^99mTc pertechnetate uptake at the site of A7r5-NL cell inoculation in nude mice.ConclusionThe enhanced antiproliferative effect on VSMCs was achieved by a combination of NIS-based radioiodine and lentivirus-mediated HKII shRNA gene therapy. Successful demonstration of in vivo dual reporter gene imaging assures the potential for further application in an animal model.     

Does thyroid stunning exist? A model with benign thyroid disease

With regard to the treatment of differentiated non-medullary thyroid carcinoma, there is controversy over whether radiation from a diagnostic radioiodine (131I) application really does have a suppressive effect on the uptake of subsequent therapeutic 131I (so-called thyroid stunning). However, inherent difficulties in exact remnant/metastatic tissue volumetry make it difficult to quantify how much diagnostic 131I is actually absorbed (absorbed energy dose) and hence to decide whether a threshold absorbed dose exists beyond which such stunning would occur. Since in benign thyroid disease the target volume can be readily quantified by ultrasonography, we sought to determine definitely whether stunning of thyroid cells occurs upon a second application of radioiodine 4 days following the first one. We therefore studied 171 consecutive patients with benign thyroid disease (diffuse goitre, Graves' disease, toxic nodular goitre) who received two-step 131I therapy during a single in-patient stay. For application of both calculated 131I activities we performed kinetic dosimetry of 131I uptake, effective half-life and absorbed dose. At the second application, patients showed significant stunning (a 31.7% decrease in 131I uptake, from 34.7% +/- 15.4% at first application to 23.7% +/- 12.3% at second application, P < 0.0005) without a significant difference in effective half-life (4.9 +/- 1.3 vs 5.0 +/- 1.7 days, P > 0.2). ANOVA showed that the extent of stunning was influenced significantly only by the absorbed energy dose at first application (F = 13.5, P < 0.0005), while first-application 131I activity, target volume, gender and thyroid function had no influence (all F < or = 0.71, all P > 0.4). There was no significant correlation between extent of thyroid stunning and first-application 131I activity ( r = 0.07, P > 0.3), whereas there was a highly significant correlation between thyroid stunning and first absorbed energy dose (r = 0.64, P < 0.00005), the latter correlation fitting a logarithmic model best. Multivariate factor analysis also revealed first absorbed energy dose to be the only decisive stunning factor. In conclusion, our study confirms that stunning exists in benign thyroid conditions and that it is a purely radiobiological inhibitory phenomenon related to absorbed dose.     

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.     

甲状腺癌术后131I治疗

甲状腺癌确诊后，经典的治疗方法是近全切除术后加131I治疗。研究表明，NIS(钠／碘同向转运体)具有聚碘能力，而TPO(甲状腺过氧化物酶)能抑制碘从细胞中流出，NIS和TPC基因联合转染肿瘤细胞介导~(131)I治疗有可能成为一种新的治疗方法；维加酸可诱导失分化肿瘤细胞的摄碘能力恢复或提高，也有利于~(131)I治疗。     

Absence of thyroid stunning after diagnostic whole-body scanning with 185 MBq 131I.

There has been recent controversy regarding the optimal protocol for imaging and ablation of post-thyroidectomy patients. Several authors have suggested that a scanning dose of 185-370 MBq (5-10 mCi) (131)I may be capable of producing a stunning effect on thyroid tissue that may interfere with the uptake and efficacy of the subsequent ablation dose of radioiodine. The purpose of this study was to determine whether a 185-MBq (5 mCi) diagnostic dose of (131)I produces a visually apparent stunning effect 72 h before (131)I ablation therapy. METHODS: One hundred twenty-two consecutive post-thyroidectomy patients for differentiated thyroid carcinoma received a 185-MBq (5 mCi) diagnostic dose of (131)I followed by a whole-body diagnostic scan at 72 h. On the same day the diagnostic scan was completed, the patient was admitted to the hospital and received an (131)I ablation therapy dose of 5550 MBq (150 mCi) in most cases. A postablation, whole-body scan was obtained at 72 h and compared with the previous diagnostic scan for any visual evidence of stunning. RESULTS: No cases of visually apparent thyroid stunning were observed on any of the postablation scans with regard to the number of (131)I foci identified or the relative intensity of (131)I uptake seen. CONCLUSION: Diagnostic whole-body scanning can be performed effectively with a 185-MBq (5 mCi) dose of (131)I 72 h before radioiodine ablation without concern for thyroid stunning.     

Effect of all-trans retinoic acid on sodium/iodide symporter expression, radioiodine uptake and gene expression profiles in a human anaplastic thyroid carcinoma cell line

The plasma membrane glycoprotein sodium/iodide symporter (NIS) is crucial for thyroid hormone biosynthesis and mediates the iodide uptake of thyrocytes. It has been shown that retinoic acid (RA) alters NIS gene expression in thyroid carcinoma lines and stimulates their iodide uptake. Here, we generated an ARO human thyroidal cancer cell line that expresses the NIS gene (ARO-NIS) and found that its baseline 125I uptake was threefold higher than that of its parental ARO cells. However, a 1-microM all-trans retinoic acid (tRA) treatment significantly increased this 125I uptake up to approximately approximately 6.5-fold on Day 3. tRA also elevated NIS mRNA expression in ARO-NIS cells, with peaks of expression being observed on Day 3. To investigate the underlying genomic mechanisms involved in these tRA-induced phenotypic changes, we subjected tRA-treated and untreated ARO-NIS cells to cDNA microarray analysis. Of 1152, genes spotted onto the microarray membrane, 18 were up-regulated (z ratio>2.0) and 33 were down-regulated (z ratio<-2.0) in ARO-NIS cells after 3 days of tRA treatment. More specifically, tRA increased the expression of BCL3, CSRP3, v-fos, and CDK5 genes and decreased the expression of the FGF12 and IGFBP6 genes. Thus, tRA treatment of human anaplastic thyroid carcinoma cells stably expressing the NIS gene significantly elevates their NIS-mediated radioiodine uptake and alters the expression of many genes involved in cell growth and cellular differentiation. Therefore, tRA treatment and NIS gene transfection are potential tools for the diagnosis and treatment of thyroid cancer.     

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.     

Does thyroid stunning exist? A model with benign thyroid disease

With regard to the treatment of differentiated non-medullary thyroid carcinoma, there is controversy over whether radiation from a diagnostic radioiodine (¹³¹I) application really does have a suppressive effect on the uptake of subsequent therapeutic ¹³¹I (so-called thyroid stunning). However, inherent difficulties in exact remnant/metastatic tissue volumetry make it difficult to quantify how much diagnostic ¹³¹I is actually absorbed (absorbed energy dose) and hence to decide whether a threshold absorbed dose exists beyond which such stunning would occur. Since in benign thyroid disease the target volume can be readily quantified by ultrasonography, we sought to determine definitely whether stunning of thyroid cells occurs upon a second application of radioiodine 4 days following the first one. We therefore studied 171 consecutive patients with benign thyroid disease (diffuse goitre, Graves' disease, toxic nodular goitre) who received two-step ¹³¹I therapy during a single in-patient stay. For application of both calculated ¹³¹I activities we performed kinetic dosimetry of ¹³¹I uptake, effective half-life and absorbed dose. At the second application, patients showed significant stunning (a 31.7% decrease in ¹³¹I uptake, from 34.7%ᆣ.4% at first application to 23.7%ᆠ.3% at second application, P<0.0005) without a significant difference in effective half-life (4.9ǃ.3 vs 5.0ǃ.7 days, P>0.2). ANOVA showed that the extent of stunning was influenced significantly only by the absorbed energy dose at first application (F=13.5, P<0.0005), while first-application ¹³¹I activity, target volume, gender and thyroid function had no influence (all FА.71, all P>0.4). There was no significant correlation between extent of thyroid stunning and first-application ¹³¹I activity (r=0.07, P>0.3), whereas there was a highly significant correlation between thyroid stunning and first absorbed energy dose (r=0.64, P<0.00005), the latter correlation fitting a logarithmic model best. Multivariate factor analysis also revealed first absorbed energy dose to be the only decisive stunning factor. In conclusion, our study confirms that stunning exists in benign thyroid conditions and that it is a purely radiobiological inhibitory phenomenon related to absorbed dose.     

Self-stunning in thyroid ablation: evidence from comparative studies of diagnostic 131I and 123I

Twenty-six patients who had undergone recent surgery for differentiated thyroid cancer were investigated using iodine-131 iodide (120 MBq). Uptake in the thyroid bed was measured at 3 days using a dual-head gamma camera. An ablation activity of 131I iodide (4,000 MBq) was administered 3-38 (median 14) days later and uptake in the thyroid bed measured once or twice, 1-3 days post therapy. For measurements post therapy, the gamma camera was operated in the high-count rate mode with appropriate correction factors to compensate for any count loss. A further 16 patients were given iodine-123 iodide (200 MBq) as the diagnostic agent and uptake was measured at 24 h. The ablation activity was administered 5-47 (median 19) days later and uptake again measured at 24 h. In some cases, a further measurement of uptake was made within the period 1-3 days post therapy. Reduced uptake of the therapeutic administration ( P<0.001) was observed in all 26 patients given diagnostic 131I, with a median value of 32.8% (range 6%-93%) of the uptake in the diagnostic study. In the patients given diagnostic 123I, reduced uptake of the ablative radioiodine was observed in 15 of the 16 patients ( P<0.001), and overall the median value was 58.8% (range 17%-130%) of the diagnostic uptake. In one case the uptake post therapy was increased. The stunning observed in the group given 123I was significantly less ( P<0.001) than in the group given 131I. In the patients given diagnostic 131I, stunning appeared to increase in severity the longer the time interval between the diagnostic and therapeutic radionuclides, for intervals up to 25 days. Thereafter, there seemed to be some recovery of uptake capability. Overall there was no evidence of a large rapid loss of radionuclide from the thyroid bed 1-3 days post therapy. The stunning observed using 123I could not be explained by errors in the estimation of relative uptake due to different tissue absorption of the 131I and 123I photons, nor by the radiation dose delivered by the 123I. However, the ablative 131I itself may cause stunning because the cumulated activity, over the first few hours of uptake, is not insignificant when compared with all the cumulated activity from a diagnostic administration of 131I. The resultant radiation dose to the thyroid remnant, as the therapeutic radioiodine is being taken up, may be sufficient to inhibit the uptake process, thus leading to a reduction in maximum uptake when compared with that of a diagnostic activity of radioiodine.     

Reduced iodide transport (stunning) and DNA synthesis in thyrocytes exposed to low absorbed doses from 131I in vitro.

Thyroid stunning refers to reduced uptake of (131)I in the thyroid tissue (or tumor) during radioiodine ((131)I) therapy compared with the uptake measured after the previous administration of (131)I for diagnostic purposes. The phenomenon is clinically important, as it can potentially lead to the undertreatment of thyroid cancer or to unnecessarily high absorbed doses in critical organs. Previous clinical and experimental studies indicated that thyroid stunning is absorbed dose dependent. The aim of this study was to investigate the effects of (131)I irradiation on (125)I(-) transport and cell proliferation at low absorbed doses in vitro. METHODS: Primary cultured porcine thyroid cells were grown to form a confluent monolayer of epithelial cells on a filter in a bicameral culture system. The cells were continuously irradiated with (131)I in the culture medium for 48 h to obtain 0.0015-1.5 Gy. At 3 d after irradiation was stopped, the transepithelial iodide transport capacity was evaluated by measuring (125)I(-) transport from the basal chamber compartment to the apical chamber compartment. The effect of (131)I irradiation on DNA synthesis was estimated by pulse labeling with (3)H-thymidine of both subconfluent and confluent cells irradiated with up to 9 Gy. Total DNA content was measured to quantify cell numbers. RESULTS: A statistically significant reduction in (125)I(-) transport was seen at absorbed doses of >or=0.15 Gy, with a 50% reduction at 1.5 Gy, compared with the results observed for nonirradiated control cells. (3)H-Thymidine incorporation was already statistically significantly reduced at absorbed doses of 0.01-0.1 Gy, but 0.15-0.3 Gy did not affect DNA synthesis. However, absorbed doses of >or=1 Gy again resulted in reduced DNA synthesis. A 50% reduction was obtained at 4 Gy. Total DNA measurements revealed a statistically significant reduction in cell numbers at 8 Gy. CONCLUSION: The lowest absorbed dose from (131)I that reduced iodide transport was 0.15 Gy. Because stunning was found at low absorbed doses, it might occur for (131)I treatment not only of thyroid cancer but also of thyrotoxicosis. On the basis of differences in dose responses, radiation-induced thyroid stunning and cell cycle arrest may be independent phenomena.     

Clinical implications of the differences between diagnostic 123I and post-therapy 131I scans

BACKGROUND: 123I has been promoted for diagnostic imaging as a means of avoiding 'stunning'. It has also been suggested that the more favourable physical characteristics and consequent enhanced imaging resolution provided by 123I offers a more accurate diagnostic assessment of the extent of disease prior to therapy. This study evaluated pairs of diagnostic 123I and post-therapy 131I scans for differences in patterns of radioiodine uptake. METHODS: Thirty-eight patients (31 women and seven men) with a history of differentiated thyroid cancer underwent 41 diagnostic 123I studies. 131I therapy was administered to 29 patients as soon as possible after positive diagnostic findings were confirmed (with one patient being treated twice during the study period, making 30 treatments). Post-treatment scans were obtained an average of 5.8 days after therapy. RESULTS: Qualitative comparison of diagnostic 123I and post-therapy 131I scans revealed a decrease in the extent of post-treatment uptake in four of the 30 treatments (13%). Seven patients (23%) demonstrated increased uptake on their post-therapy 131I scan. CONCLUSIONS: Because the physical characteristics of 123I make it inconceivable that it could cause stunning, the decrease in post-treatment uptake seen in 13% of patients from this series increases the likelihood that this pattern is due to factors other than stunning, such as differential rates of radioiodine turnover. In addition, the increase in extent of post-therapy uptake seen in 23% of patients suggests that diagnostic imaging with 123I is vulnerable to the same pre-therapy staging inaccuracies as is low-dose diagnostic imaging with 131I. Further work is needed to determine whether larger diagnostic doses of 123I might mitigate this problem.     

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.     

Comparison of radioiodine biokinetics following the administration of recombinant human thyroid stimulating hormone and after thyroid hormone withdrawal in thyroid carcinoma

Iodine kinetics were studied in patients with differentiated thyroid cancer while euthyroid under exogenous thyroid stimulating hormone (TSH) and while hypothyroid to detect differences in radioiodine uptake, distribution and elimination. Nine patients with total or near-total thyroidectomy on thyroid hormone suppressive therapy received two or three daily doses of 0.9 mg recombinant human TSH (rhTSH) followed by administration of a diagnostic activity of 2 mCi (74 MBq) iodine-131. After the biokinetics assessments had been performed, patients stopped taking thyroid hormones to become hypothyroid. A second 2 mCi (74 MBq) diagnostic activity of ¹³¹I was administered, followed by a second set of biokinetics assessments. One week later the patients underwent remnant ablation with a therapeutic activity of ¹³¹I. A comparison of the ¹³¹I kinetics in the patients while euthyroid and while hypothyroid showed major differences in the doses to the remnant as well as in residence times and radiation exposure to the blood. In the first diagnostic assessment the remnant dose was higher in eight of the nine patients and clearance of the activity from the blood was faster in all of them. The data from this study suggest that radioiodine administration is potent and safe when administered to euthyroid patients following rhTSH administration. Enhanced residence time in the remnant and decreased radiation exposure to the blood were noted when patients were euthyroid compared to when they were rendered hypothyroid. However, all patients received diagnostic activities in the same order: first while euthyroid, followed by hypothyroidism. It is quite possible that "stunning" from the radioiodine administered in the initial uptake study inhibited the subsequent uptake of radioiodine by the remnant lesions in the second uptake study.     

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.     

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.     

双启动子杆状病毒介导131I肿瘤靶向治疗的实验研究

目的构建由人端粒酶逆转录酶（hTERT）启动子调控的N1S基因以及由早期生长应答因子1（Egr1）启动子调控的人纤溶酶原Kringle5（K5）基因的双启动子重组杆状病毒载体,探讨同时靶向肿瘤细胞与血管内皮细胞的基因治疗模式的可行性。方法将hTERT启动子和N1S基因片段以及Egr1启动子和麟基因片段分别亚克隆至杆状病毒载体,经草地贪夜蛾卵巢细胞（Sf9）包装并扩增得到重组杆状病毒（Bac—hTERT-N1S—Egr1-K5）,同时将CMV启动子调控的重组杆状病毒（Bac—CMV-NIS—Egr1-K5）以及不含NIS基因或不含硒基因的重组杆状病毒（Bac—hTERT-O—Egrl-K5、Bac-hTERT-NIS—Egr1-0）作为对照组。采用荧光定量PCR及Westernblot分析NISmRNA和蛋白在人宫颈癌细胞HeLa中的靶向表达,以及131I辐射对K5mRNA和蛋白的表达调控。通过摄碘实验、NaClO4抑制实验以及细胞增殖抑制实验验证NIS蛋白的功能及由其介导的131I抑瘤作用。通过细胞凋亡实验评估K5蛋白对人脐静脉内皮细胞（HUVEC）的促凋亡作用。统计学检验采用方差分析。结果成功构建重组杆状病毒Bac—hTERT-NIS—Egr1-K5。荧光定量PCR及Westernblot显示肿瘤特异性启动子hTERT介导的NIS基因仅在HeLa细胞中有表达,而在正常肺纤维细胞MRC5中无表达。131I可以调控辐射敏感启动子Egr1下游您基因的转录和翻译。细胞摄碘实验显示Bac-hTERT-NIS—Egr1-K5感染的HeLa细胞摄碘增加了5．6倍,与未加NaClO4组比,其摄碘能被NaClO4显著抑制（F=199．296,P〈0．05）。131I对Bac—hTERT-NIS—Egr1-K5感染的HeLa细胞的抑制效果明显,细胞存活率仅为38．3％。Bac—hTERT-NIS—Egrl一K5感染的HUVEC细胞在131I照射下的凋亡率（30．8％）显著高于Bac．hTERT-NIS—Egr1-0组和未加病毒组（11．2％和10．9％,F=19．926、45．409,均P〈0．05）。结论重组杆状病毒Bac-hTERT-NIS—Egrl．K5可使NIS基因在肿瘤细胞?     

Impact of 131I diagnostic activities on the biokinetics of thyroid remnants.

Recent publications described many discrepant findings about thyroid "stunning" after the administration of (131)I diagnostic activities to patients with differentiated thyroid carcinoma. Stunning may play a major role in reducing the therapeutic efficacy of high (131)I activities given for ablation therapy. METHODS: Participation in a multicenter study to investigate differences in iodine biokinetics in the hypothyroid state and after the application of recombinant human thyroid-stimulating hormone enabled us to study quantitative changes in thyroid iodine biokinetics after the administration of 74 MBq of (131)I twice within 6 wk and an ablation activity of 3-4 GBq 7-12 d after the second diagnostic administration of (131)I in 6 patients. RESULTS: The uptake and half-life of the first 74 MBq of (131)I were significantly reduced to a mean of 44% and a mean of 51%, respectively, after the second diagnostic administration and further reduced to a mean of 40% and a mean of 30%, respectively, during ablation therapy. The residence times were reduced to 25% in the second dosimetric assessment and to 10% during therapy compared with the value in the first assessment. For one patient, an estimated absorbed dose as high as 38 Gy was found in the first diagnostic study. The mean dose for all patients after the first assessment was 15 Gy; after each further assessment, the dose was reduced according to the decrease in residence time. CONCLUSION: This study shows a severe impact of 74 MBq of (131)I on the biokinetics of thyroid remnants during subsequent radioiodine therapy.